Computational study of Be, Mg and Ca cations interacting with Isatin

Abstract

Theoretical investigation of isatin (Is) interaction with Be²⁺, Mg²⁺, and Ca²⁺ cations has been performed at the B3LYP/6-311G (d, p) level of Density Functional Theory (DFT). Be-Is_a, Mg-Is_a, Ca-Is_a, Be-Is_b, Mg-Is_b, Ca-Is_b complexes show -324.37, -192.55, -144.15, -230.482, -113.581, -72.23 kcal/mol interaction energy. Topology analyses such as the Quantum Theory of Atoms in Molecules (QTAIM) and the non-covalent index (NCI) analysis based on the reduced density gradient (RDG) method indicate that the interactions between the isatin and Be²⁺ cation are more substantial than those of the other cations. The non-covalent interactions between Is molecule and Be²⁺, Mg²⁺, and Ca²⁺ cations are evidenced by the colour-filled RDG isosurfaces. The aromaticity change of phenyl induced upon complex formation was evaluated with the Harmonic Aromaticity Oscillator Model (HOMA) index. The vertical electron affinity (VEA) and the vertical ionization energy (VIE) for Is molecule, Be²⁺, Mg²⁺, and Ca²⁺ cations and their complexes were calculated and Electron Donor-Acceptor Map (DAM) was drawn.