Abstract
During the first eight months of the second contract period substantial progress was made on a number of the projects proposed. Ab initio configuration interaction calculations on magnesium prophine, porphine, magnesium chlorin, and chlorin were completed, and the electronic structure and properties (e.g. transition energies and oscillator strengths) of their low-lying singlet and triplet states analyzed. Preliminary results from similar calculations on ethyl pheophorbide a and ethyl chlorophyllide a were also obtained, and a detailed analysis of these results is in progress. In order to investigate the geometric aspects of monomeric and aggregated chlorophyll systems, extensive characterization and development of empirical potential functions was undertaken. A set of potential functions suitable for the study of chlorophyll-type systems has been obtained, and initial studies on the geometry of ethyl chlorophyllide a were completed with excellent results. Currently, conformational analysis of chlorophyllide macrocycle substituents is being carried out to assess the presence of energetically important conformational states. Methodology assessment, development, and implementation was also continued. Of particular importance in this regard is the implementation of an N/sup 5/ algorithm for transforming atomic into molecular two-electron integrals. Work has continued on basis set development, and double-zeta quality basis sets are now available formore » carbon, nitrogen, and oxygen. Development of comparable single-zeta basis sets and inclusion of polarization functions in the double-zeta basis sets are currently being investigated.« less
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