Elucidating Solvation Structures for Rational Design of Multivalent Electrolytes—A Review Top. Curr. Chem. (IF 5.537) Pub Date : 2018-04-26 Nav Nidhi Rajput, Trevor J. Seguin, Brandon M. Wood, Xiaohui Qu, Kristin A. Persson
Fundamental molecular-level understanding of functional properties of liquid solutions provides an important basis for designing optimized electrolytes for numerous applications. In particular, exhaustive knowledge of solvation structure, stability, and transport properties is critical for developing stable electrolytes for fast-charging and high-energy-density next-generation energy storage systems. Accordingly, there is growing interest in the rational design of electrolytes for beyond lithium-ion systems by tuning the molecular-level interactions of solvate species present in the electrolytes. Here we present a review of the solvation structure of multivalent electrolytes and its impact on the electrochemical performance of these batteries. A direct correlation between solvate species present in the solution and macroscopic properties of electrolytes is sparse for multivalent electrolytes and contradictory results have been reported in the literature. This review aims to illustrate the current understanding, compare results, and highlight future needs and directions to enable the deep understanding needed for the rational design of improved multivalent electrolytes.
Green and Bio-Based Solvents Top. Curr. Chem. (IF 5.537) Pub Date : 2018-04-24 Francisco G. Calvo-Flores, María José Monteagudo-Arrebola, José A. Dobado, Joaquín Isac-García
Chemical reactions and many of the procedures of separation and purification employed in industry, research or chemistry teaching utilize solvents massively. In the last decades, with the birth of Green Chemistry, concerns about the employment of solvents and the effects on human health, as well as its environmental impacts and its dependence on non-renewable raw materials for manufacturing most of them, has drawn the attention of the scientific community. In this work, we review the concept of green solvent and the properties and characteristics to be considered green. Additionally, we discuss the different possible routes to prepare many solvents from biomass, as an alternative way to those methods currently applied in the petrochemical industry.
Fundamental Challenges for Modeling Electrochemical Energy Storage Systems at the Atomic Scale Top. Curr. Chem. (IF 5.537) Pub Date : 2018-04-23 Axel Groß
There is a strong need to improve the efficiency of electrochemical energy storage, but progress is hampered by significant technological and scientific challenges. This review describes the potential contribution of atomic-scale modeling to the development of more efficient batteries, with a particular focus on first-principles electronic structure calculations. Numerical and theoretical obstacles are discussed, along with ways to overcome them, and some recent examples are presented illustrating the insights into electrochemical energy storage that can be gained from quantum chemical studies.
Interfaces and Materials in Lithium Ion Batteries: Challenges for Theoretical Electrochemistry Top. Curr. Chem. (IF 5.537) Pub Date : 2018-04-18 Johannes Kasnatscheew, Ralf Wagner, Martin Winter, Isidora Cekic-Laskovic
Energy storage is considered a key technology for successful realization of renewable energies and electrification of the powertrain. This review discusses the lithium ion battery as the leading electrochemical storage technology, focusing on its main components, namely electrode(s) as active and electrolyte as inactive materials. State-of-the-art (SOTA) cathode and anode materials are reviewed, emphasizing viable approaches towards advancement of the overall performance and reliability of lithium ion batteries; however, existing challenges are not neglected. Liquid aprotic electrolytes for lithium ion batteries comprise a lithium ion conducting salt, a mixture of solvents and various additives. Due to its complexity and its role in a given cell chemistry, electrolyte, besides the cathode materials, is identified as most susceptible, as well as the most promising, component for further improvement of lithium ion batteries. The working principle of the most important commercial electrolyte additives is also discussed. With regard to new applications and new cell chemistries, e.g., operation at high temperature and high voltage, further improvements of both active and inactive materials are inevitable. In this regard, theoretical support by means of modeling, calculation and simulation approaches can be very helpful to ex ante pre-select and identify the aforementioned components suitable for a given cell chemistry as well as to understand degradation phenomena at the electrolyte/electrode interface. This overview highlights the advantages and limitations of SOTA lithium battery systems, aiming to encourage researchers to carry forward and strengthen the research towards advanced lithium ion batteries, tailored for specific applications.
Sulfur-Based Ylides in Transition-Metal-Catalysed Processes Top. Curr. Chem. (IF 5.537) Pub Date : 2018-04-13 James D. Neuhaus, Rik Oost, Jérémy Merad, Nuno Maulide
Traditionally employed in the synthesis of small ring systems and rearrangement chemistry, sulfur-based ylides occupy a unique position in the toolbox of the synthetic organic chemist. In recent years a number of pioneering researchers have looked to expand the application of these unorthodox reagents through the use of transition metal catalysis. The strength and flexibility of such a combination have been shown to be of key importance in developing powerful novel methodologies. This chapter summarises recent developments in transition metal-catalysed sulfonium/sulfoxonium ylide reactions, as well as providing a historical perspective. In overviewing the successes in this area, the authors hope to encourage others into this growing field.
Sulfur–Sulfur Bond Construction Top. Curr. Chem. (IF 5.537) Pub Date : 2018-04-10 Ming Wang, Xuefeng Jiang
Disulfide, as a common structural motif, has been frequently used in pharmaceuticals, nature products, and chemical biology. This chapter focuses on the methodologies that were reported recently for the synthesis of disulfide-containing compounds with particular emphasis on the synthesis of unsymmetrical disulfides. The presentation is organized according to the structure of the disulfides and the synthetic method.
Carbon Materials from Technical Lignins: Recent Advances Top. Curr. Chem. (IF 5.537) Pub Date : 2018-07-11 Alexander M. Puziy, Olga I. Poddubnaya, Olena Sevastyanova
Lignin, a major component of lignocellulosic biomass, is generated in enormous amounts during the pulp production. It is also a major coproduct of second generation biofuels. The effective utilization of lignin is critical for the accelerated development of the advanced cellulosic biorefinery. Low cost and availability of lignin make it attractive precursor for preparation of a range of carbon materials, including activated carbons, activated carbon fibers (CF), structural CF, graphitic carbons or carbon black that could be used for environmental protection, as catalysts, in energy storage applications or as reinforcing components in advanced composite materials. Technical lignins are very diverse in terms of their molecular weight, structure, chemical reactivity, and chemical composition, which is a consequence of the different origin of the lignin and the various methods of lignin isolation. The inherent heterogeneity of lignin is the main obstacle to the preparation of high-performance CF. Although lignin-based CF still do not compete with polyacrylonitrile-derived CF in mechanical properties, they nevertheless provide new markets through high availability and low production costs. Alternatively, technical lignin could be used for production of carbon adsorbents, which have very high surface areas and pore volumes comparable to the best commercial activated carbons. These porous carbons are useful for purifying gas and aqueous media from organic pollutants or adsorption of heavy metal ions from aqueous solutions. They also could be used as catalysts or electrodes in electrochemical applications.
The Construction and Application of C=S Bonds Top. Curr. Chem. (IF 5.537) Pub Date : 2018-07-10 Toshiaki Murai
The current section presents an overview of the fundamental aspects of thiocarbonyl compounds, such as thioaldehydes and thioketones. Firstly, a theoretical approach and a physical-organic experimental approach disclose their properties. Secondly, their synthetic reactions are introduced. Finally, a focus is given to their synthetic applications, including nucleophilic and electrophilic reactions, as well as concerted reactions.
