Transfer Luminescence

In the case of charge transfer, the optical transition takes place between different kinds of orbitals or between electronic states of different ions. In these cases, too, the width and position of the emission bands depend on the chemical environment. 

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J. N. Demas and G. A. Crosby, Quantum efficiencies of transition metal complexes. II. Charge transfer luminescences, /. Am. Chem. 93, 2841-2847 (1971). 

C. Anion-Cation Annihilation and Charge-Transfer Luminescence 433... 

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... 

The majority of the electron-transfer luminescence spectra that have been measured8-16,17 have been found to show shape and structure which quite closely conform to the fluorescence spectra of the electroactive component (cf. Fig. 7). A substantial minority of both chemical and electrochemical experiments have, however, produced emission which shows no similarity to the known fluorescence of the electroactive substance. Assignment of these emissions has been more difficult and the conclusions less certain. 

At this point it is necessary to consider the mechanism of electron-transfer luminescence in solutions which cannot involve ion-radical annihilation because both cation and anion of the fluorescer are not formed. Such emission can be achieved by treating anion radicals with chemical oxidants or electrochemically under conditions where the corresponding cation cannot be produced, and it may also be achieved by electrochemical reduction of cations without producing the corresponding anion. In addition to triplets, three types of processes and pathways have been proposed to help explain why such emission occurs. These may be described as (7) impurities, (2) ion-radical aggregates, and (5) heterogeneous electron transfer. It is evident63 that impurities,... 

Much has been learned about electron-transfer luminescence in solution in the few years since its discovery. However, an understanding of the mechanistic details of this energy conversion process is not satisfactory. Much also remains to be learned about the sources of the emissions which are not due to the fluorescence of the substrate. 

Iki, N. Horiuchi, T. Oka, H. Koyama, K. Morohashi, N. Kabuto, C. Miyano, S. Energy transfer luminescence of Tb3+ ion complexed with calix[4]arenetetrasulfo-nate and the thio and sulfonyl analogue. The effect of bridging groups. J. Chem. Soc., Perkin Trans. 2 2001, 2219-2225. 

McClenaghan ND, Leydet YM, Indelli MT, Campagna S. Excited-state equilibration a process leading to long-lived metal-to-ligand charge transfer luminescence in supramolecular systems. Coord Chem Rev 2005 249 1336-50. 

A range of vinyl and carboxypyridyl derivatives of [Ru(bipy)2]2+ have been prepared and electron transfer reactions and the photochemical activity of these complexes as polymer films at electrode surfaces studied.745,861,953 1058 1138-1148 Some chemical transformations involving polyvinyl pyridine (PVP) are illustrated in Scheme 28.1138,1142-1144,1149 The charge transfer luminescence spectra of cis- and tranA-[Ru(bipy)2py2]2+,1096,1150 czs-[Ru(bipy)2L2]4+ (L = 2-methyl-4,4 -bipyridinium+),1151 cis- and traru-[Ru bipy)(phen)py2]2+, [Ru(bipy)py2(L)]2+ (L = en, (NH3)2, 2-methylaminopyridine, 2-ethylaminopyridine) and [RuCl(bipy)py3]+ have been measured.1096... 

Absorbance Internal conversion Fluorescence Intersystem crossing Phosphorescence Energy transfer Luminescence... 

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