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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: 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]

Reaction of 2-(2-pyridinyl)-benzthiazole (Pbt), KSCN, and copper(II)perchlorate hexahydrate in 1 : 2 : 1 molar proportion in dimethyl sulfoxide gives monomeric [Cu(Pbt)(SCN)2DMSO] (1a). In another run, identical proportions of the same reactants in methanol generates a symmetric thiocyanate bridged dimeric copper(II) compound, [Cu2(Pbt)2(SCN)2] (2a), in 72% yield. Both1aand2ahave been characterized by C, H, and N microanalyses, copper estimation, FTIR, UV–vis spectra, and room temperature magnetic susceptibility measurements. The X-ray crystal structures of1aand2ahave been determined. Electrochemical studies of1aand2ashow Cu(II) to Cu(III) oxidation in solution. The thermal behaviors of1aand2ahave been studied. Bond valence sum method of analysis was performed to assign the oxidation state for each copper center in1aand2a. Geometry optimization of1a,2a,and their linkage isomers has also been performed at the level of the density functional theory to show that1aand2aare the most stable congeners. These results corroborate our experimental findings. [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: One monomeric neutral Cu(II) complex [(pmtpm)CuCl2] (1) is reported by Lindoy and Livingstone . Two new complexes namely, μ-Cl bridged binuclear Cu(II) complex [{(pmtpm)Cu(Cl)}2 μ-Cl](ClO4) (2) and a bis μ-Cl bridged binuclear Cu(II) complex [{(pmtpm)Cu}2(μ-Cl)2](ClO4)2 (3) derived from a tridentate Schiff base ligand, 2-pyridyl-N-(2′-methylthiophenyl)methyleneimine (pmtpm) were synthesized and characterized by various spectroscopic methods and by X-ray crystallography. (N2S)CuCl2 chromophore(s) of distorted square pyramidal coordination geometries around Cu(II) ion(s) have been observed for all the complexes 1–3. The equatorial sites of the square plane comprise two N and a thioether S donor atoms of the pmtpm ligand as well as one Cl− ion (terminal in 1 and 2, and bridging in 3) while the remaining axial site is occupied by a terminal Cl− ion (for 1) or a bridging Cl− ion (for 2 and 3). The equatorial Cu–Cl distances are much shorter [1: 2.2511(4)Å, 2: 2.2307(12)Å, 3: 2.2513(12)Å] than the axial Cu–Cl distances [1: 2.4394(4)Å, 2: 2.5597(9)Å, 3: 2.7037(12)Å]. The correlation of an axial Cu–Cl bond elongation with a lower g|| value in the solid state EPR spectrum and a blue shifted ligand field transition in the solid and solution phase absorption spectrum has been observed. [Copyright &y& Elsevier]

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]

Abstract: Three new Ag(I) complexes, 1, 2, and 3 of two azine ligands diacetyl dihydrazone (L1) and benzil dihydrazone (L2) have been synthesized and characterized by single crystal X-ray diffraction studies (for 2 and 3), X-ray powder diffraction studies(1 and 2), elemental analyses, IR and UV–VIS spectroscopy and TGA analysis. They represent one-dimensional polymeric assemblies and discrete dinuclear Ag(I) complex depending on functionality of the ligands and the counter anions. Tetrahedral as well as square pyramidal coordination motifs of the silver (I) ions have been observed in the supramolecular designing of such hybrid organic–inorganic materials. [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]

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]

