Theoretical modeling of complex molecular machines in solution environments

What is it about?

A recently released third-generation artificial photo-molecular motor, featuring two photo-switchable rotating moieties in connection with a pseudo-asymmetric molecular center, is investigated by combining Quantum-Mechanics (QM) algorithms with classical molecular dynamics (MD) propagators. In particular, we have addressed such a molecular motor in different rotational isomers following the experimental observations arising from the application of multiple spectroscopic techniques in dilute solutions. At first, we focused our attention on the reproduction of the UV/Vis absorption spectrum in two solvents (acetonitrile and cyclohexane) with several gradient-corrected Density Functional Theory functionals in conjunction with the Conductor-like and Polarizable Continuum model (C-PCM). Furthermore, we refine the absorption signals by combining a classical MD sampling at room-temperature with DFT-based electronic degrees of freedom to define perturbed excitation wavelengths driven by thermal fluctuation and solvation effects. In this respect, we have modeled the investigated artificial motor within solution nanodroplets with solvent molecules treated contextually at atomistic level and via a dielectric and polarizable continuum model.

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Photo by Mike Hindle on Unsplash

Photo by Mike Hindle on Unsplash

Why is it important?

This contribution basically highlights once more the potentialities of modern and hybrid (QM(MM) computational techniques to fully simulate complex and flexible devices in which external stimuli can finely modulate energy-conversion schemes working at the nanoscale level. Moreover, we fully characterized the perturbed electronic degrees of freedom responsible for the interaction of the first-released molecular rotor with light photons.

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