Two-dimensional electronic spectroscopy (2DES) based on ultrashort laser pulses is a cutting-edge technique to track electronic transitions in complex systems with unprecedented spectral and time resolution.^[1-4] 2DES can be used to investigate energy transfer, structure, conformation dynamics and chemical reactivity in a wide range of systems in physical chemistry, energy sciences and biophysics.^{[2, 5]} By spreading the information content of the nonlinear signal on two frequency axes, 2DES provides a wealth of novel information on molecular structure and dynamics with respect to the linear signal collected in traditional 1D experiments. However, the interpretation of 2D electronic spectra is challenging and computational modeling is required to disentangle the information contained in the nonlinear optical response of the sample. In this talk a computational tool^[6] that can be routinely applied to accurately simulate 2DES spectra of multichromophoric systems is introduced. Multiconfigurational and multireference perturbative methods have been used to reliably calculate the electronic properties of multichromophoric systems within a hybrid QM/MM scheme in conjunction with molecular dynamics techniques to assess environmental and conformational effects that shape the 2D electronic spectra. Applications of this methodology for the study of structure and folding dynamics of proteic systems^[7] in solution and photochemistry of retinal chromophores^[8] are showed, demonstrating that 2DES holds the promise to become a novel diagnostic tool complementary to well-established multidimensional NMR and 2DIR techniques.

[1] S. Mukamel Annu. Rev. Phys. Chem. 2000, 51, 691-729.

[2] T. Brixner, J. Stenger, H. M. Vaswani, M. Cho, R. E. Blankenship, G. R. Fleming Nature. 2005, 434, 625-628.

[3] M. H. Cho Chem. Rev. 2008, 108, 1331-1418.

[4] B. A. West, A. M. Moran J. Phys. Chem. Lett. 2012, 3, 2575-2581.

[5] N. S. Ginsberg, Y.-C. Cheng, G. R. Fleming Acc. Chem. Res. 2009, 42, 1352-1363.

[6] I. Rivalta, A. Nenov, G. Cerullo, S. Mukamel, M. Garavelli Int. J. Quantum Chem. 2014, 114, 85-93.

[7] A. Nenov, I. Rivalta, G. Cerullo, S. Mukamel, M. Garavelli J. Phys. Chem. Lett. 2014, 5, 767-771.

[8] I. Rivalta, A. Nenov, O. Weingart, G. Cerullo, M. Garavelli, S. Mukamel J. Phys. Chem. B. 2014,8, 8396-405