β,β-Diborylated Subporphyrinato Boron(III) Complexes as Useful Synthetic Precursors

Iridium-catalyzed borylation of B-aryl meso-free subporphyrinato boron(III) complexes (hereinafter referred to simply as subporphyrins) with bis(pinacolato)diboron gave 2,13-diborylated subporphyrins regioselectively, which served as promising synthetic precursors for 2,13-diarylated subporphyrins and doubly β-to-β 1,3-butadiyne-bridged subporphyrin dimers. 2,13-Diarylated subporphyrins display perturbed absorption spectra, depending upon the β-aryl substituents. Doubly 1,3-butadiyne-bridged syn and anti subporphyrin dimers thus prepared exhibit differently altered absorption spectra with split Soret-like bands, which have been accounted for in terms of exciton coupling.