Search

Abstract: The [Zn(SRaaiNR′)(H2O)X2] (SRaaiNR′=1-alkyl-2-{(o-thioalkyl)phenylazo}imidazole; X=Cl, Br, I) complexes have been characterized by spectroscopic studies. The X-ray structure of [Zn(SEtaaiNEt)(H2O)Cl2] (where SEtaaiNEt=1-ethyl-2-{(o-thioalkyl)phenylazo}imidazole) shows bidentate imidazolyl-N, azo-N chelation of SEtaaiNEt and the other donors are H2O and 2Cl−. UV light irradiation to a MeCN solution of the complexes shows E-to-Z (E and Z refer to trans and cis-configurations about –N N–, respectively) isomerisation of the coordinated azoimidazole. The rate of isomerisation follows the sequence: [Zn(SRaaiNR′)(H2O)Cl2]<[Zn(SRaaiNR′)(H2O)Br2]<[Zn(SRaaiNR′)(H2O)I2]. The quantum yields (ϕ E→Z) and the activation energies (E a) of the isomerisation of the complexes are lower than those of the free ligands. The observation has been explained considering the molecular association that increases the mass and rotor volume of the complexes. [Copyright &y& Elsevier]

One-pot synthesis using a 2:2:1:2 molar ratio of Pb(OAc)·3HO, L, piperidinum terephthalate (ptp) and NaClO/NHPF at room temperature affords two dinuclear compounds of the type [Pb(L) $_{2}(\upmu $-tp)](ClO/PF) ( 1/2) [L=N,N-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine and tp = terephthalate dianion]. The compounds are characterized by microanalytical, spectroscopic, thermal and other physicochemical results. X-ray structural analyses of 1 and 2 reveal that each heptacoordinated lead(II) centre with a PbNO chromophore are bound by five N atoms of L and connected through O atoms of a bis(bidentate) tp bridge. The arrangements of L and tp suggest a gap around the metal centre due to occupation of a stereo-active lone pair of electrons reflecting a hemidirected coordination around the metal centre. The complexes exhibit reasonable thermal stabilities with the tolerate temperatures ca. 255°C for 1 and 263°C for 2. The complexes display intraligand ( π- π*) fluorescence in the solid state and in DMF solutions at room temperature. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

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]

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]

Abstract: Reaction of equimolar proportion of trans-ReOCl3(PPh3)2 with HL, a 1:1 Schiff-base condensate of salicylaldehyde and allylamine, in chloroform gives rise to ReO(L)(PPh3)Cl2 1a in optimal yield. 1a has been characterized by C, H and N microanalyses, ESI-MS, FT-IR, UV–Vis spectra, molar conductivity measurements. The X-ray crystal structure of 1a reveals that it is an octahedral cis-Cl,Cl oxorhenium(V) complex. The rhenium center is in ‘NO2Cl2P’ coordination sphere. 1a crystallizes in the orthorhombic space group Pna21 with a =17.3541(11), b =10.2737(6), c =15.2113(10)Å, V =2712.0(3)Å3 and Z =4. The photophysical and electrochemical aspects of 1a have been studied. Electrochemical studies in dichloromethane show Re(V) to Re(VI) oxidation at 1.437V along with a reduction of Re(V) to Re(IV) at −0.705V versus Ag/AgCl. Excitation of 1a in chloroform at 460nm leads to a fluorescent emission at 525nm with a quantum yield (Ф) of 0.17. Geometry optimization of the cis-Cl,Cl complex 1a vis-à-vis its trans analogue, trans-Cl,Cl complex 1b, have been performed at the level of the density functional theory (DFT). It is revealed that 1b is more stable than 1a by 4kcal per mole of energy in gas phase. [Copyright &y& Elsevier]