Highly Electron-Donating Antiaromatic N,N′-Dimethyldiazaporphyrins via Reductive Dimethylation

Ni(II) N,N′-dimethyl-5,15-diazaporhyrins are efficiently prepared through reductive dimethylation of 5,15-diazaporphyrin Ni(II) complexes with sodium dispersion in the presence of dimethyl sulfate. The obtained reduced diazaporphyrins exhibit highly upfield-shifted ¹H NMR spectra and narrowed HOMO–LUMO gaps originating from their distinct antiaromatic nature. The electrochemical analysis reveals their highly electron-donating property, which leads to the formation of a charge transfer (CT) complex with tetracyanoquinodimethane (TCNQ) as an electron acceptor. The CT complex of Ni(II) N,N′-dimethyl-10,20-diphenyl-5,15-diazaporphyrin with TCNQ exhibits alternate π-stacking orientation in the solid state. N,N′-Dimethyl-5,15-diazaporphyrins also interact with C₆₀ in the solid state to yield cocrystals.