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

Benzodioxine-fused tetrapyrazinoporphyrazine complexes (BzO₂)₄TPyzPzM (M = 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-2,3-dicarbonitrile, and (ii) post-functionalization of octachloro-substituted precursors Cl₈TPyzPzM (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) and the bathochromic shift of the Q-band upon benzodioxine annulation. Comparative analysis of both synthetic approaches shows comparable yields (~25 %), supporting the feasibility of postfunctionalization for constructing covalent organic frameworks (COFs) based on peripherally substituted tetrapyrazinoporphyrazines.