The synthesis of a bithiophene-bridged 34π conjugated aromatic expanded porphycene 1 and a cyclopentabithiophene bridged 32π conjugated anti-aromatic expanded porphycene 2 by a McMurry coupling strategy is presented. Magnetic measurements and theoretical calculations reveal that both 1 and 2 exhibit an open-shell singlet ground state with significant radical character (y =0.63 for 1; y =0.68, y =0.18 for 2; y : diradical character, y : tetraradical character) and a small singlet-triplet energy gap (ΔE =-3.25 kcal mol for 1 and ΔE =-0.92 kcal mol for 2). Despite the open-shell radical character, both compounds display exceptional stability under ambient air and light conditions owing to effective delocalization of unpaired electrons in the extended cyclic π-conjugation pathway.
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