Thermosetting Polymers from Lignin Model Compounds and Depolymerized Lignins Top. Curr. Chem. (IF 5.537) Pub Date : 2018-07-10 Elias Feghali, Kirk M. Torr, Daniel J. van de Pas, Pablo Ortiz, Karolien Vanbroekhoven, Walter Eevers, Richard Vendamme
Lignin is the most abundant source of renewable ready-made aromatic chemicals for making sustainable polymers. However, the structural heterogeneity, high polydispersity, limited chemical functionality and solubility of most technical lignins makes them challenging to use in developing new bio-based polymers. Recently, greater focus has been given to developing polymers from low molecular weight lignin-based building blocks such as lignin monomers or lignin-derived bio-oils that can be obtained by chemical depolymerization of lignins. Lignin monomers or bio-oils have additional hydroxyl functionality, are more homogeneous and can lead to higher levels of lignin substitution for non-renewables in polymer formulations. These potential polymer feed stocks, however, present their own challenges in terms of production (i.e., yields and separation), pre-polymerization reactions and processability. This review provides an overview of recent developments on polymeric materials produced from lignin-based model compounds and depolymerized lignin bio-oils with a focus on thermosetting materials. Particular emphasis is given to epoxy resins, polyurethanes and phenol-formaldehyde resins as this is where the research shows the greatest overlap between the model compounds and bio-oils. The common goal of the research is the development of new economically viable strategies for using lignin as a replacement for petroleum-derived chemicals in aromatic-based polymers.
Perspective on Lignin Oxidation: Advances, Challenges, and Future Directions Top. Curr. Chem. (IF 5.537) Pub Date : 2018-07-04 Thijs Vangeel, Wouter Schutyser, Tom Renders, Bert F. Sels
Lignin valorization has gained increasing attention over the past decade. Being the world’s largest source of renewable aromatics, its valorization could pave the way towards more profitable and more sustainable lignocellulose biorefineries. Many lignin valorization strategies focus on the disassembly of lignin into aromatic monomers, which can serve as platform molecules for the chemical industry. Within this framework, the oxidative conversion of lignin is of great interest because it enables the formation of highly functionalized, valuable compounds. This work provides a brief overview and critical discussion of lignin oxidation research. In the first part, oxidative conversion of lignin models and isolated lignin streams is reviewed. The second part highlights a number of challenges with respect to the substrate, catalyst, and operating conditions, and proposes some future directions regarding the oxidative conversion of lignin.
Degradation of Vanillin During Lignin Valorization Under Alkaline Oxidation Top. Curr. Chem. (IF 5.537) Pub Date : 2018-07-02 Yuting Zhu, Jing Liu, Yuhe Liao, Wei Lv, Longlong Ma, Chenguang Wang
The preparation of vanillin from lignin is one of the lignin valorization strategies. However, obtaining high vanillin yield is still a challenge. Therefore, the process of vanillin production and factors that affect yield of vanillin has attracted much attention. Here, oxidation of vanillin was performed to study its degradation behavior under lignin alkaline oxidation conditions. High-performance liquid chromatography, liquid chromatography–electrospray mass spectrometry, gas chromatography–mass spectrometer and gel permeation chromatography were employed to analyze the products including monomers and dimers. Results demonstrated that reaction temperature and time greatly affected vanillin degradation; vanillin can be completely converted in 5 h at 160 °C. At 160 °C, the main products of vanillin oxidation were small molecule acids and alcohols, other monophenols, and even condensed dimers. A possible vanillin degradation pathway was proposed. The results indicate that vanillin degradation and condensation are the main reasons for decreasing vanillin yield during lignin valorization under alkaline oxidation circumstances.
Introduction to State-of-the-Art Multidimensional Time-Resolved Spectroscopy Methods Top. Curr. Chem. (IF 5.537) Pub Date : 2018-06-25 Jan Philip Kraack, Tiago Buckup
The field of multidimensional laser spectroscopy comprises a variety of highly developed state-of-the-art methods, which exhibit broad prospects for applications in several areas of natural, material, and even medical sciences. This collection summarizes the main achievements from this area and gives basic introductory insight into what is currently possible with such methods. In the present introductory contribution, we briefly outline the general concept behind multidimensional laser spectroscopy, for instance by highlighting the often-employed analogy between multidimensional laser spectroscopy and NMR methods. Our initial introduction is followed by an overview of the most important and widely used multidimensional spectroscopies’ classification. Special emphasis is placed on how the contributing spectral region defines a natural way of grouping the techniques in terms of their information content. On this basis, we introduce the most important graphical ways in which multidimensional data is generally visualized. This is done by comparing specifically temporal and spectra axes that make up each single multidimensional data plot. Several central experimental methods that are common to the various techniques reviewed in this collection are addressed in the perspective of recent developments and their impact on the field. These methods include, for example, heterodyne/homodyne detection, fast scanning, spatial light modulation, and sparse sampling methods. Importantly, we address the central and fundamental questions where multidimensional ultrafast spectroscopy can be used to help understanding chemical dynamics and intermolecular interactions. Finally, we briefly pinpoint what we believe are the main open questions and what will be the future directions for technical developments and promotion of scientific understanding that multidimensional spectroscopy can provide for chemistry, physics, and life sciences.
Glycosyl Sulfoxides in Glycosylation Reactions Top. Curr. Chem. (IF 5.537) Pub Date : 2018-06-12 Jing Zeng, Yan Liu, Wei Chen, Xiang Zhao, Lingkui Meng, Qian Wan
Carbohydrate chemistry has benefited a lot from the intrinsic reactivity of sulfoxide since it was introduced in glycosylation reactions by Kahne in 1989. Since then, extensive studies have been explored by employing sulfoxide as glycosyl donors and activation reagents in construction of glycosidic bonds. As glycosyl donors, the sulfinyl groups could locate either directly or remotely at anomeric position. This chapter focuses on the establishment and development of sulfoxides as glycosyl donors in glycosylation reactions, with an emphasis on their applications and postulated mechanisms.
Recent Developments in Acenaphthoquinone-Based Multicomponent Reactions: Synthesis of Spiroacenaphthylene Compounds Top. Curr. Chem. (IF 5.537) Pub Date : 2018-06-05 Mohammad Bayat, Zeinab Amiri
This review characterizes the multicomponent reactions of acenaphthoquinone as building blocks for the synthesis of a variety of heterocyclic compounds with medicinal chemistry interest. There is a wide range of reactions that include acenaphthoquinone in the synthesis of heterocyclic compounds. Also this review gives an overview spirocyclic compounds has important applications in pharmacological during the period from 2000 to 2017. Spiro compounds having cyclic structures fused at a central carbon are of recent interest due to their interesting adjustable overall qualities and their structural implications on biological systems.
Engineered C–S Bond Construction Top. Curr. Chem. (IF 5.537) Pub Date : 2018-06-04 Chin-Fa Lee, R. Sidick Basha, Satpal Singh Badsara
Due to the versatile applications of thioethers and thioesters in organic synthesis, medicinal chemistry, the pharmaceutical industry, and materials science, recently the construction of C–S bonds has emerged as the forefront in the field of cross-coupling reactions. Enough progress has been made in this direction by using both metal catalysis and other alternative processes. A brief review of the recent developments in the area of C–S coupling reaction is described.
Towards Synergistic Electrode–Electrolyte Design Principles for Nonaqueous Li–O $$_2$$ 2 batteries Top. Curr. Chem. (IF 5.537) Pub Date : 2018-03-20 Abhishek Khetan, Dilip Krishnamurthy, Venkatasubramanian Viswanathan
One route toward sustainable land and aerial transportation is based on electrified vehicles. To enable electrification in transportation, there is a need for high-energy-density batteries, and this has led to an enormous interest in lithium–oxygen batteries. Several critical challenges remain with respect to realizing a practical lithium–oxygen battery. In this article, we present a detailed overview of theoretical efforts to formulate design principles for identifying stable electrolytes and electrodes with the desired functionality and stability. We discuss design principles relating to electrolytes and the additional stability challenges that arise at the cathode–electrolyte interface. Based on a thermodynamic analysis, we discuss two important requirements for the cathode: the ability to nucleate the desired discharge product, Li\(_2\)O\(_2\), and the ability to selectively activate only this discharge product while suppressing lithium oxide, the undesired secondary discharge product. We propose preliminary guidelines for determining the chemical stability of the electrode and illustrate the challenge associated with electrode selection using the examples of carbon cathodes and transition metals. We believe that a synergistic design framework for identifying electrolyte–electrode formulations is needed to realize a practical Li–O\(_2\) battery.
