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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]

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]

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]

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]

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: Starting from the proligands 1-methyl-3-picolylbenzimidazoliumhexaflurophosphate (1) and 1-benzyl-3-picolylbenzimidazoliumhexaflurophosphate (2) Ag(I)–NHC complexes, 1-methyl-3-picolylbenz-imidazolylidenesilver(I)hexaflurophosphate (3) and 1-benzyl-3-picolylbenzimidazolylidenesilver(I)hexaflurophosphate (4) have been synthesized. PO2F2 bridged Ag(I)-bimetallic system (5 and 6) developed from 3 and 4 after treatment of AgPF6 and water. 1-Methyl-3-picolyl-benzimidazolylidene-gold(I)hexaflurophosphate(7) and 1-benzyl-3-picolylbenzimidazolylidenegold(I)hexaflurophosphate (8) have been synthesized by Ag–carbene transmetallation method. Further reaction of AgPF6 with 7 and 8 build up the heterobimetallic Ag(I)–Au(I) systems (9 and 10); significantly, PO2F2 unit holds two heterobimetallic Ag(I)–Au(I) units together. Solid state structures of 3, 5, 8 and 9 have been determined by X-ray diffraction studies. Closed shell d10–d10 interactions are ascertained by the luminescence of bimetallic systems 7–10 upon irradiation of UV light. [Copyright &y& Elsevier]

Abstract: Experimental and theoretical studies of a new class of novel annulated imidazolium scffords 2a, 2b, 2c and their Hg(II)–NHC complexes 3a, 3b and 3c have been synthesized and characterized by different spectroscopic techniques. Molecular structures of 3a and 3b have been determined by single crystal X-ray diffraction studies. Virtual linear geometry [Ccarbene–Hg–Ccarbene 176.56(17)°] around Hg of the complex 3b is observed where as in 3a and 3c its deviate a more. DFT calculations provide geometrical parameters in conformity with the experimental values in case of 3a. The molecules prefer syn configuration over the anti due to lower energy supported by theoretical studies. Attention has given paid for theoretical calculations and comparison of 3a and 3c to observe the steric effect of –CH3 group in the scaffords where as in case of 3b the –CH3 group remain innocent. [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 dinuclear cadmium(II) compounds of the types [Cd(L)(μ-Cl)]2(PF6)2 (1) and [Cd(L)(μ1,5-dca)]2(ClO4)2.0.66MeOH (2) [L=N,N′-(bis(pyridin-2-yl)benzylidene)-1,3-propanediamine; dca=dicyanamide] have been synthesized and characterized on the basis of microanalytical, spectroscopic and other physicochemical results. X-ray structural studies show that in 1 and 2 each hexacoordinated cadmium(II) adopts a distorted octahedral geometry with CdN4Cl2 (1)/CdN6 (2) chromophore ligated through four N atoms of L along with two chlorides in 1 forming a four-membered Cd–(Cl)2–Cd rhombohedral bridging loop and two nitrile N atoms of two μ1,5 dicyanamides in 2 affording a larger 12-membered Cd–(NCNCN)2–Cd ring with boat conformation. In the crystalline state, individual units in 1 are packed through multiple weak CF hydrogen bonds and Cπ and π ⋯π interactions affording a 2D sheet structure. The dinuclear units in 2 are engaged in weak intermolecular CO and CN hydrogen bondings to give a 2D continuum, which is further stabilized by π⋯π interactions through pyridine rings of L. In DMF solutions, 1 and 2 show high-energy intraligand 1(π–π *) fluorescence at room temperature. [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]

Abstract: Three dinuclear compounds [Cd2(bpbd)3](Y)4 (Y= , 1; , 2) and [Cd(bpbd)(Cl)]2(PF6)2 (3) [bpbd=N,N′-(bis(pyridine-2-yl)benzylidene)-1,4-butanediamine] are prepared and characterized. Structures of 1 and 3 are solved by X-ray study that reveals interesting variation in ligational motifs of bpbd from classical tetradentate chelation binding a single metal ion to bis(bidentate) congregation encapsulating two cadmium(II) centers. In the crystalline state, the dinuclear units of 1 pack through cooperative face-to-face π⋯π interactions and C–H⋯O hydrogen bonds whereas those of 3 are engaged in edge-to-face C–H⋯π interactions and C–H⋯F and C–H⋯Cl hydrogen bonds each leading to 2D sheet structure. High-energy intraligand 1(π–π∗) fluorescence at room temperature in DMF solutions and intraligand 3(π–π∗) phosphorescence in glassy solutions (DMF at 77K) are seen in all the complexes. [Copyright &y& Elsevier]

Abstract: Two heptacoordinated one-dimensional coordination polymers of the type [Cd(L)(dca)] n (X) n (1 and 2) [L= N,N′-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine; dca=dicyanamide; X= (1), (2)] have been prepared and characterized on the basis of microanalytical, spectroscopic and other physicochemical properties. Structures of 1 and 2 are solved by single crystal X-ray diffraction measurements. Structural study reveals that in both compounds each cadmium(II) center adopts a distorted pentagonal bipyramidal geometry with a CdN7 chromophore coordinated by five N atoms of the pentadentate Schiff base and two nitrile N atoms of single bridged dca in μ1,5 fashion. The polynuclear units in 1 are engaged in weak N–H…O and C–H…O hydrogen bondings with perchlorate ions embedded among the chains to give a 2D sheet structure. In the long-range form, the 1D polymeric chains of 2 pack through N–H…F and C–H…F hydrogen bonds with hexafluorophosphate placed in between chains resulting a 2D continuum. The complexes display intraligand 1(π–π∗) fluorescence in DMF solutions at room temperature. [Copyright &y& Elsevier]