1La-1Lb Coupling in the Excited State of 3-Methylindole and Its Polar Clusters

Demmer, David; Leach, Garry W.; Wallace, Stephen C.

doi:10.1021/j100100a007

Cited by 42 publications

(58 citation statements)

References 4 publications

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“…12 Their quoted frequency of 614 cm -1 falls between peaks at 611 and 619 cm -1 , both of which we and Sammeth et al find to have 1 L a character. However, the 718 cm -1 peak was found to be 1 L b by Sammeth et al, and we found a corresponding L b peak in the complex spectra.…”

Section: -Misupporting

confidence: 53%

“…Our findings are consistent with an amended Wallace group hypothesis concerning the 1 L a radiationless channel. 12 They propose that N-H dissociation occurs through coupling to levels of another state, a triplet or high-energy dissociative levels of the ground state. Another possibility not ruled out by our results is excited state tautomerization.…”

Section: -Methoxyindole (5-moi)mentioning

confidence: 99%

“…12 Their studies relate the lowering of 1 L a to the basicity of the solvent adduct at the N-H, and they also address the reason why progression structure is seen concomitant with 1 L a lowering. For a number of solvent adducts considered, they found that until the solvent adduct proton affinity exceeded 200 kcal/mol (values for water and methanol are 166.5 and 181.9 kcal/mol, respectively), they continued to find complex lifetimes that exceed 10 ns.…”

Section: -Mimentioning

confidence: 99%

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Jet-Cooled Solvent Complexes with Indoles

and

Sulkes

1996

J. Phys. Chem.

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Cold mass-resolved excitation spectra have been obtained for substituted and unsubstituted indoles complexed with one or two polar solvent molecules. Frequency scans were carried out to more than 1000 cm -1 above the complex origins. Sharp excitation features persisted to the blue for the N-H site complexes, but no features further to the blue were attributable to the π site complexes. In 3-methylindole a number of vibrations 400-900 cm -1 above the S 1 origin in the bare chromophore did not appear in corresponding locations above the S 1 complex origins for n ) 1 water and methanol clusters. It is likely that these peaks underwent much greater red shifts in the complexes than the S 1 origins because the former possess substantial 1 L a character. Any of the indoles studied that was complexed with two polar solvent molecules showed broad excitation features. The extended structure most likely arises in at least some instances because of π site interactions. In 2,3-dimethylindole, postulated to undergo N-H bond dissociation in S 1 , mass-resolved REMPI spectra did not disclose a lower mass product arising from N-H bond breaking. However, when the chromophore was complexed at the N-H site with a strong proton acceptor, triethylamine, evidence was found that zwitterions were formed in the S 1 complex arising from N-H site proton donation to the base.

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Section: -Misupporting

confidence: 53%

Section: -Methoxyindole (5-moi)mentioning

confidence: 99%

Section: -Mimentioning

confidence: 99%

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Jet-Cooled Solvent Complexes with Indoles

and

Sulkes

1996

J. Phys. Chem.

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“…( 1 L a state), see also Figure 2. For aromatic molecular systems such as indoles, [27][28][29][30][31][32][33] tryptophane, [34] or pyrene derivatives [35] internal conversion between these 1 L b and 1 L a levels has been suggested in the interpretations. For 1-naphthol [36,37] the 1 L b !…”

Section: Introductionmentioning

confidence: 99%

Solvent‐Dependent Photoacidity State of Pyranine Monitored by Transient Mid‐Infrared Spectroscopy

et al. 2005

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We investigate with femtosecond mid‐infrared spectroscopy the vibrational‐mode characteristics of the electronic states involved in the excited‐state dynamics of pyranine (HPTS) that ultimately lead to efficient proton (deuteron) transfer in H2O (D2O). We also study the methoxy derivative of pyranine (MPTS), which is similar in electronic structure but does not have the photoacidity property. We compare the observed vibrational band patterns of MPTS and HPTS after electronic excitation in the solvents: deuterated dimethylsulfoxide, deuterated methanol and H2O/D2O, from which we conclude that for MPTS and HPTS photoacids the first excited singlet state appears to have charge‐transfer (CT) properties in water within our time resolution (150 fs), whereas in aprotic dimethylsulfoxide the photoacid appears to be in a nonpolar electronic excited state, and in methanol (less polar and less acidic than water) the behaviour is intermediate between these two extremes. For the fingerprint vibrations we do not observe dynamics on a time scale of a few picoseconds, and with our results obtained on the OH stretching vibration we argue that the dynamic behaviour observed in previous UV/Vis pump–probe studies is likely to be related to solvation dynamics.

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“…More interestingly, the combination of the present and previous results can help to clarify the models reported in the bibliography for the explanation of the anomalous large Stokes shift and fluorescence quenching of indole in polar solvents. Most of these models highlight the crucial role played by the solvent on the relative stabilisation and relaxation of the two close low-lying excited states 1 L a and 1 L b of the indole chromophore [27][28][29]. In gas phase, the 1 L b state lies below the 1 L a state by about 1400 cm À1 [30].…”

Section: Steady-state and Time-resolved Fluorescence Measurementsmentioning

confidence: 99%