Fluoreszenzspektrum Und Franck-Condon-Prinzip in Lösungen Aromatischer Verbindungen

Lippert, E.; Lüder, W.; Boos, H.

doi:10.1016/b978-1-4832-1332-3.50070-6

Cited by 287 publications

(227 citation statements)

References 7 publications

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“…Mainly, this is because of its "anomalous" emission spectrum in the condensed phase. In addition to the normal fluorescence that is always present, DMABN exhibits an additional, redshifted emission in polar solvents that was first attributed by Lippert et al 1 to an intramolecular charge transfer ͑ICT͒ state. Later, recognizing that charge separation and/or flow would be inhibited by orbital overlap between the two ends of the molecule, Grabowski and co-workers 2 suggested that the process involved an internal twisting of the dimethylamino ͑DMA͒ group.…”

Section: Introductionmentioning

confidence: 99%

Twisted intramolecular charge transfer states: Rotationally resolved fluorescence excitation spectra of 4,4′-dimethylaminobenzonitrile in a molecular beam

Nikolaev

Myszkiewicz

Berden

et al. 2005

The Journal of Chemical Physics

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We report the observation at high resolution of seven vibronic bands that appear within ϳ200 cm −1 of the electronic origin in the S 1 -S 0 fluorescence excitation spectrum of 4,4Ј-dimethylaminobenzonitrile ͑DMABN͒ in a molecular beam. Surprisingly, each band is found to be split into two or more components by a ͑coordinated͒ methyl group tunneling motion which significantly complicates the analysis. Despite this fact, high quality ͓͑Observed− Calculated͒ ഛ 30 MHz͔ fits of each of the bands have been obtained, from which the rotational constants, inertial defects, torsion-rotation interaction constants, methyl group torsional barriers, and transition moment orientations of DMABN in both electronic states have been determined. The data show that DMABN is a slightly pyramidalized ͑ϳ1°͒ but otherwise ͑heavy-atom͒ planar molecule in its ground S 0 state, and that its electronically excited S 1 state has both a more pyramidalized ͑ϳ3°͒ and twisted ͑ϳ25°͒ dimethylamino group. Large reductions in the methyl group torsional barriers also show that the S 1 ← S 0 electronic transition is accompanied by significant charge transfer from the nitrogen atom to the ‫ء‬ orbitals of the aromatic ring. Thereby established is the participation of all three vibrational coordinates in the dynamics leading to the "anomalous" emissive behavior of DMABN in the condensed phase.

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Section: Introductionmentioning

confidence: 99%

Twisted intramolecular charge transfer states: Rotationally resolved fluorescence excitation spectra of 4,4′-dimethylaminobenzonitrile in a molecular beam

Nikolaev

Myszkiewicz

Berden

et al. 2005

The Journal of Chemical Physics

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“…Emission from a TICT state seems to be more the exception than the rule. In the favourable cases of observable TICT emission, however, which often goes along with dual fluorescence (8,(14)(15)(16)(17)(18)(19), this emission can yield important information on the properties of this state. Solvatochromic measurements show that the TICT state involves a complete charge separation even for symmetric compounds (18).…”

Section: Introductionmentioning

confidence: 99%

Intramolecular fluorescence quenching in aminocoumarines. Identification of an excited state with full charge separation

Rettig¹,

Klock²

1985

Can. J. Chem.