Quinodimethanes Incorporated in Non-Benzenoid Aromatic or Antiaromatic Frameworks Top. Curr. Chem. (IF 5.537) Pub Date : 2018-03-20 Yoshito Tobe
Three isomers of quinodimethanes (QDMs) adopt different electronic configurations and geometries, generating their own characteristic physical properties. Incorporation of QDMs into non-benzenoid aromatic or antiaromatic frameworks not only planarizes the whole π system optimizing conjugation, but also changes the electronic properties inherent to QDMs, sometimes drastically, due to the topology of the π system, through interaction with the remaining part of the molecules. In non-benzenoid systems, molecular orbital levels and orbital distribution are uneven compared to benzenoid systems, thereby polarizing the ground state and leading to unique behavior in excited states. In antiaromatic systems, open-shell, diradical character, which is inherent to QDMs, may be enhanced due to small HOMO–LUMO energy gap. In this chapter, effects of incorporating QDMs into non-benzenoid aromatic or antiaromatic frameworks are discussed focusing on the open-shell, diradical character with respect to their molecular structures, antiaromaticity, and physical properties related to the open-shell character and molecular orbital levels and materials applications, as well as covering historical works to the current state-of-the-art achievements.
Electronic Couplings in (Bio-) Chemical Processes Top. Curr. Chem. (IF 5.537) Pub Date : 2018-03-20 Margherita Maiuri, Johanna Brazard
Main fields impacted by two-dimensional electronic spectroscopy (2DES) in condensed phase. The major discoveries of each field will be described in different paragraphs
Electrochemical Synthesis of Battery Electrode Materials from Ionic Liquids Top. Curr. Chem. (IF 5.537) Pub Date : 2018-02-21 Abhishek Lahiri, Natalia Borisenko, Frank Endres
Electrode materials as well as the electrolytes play a decisive role in batteries determining their performance, safety, and lifetime. In the last two decades, different types of batteries have evolved. A lot of work has been done on lithium ion batteries due to their technical importance in consumer electronics, however, the development of post-lithium systems has become a focus in recent years. This chapter gives an overview of various battery materials, primarily focusing on development of electrode materials in ionic liquids via electrochemical route and using ionic liquids as battery electrolyte components.
Chemical Valorization of Cashew Nut Shell Waste Top. Curr. Chem. (IF 5.537) Pub Date : 2018-02-13 E. B. Mubofu, J. E. Mgaya
Cashew nut shells are agro-wastes produced from cashew nut processing factories and contain about 30–35 wt% oil called cashew nut shell liquid (CNSL). This liquid is a mixture of four potential compounds, namely anacardic acid, cardanol, cardol and 2-methyl cardol. Various reactions have been developed to convert the components of cashew nut shell liquid into industrially important chemicals, and these materials are herein described. Such reactions employed in the transformation include transfer hydrogenation reactions, isomerization reactions, metathesis reactions, carbonylation reactions, polymerization reactions, isomerizing metathesis reaction, and isomerizing carbonylation reactions. Through these descriptions, one realizes that cashew nut shells are not a waste, but they are rather a good source of a potential liquid, CNSL, which is a promising renewable resource for synthesizing various industrial chemicals.
Assessment of Simple Models for Molecular Simulation of Ethylene Carbonate and Propylene Carbonate as Solvents for Electrolyte Solutions Top. Curr. Chem. (IF 5.537) Pub Date : 2018-02-12 Mangesh I. Chaudhari, Ajay Muralidharan, Lawrence R. Pratt, Susan B. Rempe
Progress in understanding liquid ethylene carbonate (EC) and propylene carbonate (PC) on the basis of molecular simulation, emphasizing simple models of interatomic forces, is reviewed. Results on the bulk liquids are examined from the perspective of anticipated applications to materials for electrical energy storage devices. Preliminary results on electrochemical double-layer capacitors based on carbon nanotube forests and on model solid-electrolyte interphase (SEI) layers of lithium ion batteries are considered as examples. The basic results discussed suggest that an empirically parameterized, non-polarizable force field can reproduce experimental structural, thermodynamic, and dielectric properties of EC and PC liquids with acceptable accuracy. More sophisticated force fields might include molecular polarizability and Buckingham-model description of inter-atomic overlap repulsions as extensions to Lennard-Jones models of van der Waals interactions. Simple approaches should be similarly successful also for applications to organic molecular ions in EC/PC solutions, but the important case of Li\(^+\) deserves special attention because of the particularly strong interactions of that small ion with neighboring solvent molecules. To treat the Li\(^+\) ions in liquid EC/PC solutions, we identify interaction models defined by empirically scaled partial charges for ion-solvent interactions. The empirical adjustments use more basic inputs, electronic structure calculations and ab initio molecular dynamics simulations, and also experimental results on Li\(^+\) thermodynamics and transport in EC/PC solutions. Application of such models to the mechanism of Li\(^+\) transport in glassy SEI models emphasizes the advantage of long time-scale molecular dynamics studies of these non-equilibrium materials.
Two-Dimensional Spectroscopy at Terahertz Frequencies Top. Curr. Chem. (IF 5.537) Pub Date : 2018-01-23 Jian Lu, Xian Li, Yaqing Zhang, Harold Y. Hwang, Benjamin K. Ofori-Okai, Keith A. Nelson
Multidimensional spectroscopy in the visible and infrared spectral ranges has become a powerful technique to retrieve dynamic correlations and couplings in wide-ranging systems by utilizing multiple correlated light-matter interactions. Its extension to the terahertz (THz) regime of the electromagnetic spectrum, where rich material degrees of freedom reside, however, has been progressing slowly. This chapter reviews some of the THz-frequency two-dimensional (2D) spectroscopy techniques and experimental results realized in recent years. Examples include gas molecule rotations, spin precessions in magnetic systems, and liquid molecular dynamics studied by 2D THz or hybrid 2D THz-Raman spectroscopy techniques. The methodology shows promising applications to different THz-frequency degrees of freedom in various chemical systems and processes.
Analysis of US FDA-Approved Drugs Containing Sulfur Atoms Top. Curr. Chem. (IF 5.537) Pub Date : 2018-01-22 Kevin A. Scott, Jon T. Njardarson
In this review, we discuss all sulfur-containing FDA-approved drugs and their structures. The second section of the review is dedicated to structural analysis and is divided into 14 subsections, each focusing on one type of sulfur-containing moiety. A concise graphical representation of each class features drugs that are organized on the basis of structural similarity, evolutionary relevance, and medical indication. This review offers a unique and comprehensive overview of the structural features of all sulfur-containing FDA-approved drugs to date.
