From Computational Photobiology to the Design of Vibrationally Coherent Molecular Devices and Motors

In the past multi-configurational quantum chemical computations coupled with molecular mechanics force fields have been employed to investigate spectroscopic, thermal and photochemical properties of visual pigments. [1,2] Here we show how the same computational technology can nowadays be used to design, characterize and ultimately, prepare light-driven molecular switches which mimics the photophysics of the visual pigment bovine rhodopsin (Rh) [2,3]. When embedded in the protein cavity the chromophore of Rh undergoes an ultrafast and coherent photoisomerization. In order to design a synthetic chromophore displaying similar properties in common solvents, we recently focused on indanylidene-pyrroline (NAIP) systems. [3,4] We found that these systems display light-induced ground state coherent vibrational motion similar to the one detected in Rh. Semi-classical trajectories provide a mechanistic description of the structural changes associated to the observed coherent motion which is shown to be ultimately due to periodic changes in the $\pi $-conjugation. \\[4pt] [1] I. Schapiro, M. N. Ryazantsev, L. M. Frutos, N. Ferr\'{e}, R. Lindh {\&} M. Olivucci; \textit{J Am Chem Soc }\textbf{2011}\textit{, 133}, 3354. \\[0pt] [2] S. Gozem, I. Schapiro, N. Ferr\'{e}, M. Olivucci; \textit{Science} \textbf{2012}, \textit{337}, 1225.\\[0pt] [3] A. Melloni, R. Rossi Paccani, D. Donati, V. Zanirato, A. Sinicropi, M. L. Parisi, E. Martin, M. Ryazantsev, W. J. Ding, L. M. Frutos, R. Basosi, S. Fusi, L. Latterini, N. Ferr\'{e}, M. Olivucci; \textit{J Am Chem Soc} \textbf{2010},\textit{ 132}, 9310. \\[0pt] [4] J. L\'{e}onard, I. Schapiro, J. Briand, S. Fusi, R. Rossi Paccani, M. Olivucci, S. Haacke \textit{Chem Eur J }\textbf{2012}, \textit{18}, 15296.