Picosecond laser spectroscopy of 4-(9-anthryl)-N,N-dimethylaniline and related compounds

Okada, Tadashi; Mataga, Noboru; Baumann, Wolfram; Siemiarczuk, Aleksander

doi:10.1021/j100301a014

Cited by 73 publications

(76 citation statements)

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“…These observations suggest that the 1 FC state is of substantial 1 L b character mixed with the 1 L a -type 1 CT state. Thus, the excited-state electron transfer in the investigated donor-acceptor biphenyls is accompanied with more spectral features than in the extensively studied biaryls 9,9′-bianthryl (BA) 7,11,12, or 4-(9-anthryl)-N,N-dimethylaniline (ADMA) 15 and derivatives as well as in the recently studied 9-dimethylanilinophenanthrene (9DPhen) biaryl compounds. 13,14 For BA in triacetine, the 1 LE and 1 CT transient absorption bands could be separated, 12 but in ADMA, 15 9DPhen, 13 and related molecules, the time-resolved transient absorption spectra exhibit only a gradual shift with increasing time delay but not such clear spectral differences between the species before and after the electron-transfer step as it is shown for I-III.…”

Section: Effects Of Solvent Polarity and Twist Anglementioning

confidence: 91%

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Subpicosecond Transient Absorption of Donor−Acceptor Biphenyls. Intramolecular Control of the Excited State Charge Transfer Processes by a Weak Electronic Coupling

et al. 1998

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The photoinduced intramolecular charge transfer processes of three differently twisted 4-(dimethylamino)-4′-cyanobiphenyl derivatives (I-III) have been investigated using time-resolved transient absorption and gain spectroscopy in the subpicosecond range. Independent of twist angle and solvent polarity, the kinetics and spectral evolutions after excitation clearly reveal a precursor-sater relationship for the electron transfer from a less emissive state of mixed 1 L b /CT character to a highly emissive charge transfer ( 1 CT) state. Beside the occurrence of dual fluorescence gain, two transient absorption bands for the 1 CT state and one for the precursor state ( 1 FC) are observed. All bands are assigned to electronic transitions and correlated for all solvents and compounds. The band intensities are discussed with solvent polarity and twist angle controlled mixing between the charge transfer state 1 CT and the higher lying 1 L b and 1 L a states. In acetonitrile, the transient spectra of the pretwisted donor-acceptor biphenyl III, in contrast to the planar I and II, can be approximated by the sum of cation and anion spectra of the subunits demonstrating decoupled moieties. The kinetics of the CT processes are not dominated by solvation dynamics alone. As an example, in acetonitrile, (τ l ) 0.2 ps, τ s < 1 ps) the kinetics are slower than 2.5 ps. The involvement of a weak electronic coupling matrix element is favored as a source for the intramolecular control of the CT reactions. Furthermore, for the strongly twisted biphenyl derivative III, a secondary intramolecular process to a more relaxed species (CTR) occurs after the initial CT step, in agreement with fluorescence studies.

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Section: Effects Of Solvent Polarity and Twist Anglementioning

confidence: 91%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] ET dynamics in solution are determined by an interplay of solvation and intramolecular modes leading to two borderline cases (A) solvent control and (B) intramolecular control.…”

Section: Introductionmentioning

confidence: 99%

Subpicosecond Transient Absorption of Donor−Acceptor Biphenyls. Intramolecular Control of the Excited State Charge Transfer Processes by a Weak Electronic Coupling

et al. 1998

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“…It should be expected that the maximum of k(t) is reached the earlier the higher the amounts of the original potential energy U« and of the driving force -(grad U)o of the molecular system at t = O. A first attempt to study the potential shape of the nCT reaction pathway by transient absorption spectroscopy has already been published [29].…”

Section: Time-resolved Spectroscopymentioning

confidence: 99%

Photophysics of Internal Twisting II. Fluorescence Spectroscopic Studies of Horizontal Transitions

