DFT calculation of the interplay effects between cation–π and intramolecular hydrogen bond interactions of mesalazine drug with selected transition metal ions (Mn+, Fe2+, Co+, Ni2+, Cu+, Zn2+)

Density functional theory calculations are performed to determine the effect of cation- π and intramolecular hydrogen bond (IMHB) interactions on each other in the formed complexes between transition metal cations (Mn + , Fe 2+ , Co + , Ni 2+ , Cu + , Zn 2+ ) with mesalazine drug. The strength of these interactions is evaluated by energetic, geometric, spectroscopic and topological parameters to explore the mutual effects between them. Atomic charge distribution and characterization of bonds in the studied systems are investigated by natural bond orbital and atoms in molecules analyses, respectively. Our findings show that the presence of IMHB increases the energies of cation– π interaction for the divalent complexes and Co + complex, while for the other monovalent complexes the reverse process is observed. The results also display that, in most cases, the coexistence of IMHB and cation– π interactions decreases the IMHB strength.