Spirooxazine-based multifunctional molecular switches with tunable photochromism and nonlinear optical response

A new type of organic photochromic spirooxazine has been synthesized, incorporating increasing numbers of thiophene units by vinyl bridges. These compounds exhibit tunable photochromic properties that are sensitive to low-energy visible light compared with traditional UV. Furthermore, the ring-opening mechanism is put in relation to the interaction of fragment molecular orbitals. The result shows that the effective excitation with significant intensity is centred mainly on the naphthoxazine part and vinyl thiophene plays a crucial role in the photochemical and photophysical process. Density functional calculations are performed to rationalize the "on and off" switching nonlinear optical behaviors of compounds, showing the potential for applying the materials in nonlinear optical switches.