Optical properties of solvated molecules calculated by a QMMM method Chlorophyll a and bacteriochlorophyll a

Abstract

We have applied a hybrid quantum mechanical–molecular mechanical (QMMM) approach to the calculation of electronic–vibrational coupling. To test the validity of this approach, we compare results to the steady state absorption and emission spectra of chlorophyll a (Chl-a) and bacterio-chlorophyll a (BChl-a). We find that the Stokes shift and the widths of the spectra are reasonably well represented while the amplitudes of the vibrational side band in both molecules are greatly underestimated.