Giant static dipole moment change on electronic excitation in highly oriented J-aggregates

Abstract

A large change in the static dipole moment upon electronic excitation was unexpectedly observed in highly oriented one-dimensional J-aggregates of 1,1′-diethyl-2,2′-quinocyanine bromide (PIC-Br) prepared by a method developed by our group. Difference absorption spectra due to the Kerr effect were induced by changes in a static dipole moment and a polarizability separated by the dual-phase lock-in detection. The change in the static dipole moment associated with the transition from the ground state to the exciton state was measured with an applied ac field ( F ) of 300 Hz and polarization ( e ) parallel and perpendicular to the one-dimensional axis ( d ) of the oriented J-aggregates, and obtained in each configuration to be 18 ( F || d / e || d ), 12 ( F ⊥ d / e || d ), 27 ( F || d / e ⊥ d ), and 14 ( F ⊥ d / e ⊥ d ) D.