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Article: Solvent effects on the charge transfer excited states of 4-dimethylaminobenzonitrile (DMABN) and 4-dimethylamino-3,5-dimethylbenzonitrile (TMABN) studied by time-resolved infrared spectroscopy: A direct observation of hydrogen bonding interactions

TitleSolvent effects on the charge transfer excited states of 4-dimethylaminobenzonitrile (DMABN) and 4-dimethylamino-3,5-dimethylbenzonitrile (TMABN) studied by time-resolved infrared spectroscopy: A direct observation of hydrogen bonding interactions
Authors
Issue Date2007
PublisherRoyal Society of Chemistry. The Journal's web site is located at http://www.rsc.org/pps
Citation
Photochemical And Photobiological Sciences, 2007, v. 6 n. 9, p. 987-994 How to Cite?
AbstractTime-resolved infrared absorption spectra of the C≡N bands of photoexcited TMABN and DMABN have been measured in non-polar hexane, polar aprotic THF and polar protic butanol with high temporal and spectral resolution (<0.5 ps and 5 cm -1, respectively). In butanol, the intramolecular charge transfer (ICT) state C≡N infrared absorption bands of DMABN and TMABN both develop from an initial singlet into a doublet, demonstrating the co-existence of two charge transfer excited states, one of which is hydrogen-bonded and the other similar to the state formed in aprotic solvents. The ICT C≡N absorption band of TMABN is already strong at the earliest measurement time of 2 ps in THF, hexane, and butanol, indicating prompt population of ICT by a barrierless process, as expected from the pre-twisted structure of this molecule. There are little or no subsequent fast kinetics in hexane and THF but the signal observed in butanol continues to grow substantially at later times, prior to decay, indicating population transfer from a second state excited at 267 nm. No CN absorption band attributable to this state is observed, consistent with it being similar to the LE state of DMABN. The kinetics of the later stages of the hydrogen-bonding of both DMABN and TMABN in butanol takes place on timescales consistent with known values for dipolar solvation relaxation and result in a ratio of the hydrogen-bonded to non-bonded species of ∼3:1 at equilibrium for both molecules. The contrast between the prompt population of the charge transfer state of TMABN in all three solvents and charge transfer rates in DMABN limited to 13 ps -1 in THF and 9 ps -1 in butanol is fully consistent with the TICT description for the ICT state structure. © The Royal Society of Chemistry and Owner Societies.
Persistent Identifierhttp://hdl.handle.net/10722/168137
ISSN
2015 Impact Factor: 2.235
2015 SCImago Journal Rankings: 0.829
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorKwok, WMen_US
dc.contributor.authorMa, Cen_US
dc.contributor.authorGeorge, MWen_US
dc.contributor.authorGrills, DCen_US
dc.contributor.authorMatousek, Pen_US
dc.contributor.authorParker, AWen_US
dc.contributor.authorPhillips, Den_US
dc.contributor.authorToner, WTen_US
dc.contributor.authorTowrie, Men_US
dc.date.accessioned2012-10-08T03:15:32Z-
dc.date.available2012-10-08T03:15:32Z-
dc.date.issued2007en_US
dc.identifier.citationPhotochemical And Photobiological Sciences, 2007, v. 6 n. 9, p. 987-994en_US
dc.identifier.issn1474-905Xen_US
dc.identifier.urihttp://hdl.handle.net/10722/168137-
dc.description.abstractTime-resolved infrared absorption spectra of the C≡N bands of photoexcited TMABN and DMABN have been measured in non-polar hexane, polar aprotic THF and polar protic butanol with high temporal and spectral resolution (<0.5 ps and 5 cm -1, respectively). In butanol, the intramolecular charge transfer (ICT) state C≡N infrared absorption bands of DMABN and TMABN both develop from an initial singlet into a doublet, demonstrating the co-existence of two charge transfer excited states, one of which is hydrogen-bonded and the other similar to the state formed in aprotic solvents. The ICT C≡N absorption band of TMABN is already strong at the earliest measurement time of 2 ps in THF, hexane, and butanol, indicating prompt population of ICT by a barrierless process, as expected from the pre-twisted structure of this molecule. There are little or no subsequent fast kinetics in hexane and THF but the signal observed in butanol continues to grow substantially at later times, prior to decay, indicating population transfer from a second state excited at 267 nm. No CN absorption band attributable to this state is observed, consistent with it being similar to the LE state of DMABN. The kinetics of the later stages of the hydrogen-bonding of both DMABN and TMABN in butanol takes place on timescales consistent with known values for dipolar solvation relaxation and result in a ratio of the hydrogen-bonded to non-bonded species of ∼3:1 at equilibrium for both molecules. The contrast between the prompt population of the charge transfer state of TMABN in all three solvents and charge transfer rates in DMABN limited to 13 ps -1 in THF and 9 ps -1 in butanol is fully consistent with the TICT description for the ICT state structure. © The Royal Society of Chemistry and Owner Societies.en_US
dc.languageengen_US
dc.publisherRoyal Society of Chemistry. The Journal's web site is located at http://www.rsc.org/ppsen_US
dc.relation.ispartofPhotochemical and Photobiological Sciencesen_US
dc.titleSolvent effects on the charge transfer excited states of 4-dimethylaminobenzonitrile (DMABN) and 4-dimethylamino-3,5-dimethylbenzonitrile (TMABN) studied by time-resolved infrared spectroscopy: A direct observation of hydrogen bonding interactionsen_US
dc.typeArticleen_US
dc.identifier.emailMa, C:macs@hkucc.hku.hken_US
dc.identifier.authorityMa, C=rp00758en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1039/b708414een_US
dc.identifier.pmid17721598-
dc.identifier.scopuseid_2-s2.0-34548166474en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-34548166474&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume6en_US
dc.identifier.issue9en_US
dc.identifier.spage987en_US
dc.identifier.epage994en_US
dc.identifier.isiWOS:000248986000017-
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridKwok, WM=7103129332en_US
dc.identifier.scopusauthoridMa, C=7402924979en_US
dc.identifier.scopusauthoridGeorge, MW=26325262600en_US
dc.identifier.scopusauthoridGrills, DC=6601986706en_US
dc.identifier.scopusauthoridMatousek, P=7005659005en_US
dc.identifier.scopusauthoridParker, AW=7403267977en_US
dc.identifier.scopusauthoridPhillips, D=22998496000en_US
dc.identifier.scopusauthoridToner, WT=6701364578en_US
dc.identifier.scopusauthoridTowrie, M=7004415080en_US

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