| Abstract: | ![]()
Within the framework of a procedure proposed previously for fragment-by-fragment quantum-chemical calculation of aggregates of molecules with π-electronic chromophore groups, account is taken of hyperconjugation, which allows practically exact reproduction of results obtained by the all-valence CNDO/S method. Calculations of excited electronic states of sandwichlike Mg-chlorin (Mg-Ch)2 and Mg-bacteriochlorin (Mg-BCh)2 dimers with variation of the interplanar distance between monomers are made. It is shown that on passing from a Mg-porphin dimer to the (Mg-Ch)2 and (Mg-BCh)2 dimers there is a considerable decrease in the energies of charge-transfer states, which are resonant in nature (CR-states). Moreover, (Mg-BCh)2 has a considerably reduced energy interval between the lower CR-state and the forbidden component of the lower Q-state, which is indicative of easier charge separation in the lower excited electronic singlet states under the action of the field of the environment of tetrahydroporphyrin dimers than of dimers of porphyrins and hydroporphyrins, which can be of biological importance. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 2, pp. 166–175, March–April, 1998. |
