Complexation of Benzoannelated Porphyrazines with Zinc(II) and Cobalt(II) Acetates in Pyridine

Complexation of tribenzodiazepinoporphyrazine with Cu(II), Zn(II), and Co(II) acetates has been studied. Cu(II) complex of tribenzodiazepinoporphyrazine forms immediately, therefore Zn(II) and Co(II) acetates have been used as salts. It has been found that the rate of complex formation of tribenzodiazepinoporphyrazine with metal ions in pyridine decreases in the series: Cu(II) > Zn(II) > Co(II), this order agrees well with literature data obtained for tetraazaporphin. When diazepine fragment is replaced by pyrazine one, the rate of porphyrazine complexation with Zn(II) decreases. It is supposed that, in the case of tribenzodiazepinoporphyrazine, the reaction of metal insertion proceeds through formation of outer complex, which favors to the further introduction of zinc(II) ion in coordination center of the macrocycle. The complexation of Zn(II) and Co(II) with studied porphyrazines is characterized by low values of activation energy and entropy, which may indicate the strong solvation of transition state.