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A combined Monte Carlo/ DFT approach to simulate UV ‐vis spectra of molecules and aggregates: Merocyanine dyes as a case study
Author(s) -
Tirri Bernardino,
Mazzone Gloria,
Ottochian Alistar,
Gomar Jerôme,
Raucci Umberto,
Adamo Carlo,
Ciofini Ilaria
Publication year - 2021
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.26505
Subject(s) - monte carlo method , density functional theory , chromophore , merocyanine , chemistry , spectral line , molecular dynamics , computational chemistry , monomer , absorption spectroscopy , molecule , statistical physics , chemical physics , physics , quantum mechanics , photochemistry , polymer , mathematics , statistics , organic chemistry
The combination of a Monte Carlo (MC) sampling of the configurational space with time dependent‐density functional theory (TD‐DFT) to estimate vertical excitations energies has been applied to compute the absorption spectra of a family of merocyanine dyes in both their monomeric and dimeric forms. These results have been compared to those obtained using a static DFT/TD‐DFT approach as well as to the available experimental spectra. Though suffering of the limitations related to the use of DFT and TD‐DFT for this type of systems, our data clearly show that the classical MC sampling provides a suitable alternative to classical molecular dynamics to explore the structural flexibility of these donor‐acceptor (D‐π‐A) chromophores enabling a realistic description of the potential energy surface of both their monomers and aggregates (here dimers) and thus of their spectra. Overall, the combination of MC sampling with quantum mechanics (TD‐DFT) calculations, carried out in implicit dioxane solvent on random snapshots, provides a workable compromise to solve the combined challenge of accuracy and time‐consuming problem not only for merocyanines momers, but also for their dimers, up to now less investigated. Indeed, the simulated absorption spectra fairly agree with the experimental ones, suggesting the general reliability of the method.