Laser-induced fluorescence, hydrogen bonds

In nonhydrogen bonding solvents, this molecule was shown to emit only at 500 nm. Emission at 390 nm could only be obtained in alcohols. These results demonstrate that the ultraviolet fluorescence component is due to molecules in which the carbonyl oxygen is not hydrogen bonded to the hydroxyl group. Equilibrium cannot be established between the two tautomers in the excited state only molecules which are in the correct ground state configuration will participate in a proton translocation. This proton translocation takes place in under 10 ps. Since neither a temperature dependence nor an isotope effect could be observed, the dynamic measurements do not elucidate the mechanism for the proton translocation. This question has been answered in part by the appUcation of laser-induced fluorescence. 

A brief report has appeared on the crossed-beam reaction between Ba and LiCl, using laser-induced fluorescence detection of the BaCl product, which gives a lower bound for the bond-dissociation energy of BaCl of 110 3 kcal mol-1.242 Similar studies on the reactions of alkali-metal dimers with hydrogen atoms and molecules 243 and the photodissociation of alkali-metal iodides244 have been reported. 

Deactivation of 2-naphthylamine singlet state by pyridines in enhanced by dipole moment and the ability to form hydrogen bonds. Picosecond laser spectroscopy shows charge transfer from the excited amine. The fluorescence of 2-iV,A -dimethylaminopyridine induced by p-nitroaniline is also caused by exciplex formation. The latter enhances triplet population of p-nitroaniline. The quenching of the fluoresence of carbazole and some derivatives by trichloroacetic acid and related compounds in fluid solutions has been studied by Johnson.A charge-transfer interaction is involved and the basicity of carbazole and derivatives determined. Charge transfer is also involved by quenching of carbazole by halocarbons. The A -isopropylcarbazole-dimethylterephthalate exciplex has been observed in PMMA films.Photoinduced electron-transfer in the p-phenylenediamine-paraquat complex yields the paraquat cation. ... 

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