A theoretical study of the perfluoro-diarylethenes electronic spectra

Using a combination of the time-dependent density functional theory and the polarizable continuum model, we have investigated the visible spectra of 129 closed-ring perfluorocyclopentene diarylethenes, solvated in various environments (185 cases). The theoretical simulations are able to reproduce the major experimental trends, especially the auxochromic shifts though solvatochromic effects in protic media are not correctly modelled. A quantitative agreement, that is mean absolute deviations limited to 13 nm or 0.05 eV, is reached with a simple linear regression. The topology of the frontier orbitals qualitatively support the role played by side groups, heteroatoms, as well as isomerism in the absorption phenomenon. Within similar structures, the bond length alternation in the central part of the photochrom can be related to the longest wavelength of maximal absorption (λmax⁡λmax⁡). In addition, a correlation between the central bond length and the thermal stability of the closed-ring form is unravelled.