Synthesis, spectroscopy and cyclic voltammetry of cobalt(III) complexes with 5-methyl-3-formylpyrazole N(4)-cyclohexylthiosemicarbazone (HMPz4Cy): X-ray crystal structure of [Co(MPz4Cy)2]Cl.2.75H2O
TL;DR: In this article, the coordination behavior of the free ligand, HMPz4Cy, and its diamagnetic cobalt(III) complexes was reported, together with solid state isolation of their diamagnetic co-occurrence.
Abstract: The coordination behaviour of the novel ligand, HMPz4Cy, is reported, together with solid state isolation of its diamagnetic cobalt(III) complexes, [Co(MPz4Cy)2]X · nH2O (X = Cl, Br, NO3, ClO4 and BF4). I.r. and 1H-n.m.r. data for the free ligand and its CoIII complexes confirm that the ligand, HMPz4Cy, acts as a uninegative anion with NNS tridentate function via the pyrazolyl nitrogen (tertiary), azomethine nitrogen and thiol sulphur. Electronic spectra (both solid and solution) are commensurate with a distorted octahedral environment for the reported CoIII species. Cyclic voltammograms of CoIII complexes indicate a quasireversible Co+3/Co+2 couple. X-ray crystallography of a representative species, [Co(MPz4Cy)2]Cl · 2.75H2O (C2, monoclinic), has shown unambiguously that the two ligands are orthogonally coordinated to the central CoIII ion with both the thiolato sulphurs and both pyrazolyl nitrogen atoms in cis positions.
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TL;DR: In this article, the coordination chemistry of thiosemicarbazones and all the metals for which complexes are reported are discussed with respect to their bonding and structures, variable bonding properties, metallation, metal-metal interactions, role of solvents/other factors in stabilization of sulfur-bridging in coinage metals, and the nature of substituents at azomethine carbon.
526 citations
TL;DR: X-ray crystallography of a representative species, [Cu(HMPz4BM)(NO3)2] (C2/c, monoclinic ), has unambiguously documented the conjectural findings from i.r.r parameters (RT and LNT) of the reported copper(II) complexes are indicative of a dxx2–y2 ground state for the reported species.
Abstract: The coordination behaviour of the title ligand, 5-methyl-3-formylpyrazole N(4)-benzyl-N(4)-methylthiosemicarbazone(HMPz4BM), is reported with solid state isolation of copper(II) complexes, [Cu(HMPz4BM)X2] (X = Cl, Br, NO3, ClO4 and BF4) which have been spectroscopically and structurally characterised Ir data for the free ligand and its Cu(II) complexes indicate that HMPz4BM exhibits a neutral NNS tridentate function via the pyrazolyl nitrogen(tertiary), azomethine nitrogen and thione sulphur Electronic spectral data are suggestive of a square pyramidal environment for the seemingly pentacoordinated Cu(II) species Esr parameters (RT and LNT) of the reported copper(II) complexes are indicative of a dxx2–y2 ground state for the reported species Cyclic voltammograms of Cu(II) complexes show a quasireversible CuII/CuIII couple and also an irreversible CuII/CuI couple X-ray crystallography of a representative species, [Cu(HMPz4BM)(NO3)2] (C2/c, monoclinic ), has unambiguously documented the conjectural findings from ir data that coordinating sites of the title ligand are pyrazolyl (tertiary)nitrogen, azomethine nitrogen and the thione sulphur (NNS); and the oxygen of one of the nitrate ions has occupied the basal plane; the fifth coordination position has been occupied by the oxygen of another nitrate ion in a square pyramidal geometry The antibacterial properties of the ligand and its copper(II) complexes studied on microorganism, Staphylococcus aureus have pointed out that most of the complexes have higher activities than that of the free ligand
77 citations
TL;DR: In this paper, the coordinating properties of the title ligand, 5-methyl-3-formyl pyrazole 3-hexamethyleneiminyl thiosemicarbazone (HMPz3Hex), synthesized and characterized (elemental analysis, MS, IR, 1H and 13C NMR and X-ray crystallography) for the first time, are reported by solid-state isolation of cobalt(III) complexes.
37 citations
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TL;DR: This chapter serves to cover the extensive literature on pyrazoles during the 10 year period, 1996–2006, with a focus on the medicinal chemistry applications of pyrazole and fused ring systems.
Abstract: Five-membered ring systems containing two nitrogen atoms adjacent to each other are called pyrazoles. This chapter serves to cover the extensive literature on pyrazoles during the 10 year period, 1996–2006. The previous two chapters of this series, on pyrazoles, dealt more with the theoretical, experimental structural, and thermodynamic methods and less with the reactivity, synthesis, and applications of pyrazoles. During the last 10 years, more literature has appeared on the synthesis and reactivity of pyrazole-fused ring systems. Furthermore, the medicinal chemistry applications of pyrazoles and fused ring systems have found numerous applications in drug discovery. Also, pyrazoles have been utilized as reagents in synthesis. This chapter focuses on these current developments.
27 citations
TL;DR: In this article, six new mononuclear complexes of transition metal ions (1-6) with (E)-2-(1-methyl-2-yl)ethylidene)hydrazinyl)-1H-benzoimidazole L were synthesized and characterized by spectroscopic methods as well as X-ray diffraction analysis.
Abstract: Six new mononuclear complexes of transition metal ions (1–6) with (E)-2-(1-methyl-2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)-1H-benzoimidazole L were synthesized and characterized by spectroscopic methods as well as X-ray diffraction analysis. Structures of these complexes can be divided into three groups depending on the coordination number and environment of the metallic center: the first one of general formula [ML2]X2, the second one - [MLX3] and the third one - [MLX2], where X is anion or solvent molecule. Electrochemical and electrochromic properties of complexes were investigated. Complexes Fe(II) 1, Cu(II) 2–4 and Co(II) 5 were found to be electroactive and their colors depend on the oxidation state of metal center and ligand molecule. Fe(II) complex 1 exhibits purple color in the neutral state and its color changes to yellow after Fe(II) → Fe(III) oxidation, followed by pale-yellow after further oxidation of ligand molecule and to green when the metal center is reduced to Fe(I). The original color can be restored after electrochemical oxidation Fe(I) to Fe(II). It was found that this complex exhibits high color stability in solution during multiple oxidation/reduction cycles. This complex can be therefore regarded as very interesting material for the construction of multielectrochromic devices.
27 citations
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1,249 citations
TL;DR: In this paper, the unifying concept that allows one to extract geometric and electronic structural information from ligand field spectral features is ligand fields theory, which can also be used to obtain ground state spin Hamiltonian parameters, providing further insight into the covalency of the active site.
Abstract: Publisher Summary This chapter focuses on spectroscopy in bioinorganic chemistry, including analytical and kinetic applications. The chapter provides molecular level insight into reaction mechanisms. The unifying concept that allows one to extract geometric and electronic structural information from ligand field spectral features is ligand field theory. These transitions can be interpreted in terms of crystal field theory and ligand field theory to obtain geometric and electronic structure information and can additionally be used to obtain ground state spin Hamiltonian parameters, providing further insight into the covalency of the active site.
181 citations
134 citations
TL;DR: In this paper, the coordination mode of the title ligand, HMPzSB (synthesized for the first time and characterised by elemental analysis, mass, IR and PMR spectral parameters), is reported by solid state isolation and physicochemical identification of cobalt(III) complexes.
36 citations