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Two dinuclear mercury(II) iodide complexes of the types [(L1)Hg( μ-I)HgI] ( 1) and [Hg(L2)(I)] ⋅ HO ( 2) [L1 = tris(2-aminoethyl)amine and L2 = N,N-( bis-(pyridin-2-yl)benzylidene)diethylenetriamine] have been synthesized and characterized using microanalytical, spectroscopic, thermal and other physicochemical results. Structures of both the compounds are solved by X-ray diffraction measurements. Structural analyses show that one mercury (II) centre in 1 adopts a distorted tetrahedral geometry with an HgI chromophore surrounded by four iodides, while the other has a distorted trigonal bipyramidal environment with an HgNI chromophore bound by four N atoms of L1 and one bridging iodide. Pentadentate Schiff base (L2) in 2 shows unusual binucleating bis(bidentate) behaviour to bind two different mercury(II) centres-Hg1 with an HgN I chromophore in a distorted square pyramidal geometry and Hg2 with an HgN I chromophore in a tetrahedral environment. Weak intermolecular N-H ⋅⋅⋅I hydrogen bonds in 1 and cooperative C-H ⋅⋅⋅ π and π⋅⋅⋅ π interactions in 2 promote dimensionalities. The Schiff base complex, 2, shows intraligand ( π- π*) fluorescence in DMF solution at room temperature, whereas compound 1 containing tripodal amine is fluorescent-inactive. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Mixed ligand complexes of Cu(I) and Ag(I) with bis(diphenylphosphino)methane (dppm)/1,2-bis(diphenylphosphino)ethane (dppe) and N-{(2-pyridyl) methyliden}-6-coumarin (L) have been synthesized and characterized by elemental analyses, conductivity, 1H NMR, UV–Vis and fluorescence spectral data. The coordination of dppm to M(I) forms a binuclear metallacycle, [(L)M(μ-dppm)2M(L)](X)2 (X=NO3 or ClO4), and one of the complexes has been characterized by single crystal X-ray structure analysis. The dppe ligand is a bidentate chelator, which is supported by the X-ray structure of [Cu(dppe)(L)]ClO4. In the Ag(I) complex, dppe is serving as a bridging agent to form the binuclear complex [(L)Ag(μ-dppe)Ag(L)](NO3)2, and NO3 − asymmetrically chelates Ag(I), which exhibits solvent polarity dependent coordination. In a coordinating polar solvent, like MeCN, the nitrate group dissociates and shows conductivity, while in nitrobenzene the complex is non-conducting and supports no dissociation. The complexes are more fluorescent than free L. Cyclic voltammetry shows a Cu(II)/Cu(I) quasireversible couple, while the Ag(I) complexes exhibit deposition of Ag(0) on the electrode surface. The coulometric and Cl2 oxidation of the Cu(I) complexes have isolated Cu(II) complexes that are established by spectroscopic and magnetic data. The electronic configuration of the complexes is assessed by DFT computation, and the spectral and redox properties are explained. [Copyright &y& Elsevier]

Two pentacoordinated dinuclear copper(II) compounds of the type [Cu2(bpbd)2(dca)](ClO4/PF6)3 (1/2) [bpbd = N,N′-(bis-(pyridin-2-yl)benzylidene)-1,4-butanediamine; dca = dicyanamide] have been synthesized and characterized on the basis of microanalytical, spectroscopic, thermal and other physicochemical results. Single crystal X-ray diffraction measurements of 1 and 2 have been made to define their coordination spheres as well as intermolecular interactions. Structural analyses reveal that 1 and 2 have two copper(II) centers bound by four N atoms of bpbd and the metal centers are connected by a single μ1,5 dca bridge. Both the copper(II) centers in 1 have distorted trigonal bipyramidal geometry; whereas, in 2 one copper(II) center has a distorted trigonal bipyramidal geometry and the other adopts a distorted square pyramidal environment. In the crystalline state, individual 0D units in 1 and 2 are self-assembled with C—H···π interactions promoting dimensionalities. Both complexes show intraligand 1(π—π*) fluorescence in DMF solutions at room temperature. Variable-temperature (300–2 K) magnetic susceptibility studies reveal that long μ1,5 dca bridges mediate very weak antiferromagnetic interactions. [Copyright &y& Elsevier]

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]

Abstract: A series of pentacoordinated mono-/dinuclear compounds, [Zn(L)(Br)]PF6 (1), [Zn(L)(NCS)]ClO4 (2) and [Zn2(L)2(μ-tp)](ClO4/PF6)2 (3/4) [L=N,N′-(bis(pyridin-2-yl)benzylidene)-1,3-propanediamine, tp=terephthalate dianion], have been synthesized using one-pot reactions of the building components. All the complexes are characterized using microanalytical, spectroscopic and other physicochemical results. Structures of 1–4 are solved by single crystal X-ray diffraction measurements. Structural analyses reveal that each zinc(II) center in 1 and 3 adopts a distorted trigonal bipyramidal geometry with ZnN4Br and ZnN4O chromophores, respectively, whereas zinc(II) centers in 2 and 4 have a distorted square pyramidal geometry with ZnN5 and ZnN4O chromophores, respectively. Intermolecular CBr, CF and CO hydrogen bondings along with Cπ and π⋯π interactions as the case in 1–4 lead to different crystalline aggregates. The compounds show intraligand π–π* fluorescence in solid states and in DMF solutions at room temperature. [Copyright &y& Elsevier]