Thermodynamic of solvation, solute - Solvent electron transfer and ionization potential of BSCAPE molecule and its UV-vis spectra in aqueous solution.

The molecular system 2-Phenylethyl (2E)-3-(1-benzenesulfonyl-4,5-dihydroxyphenyl) acrylate (BSCAPE) is a phenolic acid that covers a large spectrum of biological properties. The investigations of solvation and oxidation processes of BSCAPE molecule by computational means were the challenge of this present work. Water was required for solvation throughout the work. The explicit HO were sequentially added to form the complexes BSCAPE(HO). The discrete - continuum model was at the heart of this work. DFT and TD-DFT both associated to the continuum model SMD were required. Hence, the structures, the solvation energies, the energies of solute - solvent electron transfer (SSET), the ionisation potential (IP), and the UV-vis spectra were studied. It comes out that, the structure of the CAPE part included in BSCAPE agrees well with the available experimental values of CAPE but with a minor influence due to the presence of benzensulfonyl group. The enthalpy and free energy of solvation increase linearly with nHO. The global reactivity indexes were assessed to appreciate the oxidation of BSCAPE. The latter quality was strongly assessed by the enthalpy and free energy of SSET and IP. The SSET potential increase with nHO and the size of water clusters. The values 723.16 and 711.62 kJ/mol were found for enthalpy and free energy of IP respectively. Then in aqueous solution, the results fall down and upon addition of nHO, they approach gas phase value for 11HO and still are not stabilized. Therefore, the resistance to oxidation starts to raise at this level. Elsewhere, the UV-vis spectra of BSCAPE present four important peaks about 279.3, 234.8, 208.4 and 199.4 nm in gaseous state. The excitation shifts to the red as the number of HO increase. Their oscillator strengths also increase with solvation.