Specific and non-specific solvent effects on chlorophyll a visible spectral maxima

Abstract The wavenumbers of the chlorophyll a S 0 –S 1 as well as Soret band maxima for 37 solvents were correlated with non-specific [polarity (e − 1/e + 2), polarizability ( n 2 − 1/ n 2 + 2)] and specific (electrophilicity, nucleophilicity, steric hindrance to solvation) solute—solvent interaction parameters using multi-parameter linear regression analysis. Besides the dominating influence of the non-specific dispersion interaction with the medium, hydrogen bonding is responsible for both bands' specific red shift of 100–200 cm −1 in protic solvents. The polarizability differences of S 0 and excited states have been evaluated on the basis of universal (non-specific) intermolecular interaction functions.