Molecular design principles for biomimetic solar-energy conversion systems. Final progress report, 1985

Technical Report · Wed Jan 01 00:00:00 EST 1986

OSTI ID:5293954

Maggiora, G M

Theoretical chemical studies of excited charge-transfer (CT) states of porphyrin heterodimers and molecular exciton states of methyl bacterio-pheophorbide ..cap alpha.. crystals were carried out using a configuration interaction (CI) approach. The influence of dimer geometry and microenvironmental effects on CT states was investigated. Microenvironmental effects tend to dominate geometry effects so that with proper microenvironmental tuning it is possible to stabilize the lowest excited CT state, (a MgP ..-->.. P CT state) such that it becomes the lowest excited singlet state whose lifetime is influenced by radiationless pathways, some of which are important in photo-induced electron transfer processes. A generalized molecular exciton theory approach, analogous in form to the CI procedure employed in the study described above, was used to investigate the large spectral red shifts observed in aggregated photosynthetic pigments. Although the magnitude of the calculated spectral shift was less than that observed experimentally, a number of insights of importance in the application of molecular exciton theory to macrocyclic aggregates were obtained. In particular, use of the dipole approximation for evaluating intermolecular electrostatic interactions was shown to produce significant errors, while use of distributed point-charge models yielded results in much closer agreement with exact values. In addition, neighboring group effects and the need for charge-resonance configurations were also described. 12 refs.

• Research Organization: Kansas Univ., Lawrence (USA)
• DOE Contract Number: AC02-76ER02837
• OSTI ID: 5293954
• Report Number(s): DOE/ER/02837-10; ON: DE86015897
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
PORPHYRINS
CHARGE STATES
STRUCTURE-ACTIVITY RELATIONSHIPS
CHARGE TRANSPORT
ELECTRON TRANSFER
MATHEMATICAL MODELS
CARBOXYLIC ACIDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
140505* - Solar Energy Conversion- Photochemical
Photobiological
& Thermochemical Conversion- (1980-)