Transient absorption spectra of excitation energy transfer in supramolecular complexes: A mixed quantum-classical description of pheophorbide-a systems

A mixed quantum-classical methodology is utilized to compute transient optical spectra reflecting excitation energy transfer in large pheophorbide-a complexes dissolved in ethanol. Room-temperature molecular dynamics simulations are used to describe the nuclear dynamics of the whole solvent–solute complex. The electronic excitation energy dynamics is accounted for by solving the time-dependent electronic Schrödinger equation. All computations are carried out in the framework of the ground-state classical path approximation and in the presence of optical excitations to determine the nonlinear response. A specification to a pump–probe scheme allows to determine spectra of transient anisotropy which offer signatures of a 10 ps excitation energy redistribution already found in earlier studies (Chem. Phys. Chem. 12, (2011) 645).