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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: 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]