Lippert

1988

Ber Bunsenges Phys Chem

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Molecular motions are investigated by experimental and theoretical studies on subnanosecond photoproduction of twisted biradicaloid excited states of aromatic compounds in liquid solutions.*) For I see Ref. [9]. Because twisting around one chemical bond cannot completely suppress all overlap between the electron donor and acceptor group orbitals no electron transfer (ET) will occur as in bi-molecular diffusion controlled reactions but only some charge will be transferred. Grabowski's term "TICT" can readily be accepted, therefore, but ET not.Especially 9,9'-bianthryl (BA) in sufficient polar solvents fluoresces from an excited state which is no longer non-polar but possesses a certain CT-character. In 1970 we predicted Quantum Chemical Verification of nCT StateSince the photochemical sudden polarization of ethylene had been predicted by allowing other molecular orbitals than those belonging to D 2h symmetry to contribute to its excited electronic states it seemed to be reasonable to decrease excited states energy of polar aromatic compounds like DMABN (para-dimethylaminobenzonitrile, Fig. 1) by adding nCT state functions to computational programs. Fig. 2 shows the results for aminoborane, the simplest conceivable, event hough hypothetical twisting electron donor-acceptor compound. It possesses the electron donor and acceptor groups NH 2 and BH 2 , respectively, which are linked together by one single bond and their planes can be twisted by an angle 0 allowing for orthogonal biradicaloid excited states. It turned out that:1. In the approximation used the second excited singlet state IA 2 of that model compound possesses a minimum at o = 90", with 92% weight for the charge-transfer contribution.2. Both the nCT state and the ground state have same electronic symmetry.3. Twisting needs no activation energy. 4. The driving force is almost constant since it is proportional to grad E po ! (Hellmann-Feynman theorem, for further literature see Ref. 7).5. For ethylene and DMABN it had been evaluated that the molecular dipole moment increases only slowly at the beginning of the twist reaction, but almost suddenly at the end of the reaction (Fig. 3).6. The transition moment between an orthogonal nCT state A* and a planar ground state So definitively equals an equilibrium torsional displacement from 0 = 90" in So to 0 = 78') in S, of the free BA molecule due to chargeresonance and nonbonded repulsions, and noticed even larger displacements in solution due to intramolecular charge transfer (CT) as induced by solvent polarity [3], and this in excellent agreement with supersonic beam results by Khundhar and Zewail [34] for the free BA molecule, for Argon clusters in which BA shows a displacement value of (67 ± 5)" [4], and since even the influence of an external electric field on the fluorescence intensity of BA in non-polar and medium polar solvents and solvent mixtures show that the single fluorescence band is not due to a homogeneous transition between two states [38].

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“…In this model, the reaction rate depends on the energy gap, [11][12][13] the coupling between the two states, [14][15][16] and the fluctuating motion of solvent molecules. [17][18][19] Moreover, when an electron moves from one molecular orbital to another, molecular structure could also change as a consequence of the change in bonding ability.…”

Section: Introductionmentioning

confidence: 99%

Femtosecond degenerate four-wave-mixing measurements of coherent intramolecular vibrations in an ultrafast electron transfer system

Nagasawa

Yoneda

Nambu

et al. 2014

Vibrational Spectroscopy

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Femtosecond degenerate four-wave-mixing (DFWM) spectroscopy was carried out to investigate the behavior of coherent wavepacket motion in an ultrafast intermolecular electron transfer (ET) system which consists of a dye molecule, oxazine 1 (Ox1), in an electron donating solvent, N,N-dimethylaniline (DMA). Due to the ultrafast ET in DMA with time constant of ca. 59-81 fs, acceleration of the vibrational dephasing for the excited state mode at 562 cm-1 were observed by the DFWM measurement and confirmed by pump-probe (PP) spectroscopy. Interestingly, the dephasing time of the excited state mode in DMA is in the order of 160-240 fs which is significantly longer than the time constant of ET which indicates that the oscillation is not diminished instantaneously by the ET but somewhat persists into the product state.

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Picosecond laser spectroscopy of 4-(9-anthryl)-N,N-dimethylaniline and related compounds

Cited by 73 publications

References 0 publications

Subpicosecond Transient Absorption of Donor−Acceptor Biphenyls. Intramolecular Control of the Excited State Charge Transfer Processes by a Weak Electronic Coupling

Subpicosecond Transient Absorption of Donor−Acceptor Biphenyls. Intramolecular Control of the Excited State Charge Transfer Processes by a Weak Electronic Coupling

Photophysics of Internal Twisting II. Fluorescence Spectroscopic Studies of Horizontal Transitions

Femtosecond degenerate four-wave-mixing measurements of coherent intramolecular vibrations in an ultrafast electron transfer system

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