Modeling solvent effects on the nonlinear optical response of QMAP: a combined molecular dynamics and DFT study

In this work, we present a comprehensive theoretical investigation of the nonlinear optical response of the 4-(quinolin-2-ylmethylene)aminophenol (QMAP) molecule under different solvation regimes. Using a combined molecular dynamics (MD) and density functional theory (DFT) approach, we explore the effects of vacuum, implicit solvation (PCM), and explicit aqueous environments on the molecule's electronic and nonlinear optical properties. Classical MD simulations are employed to assess the structural and energetic stability of a QMAP crystal composed of eight molecular units in water, revealing that the crystal remains intact. Subsequently, quantum chemical calculations are performed on representative conformations extracted from the solvated system to evaluate dipole moments, polarizabilities, and hyperpolarizabilities. Our results demonstrate that explicit solvent models significantly enhance the nonlinear behavior compared to implicit and vacuum approaches, underscoring the crucial role of solute–solvent interactions and conformational fluctuations in modulating the electro-optical behavior. This integrated multiscale methodology bridges the gap between theoretical predictions and experimental observables, providing valuable insights for the rational design of solvent-sensitive optoelectronic materials.