Département de chimie moléculaire

The excited-state relaxation of retinal protonated Schiff bases (PSBs) is an important test case for biol. applications of time-dependent (TD) d.-functional theory (DFT). While known shortcomings of approx. TD-DFT might seem discouraging for application to PSB relaxation, progress continues to be made in the development of new functionals and of criteria allowing problematic excitations to be identified within the framework of TD-DFT itself. Furthermore, exptl. and theor. ab initio advances have recently lead to a revised understanding of retinal PSB photochem., calling for a reappraisal of the performance of TD-DFT in describing this prototypical photoactive system. Here, the authors re-study the performance of functionals in (TD-)DFT calcns. in light of these new benchmark results, which the authors extend to larger PSB models. The authors focus on the ability of the functionals to describe primarily the early skeletal relaxation of the chromophore and study how far along the out-of-plane pathways these functionals are able to describe the subsequent rotation around formal single and double bonds. Conventional global hybrid and range-sepd. hybrid functionals were studied as the presence of Hartree-Fock exchange reduces problems with charge-transfer excitations as detd. by the Peach-Benfield-Helgaker-Tozer $Łambda$ criterion and by comparison with multi-ref. perturbation theory results. While most functionals cannot render the complex photobehavior of the retinal PSB, do also LC-BLYP gives the best description of the initial part of the photoreaction. (c) 2015 American Institute of Physics. [on SciFinder(R)]