π-Expanded Axially Chiral Biaryls and Their Emissions: Molecular Design, Syntheses, Optical Resolution, Absolute Configuration, and Circularly Polarized Luminescence of 1,1′-Bipyrene-2,2′-diols

Axially chiral biaryls based on pyrene, 1,1'-bipyrene-2,2'-diol derivatives 2, were designed and synthesized from 2-hydroxypyrene. Simple optical resolution was carried out and the absolute configuration was determined by diffraction study. Title compounds 2 and corresponding menthylcarbonate 4 showed clear circularly polarized luminescence (CPL) spectra. The degree of dimensionless Kuhn's anisotropy in the photoexcited state (vertical bar g(em)vertical bar) of 2 and 4 were ca. 3.6 x 10(-4) and ca. 1.2 x 10(-3), respectively. Noteworthy properties were as follows: 1) high fluorescent quantum yields of 2 and 4, 0.57 and 0.80, respectively, in marked contrast to that of BINOL, 0.04 and 2) bathochromic shifts of lambda(CPL).