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Article: Unravelling the reaction mechanism for the fast photocyclisation of 2-benzoylpyridine in aqueous solvent by time-resolved spectroscopy and density functional theory calculations
Title | Unravelling the reaction mechanism for the fast photocyclisation of 2-benzoylpyridine in aqueous solvent by time-resolved spectroscopy and density functional theory calculations | ||||||||||
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Authors | |||||||||||
Keywords | Cyclization Photochemistry Raman spectroscopy Reaction mechanisms Solvent effects Time-resolved spectroscopy | ||||||||||
Issue Date | 2010 | ||||||||||
Publisher | Wiley - V C H Verlag GmbH & Co KGaA. The Journal's web site is located at http://www.wiley-vch.de/home/chemistry | ||||||||||
Citation | Chemistry - A European Journal, 2010, v. 16 n. 23, p. 6961-6972 How to Cite? | ||||||||||
Abstract | A combined femtosecond transient absorption (fs-TA) and nano-second time-resolved resonance Raman (ns-TR 3) spectroscopic investigation of the photoreaction of 2-benzoylpyridine (2-BPy) in acetonitrile and neutral, basic and acidic aqueous solvents is reported. fs-TA results showed that the nit* triplet 2-BPy is the precursor of the photocyclisation reaction in neutral and basic aqueous solvents. The cis triplet biradical and the cis singlet zwitterionic species produced during the photocyclisation reaction were initially characterised by ns-TR 3 spectroscopy. In addition, a new species was uniquely observed in basic aqueous solvent after the decay of the cis singlet zwitterionic species and this new species was tentatively assigned to the photocyclised radical anion. The ground-state conformation of 2-BPy in acidic aqueous solvent is the pyridine nitrogen-protonated 2-BPy cation (2BPy-NH +) rather than the neutral form of 2-BPy. After laser photolysis, the singlet excited state (Si) of 2-BPy-NH + is generated and evolves through excited-state proton transfer (ESPT) and efficient intersystem crossing (ISC) processes to the triplet exited state (T 1) of the carbonyl oxygen-protonated 2BPy cation (2-BPy-OH +) and then photocyclises with the lone pair of the nitrogen atom in the heterocyclic ring. Cyclisation reactions take place both in neutral/basic and acidic aqueous solvents, but the photocyclisation mechanisms in these different aqueous solvents are very different. This is likely due to the different conformation of the precursor and the influence of hydrogen-bonding of the solvent on the reactions. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. | ||||||||||
Persistent Identifier | http://hdl.handle.net/10722/142057 | ||||||||||
ISSN | 2023 Impact Factor: 3.9 2023 SCImago Journal Rankings: 1.058 | ||||||||||
ISI Accession Number ID |
Funding Information: This work was supported by a grant from the Research Grants Council of Hong Kong (HKU 7035/08P and HKU 1/01C), the award of a Croucher Foundation Senior Research Fellowship (2006-07) front the Croucher Foundation and an Outstanding Researcher Award (2006) from the University of Hong Kong to D.L.P. Work performed at the University of Rochester was supported by start-up funding to D.W.M. | ||||||||||
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DC Field | Value | Language |
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dc.contributor.author | Du, Y | en_HK |
dc.contributor.author | Xue, J | en_HK |
dc.contributor.author | Li, MD | en_HK |
dc.contributor.author | Guan, X | en_HK |
dc.contributor.author | McCamant, DW | en_HK |
dc.contributor.author | Phillips, DL | en_HK |
dc.date.accessioned | 2011-10-17T07:06:39Z | - |
dc.date.available | 2011-10-17T07:06:39Z | - |
dc.date.issued | 2010 | en_HK |
dc.identifier.citation | Chemistry - A European Journal, 2010, v. 16 n. 23, p. 6961-6972 | en_HK |
dc.identifier.issn | 0947-6539 | en_HK |
dc.identifier.uri | http://hdl.handle.net/10722/142057 | - |
