Synthesis and electrochemical study of 2-(2-pyridyl)benzothiazole complexes with transition metals (Co^II, Ni^II, and Cu^II). Molecular structure of aquabis[2-(2-pyridyl)benzothiazole]copper(II) diperchlorate

The reactions of 2-(2-pyridyl)benzothiazole (1) with MX2·nH2O salts (M = NiII, CoII, or CuII; X = Cl or ClO4; n = 0–2) in EtOH afforded the corresponding complexes. Depending on the nature of the counterion in the starting metal salt, the reactions give compounds of composition M(1)Cl2·nH2O or Cu(1)2(ClO4)2·H2O. The molecular and crystal structure of the CuII(1)2(ClO4)2·H2O complex was established by X-ray diffraction. The copper atom in this complex has a distorted tetragonal-pyramidal ligand environment and is coordinated by four nitrogen atoms of two ligand molecules and one water molecule. Electrochemical study of the ligand and the resulting complexes by cyclic voltammetry and at a rotating disk electrode demonstrated that ligand 1 stabilizes reduced forms of complexes containing Ni, Co, or Cu atoms in the oxidation state +1.