Synthesis, structure and property of cobalt(II) complexes with 3,5-di(1H-imidazol-1-yl)benzoic acid

Abstract

Two novel cobalt(II) complexes [Co(L)(NO₃)] (1) and [Co(L)(H₂O)₂]ClO₄ (2) were synthesized by reactions of 3,5-di(1H-imidazol-1-yl)benzoic acid (HL) with corresponding cobalt(II) salts, and their structures were determined by single crystal X-ray diffraction analysis. In the title complexes, the carboxylate group of L⁻ ligand adopts a µ₂–ŋ¹:ŋ¹-bridging mode to connect two cobalt(II) atoms, and each L⁻ ligand acts as a 4-connector, and the cobalt(II) has distorted octahedral coordination geometry. In 1, one oxygen atom of the nitrate anion links two cobalt(II) atoms to complete a 3D structure which is a binodal (4,6)-connected net with Schläfli symbol of (3·4²·5²·6)(3²·4²·5²·6⁴·7⁴·8). While in 2, the 3D structure has topology related to SrAl₂, CeCu₂ and KHg₂ with Schläfli symbol of (4²·6³·8) and there are 1D channels filled with perchlorate anions. The results revealed that the nature of the counteranions, such as their shape, size and coordination ability, has a remarkable influence on the structure of the complexes. The results of the magnetic measurements showed that there are antiferromagnetic interactions between the neighboring Co(II). Furthermore, complex 2 exhibited a modest second-harmonic-generation (SHG) efficiency and anion-exchange property.