Fluorescence study of two- and three-dimensional organization of a thermotropic liquid crystal containing biphenyl–ester moieties

Fluorescence dynamics of biphenyl–ester moieties of two- or three-dimensional phases of a thermotropic liquid crystal were explored. In the 2D crystalline-to-3D cubic phase transition, a broad excitation band centered at 280 nm and a 10 nm fluorescence redshift were observed. A drastic change in the fluorescence time-decay constant from ∼90 to ∼130 ps was seen. These changes resulted from cooperative contribution of intermolecular configurational change from biphenyl–biphenyl to biphenyl–ester and polarity alterations surrounding the charge transfer emissive chromophores. The material exhibited higher charge transfer emissions in the cubic and columnar 3D phases than in the 2D crystalline phase.