Conformational Flexibility and Size of Large trans-Vinylene-Bridged Thiaporphyrinoids Influences Boron Coordination Modes

Two π-extended core-modified porphyrinoids were synthetized and structurally characterized to probe boron-induced geometry switching and modulation of electron delocalization. Trans -vinylene-bridged hexathia-dodecaphyrin forms the largest, fully characterized, porphyrinoid BODIPY-type complex while retaining parent, open-form geometry, whereas octathia-hexadecaphyrin does not support boron coordination. Notably, a smaller, figure-of-eight tetrathia-octaphyrin analogue exhibits unusual, direct C–B bond formation, highlighting pronounced structural sensitivity of expanded porphyrinoids and their utility in accessing unconventional bonding and coordination modes.