Towards Accurate Simulation of Two-Dimensional Electronic Spectroscopy Top. Curr. Chem. (IF 5.537) Pub Date : 2018-06-01 Javier Segarra-Martí, Shaul Mukamel, Marco Garavelli, Artur Nenov, Ivan Rivalta
We introduce the basic concepts of two-dimensional electronic spectroscopy (2DES) and a general theoretical framework adopted to calculate, from first principles, the nonlinear response of multi-chromophoric systems in realistic environments. Specifically, we focus on UV-active chromophores representing the building blocks of biological systems, from proteins to nucleic acids, describing our progress in developing computational tools and protocols for accurate simulation of their 2DUV spectra. The roadmap for accurate 2DUV spectroscopy simulations is illustrated starting with benchmarking of the excited-state manifold of the chromophoric units in a vacuum, which can be used for building exciton Hamiltonians for large-scale applications or as a reference for first-principles simulations with reduced computational cost, enabling treatment of minimal (still realistic) multi-chromophoric model systems. By adopting a static approximation that neglects dynamic processes such as spectral diffusion and population transfer, we show how 2DUV is able to characterize the ground-state conformational space of dinucleosides and small peptides comprising dimeric chromophoric units (in their native environment) by tracking inter-chromophoric electronic couplings. Recovering the excited-state coherent vibrational dynamics and population transfers, we observe a remarkable agreement between the predicted 2DUV spectra of the pyrene molecule and the experimental results. These results further led to theoretical studies of the excited-state dynamics in a solvated dinucleoside system, showing that spectroscopic fingerprints of long-lived excited-state minima along the complex photoinduced decay pathways of DNA/RNA model systems can be simulated at a reasonable computational cost. Our results exemplify the impact of accurate simulation of 2DES spectra in revealing complex physicochemical properties of fundamental biological systems and should trigger further theoretical developments as well as new experiments.
Cross-Dehydrogenative Coupling Reactions Between P(O)–H and X–H (X = S, N, O, P) Bonds Top. Curr. Chem. (IF 5.537) Pub Date : 2018-05-26 Akram Hosseinian, Sepideh Farshbaf, Leila Zare Fekri, Mohammad Nikpassand, Esmail Vessally
P(O)–X (X = S, N, O, P) bond-containing compounds have extensive application in medicinal chemistry, agrochemistry, and material chemistry. These useful organophosphorus compounds also have many applications in organic synthesis. In light of the importance of titled compounds, there is continuing interest in the development of synthetic methods for P(O)–X bonds construction. In the last 4 years, the direct coupling reaction of P(O)–H compounds with thiols, alcohols, and amines/amides has received much attention because of the atom-economic character. This review aims to give an overview of new developments in cross-dehydrogenative coupling reactions between P(O)–H and X–H (X = S, N, O, P) bonds, with special emphasis on the mechanistic aspects of the reactions.
Sulfur Radicals and Their Application Top. Curr. Chem. (IF 5.537) Pub Date : 2018-05-09 Richard S. Glass
The present review highlights recent developments in the chemistry of sulfur radicals. Background material essential to the understanding of these developments is briefly reviewed and references to previous in depth reviews are cited. The exciting applications of current research involving sulfur radicals in bonding theory, organic synthesis, polymer chemistry, materials science, and biochemistry are outlined.
Lignin-Based Composite Materials for Photocatalysis and Photovoltaics Top. Curr. Chem. (IF 5.537) Pub Date : 2018-05-02 Ayesha Khan, Vaishakh Nair, Juan Carlos Colmenares, Roger Gläser
Depleting conventional fuel reserves has prompted the demand for the exploration of renewable resources. Biomass is a widely available renewable resource that can be valorized to produce fuels, chemicals, and materials. Among all the fractions of biomass, lignin has been underutilized. Due to its complex structure, recalcitrant nature, and heterogeneity, its valorization is relatively challenging. This review focuses on the utilization of lignin for the preparation of composite materials and their application in the field of photocatalysis and photovoltaics. Lignin can be used as a photocatalyst support for its potential application in photodegradation of contaminants. The interaction between the components in hybrid photocatalysts plays a significant role in determining the photocatalytic performance. The application of lignin as a photocatalyst support tends to control the size of the particles and allows uniform distribution of the particles that influence the characteristics of the photocatalyst. Lignin as a semiconductive polymer dopant for photoanodes in photovoltaic cells can improve the photoconversion efficiency of the cell. Recent success in the development of lignosulfonates dopant for hole transport materials in photovoltaics will pave the way for further research in lignin-based high-performance organic electronic devices.
Functional Calixphyrins: Synthetic Strategies and Applications Top. Curr. Chem. (IF 5.537) Pub Date : 2018-05-02 Anchal Singhal
Calixphyrins are hybrid macrocycles that contain both sp2- and sp3-hybridized carbon atoms and hence bear analogy to both porphyrins and calixpyrroles. Due to the presence of sp3-hybridized carbon atoms, π-conjugation is disrupted in calixphyrins, which leads to conformational flexibility. Hence, these molecules find a use in anion binding, host-guest chemistry and metal-coordination chemistry. During the last decade, studies on calixphyrins have been a topic of wide interest to researchers. Various functionalities have been introduced to the structure of calixphyrins, leading to the development of expanded calixphyrins, core-modified calixphyrins and N-confused calixphyrins with diverse applications. This review outlines the detailed historical origin of the synthesis of calixphyrins with emphasis on current research and development in this area. The modular syntheses of normal calixphyrins, expanded calixphyrins, core-modified calixphyrins and N-confused calixphyrins are also discussed, along with their applicative aspects.
Recent Developments in Single-Walled Carbon Nanotube Thin Films Fabricated by Dry Floating Catalyst Chemical Vapor Deposition Top. Curr. Chem. (IF 5.537) Pub Date : 2017-11-27 Qiang Zhang, Nan Wei, Patrik Laiho, Esko I. Kauppinen
Transparent conducting films (TCFs) are critical components of many optoelectronic devices that pervade modern technology. Due to their excellent optoelectronic properties and flexibility, single-walled carbon nanotube (SWNT) films are regarded as an important alternative to doped metal oxides or brittle and expensive ceramic materials. Compared with liquid-phase processing, the dry floating catalyst chemical vapor deposition (FCCVD) method without dispersion of carbon nanotubes (CNTs) in solution is more direct and simpler. By overcoming the tradeoff between CNT length and solubility during film fabrication, the dry FCCVD method enables production of films that contain longer CNTs and offer excellent optoelectronic properties. This review focuses on fabrication of SWNT films using the dry FCCVD method, covering SWNT synthesis, thin-film fabrication and performance regulation, the morphology of SWNTs and bundles, transparency and conductivity characteristics, random bundle films, patterned films, individual CNT networks, and various applications, especially as TCFs in touch displays. Films based on SWNTs produced by the dry FCCVD method are already commercially available for application in touch display devices. Further research on the dry FCCVD method could advance development of not only industrial applications of CNTs but also the fundamental science of related nanostructured materials and nanodevices.
Integration of Waste Valorization for Sustainable Production of Chemicals and Materials via Algal Cultivation Top. Curr. Chem. (IF 5.537) Pub Date : 2017-11-27 Yong Chen, Li-ping Sun, Zhi-hui Liu, Greg Martin, Zheng Sun
Managing waste is an increasing problem globally. Microalgae have the potential to help remove contaminants from a range of waste streams and convert them into useful biomass. This article presents a critical review of recent technological developments in the production of chemicals and other materials from microalgae grown using different types of waste. A range of novel approaches are examined for efficiently capturing CO2 in flue gas via photosynthetic microalgal cultivation. Strategies for using microalgae to assimilate nitrogen, organic carbon, phosphorus, and metal ions from wastewater are considered in relation to modes of production. Generally, more economical open cultivation systems such as raceway ponds are better suited for waste conversion than more expensive closed photobioreactor systems, which might have use for higher-value products. The effect of cultivation methods and the properties of the waste streams on the composition the microalgal biomass is discussed relative to its utilization. Possibilities include the production of biodiesel via lipid extraction, biocrude from hydrothermal liquefaction, and bioethanol or biogas from microbial conversion. Microalgal biomass produced from wastes may also find use in higher-value applications including protein feeds or for the production of bioactive compounds such as astaxanthin or omega-3 fatty acids. However, for some waste streams, further consideration of how to manage potential microbial and chemical contaminants is needed for food or health applications. The use of microalgae for waste valorization holds promise. Widespread implementation of the available technologies will likely follow from further improvements to reduce costs, as well as the increasing pressure to effectively manage waste.
