Theoretical study on the interaction of phenylalaninal with group IA (Li+, Na+, K+) and IIA (Be2+, Mg2+, Ca2+) metal cations

In this study, the structural and electronic effects of the interaction of the metal cations (Li+, Na+, K+, Be2+, Mg2+, Ca2+) with the pi-system of phenylalaninal (PhA) are investigated using the M06-2X method and the 6-311++G(d,p) basis set in the gas phase and the solution. The quantum theory of atoms in molecules (QTAIM) is applied to elucidate the interaction characteristics of these complexes. Properties of the electron density (rho) and the Laplacian ( backward difference (2)rho), estimated by AIM calculations, indicate that the bond between the cations and the PhA possesses low rho and positive backward difference (2)rho values. Moreover, the natural bond orbital (NBO) analysis is performed to understand the orbital interactions and the charge delocalization during complexation. To achieve better insight on the mentioned interactions, physical properties such as the energy gap, electronic chemical potential, chemical hardness, softness, and global electrophilicity power are investigated. Several correlations based on the topological, geometrical, and energetic parameters are suggested for investigating the cation-pi interactions in the studied complexes.