Search

A new osmium(II) carbonyl complex, [Os(H)(CO)(PPh3)2(L)] (1) with thioether containg NNS donor ligand (where L = 2-(ethylthio)-N-((pyridine-2-yl)methylene))benzenamine) is synthesized and characterized by various spectroscopic techniques. The distorted octahedral environment around osmium in the complex is confirmed by single crystal X-ray structure. Cyclic voltammogram in acetonitrile exhibits Os(II)/Os(III) oxidation and ligand based reduction. The complex effectively catalyzed the transfer hydrogenation reaction of ketones in high yields in i-PrOH. The electronic structure and redox properties are interpreted by DFT studies.

Reaction of ligand, L-Ch2Ph with Na2PdCl4 in acetonitrile yielded palladium(II) complex, [Pd(L)Cl] via C S bond cleavage. It is characterized by several spectroscopic techniques and the structure is confirmed by single crystal X-ray study. The complex exhibits quasi-reversible oxidation couple at 0.86 V corresponds to ligand based thiophenolato to thiyl radical oxidation. Electronic structure, solution spectrum and redox properties are interpreted by DFT and TDDFT calculations.

The synthesis and characterization of a mixed ligand Ru(II) complex, [Ru(dppp)(L)Cl] (1) (where, dppp = bis(diphenylphosphino) propane) is reported. The distorted octahedral geometry of the complex is confirmed by X-ray diffraction method. Cyclic voltammogram in CH3CN exhibits Ru(II)/Ru(III) quasireversible oxidation couple along with reversible azo-bond reductions peaks with reference to Ag/AgCl electrode. The efficiency of the complex towards the transfer hydrogenation of ketones in i-PrOH is examined and an excellent catalytic conversion (90–98%) is observed. The electronic structure and redox properties are well corroborated with the DFT calculations.

A highly sensitive and selective pyridyl based colorimetric chemosensor (H2L) for the efficient detection of Ni(2+) has been reported. The synthesized chemosensor H2L is highly efficient in detecting Ni(2+) even in the presence of other metal ions that commonly co-exist with Ni(2+). H2L also shows distinct color change from green to deep red visible under naked eye due to specific binding with Ni(2+). This color change is due to formation of a new band at 510 nm upon gradual addition of Ni(2+). The association constant has been found to be 1.27×10(5) M(-1) with limit of detection (LOD) of 8.3×10(-7) M. Electronic structure of the H2L-Ni(2+) complex and sensing mechanism have been interpreted theoretically by DFT and TDDFT calculations.

A new rhodium(III)-triphenylphosphine mixed ligand complex, [Rh(PPh3)(L)Cl2] (1) is synthesized by benzylic C S bond cleavage of L-CH2Ph ligand (where, L-CH2Ph = 2-(benzylthio)-N-(pyridin-2-ylmethylene)aniline). The complex is thoroughly characterized by several spectroscopic techniques. Geometry of the complex is confirmed by single crystal X-ray crystallography. Electronic structure, redox properties, absorption and emission properties of the complex were studied. DFT and TDDFT calculations were carried out to interpret the electronic structure and absorption properties of the complex respectively. The synthesized Rh(III) complex was tested as catalyst towards transfer hydrogenation reaction of ketones in iPrOH and an excellent catalytic conversion was observed under mild conditions.

Two novel complexes [Mn 2 (phmp) 2 ](ClO 4 ) 2 ( 1 ) and [Ni 2 (phmp)(μ-H 2 O)(H 2 O) 4 ](NO 3 ) 3 ( 2 ) were synthesized using an “end-off” compartmental ligand [H-phmp = 4-Methyl-2,6-bis-(pyridin-2-yl-hydrazonomethyl)-phenol] with Mn(II)-perchlorate and Ni(II)-nitrate salts as metal precursors. Both these complexes were characterized by spectroscopic (IR, UV–Vis) and X-ray crystal structure analysis. The ligand, H-phmp acts as a pentadentate NNONN donor for both the metal complexes and the geometry of the complexes 1 and 2 is distorted octahedral. The DFT optimized bond distances and angles are well correlate to the X-ray structure bond parameters. For complex 1 the transitions at 435 nm and 428 nm have mixed MLCT ( dπ (Mn) → π * (L)) and ILCT ( π (L) → π * (L)) character whereas other transitions correspond to intra-ligand charge transfer transitions (ILCT). For complex 2 , weak transitions at 464 and 405 nm correspond to ligand to metal charge transfer transitions (LMCT) ( π (L) → dπ (Ni)) and most of the other transitions have ILCT character. As anticipated, various weak forces, i.e. anion–π/π–anion/anion–π/π–NH interactions as well as C–H/π interaction, play a key role in stabilizing the self-assembly process observed for both compounds.

