Benzodioxino-fused tetrapyrazinoporphyrazines: Synthesis, DFT study, spectral and electrochemical properties

Benzodioxine-fused tetrapyrazinoporphyrazine complexes (BzO[Formula: see text]TPyzPzM (M [Formula: see text] Co(II), Cu(II), Zn(II), In(III)) were synthesized via two complementary routes: (i) template cyclotetramerization of benzo[1,4]dioxino[2,3-b]pyrazine-2,3dicarbonitrile, and (ii) post-functionalization of octachloro-substituted precursors Cl 8 TPyzPzM (M [Formula: see text] 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[Formula: see text]/2[Formula: see text] and 2[Formula: see text]/1[Formula: see text] couples but also for the Cu(II) complex (2[Formula: see text]/1[Formula: see text] couple.