title: Structural investigation of microhydrated thymine clusters and vibrational study of isolated and aqueous forms of thymine using DFT level of theory.
abstract: This theoretical study provides the physically reasonable structures of the microhydrated thymine clusters, from the mono- to the penta-hydrated species, by the exploration of their B3LYP and B3LYP-D potential energy surfaces using a global search algorithm of minima (GSAM). The anharmonic vibrational computations of the isolated and aqueous thymine are also reported. They were performed from B3LYP and B3LYP-D potential electronic surfaces followed by a second order perturbative treatment of the anharmonicity. On that point, the computational strategy to properly take into account the effect of the polar protic solvent consists in considering a micro-hydrated thymine cluster [T,nH2O] surrounded by a polarizable continuum model (PCM). The number of solvent molecules was chosen in such a way that the micro-hydrated cluster presents only one dominant stable conformer at 298 K. All the VPT2 fundamental transitions obtained from the B3LYP and B3LYP-D quartic force fields are reported for the isolated form ([T,0H2O]) and for the aqueous form ([T,nH2O + PCM]). The theoretical results are compared to the available experimental data, which are for some of them reassigned, in order to assess the reliability of the B3LYP and B3LYP-D methods for the anharmonic treatment of such organic species in a polar protic solvent.
authors.affiliation: Groupe de Chimie Théorique et Réactivité, IPREM/ECP UMR CNRS 5254, Université de Pau et des Pays de l'Adour, F-64000 Pau, France.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Thicoipe
authors.forename: Philippe
authors.initials: P
authors.lastname: Carbonnière
authors.forename: Claude
authors.initials: C
authors.lastname: Pouchan
mesh_terms: D011789:Quantum Theory; D013941:Thymine / Q000737:chemistry*; D014732:Vibration; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D013941:Thymine