个人简介

B.Sc., 1975, University of Madras; M.Sc., 1977, Madurai University; Ph.D., 1982, I. I. Sc. Bangalore

研究领域

Crystal Engineering and Inorganic Materials

Crystal Engineering & Inorganic Materials (A) Crystal Engineering: Current research activities in our group includes rational design of metal coordination polymers with multi-dimensional network structures using a number of linear and angular spacer ligands. In this exploratory research we systematically study the properties of supramolecular building blocks such as shape, size and directionality of the functional groups to understand how these parameters control and influence the crystal packing and hence the supramolecular structures. Photoreactive coordination polymers, and porous materials for gas storage properties are our being investigated. Some of the recent results are presented below. Solid State Reactivity and [2+2] Cycloaddition Reactions: We are now investigating photochemical [2+2] cycloaddition reactions in organic salts, co-crystals, metal complexes, coordination polymers (SPs) and metal-organic frameworks (MOFs). We have shown that it is possible to design photoreactive CPs and MOFs and conduct single-crystal-to-single-crystal (SCSC) reactions with ease than ever before. We have used this photodimerization reaction as a tool to follow the structural transformations and post-synthetically modify the pillar ligands in MOFs. Usually MOFs are made in a single-step by self-assembly method. There are different approaches available to make them in steps, i.e., non-self-assembly methods. In our laboratory, we employ a combination of desolvation and [2+2] cycloaddition reaction to convert 1D CPs to 2D CPs and then to 3D CPs (MOFs) in a step-by-step manner. This gives full synthetic control on the nature of MOFs obtained. Figures: Structural transformation from a 2D CP to a 3D CP by [2+2] cycloaddition reaction (above). The modification of pillar ligand in a MOF by SCSC Photochemical Structural Transformations (below). You can be recycled Mr. C-C BOND!: Although the solid state [2+2] cycloaddition reactions gained popularity in CPs and MOFs, the reverse reaction of cleaving the cyclobutane rings to olefins has not been explored at all. This property can be effectively used for some potential applications such as applications in photonic devices, sensor techniques, lithographic patterning, imaging techniques, data processing and data storage. Of late we found the potassium trans-4,4'-stilbenedicarboxylate shows reversibility during the UV light driven [2+2] cycloaddition reaction and the thermal cleavage of resultant cyclobutane ring. Surprisingly the single crystals were retained during these the reversible reactions. More interestingly these compounds show different emissive properties during this reversible structural transformation. This transformation is accompanied by the loss of luminescence as shown below. This is in collaboration with Prof Masaki Kawano, POSTECH, Korea. Figures: Reversible formation and cleavage of cyclobutane ring in cycles (left) and the changes in the photoluminescence properties (right). MOF-COF Hybrid Structures:The photochemical [2+2] cycloaddition reaction has been employed to carry out the polymerization of the conjugated diene ligand, bpeb. Several 3D structures incorporating organic polymer comprising cyclobutane rings and coordination polymers have been obtained in SCSC manner. Monocrystalline metal complexes of organic polymer ligands are hitherto unknown. In one case the organic polymer can be depolymerized by the cleavage of cyclobutane rings in an SCSC manner. This is a collaborative efforts with Prof. Shim Sung Lee, Gyeongsang National University, Jinju, Korea. Figures: Formation of organic ligand by [2+2] cycloaddition reactions inside CPs and MOFs forming coordination