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The present work utilizes density functional theory (DFT) calculations to study the influence of cation–π interactions on the electronic properties of the complexes formed by Altretamine [2,4,6-tris(dimethylamino)-1,3,5-triazine], an anticancer drug, with mono- and divalent (Li+, Na+, K+, Be2+, Mg2+ and Ca2+) metal cations. The structures were optimized with the M06-2X method and the 6-311++G(d,p) basis set in the gas phase and in solution. The theory of `Atoms in Molecules' (AIM) was applied to study the nature of the interactions by calculating the electron density ρ(r) and its Laplacian at the bond critical points. The charge-transfer process during complexation was evaluated using natural bond orbital (NBO) analysis. The results of DFT calculations demonstrate that the strongest/weakest interactions belong to Be2+/K+ complexes. There are good correlations between the achieved densities and the amounts of charge transfer with the interaction energies. Finally, the stability and reactivity of the cation–π interactions can be determined by quantum chemical computation based on the molecular orbital (MO) theory.

In the current research, a comparative study of the interplay effects between cation–π and intramolecular hydrogen bond (IMHB) interactions is performed on the complexes of mesalazine with Li+, Na+, K+, Be2+, Mg2+ and Ca2+ cations using density functional theory (DFT). For this purpose, the mesalazine analogue and the equivalent values of 3-aminobenzoic acid complexes with the cited cations are selected as a set of reference points. In order to understand the mutual effects between these interactions, the descriptors of geometrical, binding energies, topological properties and charge transfer values are examined on complexes using the atoms in molecules (AIM) and natural bond orbital (NBO) analyses. Results indicate that with the exception of Be2+ complex, the coupling simultaneously weakens both of the interactions. Finally, the physical properties such as energy gap, chemical hardness as well as electronic chemical potential of complexes are systematically analyzed by using frontier molecular orbitals.

In this study, the structural and electronic effects of the interaction of the metal cations (Li+, Na+, K+, Be2+, Mg2+, Ca2+) with the π‐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 (ρ) and the Laplacian (∇2ρ), estimated by AIM calculations, indicate that the bond between the cations and the PhA possesses low ρ and positive ∇2ρ 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–π interactions in the studied complexes.

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