Molecular interactions of 1,4-dihydropyridine derivatives with selected organic solvents: A volumetric, spectroscopic and computational study

Using a combination of volumetric measurements and FTIR spectroscopy, solute–solvent interactions have been investigated for 1,4-DHPs in selected organic solvents that mimic the environments of drug production, delivery and the environment from which they reach the site of its activity. Vibrational analysis of 1,4-DHPs and 1,4-DHPs complexes with the solvents has been performed on a medium–high quantum chemical level. Uncharged 1,4-DHPs act in a protic solvent as hydrogen bond acceptors, mainly via the carbonyl group, and, in all other investigated solvents, as a hydrogen bond donor via the hydrogen on the nitrogen. The behaviour of amlodipine besilate differs significantly from that of other compounds. Volumetric measurements proved an effective method for investigating the interactions of uncharged and charged 1,4-DHPs with solvents, and correlated well with FTIR spectroscopy results. This approach can be extended to consider several solvent molecules, perform thermal averaging and to calculate the vibrational spectrum beyond the harmonic approximation. Atomic simulation of antagonistic activity of this class of compounds, by considering the receptor site and the ionic channel, remains a challenge for future decades.