N 1 -substituted 3,5-dimethylpyrazole (dmpz) namely, methyl-3,5-dimethyl pyrazole-1-dithioate (L 1 ) and benzyl-3,5-dimethyl-pyrazole-1-dithioate (L 2 ) were reacted with zinc(II), copper(II) and cadmium(II) chloride to study their coordination behavior. Ligands L 1 and L 2 produced isostructural complexes with composition [Cu I (L 1 ) 2 ][Cu I Cl 2 ] ( 1 ) and [Cu I (L 2 ) 2 ][Cu I Cl 2 ] ( 2 ), respectively when reacted with CuCl 2 ·2H 2 O. Copper (I) (d 10 system) analogues, 1 and 2 , exhibit prominent catechol oxidase activity in which a nice correlation-the easily oxidizable copper(I) center favoring the oxidation of 3,5-DTBC (3,5-ditertiary butyl catechol) is observed. Most importantly, these two compounds represent the class of copper(I) compounds that are rarely employed for the study of catecholase activity. The kinetics study exhibits a deuterium kinetic isotope effect in the catalytic oxidation of 3,5-DTBC by O 2 as evidenced by about 1.9 times rate retardation in the deuterated solvent, suggesting the hydrogen atom transfer in the rate-determining step from the substrate hydroxy group to the metal-bound superoxo species. With other d 10 cations, zinc(II) and cadmium(II) the ligand L 1 and/or L 2 undergoes dissociation into parent pyrazole unit i.e., 3,5-dimethylpyrazole (dmpz) during formation of a monomeric tetrahedral Zn(dmpz) 2 Cl 2 ( 3 ) complex and a helical 1-D polymeric chain, [Cd(dmpz) 2 Cl 2 ] n ( 4 ). The possible role of intramolecular hydrogen-bonding induced helicity has been explored in 4 . [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]

Highlights: [•] Bis-carbene. [•] Dimercury-NHC. [•] Helical complex. [•] Ligand exchange. [ABSTRACT FROM AUTHOR]

Abstract: Three dinuclear compounds of the types [Cu2(L)2(μ-tp)](ClO4/PF6)2 (1/2) and [Mn2(L)2(μ-tp)](ClO4)2 H2O (3) [L= N,N′-(bis-(pyridin-2-yl)benzylidene)-1,3-propanediamine and tp=terephthalate dianion] have been synthesized and characterized. Structures of 1–3 are solved using single crystal X-ray diffraction measurements. The structural analyses show bis(monodentate) in 1/2 and bis(bidentate) in 3 of terephthalate bridging motifs resulting dicationic dinuclear unit [M2(L)2(μ-tp)]2+ [M=Cu (1/2) and Mn (3)]. Each metal center adopts distorted trigonal bipyramidal geometry in 1/2 and a distorted octahedral geometry in 3 with MN4O and MN4O2 chromophores, respectively. Chelation by the tetradentate Schiff base along with bis(monodentate) and bis(bidentate) bridging of terephthalate complete pentacoordination around each copper(II) center in 1/2 and hexacoordination around each manganese(II) center in 3, respectively. Variable-temperature magnetic susceptibility measurements of 1–3 in the 2–300K temperature range reveal weak antiferromagnetic interaction presumably due to long bridging arm. [Copyright &y& Elsevier]

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: 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: One pentacoordinated mononuclear complex [Zn(L)(NCS)]PF6 (1), one hexacoordinated 2D coordination polymer {[Cd2(L)(NCS)4]·0.24(CH3OH)} n (2) and one pentacoordinated 1D polymeric chain [Hg2(L)(SCN)4] n (3) [L=N,N′-(bis(pyridine-2-yl)benzylidene)-1,4-butanediamine] have been synthesized and X-ray crystallographically characterized. Structural analyses revealed interesting variations in the coordination behaviour of the Schiff base (L) from tetradentate chelation to binucleating bis(bidentate) congregation on going from 1 to 2/3. The pseudohalide exhibits terminal N-coordination in 1, both μ1,3 and μ1,1 bridges in 2 and terminal S-coordination along with μ1,1 linkages in 3. In 1/3, each pentacoordinated zinc(II)/mercury(II) centre adopts a distorted trigonal bipyramidal/square pyramidal geometry with a ZnN5/HgN2S3 chromophore, whereas both Cd1 and Cd2 centres in 2 adopt a distorted octahedral geometry with CdN3S3 and CdN6 chromophores, respectively. Weak intermolecular S···S and S···π interactions with multiple C–H···N hydrogen bonds promote the dimensionalities in 1–3. The complexes display intraligand 1(π–π∗) fluorescence in the solid state and in DMF solutions at room temperature. [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: 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]