Optical properties and photo-coloration of furylfulgide single crystal

Abstract

Optical properties of the E-form single crystals of furylfulgide (2-[1-(2,5-dimethyl-3-furyl)-ethylidene]-3-isopropylidenesuccinic anhydride) have been studied through measurements of polarized reflection, absorption and luminescence spectra at 2 K. In the E⊥b configuration, a weak absorption band accompanied by the phonon sidebands is found at the lower energy side of an intense lowest π → π ∗ transition band. Photo-excitation of the weak absorption band does not induce any photo-reaction, but is followed by a radiation of luminescence. On the other hand, photo-excitation of the intense π → π ∗ band gives rise to the E → C photo-isomerization. Polarized absorption and luminescence spectra after the photoisomerization show that the photo-produced C-form molecules form a highly oriented thin film. The thickness of the film, estimated from the peak intensity of the absorption band, is more than 57 nm, which suggests that the E-form molecules inside the crystal can also change to C-form by irradiation of UV light.