Car–Parrinello molecular dynamics of QMAP‑DMSO microsolvation: first‑shell structure and solvent‑induced polarization

Abstract

Context Directional solute–solvent contacts can influence the electrostatic response of donor–acceptor chromophores, although such local effects are often represented only as averaged contributions in continuum solvent models. Quinolinylaminophenol (QMAP) in dimethyl sulfoxide (DMSO) was examined as an explicit first-shell microsolvation model to clarify how local solvent organization couples to QMAP conformation and dipolar response. The Car–Parrinello molecular dynamics trajectory indicates a geometric reorganization around 12–13 ps, accompanied by changes in the first-shell DMSO dipolar arrangement. Within the limitations of the finite microsolvated model, these results suggest that transient first-shell solvent organization contributes to the modulation of the local electrostatic environment of QMAP, rather than acting only as a static dielectric background. Methods The gas-phase QMAP geometry was optimized at the CAM-B3LYP/6–311+ +G(d,p) level using Gaussian 16. The explicit QMAP–DMSO model contained one QMAP molecule and 21 DMSO molecules in a periodic cubic cell and was propagated by Car–Parrinello molecular dynamics using the CPMD code. The production trajectory was obtained with the PBE exchange–correlation functional, Troullier–Martins norm-conserving pseudopotentials, a plane-wave basis set, NVT equilibration at 300 K, and a restarted thermostatted CPMD production protocol, with a total analyzed trajectory length of approximately 32 ps. Structural, hydrogen-bond, dipole-moment, IR-like, and orientational-correlation analyses were carried out using in-house Python scripts.