ИСТИНА

Multiconfigurational methods are often required for treating extended regions of potential energy surfaces of excited and ground electronic states and their crossings. Among various multiconfigurational approaches, multireference perturbation theory (MR-PT) methods are widely employed in the studies of photochemistry of large molecular systems. Here, we discuss a hierarchy of MR-PT2 methods and specifically the XMCQDPT2 version, which is a model-space invariant multistate multi-reference method based on the Van Vleck perturbation theory for effective Hamiltonians. We show that the XMCQDPT2 method provides accurate excited-state potentials and lifetimes for several biological chromophores. By using the high-level electronic structure theory, we also disclose the ways, by which the photoinduced dynamics of the retinal protonated Schiff base (RPSB) can be both significantly accelerated and, most notably, steered. The excited-state decay is rendered from slow picosecond to ultrafast sub-picosecond in the synthetically engineered locked retinal chromophore (L-RSB), becoming as fast as inside the evolutionary optimized retinal-binding protein pocket. Moreover, the unidirectional full rotation of L-RSB from all-trans to 9-cis and from 9-cis to all-trans proceeds in two distinct photoinduced steps, both of which are ultrafast. As a result, we get a rotary molecular motor, which addresses most, if not all, current challenges in the design principles of molecular motors featuring a double bond axle. We also show that the photoresponse of RPSB becomes vibrationally mode-specific inside rhodopsin proteins.