Reversible switching of molecular nonlinear optical properties of photochromic diarylethene systems

The vibrational contribution to the third-order molecular hyperpolarisability, γv, of a series of dithienylethenes in the two isomeric forms has been measured, revealing that a large change in nonlinear optical (NLO) response accompanies the photochromic process, thus opening a window on the possibility of application of such systems as switching NLO materials. The variation of γv which accompanies the photochromic process is strongly dependent on the molecular design and the electronic effect of the subsituents. Moreover, the closed form of diarylethene bearing strong electro-donor substituent in 5,5′-positions on thiophene ring exhibits large γv.