DFT computations on the hydrogen bonding interactions between methacrylic acid-trimethylolpropane trimethacrylate copolymers and letrozole as drug delivery systems

The hydrogen bonding interactions between letrozole (Let) anticancer drug and three copolymers of methacrylic acid-trimethylolpropane trimethacrylate (M1-M3 as molecular imprinted polymers) were studied using density functional theory (DFT) at both B3LYP and B3PW91 levels. The binding energies were corrected for the basis set superposition error (BSSE) and zero-point vibrational energies (ZPVE) so that the most negative Delta E-binding were measured for compounds 7 and 8 formed between M1 copolymer and endocyclic N1 and N2 atoms of drug, respectively. Also, among complexes 13-15 in which two copolymers were contributed in the formation of O-H center dot center dot center dot N bonds with the drug, compound 13 (containing two M1 copolymers) showed the highest Delta E-binding value. The interactions of all copolymers with drug were exergonic (spontaneous interaction) and exothermic. The QTAIM data supported the covalent character of the C-N, C-H, N-N, C-O, O-H and O-H center dot center dot center dot N bonds, the intermediate nature of C equivalent to N and C=O bonds while the electrostatic character of C-H center dot center dot center dot O, HC center dot center dot center dot HC and CH center dot center dot center dot N interactions. According to the Delta E-binding, Delta G(interaction) and Delta H-interaction values, it was suggested that t complexes 7 and 8 (among two particles systems) as well as complex 13 (among three particles systems) can be the most promising drug delivery systems.