Intramolecular charge transfer spectroscopy

So far we have exclusively discussed time-resolved absorption spectroscopy with visible femtosecond pulses. It has become recently feasible to perfomi time-resolved spectroscopy with femtosecond IR pulses. Flochstrasser and co-workers [M, 150. 151. 152. 153. 154. 155. 156 and 157] have worked out methods to employ IR pulses to monitor chemical reactions following electronic excitation by visible pump pulses these methods were applied in work on the light-initiated charge-transfer reactions that occur in the photosynthetic reaction centre [156. 157] and on the excited-state isomerization of tlie retinal pigment in bacteriorhodopsin [155]. Walker and co-workers [158] have recently used femtosecond IR spectroscopy to study vibrational dynamics associated with intramolecular charge transfer these studies are complementary to those perfomied by Barbara and co-workers [159. 160], in which ground-state RISRS wavepackets were monitored using a dynamic-absorption technique with visible pulses. 

Keywords Biofluids Chemosensors Emission spectroscopy Mechanosensors Optical properties Polarity Rheology Twisted intramolecular charge transfer Viscosity... 

Rettig W, Lapouyade R (1994) Fluorescence probes based on twisted intramolecular charge transfer (TICT) states and other adiabatic photoreactions. Topics in fluorescence spectroscopy 4 109-149... 

Loutfy RO, Law KY (1980) Electrochemistry and spectroscopy of intramolecular charge-transfer complexes. p-N, N-dialkylaminobenzylidenemanononitriles. J Phys Chem 84 2803-2808... 

Rettig W. and Lapouyade R. (1994) Fluorescent Probes Based on Twisted Intramolecular Charge Transfer (TICT) States and Other Adiabatic Reactions, in Lakowicz J. R. (Ed.), Topics in Fluorescence Spectroscopy, Vol. 4, Probe Design and Chemical Sensing, Plenum Press, New York, pp. 109-149. 

S. Tazuke, R. K. Guo, and T. Ikeda, Time-resolved fluoresence spectroscopy of a twisted intramolecular charge transfer compound bonded to polymers, /. Phys. Chem. 94, 1408(1990). 

The solvent dependence of the conformational equilibria of trans-1,4-dimethoxycyclohexane and tra s,cA-l-Me-3,5-dimethoxycyclohexane was studied by low temperature ll NMR spectroscopy (90JCR(S)152) (cf. Table VI). The conformational equilibria of trans-1 -acceptor-2-donor-substituted cyclohexanes 10ee=10aa were studied with respect to intramolecular charge-transfer (donor-acceptor) complexes (CT) in the di-equatorial conformation (02JOC6938) the CT absorptions and the... 

A comprehensive research of a large number of benzofurazan nitro derivatives using UV spectroscopy and other physical-chemical methods has been carried out [777, 1006, 1007, 1106, 1107, 1229-1241], The frequencies of long-wave absorption bands of hydroxy- and aminosubstituted of nitrobenzofurazans greatly depend on the solvent nature [1106, 1107, 1230-1233, 1235, 1236], They are assigned to the bands of intramolecular charge transfer [1007, 1232], Correlation relationships between the wave number (v) and the Kamlet-Taft solvatochromic parameter (it ) are presented in the works cited ... 

In the last part of this chapter, intramolecular charge transfer (ICT) in anthryl derivatives with linked donor-acceptor parts was discussed. Ultrafast spectroscopy has been applied both for structural characterization and for real-time probing of the ICT in this case. Microscopic solvation effects on the torsional motions and the ICT in the molecules have been examined by the use of their clusters with polar solvents. One of the most important problems which awaits for further studies is an ambiguous description of the electronic character of the charge-separated states in the systems. So far, high-level quantum-mechanical calculations have not been able to deal with such large molecular systems, but reliable evaluation of electronically... 

Electron Transfer Reactions and Exciolexes - Photoinduced electron transfer is one of the most important areas of research. A review of photoinduced electron transfer and electron acceptor complexes usefully surveys the subject . Details of the mechanisms can be obtained by very short time resolution spectroscopy. Dynamic solvent effects on intramolecular electron-transfer involve solvent fluctuations. Time resolved ps emission spectroscopy has been used to examine the kinetics of intramolecular charge transfer in bis(4-aminophenyl)sulphone in ethanol as a function of temperature in this respect 2. it has... 

Fluorescence and Chemiluminescence Spectroscopy. - The fluorescence excitation spectrum of PF3 at 9-13 eV, using monochromatised synchrotron radiation, has been examined to resolve the pyramidal geometry of the X Ai ground state of the PFs" cation, which was also confirmed by ab initio calculations. Dimethylamino-substituted triphenylphosphines exhibit dual fluorescence in polar solvents, and fluorescence-decay measurements have shown that the photo-induced intramolecular charge-transfer process occurs in a few picoseconds, even in weakly-polar solvents. 

There are various potential applications of photophysical phenomena in analytical chemistry. The relatively short lifetimes of most excited states, however, is a serious drawback to the construction of practical devices but studies which focus on finding ways to extend triplet lifetimes have now been described by Harriman et al. Kneas et al. have examined new types of luminescent sensor on polymer supports, and both Neurauter et al. and Marazuela et al. have designed sensors based on the ruthenium(II) polypyridine complex for the detection of carbon dioxide. A system, based on the formation of twisted intramolecular charge transfer states, has been devised for measuring the molecular weight of polymeric matrices (Al-Hassan et a/.), and the chemical reactivity at the interface of self-assembled monolayers has been assessed using fluorescence spectroscopy (Fox et al). 

Walker and co-workers [158] have recently used femtosecond IR spectroscopy to study vibrational dynamics associated with intramolecular charge transfer these studies are complementary to those performed by Barbara and co-workers [159. 160]. in which ground-state RISRS wavepackets were monitored using a dynamic-absorption technique with visible pulses. 

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