Biogenesis of Selenium Nanoparticles Using Green Chemistry Top. Curr. Chem. (IF 5.537) Pub Date : 2017-11-09 Sara Shoeibi, Paul Mozdziak, Afsaneh Golkar-Narenji
Selenium binds some enzymes such as glutathione peroxidase and thioredoxin reductase, which may be activated in biological infections and oxidative stress. Chemical and physical methods for synthesizing nanoparticles, apart from being expensive, have their own particular risks. However, nanoparticle synthesis through green chemistry is a safe procedure that different biological sources such as bacteria, fungi, yeasts, algae and plants can be the catalyst bed for processing. Synthesis of selenium nanoparticles (SeNPs) by macro/microorganisms causes variation in morphology and shape of the particles is due to diversity of reduction enzymes in organisms. Reducing enzymes of microorganisms by changing the status of redox convert metal ions (Se2−) to SeNPs without charge (Se0). Biological activity of SeNPs includes their protective role against DNA oxidation. Because of the biological and industrial properties, SeNPs have wide applications in the fields of medicine, microelectronic, agriculture and animal husbandry. SeNPs can show strong antimicrobial effects on the growth and proliferation of microorganisms in a dose-dependent manner. The objective of this review is to consider SeNPs applications to various organisms.
Two-Dimensional Resonance Raman Signatures of Vibronic Coherence Transfer in Chemical Reactions Top. Curr. Chem. (IF 5.537) Pub Date : 2017-11-02 Zhenkun Guo, Brian P. Molesky, Thomas P. Cheshire, Andrew M. Moran
Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in condensed phase systems. 2DRR spectroscopy is motivated by knowledge of non-equilibrium effects that cannot be detected with traditional resonance Raman spectroscopy. For example, 2DRR spectra may reveal correlated distributions of reactant and product geometries in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this chapter, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide. We show that signatures of “vibronic coherence transfer” in the photodissociation process can be targeted with particular 2DRR pulse sequences. Key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopy techniques are also addressed. Overall, recent experimental developments and applications of the 2DRR method suggest that it will be a valuable tool for elucidating ultrafast chemical reaction mechanisms.
Ultrafast structural molecular dynamics investigated with 2D infrared spectroscopy methods Top. Curr. Chem. (IF 5.537) Pub Date : 2017-10-25 Jan Philip Kraack
Ultrafast, multi-dimensional infrared (IR) spectroscopy has been advanced in recent years to a versatile analytical tool with a broad range of applications to elucidate molecular structure on ultrafast timescales, and it can be used for samples in a many different environments. Following a short and general introduction on the benefits of 2D IR spectroscopy, the first part of this chapter contains a brief discussion on basic descriptions and conceptual considerations of 2D IR spectroscopy. Outstanding classical applications of 2D IR are used afterwards to highlight the strengths and basic applicability of the method. This includes the identification of vibrational coupling in molecules, characterization of spectral diffusion dynamics, chemical exchange of chemical bond formation and breaking, as well as dynamics of intra- and intermolecular energy transfer for molecules in bulk solution and thin films. In the second part, several important, recently developed variants and new applications of 2D IR spectroscopy are introduced. These methods focus on (i) applications to molecules under two- and three-dimensional confinement, (ii) the combination of 2D IR with electrochemistry, (iii) ultrafast 2D IR in conjunction with diffraction-limited microscopy, (iv) several variants of non-equilibrium 2D IR spectroscopy such as transient 2D IR and 3D IR, and (v) extensions of the pump and probe spectral regions for multi-dimensional vibrational spectroscopy towards mixed vibrational-electronic spectroscopies. In light of these examples, the important open scientific and conceptual questions with regard to intra- and intermolecular dynamics are highlighted. Such questions can be tackled with the existing arsenal of experimental variants of 2D IR spectroscopy to promote the understanding of fundamentally new aspects in chemistry, biology and materials science. The final part of the chapter introduces several concepts of currently performed technical developments, which aim at exploiting 2D IR spectroscopy as an analytical tool. Such developments embrace the combination of 2D IR spectroscopy and plasmonic spectroscopy for ultrasensitive analytics, merging 2D IR spectroscopy with ultra-high-resolution microscopy (nanoscopy), future variants of transient 2D IR methods, or 2D IR in conjunction with microfluidics. It is expected that these techniques will allow for groundbreaking research in many new areas of natural sciences.
Thiophene-Based Organic Semiconductors Top. Curr. Chem. (IF 5.537) Pub Date : 2017-10-24 Gulsen Turkoglu, M. Emin Cinar, Turan Ozturk
Thiophene-based π-conjugated organic small molecules and polymers are the research subject of significant current interest owing to their potential use as organic semiconductors in material chemistry. Despite simple and similar molecular structures, the hitherto reported properties of thiophene-based organic semiconductors are rather diverse. Design of high performance organic semiconducting materials requires a thorough understanding of inter- and intra-molecular interactions, solid-state packing, and the influence of both factors on the charge carrier transport. In this chapter, thiophene-based organic semiconductors, which are classified in terms of their chemical structures and their structure–property relationships, are addressed for the potential applications as organic photovoltaics (OPVs), organic field-effect transistors (OFETs) and organic light emitting diodes (OLEDs).
Towards Rectifying Performance at the Molecular Scale Top. Curr. Chem. (IF 5.537) Pub Date : 2017-10-24 Guang-Ping Zhang, Zhen Xie, Yang Song, Gui-Chao Hu, Chuan-Kui Wang
Molecular diode, proposed by Mark Ratner and Arieh Aviram in 1974, is the first single-molecule device investigated in molecular electronics. As a fundamental device in an electric circuit, molecular diode has attracted an enduring and extensive focus during the past decades. In this review, the theoretical and experimental progresses of both charge-based and spin-based molecular diodes are summarized. For the charge-based molecular diodes, the rectifying properties originated from asymmetric molecules including D–σ–A, D–π–A, D–A, and σ–π type compounds, asymmetric electrodes, asymmetric nanoribbons, and their combination are analyzed. Correspondingly, the rectification mechanisms are discussed in detail. Furthermore, a series of strategies for modulating rectification performance is figured out. Discussion on concept of molecular spin diode is also involved based on a magnetic co-oligomer. At the same time, the intrinsic mechanism as well as the modulation of the spin-current rectification performance is introduced. Finally, several crucial issues that need to be addressed in the future are given.
Benzenoid Quinodimethanes Top. Curr. Chem. (IF 5.537) Pub Date : 2017-10-17 Akihito Konishi, Takashi Kubo
Reactivity and physical properties of π-conjugated hydrocarbon systems depend predominantly on the topology of π-electrons array. Quinoidal conjugations serve as giving diradical character to molecules, leading to unique chemical behaviors. The simplest member of quinodimethanes are o-, m-, and p-quinodimethanes, which are very reactive due to diradical character and cannot be isolated under normal experimental conditions. However, chemical modifications, such as π-extension or introduction of substituent groups, of quinodimethanes imparts stabilities to quinodimethanes that can be handled under ambient conditions. This chapter offers an overview of reactivity and magnetic properties of benzenoid o-, m-, and p-quinodimethanes.
Sulfur-Containing Agrochemicals Top. Curr. Chem. (IF 5.537) Pub Date : 2017-10-09 Ponnam Devendar, Guang-Fu Yang
Modern agricultural chemistry has to support farmers by providing innovative agrochemicals. In this context, the introduction of sulfur atoms into an active ingredient is still an important tool in modulating the properties of new crop-protection compounds. More than 30% of today’s agrochemicals contain at least one sulfur atom, mainly in fungicides, herbicides and insecticides. A number of recently developed sulfur-containing agrochemical candidates represent a novel class of chemical compounds with new modes of action, so we intend to highlight the emerging interest in commercially active sulfur-containing compounds. This chapter gives a comprehensive overview of selected leading sulfur-containing pesticidal chemical families namely: sulfonylureas, sulfonamides, sulfur-containing heterocyclics, thioureas, sulfides, sulfones, sulfoxides and sulfoximines. Also, the most suitable large-scale synthetic methods of the recently launched or provisionally approved sulfur-containing agrochemicals from respective chemical families have been highlighted.
