Linked Life Data

16836420

Source:http://linkedlifedata.com/resource/pubmed/id/16836420

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
28
pubmed:dateCreated
2006-7-13
pubmed:abstractText
The photophysical characterization of the two tautomers (1e and 1i) of 5,10,15,20-tetraphenyl N-confused free-base porphyrin, as well as the tautomer-locked 2-methyl 5,10,15,20-tetraphenyl N-confused free-base porphyrin, was carried out using a combination of steady state and time-resolved optical techniques. N-Confused porphyrins, alternatively called 2-aza-21-carba-porphyrins or inverted porphyrins, are of great interest for their potential as building blocks in assemblies designed for artificial photosynthesis, and understanding their excited-state properties is paramount to future studies in multicomponent arrays. Femtosecond resolved transient absorption experiments reveal spectra that are similar to those of tetraphenylporphyrin (H2TPP) with either Soret or Q-band excitation, with an extinction coefficient for the major absorbing band of 1e that was about a factor of 5 larger than that of H2TPP. The lifetime of the S1 state was determined at a variety of absorption wavelengths for each compound and was found to be consistent with time-resolved fluorescence experiments. These experiments reveal that the externally protonated tautomer (1e) is longer lived (tau = 1.84 ns) than the internally protonated form (1i, tau = 1.47 ns) by approximately 369 ps and that the N-methyl N-confused porphyrin was shorter lived than the tautomeric forms by approximately 317 ps (DMAc) and approximately 396 ps (benzene). Steady-state fluorescence experiments on tautomers 1e and 1i and the N-methyl analogues corroborate these results, with fluorescence quantum yields (Phi(Fl)) of 0.046 (1e, DMAc) and 0.023 (1i, benzene), and 0.025 (DMAc) and 0.018 (benzene) for the N-methyl N-confused porphyrin. The lifetime and quantum yield data was interpreted in terms of structural changes that influence the rate of internal conversion. The absorption and transient absorption spectra of these porphyrins were also examined in the context of DFT calculations at the B3LYP/6-31G(d)//B3LYP/3-21G(d) level of theory and compared to the spectra/electronic structure of H2TPP and tetraphenyl chlorin.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
1089-5639
pubmed:author
pubmed:issnType
Print
pubmed:day
20
pubmed:volume
110
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
8605-12
pubmed:meshHeading
pubmed:year
2006
pubmed:articleTitle
Ultrafast spectroscopy of free-base N-confused tetraphenylporphyrins.
pubmed:affiliation
Department of Chemistry and The Center for Laser and Optical Spectroscopy, Knight Chemical Laboratory, The University of Akron, Akron, Ohio 44325-3601, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't