The square planar nickel(II) complexes have been synthesized by the reaction of nickel(II) chloride hexahydrate and the in situ condensed thiophene appended Schiff base ligands of thiophene-2-ethylamine with 3,5-dimethyl-2-hydroxybenzaldehyde or 3,5-dichloro-2-hydroxybenzaldehyde for [Ni(L1)2] (1) and [Ni(L2)2] (2) respectively. The complexes have been characterized by several spectroscopic techniques, viz. FT-IR, 1H NMR, absorption and emission spectroscopy. The complexes crystallize in monoclinic crystal system with C2/c space group for 1 and triclinic crystal system with P−1 space group for 2. In complex 1 the nickel sits on an inversion centre with symmetry –x, 2–y, –z. Cyclic voltammgrams of the complexes show quasi-reversible NiII/NiIII oxidation couple along with irreversible NiII/NiI reduction. Electronic structure and spectral properties are well interpreted by DFT and TDDFT calculations.

New rhodium(III)-triphenylphosphine complex, [Rh(PPh3)(L)Cl2](PF6) (1) with thioether containing NNS donor ligand (L) (L = 2-(methylthio)-N-((pyridine-2-yl)methylene)benzenamine) has been synthesized and characterized. The pseudo octahedral geometry of the complex has been confirmed by single crystal X-ray analysis. The electronic structure, redox properties, absorption and emission properties of the complexes have been interpreted by DFT and TDDFT calculations. The complex effectively catalyzed the transfer hydrogenation reaction of ketones in 2-propanol and oxidation of alcohols in presence of NMO.

New palladium(II) complex with 2-(2-thiazolyl)-4-methylphenol (TAC) having general formula [Pd(TAC)Cl) (1) has been synthesized and characterized. The complex has been characterized by various spectroscopic techniques. Single crystal X-ray structure shows distorted square planar geometry around palladium(II). Cyclic voltammetric studies shows ligand based irreversible oxidation and reduction peaks. The electronic structure, redox properties and electronic excitations in the complex are interpreted by DFT and TDDFT calculations.

Two pyridoxal containing Schiff bases obtained by condensation of pyridoxal hydrochloride with N,N-dimethylethylenediamine (HL1) and N,N-diethylethylenediamine (HL2) are used for the syntheses of three new copper (II) complexes [Cu(HL1)(H2O)Cl]Cl (1), [Cu(L1)Cl] (2) and [Cu(L2)Cl] (3). The single crystal X-ray structures of all the three copper(II) complexes are determined. Redox potentials for the mononuclear complexes are measured by cyclic voltammetry experiments. The DFT and TDDFT results have been used to interpret the experimental properties. � 2015 Elsevier B.V. All rights reserved.

Octahedral Mn(II) complex with NNO donor Schiff base ligand (HL) containing 8-aminoquinoline moiety with general formula, [Mn(L)2] (1) has been synthesized and characterized. The structural, electronic and photoluminescent properties have been studied. The X-ray structure of complex (1) shows distorted octahedral geometry around manganese(II). Cyclic voltammetry study of the complex shows quasi-reversible Mn(II)/Mn(III) oxidation and ligand reduction. The π(L) → π∗(L) (ILCT) based emission properties of the ligand HL and Mn(II) complex, 1 have been studied. The electronic structure and spectral properties are interpreted by DFT and TDDFT computations.

The ruthenium carbonyl complexes 1 and 2 with redox noninnocent NNS donor ligand, 1-methyl-2-{(o-thiomethyl)phenylazo}imidazole (L) have been synthesized and characterized by various analytical and spectroscopic (IR, UV–Vis and 1H NMR) techniques. The complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 1.11 V for 1 and 0.76 V for 2 along with two successive one electron ligand reductions. Catalytic activity of the compounds has been investigated to the oxidation of PhCH2OH to PhCHO, 2-butanol (C4H9OH) to 2-butanone, 1-phenylethanol (PhC2H4OH) to acetophenone, cyclopentanol (C5H9OH) to cyclopentanone, cyclohexanol to cyclohexanone, cycloheptanol to cycloheptanone and cycloctanol to cycloctanone using N-methylmorpholine-N-oxide (NMO) as oxidant. The catalytic efficiency of 2 is greater than complex 1 and well correlate with the metal oxidation potential. DFT, NBO and TDDFT calculations in DFT/B3LYP/6-31G(d)/lanL2TZ(f) method are employed to interpret the structural and electronic features of the complexes.

New rhenium(I) dicarbonyl complexes containing cis-{Re(CO)2}+ fragment with redox non-innocent NNS donor ligands L1/L2 (L1, 1-methyl-2-{(o-thiomethyl)phenylazo}imidazole and L2, 1-ethyl-2-{(o-thioethyl)phenylazo}imidazole) having general formula cis-[ReX(CO)3(L1/L2)] (1/2) (X = Cl (1) and Br (2)) have been synthesized and characterized by both experimental and theoretical studies. The structural confirmation has been carried out for 1b. The complexes show quasireversible ReI/ReII oxidation and ligand based reduction in the cyclic voltammetric studies. The electronic structure and the nature of Re CO bonding has been explained by means of DFT and NBO calculations. The spin allowed singlet–singlet electronic transitions of 1b and 2b have been calculated with TDDFT method, and the experimental spectra of the complexes have been discussed on this basis.