Time-resolved resonance Raman spectra of the intramolecular charge transfer state of DMABN

Kwok, Wai Ming; Ma, Chensheng; Matousek, Pavel; Parker, Anthony W.; Phillips, David; Toner, W. T.; Towrie, Michael

doi:10.1016/s0009-2614(00)00436-x

Cited by 39 publications

(73 citation statements)

References 22 publications

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“…This is predicted from our recent TR 3 investigation. 30 The DMABN ICT spectrum in acetonitrile shown here is identical to that measured in methanol and reported in our previous paper. 30 We make the assignments of the three DMABN features according to this work as well as with reference to assignments made by Okamoto et al using TRIR spectroscopy.…”

Section: Picosecond Time-resolved Kerr-gated Resonance Raman Spectros...supporting

confidence: 88%

“…42 Time-resolved vibrational spectra of the ICT state of DEABN and TMABN have not been reported before. By comparing the results with the vibrational spectra of DMABN ICT state, that has been well documented and assigned, 30,31,[33][34][35] suggestions on band assignments should be possible for the two compounds. Furthermore, the comparison of the resonance enhancement pattern of the ps-K-TR 3 spectra and vibrational frequencies of the three compounds may provide important information on elucidating structural and electronic properties of their ICT states.…”

Section: Introductionmentioning

confidence: 90%

“…28,29 Developments in short pulse laser techniques over the last several years have lead to enormous advances in ultrafast time-resolved vibrational spectroscopy. Picosecond Kerr-gated time-resolved resonance Raman (ps-K-TR 3 ) and time-resolved infrared (TRIR) studies on DMABN by ourselves 6,13,[30][31][32] and others, [33][34][35][36] have been reported and enable a direct discussion on the ICT structure.…”

Section: Introductionmentioning

confidence: 99%

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Further time-resolved spectroscopic investigations on the intramolecular charge transfer state of 4-dimethylaminobenzonitrile (DMABN) and its derivatives, 4-diethylaminobenzonitrile (DEABN) and 4-dimethylamino-3,5-dimethylbenzonitrile (TMABN)Dedicated to Professor Dr Z. R. Grabowski and Professor Dr J. Wirz on the occasions of their 75th and 60th birthdays.

Kwok

George

et al. 2003

Phys. Chem. Chem. Phys.

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Section: Picosecond Time-resolved Kerr-gated Resonance Raman Spectros...supporting

confidence: 88%

Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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Further time-resolved spectroscopic investigations on the intramolecular charge transfer state of 4-dimethylaminobenzonitrile (DMABN) and its derivatives, 4-diethylaminobenzonitrile (DEABN) and 4-dimethylamino-3,5-dimethylbenzonitrile (TMABN)Dedicated to Professor Dr Z. R. Grabowski and Professor Dr J. Wirz on the occasions of their 75th and 60th birthdays.

Kwok

George

et al. 2003

Phys. Chem. Chem. Phys.

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“…The structures of the A and B states have been studied recently by time-resolved infrared (TRIR) 2,3 and time-resolved resonance Raman (TR 3 ) spectroscopy. 4,5 The results lend support to the generally accepted TICT (twisted intramolecular charge-transfer) model. 6 Among many solvents used in DMABN studies, carbon tetrachloride (CCl 4 ) induces unique photochemical behaviour 7 -9 manifested by rapid fluorescence quenching in both the solution and gas phases.…”

Section: Introductionsupporting

confidence: 73%

“…TRIR experiments carried out by Chudoba et al 3 and Hashimoto and Hamaguchi 2 put the wavenumber of this mode in the A state at 2096 cm 1 , recently confirmed by our Kerr-gated ps-TR 3 experiments. 5 The B state CN wavenumber measured by Kwok et al 4 is 2181 cm 1 in cyclohexane solvent. Using ns-TR 3 , we have also measured the CN wavenumber for the triplet state as 2040 cm 1 (in preparation) in both polar and non-polar solvents, consistent with an earlier TRIR study in non-polar solvents by Hashimoto and Hamaguchi.…”

Section: Tr 3 Studiesmentioning

confidence: 95%

Time‐resolved study of the photochemical reaction of 4‐dimethylaminobenzonitrile with carbon tetrachloride

Kwok

Matousek

et al. 2001

J Raman Spectroscopy

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The mechanism of 4-dimethylaminobenzonitrile (DMABN) fluorescence quenching by carbon tetrachloride was studied using time-resolved fluorescence, absorption and Raman techniques. Picosecond and nanosecond time-resolved Raman spectra of DMABN and DMABN-d 6 were obtained in resonance with different electronic states to identify intermediates, their structure and time-dependent dynamic changes. The quenching is attributed to intermolecular electron transfer between B-state DMABN and carbon tetrachloride with a time constant of ∼500 fs leading to the formation of the DMABN radical cation as the initial intermediate followed by a ∼13 ps process yielding a DMABN-Cl adduct as product with a lifetime longer than 50 ns. It is likely that the chlorine atom is located at the amino para-ring position of the highly reactive DMABN radical cation. It is suggested that this reaction mechanism is general for other donor-aromatic-acceptor type DMABN derivatives.

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Rapid relaxation pathway of the excited state of linear merocyanines in solutions

Wang

Chen

Syue

et al. 2019

J Chinese Chemical Soc

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Excited‐state relaxation of linear merocyanine dyes in solution is investigated using time‐resolved spectroscopy techniques and quantum chemical calculations. The merocyanine L‐Mero4 and phenyl‐substituted P‐L‐Mero4 have a S‐trans and S‐cis structure, respectively, consisting of indole moiety as the donor, indandione as the acceptor, and the tetramethine as the bridge. The time‐correlated single‐photon counting (TCSPC) picosecond measurements after excitation at wavelength 515 nm to the ππ* state yield emission curves with a short component τ1 in the range of 27–160 ps and a second component τ2 of 200–780 ps for L‐Mero4. In P‐L‐Mero4, τ1 lies in the range of 18–150 ps and τ2 220–520 ps. The subfemtosecond transient absorption measurements yield a short component around 0.4–1.4 ps, and the second/third components are similar to those in the TCPSC measurements. The analysis of the experimental data demonstrates that the ground state recovery exhibits a biexponential rise and rapidly indicates that the conversion back to the electronic ground state provides a fast, nonradiative pathway. Quantum chemical calculations on the electronic structures and their dependence on the molecular confirmation are performed. We identify the excited states and the relaxation path along the twist of the center double bonds in tetramethine that might be the nonradiative pathway. The C=C double bond is weakened in the ππ* state. The phenyl substitution in the conjugated double bond weakens this C=C bond, lowers the isomerization barrier, increases the nonradiative rate, and reduces the emission quantum yield. In polar solvents, the energy of the perpendicular conformer along the trans–cis isomerization path is increased to achieve less coupling to the ground state surface. Because of the small barrier to the trans form, these two conformers establish an equilibrium condition. The trans form, which lies at a lower energy, gains more population and thus has a higher emission yield.

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Time-resolved resonance Raman spectra of the intramolecular charge transfer state of DMABN

Cited by 39 publications

References 22 publications

Time‐resolved study of the photochemical reaction of 4‐dimethylaminobenzonitrile with carbon tetrachloride

Rapid relaxation pathway of the excited state of linear merocyanines in solutions

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