Linked Life Data

12375962

Source:http://linkedlifedata.com/resource/pubmed/id/12375962

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
21
pubmed:dateCreated
2002-10-11
pubmed:abstractText
We describe a two-step conversion of C-alkylated zinc chlorins to zinc oxochlorins wherein the keto group is located in the reduced ring (17-position) of the macrocycle. The transformation proceeds by hydroxylation upon exposure to alumina followed by dehydrogenation with DDQ. The reactions are compatible with ethyne, iodo, ester, trimethylsilyl, and pentafluorophenyl groups. A route to a spirohexyl-substituted chlorin/oxochlorin has also been developed. Representative chlorins and oxochlorins were characterized by static and time-resolved absorption spectroscopy and fluorescence spectroscopy, resonance Raman spectroscopy, and electrochemistry. The fluorescence quantum yields of the zinc oxochlorins (Phi(f) = 0.030-0.047) or free base (Fb) oxochlorins (Phi(f) = 0.13-0.16) are comparable to those of zinc tetraphenylporphyrin (ZnTPP) or free base tetraphenylporphyrin (FbTPP), respectively. The excited-state lifetimes of the zinc oxochlorins (tau = 0.5-0.7 ns) are on average 4-fold lower than that of ZnTPP, and the lifetimes of the Fb oxochlorins (tau = 7.4-8.9 ns) are approximately 40% shorter than that of FbTPP. Time-resolved absorption spectroscopy of a zinc oxochlorin indicates the yield of intersystem crossing is >70%. Resonance Raman spectroscopy of copper oxochlorins show strong resonance enhancement of the keto group upon Soret excitation but not with Q(y)()-band excitation, which is attributed to the location of the keto group in the reduced ring (rather than in the isocyclic ring as occurs in chlorophylls). The one-electron oxidation potential of the zinc oxochlorins is shifted to more positive potentials by approximately 240 mV compared with that of the zinc chlorin. Collectively, the fluorescence yields, excited-state lifetimes, oxidation potentials, and various spectral characteristics of the chlorin and oxochlorin building blocks provide the foundation for studies of photochemical processes in larger architectures based on these chromophores.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0022-3263
pubmed:author
pubmed:issnType
Print
pubmed:day
18
pubmed:volume
67
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7329-42
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
Synthesis and electronic properties of regioisomerically pure oxochlorins.
pubmed:affiliation
Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S.