Dynamic Behavior, Electrochromism, and Two-Photon Absorption of Dicyanomethylenated Quinacridone

Molecular structures of dicyanomethylenated
quinacridone (1) as a solid and in solution were examined
on the basis of
single-crystal X-ray structural analysis, temperature-dependent 1H NMR in CD2Cl2, and theoretical calculations.
Crystal 1 had a curved, butterfly-shaped molecular structure.
Thermally activated flipping between the curved, butterfly-shaped
structure and an armchair structure occurred in solution. Electrochemical
reduction triggered a dynamic change from the curved, butterfly-shaped
conformation in the neutral state to a planar conformation in the
dianion state, which represented electrochromic behavior with electrochemical
bistability. A large two-photon absorption cross section of compound 1 was observed in the resonance-enhancement region of 423
GM (1 GM = 1 × 10–50 cm4 s photon–1 molecule–1) at 710 nm. Multiple
donor–acceptor charge-transfer pathways of molecule 1 enhanced two-photon absorption.