Synthesis, characterization and DFT studies of complexes bearing [Re(CO)3]+ core and reactivity towards cyanide ion

https://doi.org/10.1016/j.jorganchem.2019.121098Get rights and content

Highlights

  • Reaction of Re(CO)5Cl with two Schiff base ligands provides two rhenium(I) complexes.

  • Crystal structures of two complexes are determined.

  • Red shift in UV-Vis spectra and emission intensity hike is observed in complex 2.

  • An addition reaction occurring in imine bond is responsible for spectral change.

Abstract

Mononuclear rhenium(I) complexes having fac-[Re(CO)3]+ core of general formula fac-[Re(CO)3(L)Cl] have been synthesized in excellent yield by reacting [Re(CO)5Cl] with L1 and L2in a ratio of 1:1 in toluene under inert atmosphere. Here L1 and L2 are N-((quinolin-2-yl)methylene)-9H-fluoren-2-amine and N-((anthracen-10-yl)methylene)quinolin-8-amine respectively. Spectroscopic measurements such as NMR, ESI-MS and IR spectroscopy were used to ensure the formations of desired complexes. Molecular structures of fac-[Re(CO)3(L1)Cl] and fac-[Re(CO)3(L2)Cl] were confirmed by single-crystal X-ray diffraction. The ligands are emissive whereas the metal complexes are weak emitter. A remarkable change in absorption as well as emission behavior was observed in complex 2 upon addition of cyanide ion. Interruption in intraligand charge transfer in complex 2 is the probable reason for the obvious change in spectral response of the same. 1H NMR titration was performed as the evidence of the previously stated fact. The ground and excited-state geometries, absorption properties of rhenium(I) complexes were examined by DFT and TDDFT methods. The natural transition orbital (NTO) and analysis reveal the nature of excitations.

Introduction

Rhenium tricarbonylchloro complexes with N∧N coordinating Schiff base ligands having d6 electronic configuration is one of the widely studied area in coordination chemistry due to its interesting photophysical properties [[1], [1](a), [1](b), [1](c), [2], [2](a), [2](b)] such as room-temperature luminescence from low-lying tunable metal to ligand charge transfer (MLCT) excited states [[3], [4], [5], [6], [6](a), [6](b), [7], [8], [9]], solar-energy conversion [[10], [10](a), [10](b), [11], [12]], OLED and sensor development [[13], [14], [15], [16], [17], [18], [44], [45], [46], [47], [48], [49], [50], [51]], and biological labeling [19,20]. These imine-based rhenium complexes having [Re(CO)3]+ core show interesting optical behavior in presence of toxic anions. It is possible to create a highly potential receptor molecule by varying ligand architecture with the photoactive rhenium(I) metal center. A few groups of researchers have shown the sensing properties of rhenium(I) complex by hydrogen bonding (NH···X) followed by deprotonation [[21], [22], [23], [24], [25]]. Anion sensing mechanism by deprotonation of O–H bond has also been reported [26]. But, anion recognition through the addition of an anion into the imine bond is rare. Cyanide ion is a very toxic anion which comes into environment through its use in pharmaceutical industries, insecticides, fertilizers, plastic manufacturing processes, extraction of metals, electroplating industries etc [[27], [28], [29], [30]]. It is necessary to replace the conventional methods of testing for cyanide such as titration, distillation, chromatography or potentiometry as they are expensive, laborious and time consuming. Therefore, there is still a need to develop more robust and less laborious testing methodologies for cyanide. In this context, the complexes of rhenium(I) are suitable. It has proven that [Re(CO)3]+ core potentially influence the imine based complex to detect cyanide ion selectively among other anions [31]. So, the main focus of this paper is the successful synthesis of two rhenium complexes with N∧N coordinating two different Schiff base ligands. We have also described the details of synthetic procedures of these mononuclear complexes and the characterization is done by various spectroscopic techniques and single crystal X-Ray diffraction study. The reactivity of these complexes towards various anions has also been studied. To describe the ground and excited state behavior of the Re(I)-diimine complexes, the contribution of the fundamental computational chemistry such as DFT/TDDFT [32] and NTO analysis is indispensable to get better insight into the geometry, electronic structure and optical properties, TDDFT calculations of several excited states have been performed.

Section snippets

Materials

Re(CO)5Cl, 2-Aminofluorene, 9-Anthraldehyde, 8-Aminoquinoline, Quinoline-2-carboxaldehyde were purchased from Sigma Aldrich. All solvents and chemicals are analytically pure. All the reactions with Re(CO)5Cl were carried out under argon atmosphere.

