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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]

Abstract: The reactions of Vaska’s complex [IrCl(CO)(PPh3)2] with 2-(coumaryl-6-azo)imidazole (CZ-H) and its derivatives (CZ-X) have synthesized [Ir(CZ)(CO)(PPh3)2] and [Ir(CZ-X)(CO)(PPh3)2]. All the complexes have been characterized by FT-IR, UV–Vis, 1H NMR and FAB-MS spectroscopy. The structural confirmation has been done in one case, by a single crystal X-ray diffraction study, which shows a distorted square pyramidal geometry around the central Ir atom. The complexes are emissive at room temperature. The cyclic voltammetry of the complexes shows a metal centered irreversible oxidation and ligand centered quasireversible reduction couples. To get an insight into the electronic structure, absorption spectra and electrochemical properties, detailed calculations on all three complexes have been performed at the DFT level. [Copyright &y& Elsevier]

Abstract: 6-Aminocoumarin reacts with pyridine-2-carboxaldehyde and has synthesized N-[(2-pyridyl)methyliden]-6-coumarin (L). The ligand, L, reacts with [Cu(MeCN)4]ClO4/AgNO3 to synthesize Cu(I) and Ag(I) complexes of formulae, [Cu(L)2]ClO4 and [Ag(L)2]NO3, respectively. While similar reaction in the presence of PPh3 has isolated [Cu(L)(PPh3)2]ClO4 and [Ag(L)(PPh3)2]NO3. All these compounds are characterized by FTIR, UV–Vis and 1H NMR spectroscopic data. In case of [Cu(L)(PPh3)2]ClO4 and [Ag(L)(PPh3)2]NO3, the structures have been confirmed by X-ray crystallography. The structure of the complexes are distorted tetrahedral in which L coordinates in a N,N′ bidentate fashion and other two coordination sites are occupied by PPh3. The ligand and the complexes are fluorescent and the fluorescence quantum yields of [Cu(L)(PPh3)2]ClO4 and [Ag(L)(PPh3)2]NO3 are higher than [Cu(L)2]ClO4 and [Ag(L)2]NO3. Cu(I) complexes show Cu(II)/Cu(I) quasireversible redox couple while Ag(I) complexes exhibit deposition of Ag(0) on the electrode surface during cyclic voltammetric experiments. gaussian 03 computations of representative complexes have been used to determine the composition and energy of molecular levels. An attempt has been made to explain solution spectra and redox properties of the complexes. [Copyright &y& Elsevier]

Abstract: [M(SRaaiNR′)Cl3] (M=Rh(III), Ir(III) and SRaaiNR′=1-alkyl-2-{(o-thioalkyl)phenylazo}imidazole) complexes are described in this article. The single crystal X-ray structure of one of the complexes, [Rh(SMeaaiNEt)Cl3] (3b), shows a tridentate chelation of SMeaaiNEt via N(imidazole), N(azo) and S(thioether) donor centres. Spectral characterization has been done by IR, UV–Vis and 1H NMR data. The electronic structure, redox properties and spectra are well supported by DFT and TDDFT computation on the complexes. [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: Five neutral heteronuclear compounds of the type [M(tren)(μ-NCS) z Hg(SCN)4− z ] n [M=Cu/Zn/Cd, z =1, n =1, 1/2/3; M=Ni, z =2, n =2, 4; M=Pb, z =3, n =∞, 5; tren=tris(2-aminoethyl)amine] have been synthesized and characterized. X-ray structural analyses reveal that the tetrahedral [Hg(SCN)4]2− unit forms a single Hg–SCN–M end-to-end bridge with Cu(II), Zn(II) and Cd(II) of the complementary unit [M(tren)(S) z ]2+, affording dinuclear 1–3, respectively, with a trigonal bipyramidal geometry around the heterometal ions. In tetranuclear 4, four single Hg–SCN–Ni bridges bind two different octahedrally coordinated Ni(II) centers forming a cyclic loop. A heteropolynuclear chain with heptacoordinated Pb(II) in 5 results through alternate single and double NCS bridges. Multiple N–H⋯N, N–H⋯S, C–H⋯N, C–H⋯S hydrogen bonds in 1–5 and S⋯S interactions in 1–4 promote increased dimensionalities. EPR and variable-temperature (2–300K) magnetic data of 1 and 4 have been interpreted in terms of their structures. [Copyright &y& Elsevier]