polymer-organic polymer hybrid structures. Photoactuating Materials:A visually impressive dynamic behavior of single crystals of three Zn(II) complexes which are self-propelled under UV light has been investigated with our collaboration with Prof. Pance Naumov, New York University, Abu Dhabi. This photosalient effect is a consequence of accumulation and sudden release of a strain created by crystal expansion following the formation of 1D coordination polymers by [2+2] cycloaddition reaction. Understanding of this effect, which is mechanistically analogous to the bursting of popcorn in a hot pan, could aid to harness light energy and convert it into kinetic energy in the new light-driven mechanical actuators. Here our aim is to design a reversible photosalient materials that can be reused. Figures: A schematic diagram showing the popping effect of UV light on the single crystals (left) and different types of mechanical behavior of these crystals (right) (B) Nanoscale Materials: The study of nanometer size compounds is an exciting area of research which offers opportunities for innovation and creativity. Nanoscale materials exhibit quantum behavior due to their size and are promising materials for new technologies. Our research focuses on the synthesis of nanoscale metal chalcogenide materials and the characterization of their properties. The chemical, physical, electronic, optical, magnetic and catalytic properties of nanocrystals depend on the size and shape of the nanomaterials. However synthesis of stable monodispersed nanocrystals is a real challenge in nanoscience. Currently we are also interested in developing solar cells. Single Molecular Precursor Chemistry: We have been interested in developing the chemistry of transition and main group metal compounds with chalcogen containing ligands, RC{O}E-, RE-, R2NCS2 = (where E = S, Se and Te), dithioacetylacetonato and related ligands. We have shown that many of these compounds can be used as precursors to metal chalcogenides (as amorphous or crystalline powders, films and nanoparticles). Currently we are interested in the Group 6, 11, 12, 13, 14, transition and lanthanide metals. We have also developed single precursor routes to synthesize highly monodispersed nanoparticles of ME (M = Zn, Cd, Hg & Pb), M2E (M = Cu & Ag), M2E3 (M = As, Sb & Bi), AME2 (A = Cu, Ag; M = Ga & In), where E = S, Se & Te, etc. (a) (b) Figures: (a) The formation of different size and shapes of Ag2Se nanocrystals from the precursor [(Ph3P)3Ag2(SeC{O}Ph)2]. (b) The toluene-soluble AgInS2 obtained from [(Ph3P)2AgIn(SeC{O}Ph)4] exhibits NLO properties. Battery Materials: A wide range of materials have been considered as energy storage materials; of these Li ion battery is a promising one and of late this is one of the hottest areas of research due to recent oil crisis. We entered this field by accident when reported single-molecular precursor route to LiMO2 battery materials. The compounds [Li(H2O)M(N2H3CO2)3].H2O (M = Ni, Co) on pyrolysis yield LiNiO2 and LiCoO2 at 700oC in oxygen atmosphere and at T > 700oC in air. Currently we are collaborating with Physics and Chemical Engineering colleagues in developing LiFePO4 battery materials. We synthesized LiFePO4 nanoplates with uniform coating of 5 nm thick amorphous carbon layer by solvothermal method. The thickness along b-axis is found to be 30-40 nm, and such morphology favors a shorter diffusion length for Li+ ions, while exterior conductive carbon decoration provides connectivity for facile electron diffusion, resulting in high rate performances close to theoretical value, shown below. We also filed a US Patent on this material. Figures: (Left) Galvanostatic charge - discharge cycle curves for LiFePO4C and (right) Capacity vs. Cycle number plots of LiFePO4/C nanoplates at various current rates 0.1 to 30 C