Cell Concepts of Metal–Sulfur Batteries (Metal = Li, Na, K, Mg): Strategies for Using Sulfur in Energy Storage Applications Top. Curr. Chem. (IF 5.537) Pub Date : 2017-09-29 Lukas Medenbach, Philipp Adelhelm
There is great interest in using sulfur as active component in rechargeable batteries thanks to its low cost and high specific charge (1672 mAh/g). The electrochemistry of sulfur, however, is complex and cell concepts are required, which differ from conventional designs. This review summarizes different strategies for utilizing sulfur in rechargeable batteries among membrane concepts, polysulfide concepts, all-solid-state concepts as well as high-temperature systems. Among the more popular lithium–sulfur and sodium–sulfur batteries, we also comment on recent results on potassium–sulfur and magnesium–sulfur batteries. Moreover, specific properties related to the type of light metal are discussed.
1,3-Diphenylisobenzofuran: a Model Chromophore for Singlet Fission Top. Curr. Chem. (IF 5.537) Pub Date : 2017-09-11 Justin C. Johnson, Josef Michl
In this review we first provide an introductory description of the singlet fission phenomenon and then describe the ground and electronically excited states of the parent 1,3-diphenylisobenzofuran chromophore (1) and about a dozen of its derivatives. A discussion of singlet fission in thin polycrystalline layers of these materials follows. The highest quantum yield of triplet formation by singlet fission, 200% at 80 K, is found in one of the two known crystal modification of the parent. In the other modification and in many derivatives, excimer formation competes successfully and triplet yields are low. A description of solution photophysics of covalent dimers is described in the next section. Triplet yields are very low, but interesting phenomena are uncovered. One is an observation of a separated-charges (charge-transfer) intermediate in highly polar solvents. The other is an observation of excitation isomerism in both singlet and triplet states, where in one isomer the excitation is delocalized over both halves of the covalent dimer, whereas in the other it is localized on one of the halves. In the last section we present the operation of a simple device illustrating the use of triplets generated by singlet fission for charge separation.
Nonlinear and Nonsymmetric Single-Molecule Electronic Properties Towards Molecular Information Processing Top. Curr. Chem. (IF 5.537) Pub Date : 2017-09-05 Takashi Tamaki, Takuji Ogawa
This review highlights molecular design for nonlinear and nonsymmetric single-molecule electronic properties such as rectification, negative differential resistance, and switching, which are important components of future single-molecule information processing devices. Perspectives on integrated “molecular circuits” are also provided. Nonlinear and nonsymmetric single-molecule electronics can be designed by utilizing (1) asymmetric molecular cores, (2) asymmetric anchoring groups, (3) an asymmetric junction environment, and (4) asymmetric electrode materials. This review mainly focuses on the design of molecular cores.
Lewis Acidic Ionic Liquids Top. Curr. Chem. (IF 5.537) Pub Date : 2017-08-21 Lucy C. Brown, James M. Hogg, Małgorzata Swadźba-Kwaśny
Until very recently, the term Lewis acidic ionic liquids (ILs) was nearly synonymous with halometallate ILs, with a strong focus on chloroaluminate(III) systems. The first part of this review covers the historical context in which these were developed, speciation of a range of halometallate ionic liquids, attempts to quantify their Lewis acidity, and selected recent applications: in industrial alkylation processes, in supported systems (SILPs/SCILLs) and in inorganic synthesis. In the last decade, interesting alternatives to halometallate ILs have emerged, which can be divided into two sub-sections: (1) liquid coordination complexes (LCCs), still based on halometallate species, but less expensive and more diverse than halometallate ionic liquids, and (2) ILs with main-group Lewis acidic cations. The two following sections cover these new liquid Lewis acids, also highlighting speciation studies, Lewis acidity measurements, and applications.
Functional Organometallic Poly(arylene ethynylene)s: From Synthesis to Applications Top. Curr. Chem. (IF 5.537) Pub Date : 2017-08-17 Jie Zhang, Linli Xu, Cheuk-Lam Ho, Wai-Yeung Wong
This review focuses on the recent development in the rigid-rod metallopolymers of late transition metals based on triple-bond building blocks. The synthesis, structure–property relationships and potential applications of organometallic poly(arylene ethynylene)s will be discussed in detail. These functional metal-based polymers can exhibit intriguing optical, electronic and magnetic properties. Considerable focus is placed on the design strategies towards tuning the optical bandgap and emission color (spanning almost the whole visible spectrum) of this class of metallopolymers, and the investigation of their use as active materials for light/electrical energy conversion and energy and information storage. The ongoing scientific challenges and future prospects of this research field are also highlighted.
Single-Walled Carbon Nanotubes in Solar Cells Top. Curr. Chem. (IF 5.537) Pub Date : 2018-01-22 Il Jeon, Yutaka Matsuo, Shigeo Maruyama
Photovoltaics, more generally known as solar cells, are made from semiconducting materials that convert light into electricity. Solar cells have received much attention in recent years due to their promise as clean and efficient light-harvesting devices. Single-walled carbon nanotubes (SWNTs) could play a crucial role in these devices and have been the subject of much research, which continues to this day. SWNTs are known to outperform multi-walled carbon nanotubes (MWNTs) at low densities, because of the difference in their optical transmittance for the same current density, which is the most important parameter in comparing SWNTs and MWNTs. SWNT films show semiconducting features, which make SWNTs function as active or charge-transporting materials. This chapter, consisting of two sections, focuses on the use of SWNTs in solar cells. In the first section, we discuss SWNTs as a light harvester and charge transporter in the photoactive layer, which are reviewed chronologically to show the history of the research progress. In the second section, we discuss SWNTs as a transparent conductive layer outside of the photoactive layer, which is relatively more actively researched. This section introduces SWNT applications in silicon solar cells, organic solar cells, and perovskite solar cells each, from their prototypes to recent results. As we go along, the science and prospects of the application of solar cells will be discussed.
Green and Sustainable Separation of Natural Products from Agro-Industrial Waste: Challenges, Potentialities, and Perspectives on Emerging Approaches Top. Curr. Chem. (IF 5.537) Pub Date : 2018-01-17 Vânia G. Zuin, Luize Z. Ramin
New generations of biorefinery combine innovative biomass waste resources from different origins, chemical extraction and/or synthesis of biomaterials, biofuels, and bioenergy via green and sustainable processes. From the very beginning, identifying and evaluating all potentially high value-added chemicals that could be removed from available renewable feedstocks requires robust, efficient, selective, reproducible, and benign analytical approaches. With this in mind, green and sustainable separation of natural products from agro-industrial waste is clearly attractive considering both socio-environmental and economic aspects. In this paper, the concepts of green and sustainable separation of natural products will be discussed, highlighting the main studies conducted on this topic over the last 10 years. The principal analytical techniques (such as solvent, microwave, ultrasound, and supercritical treatments), by-products (e.g., citrus, coffee, corn, and sugarcane waste) and target compounds (polyphenols, proteins, essential oils, etc.) will be presented, including the emerging green and sustainable separation approaches towards bioeconomy and circular economy contexts.
