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- Title
Photophysical properties of porphyrins with sterically distorted and partially screened macrocycles.
- Authors
Ivashin, N.; Shchupak, E.; Panarin, A.; Sagun, E.
- Abstract
We have experimentally studied the spectral-luminescent and photophysical properties, as well as interaction processes with molecular oxygen, of eclipsed β-alkyl-substituted porphyrins para-methoxyphenyl rings of which in opposite meso-positions of the macrocycle are linked with each other in the ortho-position with the (-OCH)-Ph-(CHO-) bridge. Using methods of the density functional theory, we have calculated the structures of these porphyrins in the ground and lowest triplet states, electronic transitions and vibrational states, and matrix elements of the direct spin-orbit interaction. It has been found that the lifetime of the T state of the investigated compounds is noticeably shortened due to the enhancement of the internal conversion. This enhancement is caused by the conformational dynamics, which promotes increasing Franck-Condon factors and the spin-orbit interaction between the T and S states. Nevertheless, this does not lead to a considerable decrease in the singlet-oxygen formation quantum yield. We have calculated the structures of a porphin dimer and possible dimeric forms of examined porphyrins. It has been shown that distortion of the porphyrin macrocycle according to type of ruffling weakly affects the binding energy of the porphyrin macrocycles in the dimer, this effect being unable to prevent aggregation. At the same time, the screening of the macrocycle by the phenyl ring lowers the probability of formation of oligomeric structures, which, in view of the determined photophysical properties of investigated compounds, may be used in photochemical applications that require elevated concentrations of porphyrins.
- Subjects
PORPHYRINS; STERIC factor (Chemistry); MACROCYCLIC compounds; OLIGOMERS; FRANCK-Condon principle
- Publication
Optics & Spectroscopy, 2015, Vol 118, Issue 6, p882
- ISSN
0030-400X
- Publication type
Article
- DOI
10.1134/S0030400X15060107