Synthesis of bis(benzoazaborin)-fused B(III) subporphyrin and dinaphtho[2′,1′-b:1,2-g]-fused analogue

Bis(benzoazaborin)-fused B(III)subporphyrin 7 was synthesized from meso-free B(III) subporphyrin 10 in three steps using the condensation of B(III) 2,13-di(2-aminophenyl)-5,15-di(4-tolyl)subporphyrin 6 with BBr 3 as a key step. Dinaphtho[2′,1′-b:1,2-g]-fused B(III) subporphyrin 9 was also synthesized as an isoelectronic species via B(III) 2,13-di(2-formylphenyl)-5,15-di(4-tolyl)subporphyrin 8 using a sequence of Wittig reaction and subsequent electrophilic cyclization with Bi(OTf) 3 . B(III) doubly fused subporphyrins 7 and 9 show red-shifted absorption and fluorescence bands, reflecting the expansion of [Formula: see text]-conjugated network, and restricted rotation of the meso-tolyl substituents due to the steric congestion caused by the fused parts. Characteristically, B(III) subporphyrin 7 displays a double exponential fluorescence decay and a large Stokes shift, suggesting significant structural change in the S 1 -state.