Syntheses, Structures, Magnetic Properties and Antibacterial Activities of Two Copper(II) Azido Complexes with Varied Nuclearities Containing Symmetrical 1,3-Diammine as Chelator

Two copper(II) azido complexes of the types mononuclear [Cu(TMEDA)2(N3)2] (1) and dinuclear [Cu(TMEDA)(μ1,1-N3)(N3)]2 (2) [TMEDA = trimethylenediamine; N3 – = azide ion] have been synthesized and characterized. X-ray structural analysis revealed that each copper(II) center in complex 1 adopts a distorted octahedron geometry with a CuN6 chromophore ligated through four N atoms of two different symmetrical TMEDA ligands as bidentate chelator and two N atoms of two terminal azides. In complex 2, each copper(II) center adopts a distorted square pyramidal geometry with a CuN5 chromophore ligated through two N atoms of TMEDA as bidentate chelator and two N atoms of two different azides as μ1,1-N3 bridging mode and one N atom of terminal azide ion. The two copper centers are connected through double μ1,1-N3 bridges affording a dinuclear structure with Cu···Cu separation 3.327(2) Å. In crystalline state, mononuclear units in complex 1 are associated through intermolecular N-H···N and C-H···N hydrogen bonds to form a 2D sheet structure viewed along crystallographic b-axis, whereas dinuclear entities in complex 2 are propagated through intermolecular N-H···N and C-H···N hydrogen bonds to form a 3D network structure viewed along crystallographic a-axis. The Variable-temperature magnetic susceptibility measurement evidenced a dominant antiferromagnetic interaction between the metal centers through μ1,1-azide bridges in complex 2 with J = − 0.40 cm-1. The antibacterial activities of the complexes have also been studied.

Synthesis, molecular structure and BSA-binding properties of a new binuclear Cd(II) complex based on 2-(1H-tetrazol-1-methyl)-1H-imidazole-4,5-dicarboxylic acid

A new binuclear Cd(II) complex, [Cd2(H2tmidc)4(H2O)2]·6H2O (1) based on 2-(1H-tetrazol-1-methyl)-1H-imidazole-4,5-dicarboxylic acid (H3tmidc) has been synthesized and structurally characterized. The single-crystal X-ray diffraction analysis has revealed that there are two crystallographically distinct H2tmidc– anions in complex 1, one of which is coordinated to Cd(II) ion in a terminal fashion, while the other acts as a bis-connector linking two Cd(II) cations to form the dinuclear structure. The dimeric units are stabilized by intra-molecular O–H···O hydrogen bonds and π-π stacking interactions and are further connected into a three-dimensional supramolecular architecture through inter-molecular hydrogen bonds and π-π stacking interactions. The interactions of complex 1 with bovine serum albumin (BSA) were analyzed by fluorescence measurements under physiological conditions. The results have indicated that the fluorescence intensity of BSA was decreased considerably upon the addition of complex 1 through a static quenching mechanism. The synchronous fluorescence spectrum suggested that the interaction of complex 1 with BSA affects the conformations of tryptophan and tyrosine residues and thereby has an influence on the conformation of BSA.

Dinuclear Complexes of Flexidentate Pyridine-Substituted Formazanate Ligands

In this work we show the utility of flexidentate pyridyl‐substituted formazanate ligands in assembling dinuclear coordinationcomplexes with iridium(III) and/or platinum(II) building blocks. The versatile binding modes of these ligands allow the preparation of several different dinuclear structures, highlighting the potential of these formazanates to serve as redoxactive supporting ligands for multimetallic complexes. The dinuclear complexes are typically prepared in a stepwise strategy, adding one metal unit at a time, with the coordination mode of the formazanate with the first metal dictating the binding mode in the final dinuclear structure. Eight of the new complexes, including both mononuclear precursors and dinuclear products, are structurally characterized by single‐crystal X‐ray diffraction, which along with NMR spectroscopy unambiguously establish ligand binding modes and symmetries of the compounds. All complexes are characterized by UVVis absorption spectroscopy and cyclic voltammetry. The frontier orbitals are localized on the formazanate ligand, and a characteristic, intense formazanate‐centered π→π* absorption band is observed in the absorption spectrum. Structureproperty relationships are established, relating the ligand binding mode to the redox properties and spectroscopic features. .<br>

