Linked Life Data

19264543

Source:http://linkedlifedata.com/resource/pubmed/id/19264543

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
2009-3-30
pubmed:abstractText
The ground and low-lying excited electronic states of flavone were investigated by means of quantum chemical methods including spin-orbit coupling. Minimum structures were determined employing (time-dependent) Kohn-Sham density functional theory. Spectral properties were computed utilizing a combined density functional and multi-reference configuration interaction (DFT/MRCI) method. Intersystem crossing (ISC) rate constants for the S1-->T1 transition were computed using a discretized Fermi golden rule approach. For the evaluation of phosphorescence lifetimes a multi-reference spin-orbit configuration interaction procedure (DFT/MRSOCI) was invoked. According to the calculations the phenyl ring is twisted out of the benzopyrone plane by 28 degrees in the electronic ground state whereas the nuclear frame is nearly planar in the lowest excited (npi*)1 (S1) state and is slightly V-shaped in the (pipi*)3 (T1) and (pipi*)1 (S2) states. The calculations clearly show that the T1 state has mainly pipi* character. The large spin-orbit coupling of the S1 and T1 states and their small energy gap explain the high S1-->T1 ISC rate for which a value of kISC approximately 3x10(11) s is computed, in good agreement with experimental build-up times of the Tn<--T1 absorption. In the absence of collisions and other nonradiative processes, the T1 state of flavone is predicted to be long-lived with a pure phosphorescence lifetime of tauP approximately 4 s, in qualitative agreement with low-temperature measurements. The much faster decay of triplet flavone observed in fluid solutions is ascribed to nonradiative processes.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
1386-1425
pubmed:author
pubmed:issnType
Print
pubmed:volume
73
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1-5
pubmed:meshHeading
pubmed:year
2009
pubmed:articleTitle
Spin-forbidden transitions in flavone.
pubmed:affiliation
Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany. Christel.Marian@uni-duesseldorf.de
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't