Photochromic properties of dithienylazoles and other conjugated diarylethenes

Using an ab initio approach explicitly taking into account bulk solvent effects, we have investigated open- and closed-ring diarylethenes derivatives presenting conjugated bridging units. It turns out that the topology of the open-ring form's LUMO is correlated to the (non-)photochromic character. In addition, the visible spectra of 29 closed-ring compounds have been investigated. After statistical correction, the average (maximal) theory/experiment discrepancy is limited to 6 nm (13 nm), allowing an accurate theoretical colour design for this class of diarylethenes. It is also demonstrated that no simple correlation does exist between the ground-state dipole moment or the bond length alternation and the λmax.