近期论文

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“One pot synthesis and third-order nonlinear optical properties of AgInS2 nanocrystals”, L. Tian, H. I. Elim, W. Ji and J. J. Vittal, Chem. Commun. (2006) xxx-xxx. “One Dimensional Coordination Polymers: Cu(II) and Zn(II) Complexes of N-(2-pyridylmethyl)-glycine and N-(2-pyridylmethyl)-L-alanine”, X. Wang, R.D. Ranford and J.J. Vittal, J. Mol. Struct. “Syntheses, Structures and Properties of Copper(II) Complexes Containing N-(2-Hydroxybenzyl)-Amino Amide Ligands”, X. Wang , J. Ding and J. J. Vittal, Inorg. Chim. Acta (accepted). An invited paper for the special issue dedicated to Prof. Mike Mingos) “A Rational Approach to Cross-linking of Coordination Polymers by Photochemical [2+2] Cycloaddition Reaction,” N. Mangayarkarasi and J.J. Vittal, Macromolecular Rapid Communications, 27 (2006) 1091-1099 “Synthesis, Structures and Catecholase Activity of New Series of Dicopper(II) Complexes of reduced Schiff Base Ligands”, B. Sreenivasulu, F. Zhao, S. Gao, J. J.Vittal, Eur. J. Inorg. Chem., (2006) 2656-2670. “Anisotropic Movements of Coordination Polymers upon Desolvation: Solid-state Transformation of Linear 1D Coordination Polymer to Ladder-like Structure”, N. Mangayarkarasi and J.J. Vittal, Angew. Chem. Int. Ed., 45 (2006) 4337-4341. “Asymmetric Synthesis of a P-chiral heteroditopic P�P=S ligand via chiral metal template promoted cycloaddition between 3,4-dimethyl-1-phenylphosphole and its sulfonated alalog”, S.A. Pullarkat, K.-W. Tan, M. Ma, G.-K. Tan, L.L. Koh, J.J. Vittal and P.-H. Leung, J. Organomet. Chem., 693 (2006) 3083-3088. “One Pot Synthesis of New Phase AgInSe2 Nanorods”, M. T. Ng, C. B. Boothroyd and J. J. Vittal, J. Am. Chem. Soc., 128 (2006) 1178-1179. “Inorganic complexes retain diethylether well above its boiling point through OH2���OEt2 hydrogen bonding”, L. Tian and J. J. Vittal, Crystal Growth & Design, 6(4) (2006) 822-824. “A simple way to prepare PbS nanocrystals with morphology tuning at room temperature”, Z. Zhang, S.H. Lee, J.J. Vittal and W.S. Chin, J. Phys. Chem., 110(13) (2006) 6649-6654. “Synthesis, structure and magnetic properties of [Li(H2O)M(N2H3CO2)3]�0.5H2O (M = Co,Ni) as single precursors to LiMO2 battery materials”, S.L.Tey, M.V. Reddy, G.V. Subba Rao, B.V.R. Chowdari, J. Yi, J. Ding and J. J. Vittal, Chem. Mater., 18 (2006) 1587-1594. “La2S3 Thin Films from Metal Organic Chemical Vapor Deposition of Single-source Precursor”, L. Tian, T. Ouyang, K.P. Loh and J.J. Vittal, J. Mater. Chem., 16 (2005) 272-277. (hot paper) “Stereochemical Investigations of a Novel Class of Chiral Phosphapalladacycle Complexes Derived from 1-[(2,5-Dimethyl)phenyl]ethyldiphenylphosphine”, J.K.-P. Ng, Y. Li, G.-K. Tan, L.-L. Koh, J.J. Vittal, P.-H. Leung, Inorg. Chem., 44 (2005) 9874-9886. “Crystal structures and characterizations of (Nitrato-O) (Nitrato-O,O�)(h6-Hexamethylbenzene) Ruthenium(II) and Di(Trifluoroacetato-O)(H2O-O)(h6-Hexamethylbenzene) Ruthenium(II)”, X. L. Lu, W. K. Leong, L. Y. Goh, T. S. A. Hor and J. J. Vittal, Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-metal Chemistry, 35 (2005) 743-746. “Copper(II) Complexes of Schiff Base and Reduced Schiff Base Ligands: Influence of Weakly Coordinating Sulfonate Groups on the Structure and Oxidation of 3,5-DTBC”, B. Sreenivasulu, M. Vetrichelvan, F. Zhao, S. Gao, J. J. Vittal, Eur. J. Inorg. Chem., (2005) 4635-4645. “Organooxotin Cages, {[(n-BuSn)3(�3-O)(OC6H4-4-X)3]2[HPO3]4}, X = H, Cl, Br, and I, in Double O-Capped Structures: Halogen-Bonding-Mediated Supramolecular Formation”, V. Chandrasekhar, V. Baskar, K. Gopal, and J.J. Vittal, Organometallics 24 (21) (2005) 4926-4932. “Square planar versus tetrahedral NiS4 cores in the coordination spheres of (HMB)Ru(II) and Cp*Ru(III) and a related CuS4 complex. Synthetic, single-crystal X=ray diffraction, and magnetic studies {HMB =h6-C6Me6 and Cp* =h5-C5Me5}”, R.Y.C. Shin, M.E. Teo, G.K. Tan, L.L. Koh, J.J. Vittal and L.Y. Goh, Organometallics, 24 (17) (2005) 4265-4273. “Shape and size control of Ag2Se nanocrystals from single precursor [(Ph3P)3Ag2(SeC{O}Ph)2],”, M.T. Ng, C. Boothroyd and J.J. Vittal, Chem. Commun., (2005) 3820-3822 “Synthesis and crystal structure of 5-(4'-carboxyphenyl)-10,15,20-tri(4'-t-butylphenyl)porphinato zinc(II) complex”, P. Bhyrappa, C. Arunkumar, J.J. Vittal, Journal of Chemical Sciences (Bangalore, India), 117(2) (2005) 139-143. “Topochemical photodimerization in the molecular ladder metal coordination polymer [{(CF3CO2)(�-O2CCH3)Zn}2(�-bpe)2]n (where bpe = 4,4’-bipyridylethelene) via single-crystal to single-crystal transformation”, N.L. Toh, M. Nagarathinam and J.J. Vittal, Angew. Chem. Int. Ed. Engl., 44 (2005) 2237-2241