P⋯O noncovalent conformational locks for constructing highly planar Bis(diphenylphosphanyl) Bi(benzofurano)

Bis(diphenylphosphanyl) bi(benzofurano) (BBFP) and Bis(diphenylphosphanyl) bi(benzothiophene) (BBTP) were synthesized by the reaction of dilithio(benzothienylbenzofuran) or dilithio(benzothienylbenzothiophene) with Diphenylphosphinic chloride, then reduced with trichlorosilane to afford the target. Optical and electrochemical measurements of the products and their DFT calculations revealed that P⋯O noncovalent conformational locks played an important role in constructing highly planar BBFP, while BBTP showed a distorted structure. As a result, the photoluminescence (PL) quantum yields of BBFP measured as solids were 0.25. In contrast, the PL quantum yields of BBTP was too low to be detected.