Precisely Defined Polymers for Efficient Gene Delivery Top. Curr. Chem. (IF 5.537) Pub Date : 2018-01-15 Dongsheng He, Hao Lin, Yinglan Yu, Lei Shi, Jiasheng Tu
Gene therapy requires successful delivery of therapeutic nucleic acids into target cells; thus, efficient and safe gene delivery carriers are crucial to its success. Although many polymeric materials have shown their potential as effective nucleic acid carriers, the inherent heterogeneity and polydispersity of these polymers hinder their application in clinical studies because of difficulties in their further precise modification, structure–activity relationship study, as well as consistent manufacturing. Therefore, precisely defined polymers, with potential for site-specific optimization according to structure–activity relationship information and highly controllable production, have been extensively investigated. In this review, we focus on the design and development of precisely defined polymers for efficient gene delivery, illustrated with examples including dendrimers, peptide-based polymers, and sequence-defined oligoaminoamide oligomers.
Photo- and Electrochemical Valorization of Carbon Dioxide Using Earth-Abundant Molecular Catalysts Top. Curr. Chem. (IF 5.537) Pub Date : 2017-12-06 Alonso Rosas-Hernández, Christoph Steinlechner, Henrik Junge, Matthias Beller
The dramatic increase in anthropogenic carbon dioxide emissions in recent decades has forced us to look for alternative carbon-neutral processes for the production of energy vectors and commodity chemicals. Photo- and electrochemical reduction of CO2 are appealing strategies for the storage of sustainable and intermittent energies in the form of chemical bonds of synthetic fuels and value-added molecules. In these approaches, carbon dioxide is converted to products such as CO, HCOOH and MeOH through proton-coupled electron transfer reactions. The use of earth-abundant elements as components of the catalytic materials is crucial for the large-scale applicability of this technology. This review summarizes the most recent advances related to this issue, with particular focus on studies where molecular metal complexes are used as catalysts. In addition, with the aim of aiding in the design of more robust and efficient non-noble metal-based catalysts, we discuss the lessons learned from the corresponding mechanistic studies.
Recent Trends in Sustainable Textile Waste Recycling Methods: Current Situation and Future Prospects Top. Curr. Chem. (IF 5.537) Pub Date : 2017-08-16 Nattha Pensupa, Shao-Yuan Leu, Yunzi Hu, Chenyu Du, Hao Liu, Houde Jing, Huaimin Wang, Carol Sze Ki Lin
In recent years, there have been increasing concerns in the disposal of textile waste around the globe. The growth of textile markets not only depends on population growth but also depends on economic and fashion cycles. The fast fashion cycle in the textile industry has led to a high level of consumption and waste generation. This can cause a negative environmental impact since the textile and clothing industry is one of the most polluting industries. Textile manufacturing is a chemical-intensive process and requires a high volume of water throughout its operations. Wastewater and fiber wastes are the major wastes generated during the textile production process. On the other hand, the fiber waste was mainly created from unwanted clothes in the textile supply chain. This fiber waste includes natural fiber, synthetic fiber, and natural/synthetic blends. The natural fiber is mostly comprised of cellulosic material, which can be used as a resource for producing bio-based products. The main challenge for utilization of textile waste is finding the method that is able to recover sugars as monosaccharides. This review provides an overview of valorization of textile waste to value-added products, as well as an overview of different strategies for sugar recovery from cellulosic fiber and their hindrances.
Review of Electronics Based on Single-Walled Carbon Nanotubes Top. Curr. Chem. (IF 5.537) Pub Date : 2017-08-14 Yu Cao, Sen Cong, Xuan Cao, Fanqi Wu, Qingzhou Liu, Moh. R. Amer, Chongwu Zhou
Single-walled carbon nanotubes (SWNTs) are extremely promising materials for building next-generation electronics due to their unique physical and electronic properties. In this article, we will review the research efforts and achievements of SWNTs in three electronic fields, namely analog radio-frequency electronics, digital electronics, and macroelectronics. In each SWNT-based electronic field, we will present the major challenges, the evolutions of the methods to overcome these challenges, and the state-of-the-art of the achievements. At last, we will discuss future directions which could lead to the broad applications of SWNTs. We hope this review could inspire more research on SWNT-based electronics, and accelerate the applications of SWNTs.
Ionic Liquid–Liquid Chromatography: A New General Purpose Separation Methodology Top. Curr. Chem. (IF 5.537) Pub Date : 2017-08-10 Leslie Brown, Martyn J. Earle, Manuela A. Gîlea, Natalia V. Plechkova, Kenneth R. Seddon
Ionic liquids can form biphasic solvent systems with many organic solvents and water, and these solvent systems can be used in liquid–liquid separations and countercurrent chromatography. The wide range of ionic liquids that can by synthesised, with specifically tailored properties, represents a new philosophy for the separation of organic, inorganic and bio-based materials. A customised countercurrent chromatograph has been designed and constructed specifically to allow the more viscous character of ionic liquid-based solvent systems to be used in a wide variety of separations (including transition metal salts, arenes, alkenes, alkanes, bio-oils and sugars).
Para -Quinodimethanes: A Unified Review of the Quinoidal-Versus-Aromatic Competition and its Implications Top. Curr. Chem. (IF 5.537) Pub Date : 2017-07-31 Juan Casado
In this article, some quinoidal p-quinodimethanes compounds that convert partially or completely to diradicals or biradicaloids are analyzed. The aromatic/quinoidal balance is revisited with the objective of providing a common interpretation for most of them. For that purpose, important structural and energetic parameters such as the bond length alternation pattern and the singlet–triplet gaps are analyzed and interpreted in the framework of double spin polarization and π-conjugation. p-Quinodimethanes based in oligothiophenes, polycyclic aromatic hydrocarbons, oligophenylenes, thienothiophenes, charged dications and cyclic conjugated molecules are discussed. There are excellent reviews in the field of singlet diradicals; however, a revision similar to that proposed here can help the reader to have another perspective on these promising new functional materials. The focus has been put on molecules which are well known by the author and another of relevance in the field. In this regard, the article finishes with a discussion of some important applications of these diradicals in organic electronics. New chemical systems based on the p-quinodimethane building blocks are waiting us around the corner, bringing us new and challenging structures and fascinating novel properties, which describe a very rich field of research in chemistry and in physics with an excellent present and a bright future.
Helical Polyacetylenes Induced via Noncovalent Chiral Interactions and Their Applications as Chiral Materials Top. Curr. Chem. (IF 5.537) Pub Date : 2017-07-20 Katsuhiro Maeda, Eiji Yashima
Construction of predominantly one-handed helical polyacetylenes with a desired helix sense utilizing noncovalent chiral interactions with nonracemic chiral guest compounds based on a supramolecular approach is described. As with the conventional dynamic helical polymers possessing optically active pendant groups covalently bonded to the polymer chains, this noncovalent helicity induction system can show significant chiral amplification phenomena, in which the chiral information of the nonracemic guests can transfer with high cooperativity through noncovalent bonding interactions to induce an almost single-handed helical conformation in the polymer backbone. An intriguing “memory effect” of the induced macromolecular helicity is observed for some polyacetylenes, which means that the helical conformations induced in dynamic helical polyacetylene can be transformed into metastable static ones by tuning their helix-inversion barriers. Potential applications of helical polyacetylenes with controlled helix sense constructed by the “noncovalent helicity induction and/or memory effect” as chiral materials are also described.
Potential of Casein as a Carrier for Biologically Active Agents Top. Curr. Chem. (IF 5.537) Pub Date : 2017-07-15 Tomasz Konrad Głąb, Janusz Boratyński
Casein is the collective name for a family of milk proteins. In bovine milk, casein comprises four peptides: αS1, αS2, β, and κ, differing in their amino acid, phosphorus and carbohydrate content but similar in their amphiphilic character. Hydrophilic and hydrophobic regions of casein show block distribution in the protein chain. Casein peptides carry negative charge on their surface as a result of phosphorylation and tend to bind nanoclusters of amorphous calcium phosphate. Due to these properties, in suitable conditions, casein molecules agglomerate into spherical micelles. The high content of casein in milk (2.75 %) has made it one of the most popular proteins. Novel research techniques have improved understanding of its properties, opening up new applications. However, casein is not just a dietary protein. Its properties promise new and unexpected applications in science and the pharmaceutical and functional food industries. One example is an encapsulation of health-related substances in casein matrices. This review discusses gelation, coacervation, self-assembly and reassembly of casein peptides as means of encapsulation. We highlight information on encapsulation of health-related substances such as drugs and dietary supplements inside casein micro- and nanoparticles.