Dinuclear Complexes of Flexidentate Pyridine-Substituted Formazanate Ligands

In this work we show the utility of flexidentate pyridyl‐substituted formazanate ligands in assembling dinuclear coordinationcomplexes with iridium(III) and/or platinum(II) building blocks. The versatile binding modes of these ligands allow the preparation of several different dinuclear structures, highlighting the potential of these formazanates to serve as redoxactive supporting ligands for multimetallic complexes. The dinuclear complexes are typically prepared in a stepwise strategy, adding one metal unit at a time, with the coordination mode of the formazanate with the first metal dictating the binding mode in the final dinuclear structure. Eight of the new complexes, including both mononuclear precursors and dinuclear products, are structurally characterized by single‐crystal X‐ray diffraction, which along with NMR spectroscopy unambiguously establish ligand binding modes and symmetries of the compounds. All complexes are characterized by UVVis absorption spectroscopy and cyclic voltammetry. The frontier orbitals are localized on the formazanate ligand, and a characteristic, intense formazanate‐centered π→π* absorption band is observed in the absorption spectrum. Structureproperty relationships are established, relating the ligand binding mode to the redox properties and spectroscopic features. .<br>

Ru(ii) water oxidation catalysts with 2,3-bis(2-pyridyl)pyrazine and tris(pyrazolyl)methane ligands: assembly of photo-active and catalytically active subunits in a dinuclear structure

A combined DFT and experimental study indicates that one water molecule is allowed to enter the first coordination sphere of a one-site catalyst, thus activating water oxidation.

A new binuclear NiII complex with tetrafluorophthalate and 2,2′-bipyridine ligands: synthesis, crystal structure and magnetic properties

A new NiII compound, [Ni2(tfpa)2(bipy)2(H2O)4] (1) with tetrafluorophthalate (tfpa2−) and 2,2′-bipyridine (abbreviated as bipy) ligands, has been synthesized and structurally characterized. The single-crystal X-ray diffraction analysis reveals that the tfpa2− anions act as bis-monodentate linkers connecting NiII centers to form the dinuclear structure of 1. The dimeric units are stabilized by intramolecular π–π stacking and are further connected into a layer through O–HLO hydrogen bonding. Variable-temperature magnetic susceptibility data in the 10–200 K temperature range indicate weak ferromagnetic coupling between the two NiII ions.

A Comparative Study of Molybdenum Carbonyl and Oxomolybdenum Derivatives Bearing 1,2,3-Triazole or 1,2,4-Triazoles in Catalytic Olefin Epoxidation

The molybdenum(0)-carbonyl-triazole complexes [Mo(CO)3(L)3] [L = 1,2,3-triazole (1,2,3-trz) or 1,2,4-triazole (1,2,4-trz)] have been prepared and examined as precursors to molybdenum(VI) oxide catalysts for the epoxidation of cis-cyclooctene. Reaction of the carbonyl complexes with the oxidant tert-butyl hydroperoxide (TBHP) (either separately or in situ) gives oxomolybdenum(VI) hybrid materials that are proposed to possess one-dimensional polymeric structures in which adjacent oxo-bridged dioxomolybdenum(VI) moieties are further linked by bidentate bridging triazole (trz) ligands. A pronounced ligand influence on catalytic performance was found and the best result (quantitative epoxide yield within 1 h at 70 °C) was obtained with the 1,2,3-triazole oxomolybdenum(VI) hybrid. Both molybdenum oxide-triazole compounds displayed superior catalytic performance in comparison with the known hybrid materials [MoO3(trz)0.5], which have different structures based on organic-inorganic perovskite-like layers. With aqueous H2O2 as the oxidant instead of TBHP, all compounds were completely soluble and active. A pronounced ligand influence on catalytic performance was only found for the hybrids [MoO3(trz)0.5], and only the 1,2,4-trz compound displayed reaction-induced self-precipitation behavior. An insight into the type of solution species that may be involved in the catalytic processes with these compounds was obtained by separately treating [MoO3(1,2,4-trz)0.5] with excess H2O2, which led to the crystallization of the complex (NH4)1.8(H3O)0.2[Mo2O2(μ2-O)(O2)4(1,2,4-trz)]·H2O. The single-crystal X-ray investigation of this complex reveals an oxo-bridged dinuclear structure with oxodiperoxo groups being further linked by a single triazole bridge.

