Transition metal complexes with thiosemicarbazide-based ligands. Part 63. Syntheses, structures and physicochemical characterization of the first chromium(III) complexes with pyridoxal semi- and thiosemicarbazones
作者:Ljiljana S. Vojinović-Ješić、Ljiljana S. Jovanović、Vukadin M. Leovac、Mirjana M. Radanović、Marko V. Rodić、Berta Barta Holló、Katalin Mészásaros Szécsényi、Sonja A. Ivković
DOI:10.1016/j.poly.2015.09.017
日期:2015.11
With pyridoxal semi-/thiosemicarbazones (PLSC/PLTSC) ligands for the first time chromium complexes were obtained. In the reaction of ethanolic solution of Cr(NO3)(3) and K-3[Cr(NCS)(6)] and the ligands in mole ratio 1:1 or 1:2, the following complexes were formed: [Cr(PLSC)(PLSC-H)](NO3)(2)center dot H2O (1), K[Cr(PLSC-H) (NCS)(3)]center dot EtOH (2), [Cr(PLTSC)(PLTSC-H)](NO3)(2)center dot 2H(2)O (3), [Cr(PLTSC)(2)](NO3)(3) (4) and [Cr(PLTSC)(NCS)(3)]center dot 2H(2)O (5). All the complexes have mer-octahedral structure which in the cases of the complexes 2, 4 and 5 was proved by single-crystal X-ray diffraction analysis. The Schiff bases coordinate in the usual tridentate ONX manner (X = O/S; PLSC/PLTSC). The pyridoxalic fragment is zwitter ion regardless of the form of the coordinated ligands: neutral (keto/thion) and monoanionic (enolic/thiolic). In addition to the above complexes, X-ray crystallography was used to characterize neutral and protonated forms of PLSC, i.e., PLSC center dot 2H(2)O and PLSC center dot HNCS, the latter one being obtained as a by-product of the reaction of formation of the complex 2 using K-3[Cr(NCS)(6)] and PLSC in the mole ratio 1:2. The X-ray analyses of these ligand forms have shown that in the case of PLSC center dot HNCS the ligators O-phenolic, N-azomethine, O-keto due to strong hydrogen O2-H center dot center dot center dot N3 bond are placed in cis-position to each other (pro-binding conformation) which is not the case with PLSC center dot 2H(2)O. The compounds are characterized thoroughly by also IR/UV-Vis spectral analyses, electrochemical and thermal methods. (C) 2015 Elsevier Ltd. All rights reserved.