Recent New Methodologies for Acetylenic Polymers with Advanced Functionalities Top. Curr. Chem. (IF 5.537) Pub Date : 2017-06-27 Zijie Qiu, Ting Han, Jacky W. Y. Lam, Ben Zhong Tang
Polymers synthesized from acetylenic monomers often possess electronically unsaturated fused rings and thus show versatile optoelectronic properties and advanced functionalities. To expand the family of acetylenic polymers, development of new catalyst systems and synthetic routes is critically important. We summarize herein recent research progress on development of new methodologies towards functional polymers using alkyne building blocks since 2014. The polymerizations are categorized by the number of monomer components, namely homopolymerizations, two-component polymerizations, and multicomponent polymerizations. The properties and applications of acetylenic polymers, such as aggregation-induced emission, fluorescent photopatterning, light refraction, chemosensing, mechanochromism, chain helicity, etc., are also discussed.
Poly(aryleneethynylene)s: Properties, Applications and Synthesis Through Alkyne Metathesis Top. Curr. Chem. (IF 5.537) Pub Date : 2017-06-26 Michael Ortiz, Chao Yu, Yinghua Jin, Wei Zhang
Functional polymeric materials have seen their way into every facet of materials chemistry and engineering. In this review article, we focus on a promising class of polymers, poly(aryleneethynylene)s, by covering several of the numerous applications found thus far for these materials. Additionally, we survey the current synthetic strategies used to create these polymers, with a focus on the emerging technique of alkyne metathesis. An overview is presented of the most recent catalytic systems that support alkyne metathesis as well as the more useful alkyne metathesis reaction capable of synthesizing poly(aryleneethynylene)s.
Heterocyclic Quinodimethanes Top. Curr. Chem. (IF 5.537) Pub Date : 2017-06-20 Xueliang Shi, Chunyan Chi
This chapter describes a series of heterocyclic quinodimethanes mainly containing O, N, S and Si atoms in their frameworks with either closed- or open-shell electronic structures in the ground state. Their syntheses, structural characterizations and chemical and physical properties are comprehensively reviewed. Some of them are used as materials for dyes/pigments and semiconductors for organic electronics. Some of them show an open-shell singlet diradical character with unusual properties. The purpose of this chapter is to provide fundamental understanding on the structure-property relationships of quinoidal π-conjugated compounds and give some insight into the rational design of such molecules with desirable properties.
Chemical Tongues and Noses Based upon Conjugated Polymers Top. Curr. Chem. (IF 5.537) Pub Date : 2017-06-19 Jan Freudenberg, Felix Hinkel, Daniel Jänsch, Uwe H. F. Bunz
We report the uses of conjugated polymers in multisensory applications and in chemical and optoelectronic tongues. We look at the potential of single polymers to discriminate multiple analytes and into small libraries of conjugated polymers that represent sensors. These small libraries combine several barely selective, promiscuous sensor elements and react with the analytes in a fairly non-selective fashion by change of color, emission wavelength, or emission intensity. In such optoelectronic noses and tongues, response of a single element is not specific or particularly useful at all, but the response pattern after the combination of several sensor elements is often specific for an analyte and allows discrimination and identification without any problem. These types of tongues and noses are well suited for quality control of foodstuff, beverages, and biological species such as proteins or cells. The discriminative process is often not well understood but it is powerful, particularly if the obtained data are analyzed by sophisticated statistical methods, i.e., linear discriminant analysis and/or principal component analysis. This added layer of analysis extracts the hidden information/patterns out of the data and allows visualization of the results.
An Update on Isocyanide-Based Multicomponent Reactions in Polymer Science Top. Curr. Chem. (IF 5.537) Pub Date : 2017-06-12 Audrey Llevot, Andreas C. Boukis, Stefan Oelmann, Katharina Wetzel, Michael A. R. Meier
Developments and progress in polymer science are often inspired by organic chemistry. In recent years, multicomponent reactions—especially the Passerini and Ugi reactions—have become very important tools for macromolecular design, mainly due to their modular character. In this review, the versatility of the Passerini and Ugi reactions in polymer science is highlighted by discussing recent examples of their use for monomer synthesis, as polymerization techniques, and for postpolymerization modification, as well as their suitability for architecture control, sequence control, and sequence definition.
Metal Nanoparticles in Ionic Liquids Top. Curr. Chem. (IF 5.537) Pub Date : 2017-06-06 Susann Wegner, Christoph Janiak
During the last years ionic liquids (ILs) were increasingly used and investigated as reaction media, hydrogen sources, catalysts, templating agents and stabilizers for the synthesis of (monometallic and bimetallic) metal nanoparticles (M-NPs). Especially ILs with 1,3-dialkyl-imidazolium cations featured prominently in the formation and stabilization of M-NPs. This chapter summarizes studies which focused on the interdependencies of the IL with the metal nanoparticle and tried to elucidate, for example, influences of the IL-cation, -anion and alkyl chain length. Qualitatively, the size of M-NPs was found to increase with the size of the IL-anion. The influence of the size of imidazolium-cation is less clear. The M-NP size was both found to increase and to decrease with increasing chain lengths of the 1,3-dialkyl-imidazolium cation. It is evident from such reports on cation and anion effects of ILs that the interaction between an IL and a (growing) metal nanoparticle is far from understood. Factors like IL-viscosity, hydrogen-bonding capability and the relative ratio of polar and non-polar domains of ILs may also influence the stability of nanoparticles in ionic liquids and an improved understanding of the IL-nanoparticle interaction would be needed for a more rational design of nanomaterials in ILs. Furthermore, thiol-, ether-, carboxylic acid-, amino- and hydroxyl-functionalized ILs add to the complexity by acting also as coordinating capping ligands. In addition imidazolium cations are precursors to N-heterocyclic carbenes, NHCs which form from imidazolium-based ionic liquids by in situ deprotonation at the acidic C2-H ring position as intermediate species during the nanoparticle seeding and growth process or as surface coordinating ligand for the stabilization of the metal nanoparticle.
Towards Microcapsules with Improved Barrier Properties Top. Curr. Chem. (IF 5.537) Pub Date : 2017-05-31
Microencapsulation is the generic term for numerous technologies, which are often used when the release rate of an active substance in a medium has to be controlled and/or contact between the active substance and the medium has to be prevented. This is achieved by wrapping the tiny particles or droplets of the active substance (capsule core) with a thin layer, or membrane, of another material (capsule shell). The permeability of the membrane determines whether, how fast and under which conditions the active material will be released and/or the components of the medium will enter the inner part of the capsule. Insofar as application is concerned, premature release of an active substance from microcapsules during storage is a very common problem. Prevention of diffusion of an active component or components of the outer medium through the capsule membrane is a complex challenge, which so far cannot be considered as solved. This review briefly covers the theoretical aspects of release kinetics from microcapsules and discusses how such parameters as capsule average size, capsule shell thickness as well as the chemical composition of active material and medium can influence the release profiles. All theoretical considerations are based on the dissolution-diffusion mechanism classically used for the explanation of diffusion trough flat membranes/films. In the second part of the manuscript it is discussed, which strategies have been used for the improvement of the barrier properties of microcapsules up to date and to which extent those strategies were successful.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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