QUANTUM CHEMICAL MODELING OF THE EFFECT OF INTRAMOLECULAR HYDROGEN BONDING OF MALEIC ACID ON THE STRUCTURE OF MALEIC π-AQUACOMPLEXES СOPPER(I)

Анотація

The article investigates the influence of intramolecular hydrogen bonding in the maleic acid molecule on the structure and stability of π-acidoaqua complexes of copper(I) using quantum-chemical modeling (DFT/B3LYP). A comparative analysis of geometric and energy parameters between π-acidoaquacomplexes with maleic acid of different structures with and without intramolecular hydrogen bonding was performed. The features of the coordination of Cu⁺ ions with the unsaturated C=C fragment of maleic acid, as well as the interaction with water molecules in the internal coordination sphere, are considered. It is shown that the presence of an intramolecular hydrogen bond in the acid molecule only partially affects the electronic energy of the system, but is able to stabilize some complexes, in particular [Cu(С₄Н₃О₄)(H₂O)₂]⁰ and [Cu(С₄Н₃О₄)(H₂O)₃]⁰, compared with the results of modeling without taking into account the intramolecular hydrogen bond. An analysis of the topology of the electron density was carried out, critical points were identified, which indicate the formation of six- and seven-membered rings in structures with an intramolecular hydrogen bond. It is shown that in complexes with intramolecular hydrogen bond for acids deprotonated by the first degree, a slight unfolding of the carboxyl group was observed. And it also significantly affects the distribution of the effective charge, in particular Cu⁺ ions. Calculations showed that intramolecular hydrogen bonding reduces the electron density that maleic acid transfers to the Cu⁺ ion, which affects the effective charge of the latter, as well as the dπ-pπ-binding energies. The obtained results complement the data of previous studies and allow a better understanding of the role of intramolecular interactions in the stabilization of π-complexes of Cu(I) with bifunctional ligands.