Crystal structure of a dinuclear ruthenium(II) complex with a bent CO2 2− bridge

The molecular and crystal structures of a CO2 2−-bridged dinuclear ruthenium complex is reported, namely, μ-carbonito-κ2 C:O-bis[bis(2,2′-bipyridine-κ2 N,N′)carbonylruthenium(II)] bis(hexafluoridophosphate)–acetonitrile–diethyl ether (1/1/0.5), [Ru2(CO)2(C10H8N2)4(μ:κ 2-C:O-CO2)](PF6)2·CH3CN·0.5C4H10O. The complex cation in the title compound consists of two {Ru(CO)(bpy)2}2+ units (bpy = 2,2′-bipyridine) singly bridged by a μ:κ2-C:O carbonite anion, resulting in an unsymmetrical dinuclear structure. Some of the interatomic C...O distances involving the carbonyl ligands are shorter than the sum of the van der Waals radii. There are intramolecular C—H...O and aromatic π–π contacts in the cationic complex. In the crystal, the cations are linked by pairs of C—H...F hydrogen bonds in addition to weak C—H...F interactions between the solvent molecules and PF6 − counter-anions. The equatorial F atoms of one of the PF6 − anions are disordered over two sets of sites with an occupancy ratio of 0.908 (7):0.092 (7) while the central O atom of the diethyl ether solvent molecule is disordered over an inversion centre.

A new copper(II) supramolecular coordination polymer and a dinuclear compound with multifunctional 2-amino-5-sulfobenzoic acid and flexible N-donor ligands: synthesis, structure and characterization

Multifunctional 2-amino-5-sulfobenzoic acid (H2afsb) can exhibit a variety of roles during the construction of supramolecular coordination polymers. The pendant carboxylic acid, sulfonic acid and amino groups could not only play a role in directing bonding but could also have the potential to act as hydrogen-bond donors and acceptors, resulting in extended high-dimensional supramolecular networks. Two new CuIIcoordination compounds, namelycatena-poly[[[diaquacopper(II)]-μ-1,6-bis(1H-1,2,4-triazol-1-yl)hexane-κ2N4:N4′] bis(3-amino-4-carboxybenzenesulfonate) dihydrate], {[Cu(C10H16N6)2(H2O)2](C7H6NO5S)2·2H2O}nor {[Cu(bth)2(H2O)2](Hafsb)2·2H2O}n, (1), and bis(μ-2-amino-5-sulfonatobenzoato-κ2O1:O1′)bis{μ-1,2-bis[(1H-imidazol-1-yl)methyl]benzene-κ2N3:N3′}bis[aquacopper(II)] trihydrate, [Cu2(C7H5NO5S)2(C14H14N4)2(H2O)2]·3H2O or [Cu2(afsb)2(obix)2(H2O)2]·3H2O, (2), have been obtained through the assembly between H2afsb and the CuIIion in the presence of the flexible N-donor ligands 1,6-bis(1H-1,2,4-triazol-1-yl)hexane (bth) and 1,2-bis[(1H-1,2,4-triazol-1-yl)methyl]benzene (obix), respectively. Compound (1) consists of a cationic coordination polymeric chain and 3-amino-4-carboxybenzenesulfonate (Hafsb−) anions. Compound (2) exhibits an asymmetric dinuclear structure. There are hydrogen-bonded networks within the lattices of (1) and (2). Interestingly, both (1) and (2) exhibit reversible dehydration–rehydration behaviour.

Synthesis of copper(II) and gold(III) bis(NHC)-pincer complexes

CuII and AuIII chlorido complexes bearing the bis(NHC) carbazolide pincer ligand (bimca) were synthesized by transmetallation from the respective lithium complex [Li(bimca)] (NHC=N-heterocyclic carbene). In the case of copper, two different molecular structures were obtained depending on the copper source. With Cu(II) chloride the paramagnetic mononuclear [Cu(bimca)Cl] complex is formed and has been characterized by EPR spectroscopy and X-ray structure analysis, while copper(I) chloride leads under oxidation to a dinuclear structure in which two cationic [CuII(bimca)] moieties are bridged by one chlorido ligand. The positive charge is compensated by the [CuCl2]− counter ion, as proven by X-ray structure analysis. Transmetallation of [Li(bimca)] with AuCl3 leads to the [Au(bimca)Cl]+ complex with a tetrachloridoaurate counter ion.