Dinuclear triply bridged copper(II)-carboxylato compounds with different bischelating ligands: Synthesis, crystal structure, spectroscopic and magnetic properties

A Binuclear Copper(II) Complex with Diphenoxido-bridges: Synthesis, Characterisation, Crystal Structure and Predicting the Magnetic Coupling Constant

Reaction of copper(II) acetate with 1,1′-[(2,2-dimethylpropane-1,3-diyl)bis(nitrilomethylidyne)]-di-2-naphthol (H2L) gave the diphenoxido-bridged binuclear copper(II) complex [Cu2L2]. Its crystal structure shows a slightly distorted square pyramidal geometry around both of the copper(II) ions. In the symmetric Cu2O2 core, each of the phenoxido bridges occupies an equatorial position around one of the copper(II) centres. A broken symmetry (BS) computation based on density functional theory (DFT) evaluated the magnetic interaction in the complex using the (U)B3LYP level of theory in association with the basis sets LANL2DZ for the copper atoms and 6-31G** for the other atoms. The calculations showed ferromagnetic interaction between the two magnetic copper(II) centres with a magnetic coupling constant (J) of 1.16 cm−1.

Copper complexes as catalyst precursors in the electrochemical hydrogen evolution reaction

Two copper complexes were investigated with respect to their activity in the electrocatalysed hydrogen evolution reaction. The complexes are precursors for highly active copper(0) and Cu₂O deposits.

Mixed-ligand MnII and CuII complexes with alternating 2,2'-bipyrimidine and terephthalate bridges

The novel polymeric complexes catena-poly[[diaquamanganese(II)]-μ-2,2'-bipyrimidine-κ(4)N(1),N(1'):N(3),N(3')-[diaquamanganese(II)]-bis(μ-terephthalato-κ(2)O(1):O(4))], [Mn2(C8H4O4)2(C8H6N4)(H2O)4]n, (I), and catena-poly[[[aquacopper(II)]-μ-aqua-μ-hydroxido-μ-terephthalato-κ(2)O(1):O(1')-copper(II)-μ-aqua-μ-hydroxido-μ-terephthalato-κ(2)O(1):O(1')-[aquacopper(II)]-μ-2,2'-bipyrimidine-κ(4)N(1),N(1'):N(3),N(3')] tetrahydrate], {[Cu3(C8H4O4)2(OH)2(C8H6N4)(H2O)4]·4H2O}n, (II), containing bridging 2,2'-bipyrimidine (bpym) ligands coordinated as bis-chelates, have been prepared via a ligand-exchange reaction. In both cases, quite unusual coordination modes of the terephthalate (tpht(2-)) anions were found. In (I), two tpht(2-) anions acting as bis-monodentate ligands bridge the Mn(II) centres in a parallel fashion. In (II), the tpht(2-) anions act as endo-bridges and connect two Cu(II) centres in combination with additional aqua and hydroxide bridges. In this way, the binuclear [Mn2(tpht)2(bpym)(H2O)4] entity in (I) and the trinuclear [Cu3(tpht)2(OH)2(bpym)(H2O)4]·4H2O coordination entity in (II) build up one-dimensional polymeric chains along the b axis. In (I), the Mn(II) cation lies on a twofold axis, whereas the four central C atoms of the bpym ligand are located on a mirror plane. In (II), the central Cu(II) cation is also on a special position (site symmetry -1). In the crystal structures, the packing of the chains is further strengthened by a system of hydrogen bonds [in both (I) and (II)] and weak face-to-face π-π interactions [in (I)], forming three-dimensional metal-organic frameworks. The Mn(II) cation in (I) has a trigonally deformed octahedral geometry, whereas the Cu(II) cations in (II) are in distorted octahedral environments. The Cu(II) polyhedra are inclined relative to each other and share common edges.

Dicopper(II) and dizinc(II) complexes with nonsymmetric dinucleating ligands based on indolo[3,2-c]quinolines: synthesis, structure, cytotoxicity, and intracellular distribution

Dicopper(II) and dizinc(II) complexes [Cu2((MeOOC)L(COO))(CH3COO)2] (1) and [Zn2((MeOOC)L(COO))(CH3COO)2] (2) were synthesized by reaction of Cu(CH3COO)2·H2O and Zn(CH3COO)2·2H2O with a new nonsymmetric dinucleating ligand (EtOOC)HL(COOEt) prepared by condensation of 6-hydrazinyl-11H-indolo[3,2-c]quinoline with diethyl-2,2'-((3-formyl-2-hydroxy-5-methylbenzyl)azanediyl)diacetate. The design and synthesis of this elaborate ligand was performed with the aim of increasing the aqueous solubility of indolo[3,2-c]quinolines, known as biologically active compounds, and investigating the antiproliferative activity in human cancer cell lines and the cellular distribution by exploring the intrinsic fluorescence of the indoloquinoline scaffold. The compounds have been comprehensively characterized by elemental analysis, spectroscopic methods (IR, UV-vis, (1)H and (13)C NMR spectroscopy), ESI mass spectrometry, magnetic susceptibility measurements, and UV-vis complex formation studies (for 1) as well as by X-ray crystallography (1 and 2). The antiproliferative activity of (EtOOC)HL(COOEt), 1, and 2 was determined by the MTT assay in three human cancer cell lines, namely, A549 (nonsmall cell lung carcinoma), CH1 (ovarian carcinoma), and SW480 (colon adenocarcinoma), yielding IC50 values in the micromolar concentration range and showing dependence on the cell line. The effect of metal coordination on cytotoxicity of (EtOOC)HL(COOEt) is also discussed. The subcellular distribution of (EtOOC)HL(COOEt) and 2 was investigated by fluorescence microscopy, revealing similar localization for both compounds in cytoplasmic structures.

Toward the design of ferromagnetic molecular complexes: magnetostructural correlations in ferromagnetic triply bridged dinuclear Cu(II) compounds containing carboxylato and hydroxo bridges

In the present work we present a comprehensive study of the magneto-structural correlations of a series of ferromagnetic triply heterobridged Cu(II) dinuclear compounds containing [Cu(2)(mu-O(2)CR)(mu-OH)(mu-X)(L)(2)](2+) ions (where X = OH(2), Cl(-), OMe(-) and L = bpy, phen, dpyam) which have the particularity of being all ferromagnetic. The present theoretical study, based on hybrid density functional theory (DFT) calculations, leads to strong conclusions about the role of the pentacoordination geometry of the Cu(II) ions (square base pyramidal (SP) or trigonal bipyramidal (TBP) coordination) and the nature of the third bridging ligand in determining the final value of the magnetic coupling constants in this series of compounds. These investigations point toward the existence of a maximum value for the ferromagnetic interaction and may offer some useful information to synthetic chemists aiming at obtaining new compounds with enhanced ferromagnetism.