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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]

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]

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]

The reaction of 1?:?4.4?M proportion ofcis-[ReO2I(PPh3)2] and 4-aminopyridine (ampy) in acetone–water givestrans-[ReO2(ampy)4]I·2H2O (1a) in 85% yield.1ahas been characterized by C, H, and N microanalyses, FT-IR, UV–vis,1H NMR spectroscopy, and molar conductivity. The X-ray crystal structure of1areveals an octahedraltransdioxorhenium(V) complex with a “N4O2” coordination for rhenium.1ahas an orthorhombic space groupC2221witha?=?17.576(4),b?=?19.370(4),c?=?15.730(4) Å,V?=?5355(2) Å3, andZ?=?8. Geometry optimization of thetrans-O,Ocomplex,1aand itscis-O,Oanalog,1bperformed at the level of density functional theory reveal that1ais more stable than1bby 25?kcal M–1in the gas phase. The electronic spectrum of1awas also analyzed at the level of time-dependent density functional theory. Excitation of1ain methanol at 450?nm leads to a fluorescent emission at 505?nm with a quantum yield (?) of 0.04. Electrochemical studies of1ain acetonitrile show a quasi-reversible Re(V) to Re(VI) oxidation at 0.618?VversusAg/AgCl. This redox potential matches with the calculated redox potential of 0.621?VversusAg/AgCl. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two dinuclear cadmium(II) dicarboxylate compounds with polyamine/Schiff base are isolated and characterized. [•] X-ray structures show interesting variations in coordination numbers, geometries and superstructures. [•] Thermogravimetric analyses reveal their thermal stability and decomposition pattern. [•] Fluorescence studies in DMF solution illustrate ligand based π–π* emission. [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]

Abstract: A 1D coordination polymer [Hg2(L)Br4] n (1) and one dinuclear compound [Hg2(L)I4] (2) [L=N,N′-(bis(pyridin-2-yl)benzylidene)ethane-1,2-diamine] are isolated using a 2:1M ratio of HgBr2/HgI2 and Schiff base (L) in methanol–acetonitrile solution mixture and X-ray crystallographically characterized. Structural analyses show that in 1 1D chain is formed through binucleating bis(bidentate) bridging behavior of L and asymmetric Hg-(μ-Br)2-Hg bridges in an alternate fashion; one terminal bromide unit completes the distorted square pyramidal geometry around each mercury(II). In 2, two mercury(II) centers are connected by bis(bidentate) bridging behavior of L and two iodides bound to each metal(II) center remain as terminal resulting in a discrete dinuclear entity with distorted tetrahedral geometry. Weak intermolecular Hg⋯I and I⋯I interactions in 2 promote dimensionality. In DMF solutions, 1 and 2 display intraligand 1(π–π∗) fluorescence. [Copyright &y& Elsevier]

Mononuclear [Hg(L1)Br] ( 1) and 1D polymer [Hg(L2)Br] ( 2) [L1 = ( N, N-diethyl, N′-(pyridin-2-yl)formylidene)ethane-1,2-diamine and L2 = ( N, N-diethyl, N′-(pyridin-2-yl)benzylidene)ethane-1,2-diamine] have been synthesized using appropriate molar ratios of HgBr and L1/L2 in methanol-acetonitrile solution mixtures at room temperature. Crystal structures were investigated with the help of single crystal X-ray diffraction data. In 1, the mercury(II) center adopts a distorted square pyramidal geometry bound by three N atoms of L1 and two terminal bromides. Compound 2 forms a 1D chain through Hg-Br-Hg bridges in an infinite fashion connecting two crystallographically independent mercury(II) centers; Hg1 is in a distorted square pyramidal environment coordinated by three N atoms of L2 and two bridging bromides, whereas Hg2 adopts a tetrahedral geometry bound by two terminal and two bridging bromides. 1 and 2 display intraligand (π−π*) fluorescence in DMF solutions at room temperature. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Coordination compounds of the types [Hg(atta)][HgCl4] (1), [Cd5(apda)2Cl10] n (2), [Cd3(apda)2(N3)4] n (ClO4)2 n (3) and [Cd2(bpda)(NCS)4] n (4) [atta=4-(2-aminoethyl)-triethylenetetramine; apda= N-(2-aminoethyl)piperazine-1,4-diethylamine; bpda= N,N′-bis(2-aminoethyl)piperazine-1,4-diethylamine] are isolated using tetraethylenepentamine (tepa; for 1–3)/pentaethylenehexamine (peha; for 4) in presence of cadmium(II)/mercury(II) halides/pseudohalides. Structural studies reveal that polyamines tepa and peha undergo interesting in situ rearrangement to afford atta/apda and bpda ligands, respectively. Asymmetric unit in 1 comprises of discrete [Hg(atta)]2+ cation and [HgCl4]2− anion. Compound 2 consists of neutral pentanuclear core [Cd5Cl10] formed by three different types of chloride bridges propagating through binucleating bitridentate character of apda to afford a 1D ladder structure. 2D coordination polymer 3 with (4162)(4262) topology is formed through double μ1,1- and single μ1,3-azide bridges and binucleating behavior of apda. Alternating double μ1,3-thiocyanate and binucleating bis(tridentate) bridges in 4 result in a 1D zig-zag chain. Different kinds of non-covalent interactions promote dimensionalities in 1–4. Thermal behaviors of 1–4 are examined. [Copyright &y& Elsevier]

Abstract: Two pentacoordinated dinuclear compounds of the type [M2(dca)(L)2](ClO4)3·H2O [M=Cu (1), Cd (2); L=N,N′-bis(3-aminopropyl)-1,2-ethanediamine; dca=dicyanamide] 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 pentacoordinated metal(II) center adopts a distorted square pyramidal geometry with an MN5 chromophore coordinated by four N atoms of the polyamine (L) in the basal plane and nitrile N atom of single μ1,5 bridged dca in the apical position. The dinuclear units in 1 and 2 are engaged in weak intermolecular O–H⋯O, N–H⋯O, N–H⋯N and C–H⋯O hydrogen bondings resulting in 3D network structures in which the crystalline water molecules and counter ions are embedded. Variable-temperature magnetic susceptibility measurement of 1 indicates weak antiferromagnetic interactions among the metal centers. [Copyright &y& Elsevier]

Abstract: Two hexacoordinated dinuclear compounds [Mn(L1)(dca)]2(ClO4/PF6)2·CH3OH (1/2) and two heptacoordinated coordination polymers [Mn(L2)(dca)] n (ClO4/PF6) n (3/4) [L1= N,N′-(bis-(pyridin-2-yl)benzylidene)-1,3-propanediamine; L2= N,N′-(bis-(pyridin-2-yl)benzylidene)diethylenetriamine; dca=dicyanamide] are synthesized and characterized. Structures of 1–3 have been solved by X-ray diffraction measurements. Each manganese(II) center in 1/2 is located in a distorted octahedral environment with an MnN6 chromophore coordinated by the four N atoms of L1 and two nitrile N atoms of bibridged μ1,5 dca. Interestingly, the coordination polymer 3 forms a 1D chain through single Mn–(NCNCN)–Mn units in which each manganese(II) center adopts a pentagonal bipyramidal geometry with an MnN7 chromophore occupied with five N atoms of L2 and two nitrile N atoms of monobridged μ1,5 dca. Magnetic susceptibility measurements of 1–3 in the 2–300K temperature range reveal weak antiferromagnetic interactions. [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]