Luminescent organic compounds

Solid-surface room-temperature phosphorescence (RTF) is a relatively new technique which has been used for organic trace analysis in several fields. However, the fundamental interactions needed for RTF are only partly understood. To clarify some of the interactions required for strong RTF, organic compounds adsorbed on several surfaces are being studied. Fluorescence quantum yield values, phosphorescence quantum yield values, and phosphorescence lifetime values were obtained for model compounds adsorbed on sodiiun acetate-sodium chloride mixtures and on a-cyclodextrin-sodium chloride mixtures. With the data obtained, the triplet formation efficiency and some of the rate constants related to the luminescence processes were calculated. This information clarified several of the interactions responsible for RTF from organic compounds adsorbed on sodium acetate-sodium chloride and a-cyclodextrin-sodium chloride mixtures. Work with silica gel chromatoplates has involved studying the effects of moisture, gases, and various solvents on the fluorescence and phosphorescence intensities. The net result of the study has been to improve the experimental conditions for enhanced sensitivity and selectivity in solid-surface luminescence analysis. 

Solid-surface luminescence analysis involves the measurement of fluorescence and phosphorescence of organic compounds adsorbed on solid materials. Several solid matrices such as filter paper, silica with a polyacrylate binder, sodium acetate, and cyclodextrins have been used in trace organic analysis. Recent monographs have considered the details of solid-surface luminescence analysis (1,2). Solid-surface room-temperature fluorescence (RTF) has been used for several years in organic trace analysis. However, solid-surface room-temperature phosphorescence (RTF) is a relatively new technique, and the experimental conditions for RTF are more critical than for RTF. 

Burdo and Seitz reported in 1975 the mechanism of the formation of a cobalt peroxide complex as the important intermediate leading to luminescence in the cobalt catalysis of the luminol CL reaction [116]. Delumyea and Hartkopf reported metal catalysis of the luminol reaction in chromatographic solvent systems in 1976 [117], while Yurow and Sass [118] reported on the structure-CL correlation for various organic compounds in the luminol-peroxide reaction. 

The apphcation of an optical transducer based on the fluorescence quenching effect of oxygen was described by Preininger et al. [3]. Another interesting technique is represented by the use of the luminous bacterium Photobacterium phos-phoreum [34]. This device is based on the correlation of the intensity of luminescence to the cellular assimilation of organic compounds from the wastewater. 

A remarkable number of organic compounds luminesce when subjected to consecutive oxidation-reduction (or reduction-oxidation) in aprotic solvents1-17 under conditions where anion radicals are oxidized or cation radicals are reduced. In many instances, the emission is identical with that of the normal solution fluorescence of the compound employed. In these instances the redox process has served to produce neutral molecules in an excited electronic state. These consecutive processes which result in emission are not special examples of oxidative chemiluminescence, but are more properly classified as electron transfer luminescence in solution since the sequence oxidation-reduction can be as effective as reduction-oxidation.8,10,12 A simple molecular orbital diagram, although it is a zeroth-order approximation of what might be involved under some conditions, provides a useful starting... 

Aggregation as the cause of luminescence was also probed in fluid solutions, since a dilute colorless solution was not emissive, but a concentrated (2 x 10-2 M) solution was weakly emissive a result that is consistent with the aggregation of these units in solution. Undoubtedly, this complex has potential for practical applications as a luminescent sensor for the detection of volatile organic compounds (VOCs). 

A study was made by Freeman and co-workers (93) of the effect of deuterium on the luminescence decay times of solvated rare earth chlorides. Hutchison and Mangum (94) and Robinson (95) had previously shown that there is a substantial increase in the mean triplet-state lifetimes of aromatic organic compounds when the hydrogen is replaced by deuterium. Robinson... 

The catalyzed decomposition of energy-rich organic peroxides is another typical reaction of this type. It was called "chemically initiated electron-exchange luminescence" (CIEEL) by Schuster, who used organic compounds as redox catalysts (14). However, transition... 

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