One- and two-photon photochromism of 3,4-bis-(2,4,5-trimethyl-thiophen-3-yl)furan-2,5-dione

Photochromic properties of the diarylethene derivative 3,4-bis-(2,4,5-trimethyl-thiophen-3-yl)furan-2,5-dione (1) were investigated in hexane at room temperature under one-photon (linear) and two-photon (nonlinear) excitation. Results of steady-state excitation anisotropy and quantum–chemical calculations (AM1, ZINDO/S) provide insight into the nature of the broad absorption spectrum of the open-form of 1 as an overlapped mixture of several electronic transitions. The quantum yields of cyclization and cycloreversion reactions of 1 were obtained over a broad spectral range and the photochemical stability of 1 was determined for different excitation wavelengths. The two-photon absorption (2PA) spectrum of the open-form of 1, with maximum cross-section ≈80 GM at 674 nm, was obtained using an up-converted fluorescence method. Two-photon induced cyclization reaction of 1 was accomplished under picosecond excitation and the corresponding reaction quantum yield was estimated, providing a comprehensive investigation of this 2PA photochrome.