102

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This paper is dedicated to Professor Camille Sandorb on the occasion of his 65th birthdayWOLFCAND REPIC and ANDRE KLOCK. Can. J. Chem. 63, 1649 (1985) The fluorescence of 6-aminocoumarine (A6C) is very weak and anomalously redshifted as compared to its 7-substituted analogues 4-methyl-7-aminocoumarine (A7C) and 4-methyl-7-diethylaminocoumarine (DEA7C). The solvatochromic redshift in homologous alcohols is much stronger for A6C, pointing to an increased dipole moment of the emitting state. A twisted intramolecular charge transfer (TICT) state with full charge separation is made responsible for this emission. This is rationalized by molecules-in-molecules calculations. The strong Stokes shift in n-hexane and in ethanol glass at 77 K suggests that A6C emits from a TICT state even under these conditions. WOLFCAND REPIC et ANDRE KLOCK. Can. J. Chem. 63, 1649 (1985). La fluorescence de l'amino-6 coumarine (A6C) est trks faible et elle glisse de faqon anormale vers le rouge si on fait une comparaison avec des composCs analogues substituCs en position-7 comme la methyl-4 amino-7 coumarine (A7C) et la mCthyl-4 diCthylamino-7 coumarine (DEA7C). Le glissement solvatochrome vers le rouge provoqut par les alcools homologues est plus prononct avec le A6C et ceci suggkre qu'il y a une augmentation du moment dipolaire de 1'Ctat qui Cmet. On attribue cette Cmission a un Ctat de transfert de charge intramolCculaire croist (TCIC) avec une sCparation complkte de charges.On rationalise ce fait en fonction des calculs sur des molCcules dans des moltcules. Le fort glissement de Stokes dans le n-hexane et dans 1'Cthanol a 77 K suggkre que, mCme dans ces conditions, le A6C Cmet partir de I'etat TCIC.[Traduit par le journal] Introduction Lippert and co-workers (1-5) observed several types of adiabatic and diabatic photoreactions in dilute solutions of 7-hydroxycoumarine and related compounds as revealed from multiple fluorescence spectra.Only those coumarine dyes which possess an electron donor substituent in the 7 position showed a rather high and tunable LASER efficiency, whereas donor substitution in the 6 position strongly reduces the fluorescence quantum yield. Even some 7-dialkylamino coumarines are prone to undergo fluorescence quenching in polar solvents. This has been traced back by Jones, Halpern et al. (6,7) to an adiabatic photoreaction towards a nonemissive state.From the substituent and solvent dependence, this state was shown to be connected with the donor and acceptor properties of amine and coumarine moieties, and was assigned as a Twisted Intramolecular Charge Transfer (TICT) state (8) with the dialkylamino group twisted perpendicularly to the plane of the coumarine skeleton. By making this twisting motion unavailable through ring closure to the "rigidized structure" of Coumarine 102 or 153, the fluorescence quenching is suppressed (7). For the same reason, "rigidized" rhodamines show an enhanced fluorescence quantum yield at room temperature as compared to the nonrigidized strctures (rhodamine B vs. rhodamine 10 1 (9...

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“…In unpolaren Lösungsmitteln jedoch konnte bis jetzt nur die kurzwellige F B -Bande beobachtet werden [1], Neuere Untersuchungen lassen erkennen, daß die langwellige F A -Bande von einem hochpolaren "twisted intramolecular charge transfer" (TICT)-Zustand emittiert wird, der durch eine Rotation der N(CH3)2-Gruppe um die C Ar -NBindungsachse gebildet wird [2], Die Bildung von spezifischen Exiplexen mit den Lösungsmittelmole-külen kann als Ursache für die langwellige F ABande ausgeschlossen werden [3 -5], da vor kurzem am Beispiel des p-N,N-Diäthylaminobenzoesäure-äthylester (DEABEE) gezeigt wurde, daß auch in unpolaren Lösungsmitteln prinzipiell ein TICT-Zustand gebildet werden kann [6], Aus diesem Grunde erscheint eine Klärung der Ursache für das "Ausbleiben" der dualen Fluoreszenz von DMABN in unpolaren Lösungsmitteln notwendig. Hierbei könn-ten sowohl kinetische Aspekte eine Rolle spielenwie insbesondere die Form der beiden an der Photoreaktion beteiligten Hyperflächen 'B und 'A (Punktgruppe C 2 ) entlang der Reaktionskoordinate, Sonderdruckanforderungen an Dr. G. Wermuth, Iwan N. Stranski-Institut für Physikalische und Theoretische Chemie der TU Berlin, Straße des 17.…”

Section: Introductionunclassified

Einfluß der Reaktionsenthalpie auf die Bildung von "Twisted Intramolecular Charge Transfer" (TICT) — Anregungszustände in unpolaren Lösungsmitteln: p-substituierte N,N-Dimethylaniline / The Influence of Reaction enthalpy on the Formation of “Twisted Intramolecular Charge Transfer" (TICT)-States in Inert Solvents: p-Substituted N,N-Dimethylanilines

Wermuth

1983

Zeitschrift Für Naturforschung A

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Fluoreszenzspektrum Und Franck-Condon-Prinzip in Lösungen Aromatischer Verbindungen

Cited by 287 publications

References 7 publications

Twisted intramolecular charge transfer states: Rotationally resolved fluorescence excitation spectra of 4,4′-dimethylaminobenzonitrile in a molecular beam

Twisted intramolecular charge transfer states: Rotationally resolved fluorescence excitation spectra of 4,4′-dimethylaminobenzonitrile in a molecular beam

Intramolecular fluorescence quenching in aminocoumarines. Identification of an excited state with full charge separation

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