Nickel(II) and copper(II) complexes of 2-(2-pyridyl)benzimidazole: synthesis and structural characterization

Abstract

2-(2-Pyridyl)benzimidazole (PBI) was synthesized by solvent-free aldol condensation and complexed with nickel(II) and copper(II) nitrate and perchlorate salts by simple reactions at room temperature. The transition metal complexes [Ni(PBI) were synthesized in good yield and structurally characterized by X-ray crystallography, infrared absorption spectroscopy, and elemental analysis. Complexes 1 and 3 are isostructural, crystallizing in the same space group P2 1 /c. Both the nickel(II) and copper(II) atoms have distorted square pyramidal geometries. The metal centers in these complexes are coordinated by two molecules of the bidentate ligand (PBI) and an O-atom of the coordinated nitrate anion. Complexes 2 and 4 are also isostructural but do not crystallize in the same space group: P-1 for 2 and Pccn for 4. The geometry around both the nickel(II) and the copper(II) centers is distorted octahedral. Here, the metal atoms are coordinated by three molecules of 2-(2-pyridyl)benzimidazole. The copper(II) complex 4 has 2-fold symmetry with one of the three PBI ligands being positionally disordered about the 2-fold axis. Intermolecular N-HÁÁÁO hydrogen bonds, involving the NH H-atom and an O-atom of the coordinated nitrate anion, are observed in all four complexes. In 1 and 3, this gives rise to the formation of centrosymmetric dimer-like structures that are decorated by hydrogen-bonded nitrate anions. In 2 and 4 the perchlorate anions and the water molecules of crystallization are involved in N-HÁÁÁO and O-HÁÁÁO hydrogen bonds bridging two symmetry-related cations, thus forming cyclic arrangements. In the case of complex 4, this leads to the formation of two-dimensional hydrogen-bonded networks parallel to plane (011).

Synthesis and Structure of Novel Copper(II) Complexes with N,O- or N,N-Donors as Radical Scavengers and a Functional Model of the Active Sites in Metalloenzymes

“…One of the pyBIm ligands, unlike the other two, is positionally disordered about the 2-fold axis. This type of disorder was also observed in the previously reported structure of the Cu(II) complex [ 27 ]. Additionally, the disorder can also be noticed in the case of the tetrafluoroborate groups.…”

Visible-Light Photocatalytic Conversion of Carbon Dioxide by Ni(II) Complexes with N4S2 Coordination: Highly Efficient and Selective Production of Formate

“…16 In the case of complex 1, the imine nitrogen of pbi can coordinate to the Ni(II) center instead of the secondary amine, as supported from the ESI-MS of complex 1 and reported for other pbi complexes of Ni(II), Mn(II), and Cu(II). 18,19 The absorption spectra of complexes 1 and 2 in H 2 O/EtOH were obtained (Figure 2). The spectrum of complex 1 shows high-energy absorption bands at 274 nm (ε = 14 960) and 332 nm (ε = 17 990); however, the spectrum of complex 2 exhibits bands at 278 (ε = 18 690) and 316 nm (ε = 17 230), corresponding to spin-allowed intraligand (π−π*) transitions (Figure 2).…”

Preparation, electrochemical behavior, and variable-temperature magnetic properties of Co(3,5-DBSQ)2 complexes of imidazole- or pyrazole-substituted ligands

“…1) were all prepared by following literature procedures and were isolated in reasonable yields and produced spectroscopic properties congruent with the literature results. [12][13][14] Coordination of neutral 1 was carried out in the absence of any external base by reaction with 0.25 equiv. of Co 4 (3,5-DBSQ) 8 (Pierpont's "tetramer").…”