Avijit Sen - Photophysical and electrochemical redox properties of fixed distance porphyrin-quinone systems

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        Author(s):         Sen A,         Krishnan V     
        Source: JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY         A-CHEMISTRY    Volume: 123            Issue: 1-3    Pages: 77-85            Published:   1999       


  A few fixed distance covalently linked porphyrin-quinone   molecules have been synthesized in which a benzoquinone is   directly attached to a meso/beta-pyrrole position of   tri(phenyl/pentafluorophenyl)/tetraphenylporphyrins. The choice   of fluoroarylporphyrins permit modulation of Delta G(ET) values   for photoinduced electron-transfer reactions in these systems.   All short distance porphyrin-quinone molecules showed efficient   quenching of the porphyrin singlet excited state. The   electrochemical redox data coupled with the steady-state and   time-resolved singlet emission data are analysed to evaluate the   dependence of Delta G(ET) values on the rate of electron transfer   (k(ET)) in these systems. The   meso-trifluoroarylporphyrin-quinones are found to be sensitive   probes of the surrounding dielectric environment. Varying solvent   polarity on the mechanism of fluorescence quenching and k(ET)   values revealed that short donor-acceptor distance and the   solvent dielectric relaxation properties play a dominant role.

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