dc.description.abstract | A combined femtosecond transient absorption (fs-TA) and nano-second time-resolved resonance Raman (ns-TR 3) spectroscopic investigation of the photoreaction of 2-benzoylpyridine (2-BPy) in acetonitrile and neutral, basic and acidic aqueous solvents is reported. fs-TA results showed that the nit* triplet 2-BPy is the precursor of the photocyclisation reaction in neutral and basic aqueous solvents. The cis triplet biradical and the cis singlet zwitterionic species produced during the photocyclisation reaction were initially characterised by ns-TR 3 spectroscopy. In addition, a new species was uniquely observed in basic aqueous solvent after the decay of the cis singlet zwitterionic species and this new species was tentatively assigned to the photocyclised radical anion. The ground-state conformation of 2-BPy in acidic aqueous solvent is the pyridine nitrogen-protonated 2-BPy cation (2BPy-NH +) rather than the neutral form of 2-BPy. After laser photolysis, the singlet excited state (Si) of 2-BPy-NH + is generated and evolves through excited-state proton transfer (ESPT) and efficient intersystem crossing (ISC) processes to the triplet exited state (T 1) of the carbonyl oxygen-protonated 2BPy cation (2-BPy-OH +) and then photocyclises with the lone pair of the nitrogen atom in the heterocyclic ring. Cyclisation reactions take place both in neutral/basic and acidic aqueous solvents, but the photocyclisation mechanisms in these different aqueous solvents are very different. This is likely due to the different conformation of the precursor and the influence of hydrogen-bonding of the solvent on the reactions. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. | en_HK |
dc.language | eng | - |
dc.publisher | Wiley - V C H Verlag GmbH & Co KGaA. The Journal's web site is located at http://www.wiley-vch.de/home/chemistry | en_HK |
dc.relation.ispartof | Chemistry - A European Journal | en_HK |
dc.subject | Cyclization | en_HK |
dc.subject | Photochemistry | en_HK |
dc.subject | Raman spectroscopy | en_HK |
dc.subject | Reaction mechanisms | en_HK |
dc.subject | Solvent effects | en_HK |
dc.subject | Time-resolved spectroscopy | en_HK |
dc.title | Unravelling the reaction mechanism for the fast photocyclisation of 2-benzoylpyridine in aqueous solvent by time-resolved spectroscopy and density functional theory calculations | en_HK |
dc.type | Article | en_HK |
dc.identifier.openurl | http://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0947-6539&volume=16&issue=23&spage=6961&epage=6972&date=2010&atitle=Unravelling+the+reaction+mechanism+for+the+fast+photocyclisation+of+2-benzoylpyridine+in+aqueous+solvent+by+time-resolved+spectroscopy+and+density+functional+theory+calculations | - |
dc.identifier.email | Phillips, DL:phillips@hku.hk | en_HK |
dc.identifier.authority | Phillips, DL=rp00770 | en_HK |
dc.description.nature | link_to_subscribed_fulltext | - |
dc.identifier.doi | 10.1002/chem.200903073 | en_HK |
dc.identifier.pmid | 20437422 | - |
dc.identifier.scopus | eid_2-s2.0-77953584674 | en_HK |
dc.identifier.hkuros | 181783 | - |
dc.relation.references | http://www.scopus.com/mlt/select.url?eid=2-s2.0-77953584674&selection=ref&src=s&origin=recordpage | en_HK |
dc.identifier.volume | 16 | en_HK |
dc.identifier.issue | 23 | en_HK |
dc.identifier.spage | 6961 | en_HK |
dc.identifier.epage | 6972 | en_HK |
dc.identifier.isi | WOS:000279856100029 | - |
dc.publisher.place | Germany | en_HK |
dc.relation.project | Ultrafast laser facility for investigations of novel electronic excited states and intermediates in inorganic photochemistry, semiconductor materials and nanomaterials | - |
dc.identifier.scopusauthorid | Du, Y=35310175500 | en_HK |
dc.identifier.scopusauthorid | Xue, J=23007272500 | en_HK |
dc.identifier.scopusauthorid | Li, MD=7405265795 | en_HK |
dc.identifier.scopusauthorid | Guan, X=8313149700 | en_HK |
dc.identifier.scopusauthorid | McCamant, DW=6505954265 | en_HK |
dc.identifier.scopusauthorid | Phillips, DL=7404519365 | en_HK |
dc.identifier.issnl | 0947-6539 | - |