Physical measurements

Electrospray ionization mass spectrometry (ESI-MS) spectra were recorded on a Micromass QTOF YA 263 mass spectrometer. IR spectra were observed and obtained with a Perkin–Elmer L-0100 spectrophotometer with KBr disk. 1H NMR spectra were measured on

Synthesis

The Schiff base ligands L1 and L2 are synthesized according to the conventional method by the condensation reaction of an aldehyde and amine (Scheme 1) and are used as neutral bidentate N, N donor ligands towards Re(I) metal center. These complexes consist of two different fluorophore segments i.e. 2-Aminofluorene and 9-Anthraldehyde, which are able to show interesting photophysical properties. It is to be noted that the choice of such ligands helps us to achieve our goal in the context of

Conclusion

In summary, we have synthesized two Schiff base based ligands (L1 and L2) and two monomeric rhenium(I) complexes of these two ligands. The aim of the present work is to explore their optical properties and reactivity with various anions. The complexes are characterized by different spectroscopic techniques and X-ray crystal structure determination. This work includes investigation of the ground and excited-state geometries of both the ligands and complexes as well as the study of absorption and

Declaration of competing interest

There is no declaration of interest.

Acknowledgements

Financial assistance received from Department of Science and Technology, Govt. of West Bengal, Kolkata, India. We are also thankful to the Department of Science and Technology, New Delhi, India, for data collection on the NMR facility setup (Jadavpur University) under DST-FIST program. We also acknowledge the UGC CAS II program, Department of Chemistry, Jadavpur University, the DST-PURSE program and JU RUSA 2.0 for other facilities.

References (51)

  • N. Akabar et al.

    Photophysical and biological investigation of phenol substituted rhenium tetrazolato complexes

    Dalton Trans.

    (2019)
    D. Sinha et al.

    Synthesis and characterization of acrylate cyanide bridged dimeric fac-rhenium(I) complex: photophysical, selective CO2 adsorption and theoretical studies

    J. Organomet. Chem.

    (2019)
    L.D. Ramos et al.

    Contrasting photophysical properties of rhenium(I) tricarbonyl complexes having carbazole groups attached to the polypyridine ligand

    Dalton Trans.

    (2016)
  • C.-O. Ng et al.

    Luminescent rhenium(I) pyridyldiaminocarbene complexes: photophysics, anion-binding, and CO2-capturing properties

    Inorg. Chem.

    (2016)
  • M.M. Lee et al.

    Synthesis, electrochemical and photophysical properties of 2, 4, 6-Tripyridyl-1, 3, 5-Triazine - bridged trinucleardiimine rhenium(I) tricarbonyl complexes

    Eur. J. Inorg. Chem.

    (2017)
  • P.A. Scattergood et al.

    An unexpected journey from highly tunable phosphorescence to novel photochemistry of 1,2,3-triazole-based complexes

    Dalton Trans.

    (2017)
  • P.V. Simpson et al.

    Properties and prospects for rhenium(i) tricarbonyl N-heterocyclic carbene complexes

    Chem. Commun.

    (2018)
    Y. Kim et al.

    Synthesis and photophysical properties of luminescent rhenium(I) and manganese(I) polypyridine complexes containing pendant 1,3,4-oxadiazole/triarylamine assemblies

    Inorg. Chim. Acta

    (2001)
  • A. Wilting et al.

    Dinuclear rhenium complex with a proton responsive ligand as a redox catalyst for the electrochemical CO2 reduction

    Inorg. Chem.

    (2017)
  • A. Świtlicka et al.

    Experimental and theoretical insights into spectroscopy and electrochemistry of Re(I) carbonyl with oxazoline-based ligand

    Polyhedron

    (2019)
    T.B.J. Hall et al.

    Dramatic alteration of 3ILCT lifetimes using ancillary ligands in [Re(L)(CO)3(phen-TPA)]n+ complexes: an integrated spectroscopic and theoretical Study

    J. Am. Chem. Soc.

    (2018)
  • L.A. Faustino et al.

    Photochemistry of fac-[Re(CO)3(dcbH2)(trans-stpy)]+: new insights on the isomerization mechanism of coordinated stilbene-like ligands

    Inorg. Chem.

    (2018)
  • S. Sato et al.

    Photochemical ligand substitution reactions of fac-[Re(bpy)(CO)3Cl] and derivatives

    Inorg. Chem.

    (2007)
  • N.J. Lundin et al.

    A synthetic, structural, spectroscopic and DFT study of Re(I), Cu(I), Ru(II) and Ir(III) complexes containing functionalized dipyrido[3,2-a:2′,3′-c]phenazine (dppz)

    Chem. Eur J.

    (2008)
  • S.T. Lam et al.

    Synthesis and characterization of luminescent rhenium(I) tricarbonyldiimine complexes with a triaryl boron moiety and the study of their fluoride ion-bbinding properties

    Inorg. Chem.

    (2009)
  • X. Li et al.

    Synthesis and characterization of novel rhenium (I) complexes with large Stokes shift for applications in organic electroluminescence device

    J. Photochem. Photobiol., A

    (2012)
  • W.K. Chu et al.

    A simple design for strongly emissive sky-blue phosphorescent neutral rhenium complexes: synthesis, photophysics, and electroluminescent devices

    Chem. Mater.

    (2014)
  • G.W. Zhao et al.

    High efficient OLEDs based on novel Re(I) complexes with phenanthroimidazole derivatives

    Opt. Mater.

    (2015)
  • X. Li et al.

    Very high-efficiency organic light-emitting diodes based on cyclometallated rhenium (I) complex

    Appl. Phys. Lett.

    (2008)
  • Cited by (6)

    View full text