Temperature effects on the conformational dynamics and nonlinear optical properties of donor–acceptor Stenhouse adducts in chloroform solution

The conformational behavior and nonlinear optical properties of a donor–acceptor Stenhouse adduct (DASA) derivative in chloroform solution is investigated by combining molecular dynamics (MD) simulations with quantum chemistry calculations. MD simulations are carried out at three different temperatures in order to assess the thermal effects on the structural fluctuations of the solute and the shape of the solvation shell. Next, time-dependent DFT calculations combined either with implicit or explicit solvation models are performed on statistical samples of geometries extracted from the MD runs to assess the impact of temperature on the second harmonic response of the DASA molecule. We show that geometrical distortions, which push the molecule out of its cyanine-like equilibrium geometry, largely enhance the second harmonic intensity of the DASA, and that these effects become more important with increasing temperature.