Synthetic Control of Photophysical Process and Circularly Polarized Luminescence of [5]Carbohelicene Derivatives Substituted by Maleimide Units

摘要

A series of [S]carbohelicene derivatives substituted by electron-withdrawing maleimide maleimide and electron-donating methoxy, such as maleimide-substituted [5]carbohelicene (HeliIm) and methoxy-substituted HeliIm (MeO-HeliIm), were newly designed and synthesized to examine the electrochemical properties, excited-state dynamic and circularly polarized luminescence (CPL). First, electrochemical measurements and DFT calculations of [5]carbohelicene derivatives were performed by comparing with the structural isomers: picene derivatives. Introduction of an electron-withdrawing maleimide group onto a [5]carbohelicene core contributes to the stabilized LUMO state in HeliIm as compared to that of [5]carbohelicene (Heli), whereas the energy level of HOMO state in MeO-HeliIm increases by introducing electron-donating methoxy (MeO) groups onto a HeliIm skeleton. The HOMO-LUMO gap of MeO-HeliIm is smaller than those of Realm and Heli, which is similar to the steady-state spectroscopic measurements. The absolute fluorescence quantum yield (Phi(FL)) of HeliIm (0.37) largely increased as compared to [5]carbohelicene, Heli (0.04), whereas OH, of MeO-HeliIm (0.22) was slightly smaller than that of HeliIm. Theses photophysical processes including intersystem crossing are successfully explained by the kinetic discussions. Since [5]carbohelicene derivatives show the chirality, measurements of circular dichroism (CD) and circularly polarized luminescence (CPL) were successfully performed. In particular, HeliIm and MeO-Helilm have provide excellent circularly polarized luminescence (CPL) and the values of the anisotropy factor g(lum) were estimated to be similar to 2.4 X 10(-3) and similar to 2.3 x 10(-3), relatively. This is the first observation of CPL in [5]carbohelicene derivatives.