DFT, solvation effects, reactivity and SERS analysis on structural, optical, and vibrational properties of a biomolecule of pyrimidine derivative adsorbed on metal clusters of Ag/Au/Cu

Density Functional Theory (DFT) computations were performed to investigate the optical properties of dihydropyrimidine (DHP) and metal clusters of copper (Cu), gold (Au), and silver (Ag). The charge transfers from the metal cluster to DHP through the NH group are revealed by molecular electrostatic potential (MEP) surface and Mulliken charge analysis. Bonding and antibonding orbitals of the DHP-adsorbed metal clusters are responsible for the surface resonance peak in the UV-Vis spectra of DHP adsorbed metal clusters. The polarizability values of DHP-adsorbed on metal clusters are very high in comparison with that of pristine DHP, which suggests an increase in the Non-linear optical (NLO) effect. Our study explores that the DHP adsorbed metal clusters could be used for the NLO materials. The vibrational modes of DHP are enhanced in the DHP adsorbed metal clusters due to surface-enhanced Raman scattering (SERS). Solvation energy is found to be -21.01, -29.37, and -27.82 kcal/ mol for DHP-Ag3/Au3/Cu3 which means the DHP-adsorbed metal clusters are stable in thr aqueous medium. The atom in molecule-reduced density gradient (AIM-RDG) isosurface shows weak non-covalent interactions in each DHP adsorbed metal clusters.