Two isomers containing a [Cu(Me2bpzb)] unit: Molecule (0-D) and 1-D

Electrocatalytic Water Oxidation by Mononuclear Copper Complexes of Bis-amide Ligands with N4 Donor: Experimental and Theoretical Investigation

The present work describes electrocatalytic water oxidation of three monomeric copper complexes [CuII(L1)] (1), [CuII(L2)(H2O)] (2), and [CuII(L3)] (3) with bis-amide tetradentate ligands: L1 = N,N'-(1,2-phenylene)dipicolinamide, L2 = N,N'-(4,5-dimethyl-1,2-phenylene)bis(pyrazine-2-carboxamide), L3 = N,N'-(1,2-phenylene)bis(pyrazine-2-carboxamide), for the production of molecular oxygen by the oxidation of water at pH 13.0. Ligands and all complexes have been synthesized and characterized by single crystal XRD, analytical, and spectroscopic techniques. X-ray crystallographic data show that the ligand coordinates to copper in a dianionic fashion through deprotonation of two -NH protons. Cyclic voltammetry study shows a reversible copper-centered redox couple with one ligand-based oxidation event. The electrocatalytic water oxidation occurs at an onset potential of 1.16 (overpotential, η ≈ 697 mV), 1.2 (η ≈ 737 mV), and 1.23 V (η ≈ 767 mV) for 1, 2, and 3 respectively. A systematic variation of the ligand scaffold has been found to display a profound effect on the rate of electrocatalytic oxygen evolution. The results of the theoretical (density functional theory) studies show the stepwise ligand-centered oxidation process and the formation of the O-O bond during water oxidation passes through the water nucleophilic attack for all the copper complexes. At pH = 13, the turnover frequencies have been experimentally obtained as 88, 1462, and 10 s-1 (peak current measurements) for complexes 1, 2, and 3, respectively. Production of oxygen gas during controlled potential electrolysis was detected by gas chromatography.

New ionic cobalt(iii) complexes based on the N,N-bis(2-pyrazinecarboxamide)-1,2-benzene ligand: application to the formation of organic carbonates from epoxides and CO2

New cobalt(iii) complexes based onN,N-bis(2-pyrazine-carboxamide)-1,2-benzene were tested as catalysts for the coupling of propylene- and cyclohexene oxide with CO₂.

N,N'-[2,2'-(Phenyl-aza-nedi-yl)bis-(ethane-2,1-di-yl)]dipicolinamide

The asymmetric unit of the title compound, C₂₂H₂₃N₅O₂, contains two independent mol­ecules with similar conformations; the terminal pyridine rings are oriented at dihedral angles of 23.99 (8) and 18.07 (8)° with respect to the central benzene ring in one mol­ecule and 28.99 (8) and 23.22 (8)° in the other. In the crystal, N—H⋯O and weak C—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional supra­molecular structure. Weak inter­molecular C—H⋯π inter­actions are also observed in the crystal.

N,N'-(Ethane-1,2-diyldi-o-phenyl-ene)bis-(pyridine-2-carboxamide)

The title mol-ecule, C(26)H(22)N(4)O(2), is centrosymmetric and adopts an anti conformation. Two intra-molecular hydrogen bonds, viz. amide-pyridine N-H⋯N and phen-yl-amide C-H⋯O, stabilize the trans conformation of the (pyridine-2-carboxamido)-phenyl group about the amide plane. In the crystal, the presence of weak inter-molecular C-H⋯O hydrogen bonds results in the formation of a three-dimensional network.