Stable Expanded Porphycene‐Based Diradicaloid and Tetraradicaloid

Abstract

Abstract 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 =0.63 for 1 ; y 0 =0.68, y 1 =0.18 for 2 ; y 0 : diradical character, y 1 : tetraradical character) and a small singlet–triplet energy gap (Δ E S‐T =−3.25 kcal mol −1 for 1 and Δ E S‐T =−0.92 kcal mol −1 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.