Abstract: The varying coordination modes of the title ligand, L [5-methyl-1-(pyridin-2-yl)-N′-[pyridin-2-ylmethylidene]pyrazole-3-carbohydrazide] towards the different metal centers is reported by preparation and characterization of Cu(II), Zn(II) and Cd(II) complexes, [Cu(L)NO3.H2O](NO3) (1) [Zn(L)2](ClO4)2·2DMF (2) and [Cd(L)(I)2] (3) respectively. In 1, the neutral ligand serves as tetradentate 4N donor where both pyridine and pyrazole nitrogen atoms of pyridyl–pyrazole part are coordinatively active, leaving the carbonyl oxygen of the carbohydrazide part inactive. The same pyridine and pyrazole N atoms remain abstained from the coordination process towards the Zn(II) and Cd(II) metal centers. For 2 and 3 the ligand behaves as a tridentate NNO donor where the two nitrogen atoms come from azomethine, pyridine of pyridine-2-carbaldehyde parts and O from carbonyl oxygen atoms (carbohydrazide part). The complex 1 and 2 are distorted octahedral while complex 3 adopts distorted square pyramidal geometry. All the complexes are X-ray crystallographically characterized. [ABSTRACT FROM AUTHOR]

Abstract: Two neutral nickel(II) coordination polymers [Ni(en)(dca)2] n (1) and [Ni(dmen)(dca)2] n (2) (en=ethylenediamine; dmen=N,N-dimethylethylenediamine; dca=dicyanamide) have been synthesized and X-ray crystallographically characterized. Each nickel(II) center in 1/2 adopts a distorted octahedral coordination environment with a NiN6 chromophore ligated by two amine N atoms of the bidentate amine (en/dmen) and four nitrile N atoms of μ1,5 bridged dca. The metal(II) centers are connected with each other through single μ1,5 M–NCNCN–M bridges, resulting in a 2D layer structure with a (4,4) topology in 1 and a 3D network of topology (6,6) in 2. Multiple lateral N–H···N and C–H···N hydrogen bondings promote dimensionality. The magnetic susceptibility results of 1 and 2 at very low temperature support the zero-field splitting effect of the nickel(II) ions. [Copyright &y& Elsevier]

Abstract: A tetracoordinated [Hg2(L1)(SCN)4] (1) [L1 =N,N′-(bis-(pyridin-2-yl)benzylidene)-1,2-ethanediamine] and two pentacoordinated [Hg2(L2)(X)4] [L2 =N-((1-pyridin-2-yl)formylidene)-N′-[2-(4-{2-[((1-pyridin-2-yl)formylidene) amino]ethyl}piperazin-1-yl)ethyl]amine; X= , (2) and X=NCS−, (3)] dinuclear mercury(II) compounds have been prepared and characterized using microanalytical, spectroscopic, thermal and X-ray crystallographic results. Structural analyses reveal bis(bidentate) congregation behaviour of classical tetradentate L1 and bis(tridentate) character of L2 encapsulating two metal centers. Each mercury(II) center in 1 is in a distorted tetrahedral coordination environment with HgN2S2 chromophore. Hg(1) is attached with two N atoms of L1 and two S atoms of two terminal thiocyanates whereas neighbouring Hg(1) is ligated to the other two N donor set of the same Schiff base completing its bis(bidentate) mode and two S atoms of thiocyanates. In 2 and 3 each mercury(II) center adopts a distorted square pyramidal geometry with MN5 (in 2) and MN3S2 (in 3) chromophores and two metal(II) centers are encapsulated by bis(tridentate) congregation behaviour of L2 through donation of three N donor set to each metal and the fourth and fifth positions are occupied by two N atoms of terminal azides in 2 and two S atoms of terminal thiocyanates in 3. In solid-state, dinuclear units of 1 pack through cooperative C–H⋯N and C–H⋯S hydrogen bonds and C–H⋯π interactions giving rise to a 3D network. Individual dinuclear units of 2 and 3 self-assemble through cooperative C–H⋯N hydrogen bondings and C–H⋯π interactions affording 3D network structure and 2D continuum, respectively. In DMF solutions at room temperature all the complexes display high-energy intraligand 1(π–π∗) fluorescence. [Copyright &y& Elsevier]