Synthesis and characterization of four dicyanamide bridged copper(II) complexes with N2O donor tridentate Schiff bases as blocking ligands

Crystal structure of poly[hexa-μ-bro-mido-bis{2-[1-(py-ri-din-2-yl)ethyl-idene-amino]ethanol-ato}tetracopper(II)]

The reaction of the Schiff base 2-[1-(pyridin-2-yl)ethyl-idene-amino]-ethanol (HL), which is formed by reaction of 2-amino-ethanol and 2-acetyl-pyridine with CuBr2 in ethanol results in the isolation of the new polymeric complex poly[hexa-μ-bromido-bis-{2-[1-(pyridin-2-yl)ethyl-idene-amino]-ethano-lato}tetra-copper(II)], [Cu4Br6(C9H11N2O)2]n or [Cu4Br6 L 2]n. The asymmetric unit of the crystal structure of the polymeric [Cu4Br6 L 2]n complex is composed by four copper (II) cations, two monodeprotonated mol-ecules of the ligand, and six bromide anions, which act as bridges. The ligand mol-ecules act in a tridentate fashion through their azomethine nitro-gen atoms, their pyridine nitro-gen atoms, and their alcoholate O atoms. The crystal structure shows two types of geometries in the coordination polyhedrons around Cu2+ ions. Two copper cations are situated in a square-based pyramidal environment, while the two other copper cations adopt a tetra-hedral geometry. Bromides anions acting as bridges between two metal ions connect the units, resulting in a tetra-nuclear polymer compound.

Phenoxo-bridged dinuclear mixed valence cobalt(III/II) complexes with reduced Schiff base ligands: synthesis, characterization, band gap measurements and fabrication of Schottky barrier diodes

Two homometallic class-I dinuclear mixed valence cobalt complexes, [(N3)CoIIIL1(μ-C6H4(NO2)CO2)CoII(N3)] (1) and [(N3)CoIIIL2(μ-C6H4(NO2)CO2)CoII(N3)] (2), have been synthesized using multisite N2O4 coordination ligands, H2L1 {where H2L1 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-methoxyphenol) and H2L2 = (2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-ethoxyphenol)}. Each complex has been structurally characterized by single crystal X-ray diffraction and spectral analysis. Both the cobalt centers in these dinuclear complexes adopt a distorted-octahedral geometry, where the cobalt(iii) center resides at the inner N2O2 cavity and the cobalt(ii) center resides at the outer O4 cavity of the reduced Schiff base. Both of them show good electrical conductivity, which has been rationalized by band gap measurements. The band gap in the solid state has been determined by experimental and DFT calculations and it confirms that each of the two complexes behaves as a semiconductor. The space-charge-limited current (SCLC) theory is employed to evaluate the charge transport parameters such as effective carrier mobility and transit time for both complexes. The difference in the conductivity values of the complexes may be correlated with the strengths of extended supramolecular interactions in the complexes. Bader's quantum theory of atoms-in-molecules (QTAIM) is applied extensively to get quantitative and qualitative insights into the physical nature of weak non-covalent interactions. In addition, the non-covalent interaction reduced density gradient (NCI-RDG) methods well support the presence of such non-covalent intermolecular interactions.

Estimation of conventional C-Hπ (arene), unconventional C-Hπ (chelate) and C-Hπ (thiocyanate) interactions in hetero-nuclear nickel(ii)-cadmium(ii) complexes with a compartmental Schiff base

Three new heteronuclear nickel(ii)/cadmium(ii) complexes, [(SCN)(Cl)Cd(L)Ni(DMF)₂] (1), [(SCN)(CH₃CO₂)Cd(L)Ni(CH₃OH)₂] (2) and [(SCN)(Cl)Cd(L)Ni(NH₂CH₂CH₂CH₂NH₂)]_n (3) {where H₂L = N,N'-bis(3-ethoxy-salicylidene)propane-1,3-diamine is a N₂O₄ compartmental Schiff base}, have been synthesized and characterized. The structures of the complexes have been confirmed by single crystal X-ray diffraction studies. In each complex, nickel(ii) is placed in the inner N₂O₂ environment and cadmium(ii) is placed in the outer O₄ compartment of the compartmental Schiff base. Furthermore, the importance of unconventional C-Hπ (chelate) interactions in the solid state of both complexes and C-Hπ (thiocyanate) interaction in complex 2 has been described by means of DFT and MEP calculations and characterized using NCI plots. All complexes show photoluminescence at room temperature upon irradiation by ultraviolet light. The lifetimes of excited states are in the range of 2-6 ns.

Formation of a novel ferromagnetic end-to-end cyanate bridged homochiral helical copper(ii) Schiff base complex via spontaneous symmetry breaking

A homochiral helical coordination polymer of copper(ii) has been synthesized using achiral precursors. End-to-end cyanate bridges mediate ferromagnetic exchange interactions among copper(ii) centres.

Spontaneous resolution of P and M helical copper(ii) MOFs built from achiral precursors

Enantiomorphic P and M helices have been synthesized by the self-assembly of achiral precursors via spontaneous resolution.