Benzodioxine-fused tetrapyrazinoporphyrazine complexes (BzO 2 ) 4 TPyzPzM (M = Co(II), Cu(II), Zn(II), In(III)) were synthesized via two complementary routes: (i) template cyclotetramerization of benzo1,4dioxino2,3 bpyrazine-2,3 dicarbonitrile, and (ii) post-functionalization of octachloro-substituted precursors Cl 8 TPyzPzM (M = Cu, Co) through reaction with catechol. The obtained complexes were characterized by MALDI-TOF, NMR, UV-Vis, and IR spectroscopy, and their electrochemical behavior was studied by cyclic voltammetry. Density functional theory (DFT) calculations revealed the molecular and electronic structures, highlighting the near-planar geometry of the complexes (except for the dome-shaped In(III) derivative). Electrochemical studies of graphite electrodes modified with complexes 3a-c showed that replacing chlorine atoms with dioxin fragments significantly shifts the reduction potential toward the negative region. While for the Zn complex, only the macrocyclic ligand is redox active and undergoes reduction, the redox processes associated with the central atom are observed not only for the Co(II) complex (3+/2+ and 2+/1+) couples but also for the Cu(II) complex (2+/1+) couple.
Finogenov et al. (Wed,) studied this question.