Spectroscopy of solvent complexes with indoles: induction of 1La-1Lb state coupling

Abstract

IntroductionThe indole chromophore has two low-lying ?y* electronic states, designated 'La and 'Lb.'-' Transitions to 'Lb show vibronic structure and relatively little dependence on solvent polarity, which indicates little geometry change and charge redistribution in 'Lb.By contrast, solution absorbance to 'La is broad and sensitive to solvent polarity. Initial efforts in the early 1980s to find a second set of bands due to 'La in the excitation spectra of jet-cooled indoles were unsuccessful, even when extensive scanning was carried out.8 A Emissions from CdI and HgI produced in a corona-excited supersonic jet discharge were photographed in high resolution. A study of the vibrationally and isotopically resolved spectra for the CdI ultraviolet D2113,2-X22+ transition near 338.4 nm and visible B2Z+-X2Z+ transition near 646.5 nm has yielded vibrational constants for the X, B, and D electronic states and estimates of their dissociation energies. Use of neardissociation expansion analyses has yielded much more reliable extrapolation properties for this system, and for the analogous states of ZnI, than use of conventional techniques. The analysis of the HgI B-X spectrum near 420 nm was found to be in excellent agreement with previous studies. The trends in the X-and B-state constants for the MI series (M = Zn, Cd, Hg) including dissociation energies derived from near-dissociation theory are rationalized in terms of the mixed ionic-covalent bonding expected for group IIB metal halide radicals.

Femtosecond pump-probe experiments on trapped flavin: Optical control of dissociation

“…This was observed, for example, for tryptophan with different charge states and different environments. 8,9,[11][12][13][14] This is true if the protonation or the deprotonation does not occur on the chromophore, while a strong shift can be observed when deprotonation occurs on the chromophore. [15][16][17] CID and UVPD ͑typical pump intensity= 5 ϫ 10 10 W / cm 2 ͒ spectra are compared in Fig.…”

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

“…( 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 !…”

The hydrogen-bonding topologies of indole–(water)n clusters from resonant ion-dip infrared spectroscopy

“…Several ensuing studies did precisely that. 2,3,12,13 The present study returns to the fundamental issue of the assignment of the two conformational isomers of Ind-W 1 . The technique of resonant ion-dip infrared spectroscopy ͑RIDIRS͒ is used to record IR spectra of the two species in the hydride stretch region free of interference from one another.…”

“…However, polar solvents interacting with the cloud are thought to selectively stabilize 1 L a while interaction with the N-H group shows no such preference. 2,[8][9][10][11][12][13][14][15] Accompanying the stabilization of 1 L a in the excited state is a redshift and broadening of the fluorescence, while unshifted emission is attributed to 1 L b . 8,12,13 Studies of indole-͑water͒ n clusters ͑hereafter shortened to Ind-W n ) have played a prominent role in these studies due to the unrivaled importance of water as nature's solvent.…”