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Six Ru(II) complexes with formula [Ru(terpy)(L)]X (L = tridentate N,N,S − donor thiosemicarbazone ligands, X = PF 6 − ) have been synthesized and characterized by using standard analytical and spectroscopic techniques. The X-ray crystal structures of the complexes [Ru(terpy)(L 2 )]PF 6 ( 2 ) and [Ru(terpy)(L 3 )]PF 6 ( 3 ) have been determined. It was found that during complexation the hydroxyimino functionality of the parent ligands is converted to imine, which participates in coordination through the N-atom. The complexes are found to undergo two quasi-reversible oxidations on the positive side of the potential window (0 to +0.8 V) and three successive quasi-reversible/irreversible reductions on the negative side of the potential window (0 to −2 V). The fluoride sensing properties of all the complexes have been studied in solution using absorption spectra and 1 H NMR studies, as well as by cyclic voltammetric (CV) measurements. From the absorption titration studies the association constants and detection limit values of fluoride by the complexes have been determined. The association constant values were found to be reasonably high (logK a > 5) for complexes 3 – 6 , and these values are one order of magnitude greater than those observed for the corresponding free thiosemicarbazones. Selective fluoride sensing by these complexes is also signaled by the development of vivid colors, visible with the naked eye. [ABSTRACT FROM AUTHOR]

Four new Ruthenium(II) complexes [Ru(bbp)(pyterpy)](PF 6 ) 2 ( 1 ), [Ru(bbp)(bip)Cl]PF 6 ( 2 ), [Ru(bbp)(biq)Cl]PF 6 ( 3 ) and [Ru(bbp)(phen)Cl]PF 6 ( 4 ) have been synthesized and characterized by spectroscopic techniques (IR, NMR and mass) and single crystal X-ray diffraction study of one of them ( 4 ) (where bbp = 2,6-bis(benzimidazolyl)pyridine, pyterpy = 4(4-pyridyl)terpyridine, phen = 1,10-phenanthroline, bip = 2-(benzimidazolyl)pyridine, biq = 2,2′-biquinoline). The electronic spectra of all the complexes show significant bathochromic shift of their lowest energy Metal to Ligand Charge Transfer band position with respect to [Ru(bpy) 3 ] 2+ . The position of the MLCT band is modulated by the nature of the coligand, the 2,6-bis(benzimidazolyl)pyridine ligand being present in all the complexes. The change in the Ru III/II potential is also explained on the basis of the σ/π donor characteristic of the ligands. [ABSTRACT FROM AUTHOR]

By using η 3 -(SCH 2 CH 2 SCH 2 CH 2 S) (SSS), 2-thiocytosine (HL 1 ) and 5-amino-1,3,4-thiadiazole-2-thiol (HL 2 ) as S-donor ligands two ‘3 + 1’ mixed ligand red oxorhenium(V) complexes of the type [ReO(SSS)(HL 1 )]Cl ( 1 Cl) and [ReO(SSS)(L 2 )] ( 2 ) have been synthesized. Both 1 Cl and 2 have been characterized by C, H and N microanalyses, 1 H NMR, FT-IR, UV–Vis spectra and conductivity measurements. The X-ray crystal structures of both 1 Cl and 2 have been determined. Electrochemical studies of 1 Cl in acetonitrile show four successive one-electron redox couples; while 2 in DMSO displays only two one- electron redox steps. A computational and conceptual Density Functional Theory (DFT) studies have been performed on various (3 + 1) complexes of Re(V). The fully-optimized complexes, 1 Cl and 2, adopt geometries that satisfactorily corroborate the X-ray structures. Subsequently these optimized structures were employed to investigate systematically the relative stabilities of various Re(V) complexes with varying ligands having N, O and S donor atoms. The electronic properties of 1 Cl and 2 were delved into employing the hybrid STMP TD-DFT method and the results were found to be in good harmony with the experimental observations. [ABSTRACT FROM AUTHOR]

The in situ reaction of salicyloylhydrazide and its corresponding hydrazone with [MoO 2 (acac) 2 ] afforded two novel and unusual dimeric [(Mo VI O 2 ) 2 L] ( 1 ) and tetrameric [{(C 2 H 5 OH)LO 3 Mo 2 VI } 2 (μ-O) 2 ]·C 2 H 5 OH ( 2 ) oxidomolybdenum(VI) complexes with N , N '-disalicyloylhydrazine (H 2 L). The binucleating ligand was formed by the self-combination of the acid hydrazide or corresponding hydrazone. The complexes were characterized by various spectroscopic techniques (IR, UV and NMR) and also by electrochemical study. The molecular structures of both complexes have been confirmed by X-ray crystallography. The above studies indicate that the N , N '-disalicyloylhydrazine (H 2 L) has the normal tendency to form both dimeric and tetrameric complexes coordinated through the dianionic tridentate manner. The in vitro antiproliferative activity of complexes 1 and 2 was assayed against HeLa cell line. [ABSTRACT FROM AUTHOR]