title: A TDDFT/EFP1 study on hydrogen bonding dynamics of coumarin 151 in water.
abstract: Change in energy of hydrogen bonds (HBs) upon excitation, plays an important role on the spectra of chemical and biological molecules. Effective fragment potential (EFP) method of explicit water molecules embedded in polarizable continuum medium (PCM) is used for the solvation of 7-Amino-4-(trifluoromethyl)coumarin (C151). Time dependent density functional theory (TDDFT) calculations combined with EFP/PCM had been carried out to study the electronic structure and the exited state properties of C151 with five water molecules (C151-(H2O)5 complex). S0 state and S1 state geometries were optimized using DFT/TDDFT with PBE0 functional combined with cc-pVDZ basis set, the transition energies are computed with same basis set and functional. Change in HB energy is calculated using the procedure proposed by T. Nagata et al. to calculate solute-solvent interaction energy in Nagata et al. (2011). Upon photoexcitation of C151-(H2O)5 complex, A type (N⋯H-O) HB is weakened with decrease of energy by 4.37 kJ/mol, whereas B and C type (C=O⋯H-O and N-H⋯O) HBs are strengthened with increase of 5.62 and 10.21 kJ/mol energy, respectively. This study again confirmed that the intermolecular hydrogen bonds between C151 chromophore and aqueous solvents are strengthened, not cleaved upon electronic excitation.
authors.affiliation: PG Department of Physics, Govt. College (Autonomous), Mandya 571401, India. Electronic address: hmrgowda@yahoo.com.
authors.forename: Mariyappa
authors.initials: M
authors.lastname: Ramegowda
mesh_terms: D003374:Coumarins / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D003374:Coumarins; C521215:coumarin 151; D014867:Water
keywords: C151–(H(2)O)(5) complex; DFT; EFP; PBE0; TDDFT; cc-pVDZ