How Dispersion Interactions at the Excited State Can Tune Photochromism of Embedded Chromophores

Guido, Ciro A.Cupellini, LorenzoMennucci, BenedettaCurutchet Barat, Carles E.2026-01-222026-01-140002-7863https://hdl.handle.net/2445/225923We present QM/MMPol-cLR3, a polarizable embedding quantum mechanics/molecular mechanics (QM/MM) framework that includes explicit, state-specific dispersion terms. This method enables a rigorous treatment of dispersion on top of electrostatic and induction effects in ground- and excited-state calculations. Using QM/MMPol-cLR3, we show that dispersion interactions control excited-state solvatochromism through two distinct mechanisms. In azulene, opposite shifts of the La and Lb states arise from state-specific dispersion linked to changes in excited-state polarizability. In bacteriochlorophyll a, dispersion instead stems from the interplay between polarizability changes and transition-dipole-driven response, governing the Qy and Qx shifts. Finally, application to the LH2 complex reveals pigment-dependent dispersion shifts between the B800 and B850 rings, impacting the excitation-energy transfer. These results establish dispersion as an essential, nonempirical component for predictive excited-state simulations in complex environments.11 p.application/pdfeng(c) American Chemical Society, 2026Col·loidesPolaritatDissolventsColloidsPolaritySolventsHow Dispersion Interactions at the Excited State Can Tune Photochromism of Embedded Chromophoresinfo:eu-repo/semantics/article7641762026-01-22info:eu-repo/semantics/embargoedAccess