Energy transfer photophysical

Tung CH, Zhang LP, Li Y et al (1997) Intramolecular long-distance electron transfer and triplet energy transfer. Photophysical and photochemical studies on a norbomadiene-steroid-benzidine system. J Am Chem Soc 119 5348-5354... 

Much use has been made of micellar systems in the study of photophysical processes, such as in excited-state quenching by energy transfer or electron transfer (see Refs. 214-218 for examples). In the latter case, ions are involved, and their selective exclusion from the Stem and electrical double layer of charged micelles (see Ref. 219) can have dramatic effects, and ones of potential imfKntance in solar energy conversion systems. 

Langa and co-workers have prepared fullerodendrimers 18 and 19 in which the phenylenevinylene dendritic wedge is connected to a pyrazoHno [60] fullerene core rather than to a fulleropyrrolidine one as for 12-17 (Fig. 9) [44]. Preliminary photophysical investigations suggest that the efficient energy transfer from the excited antenna moiety to the pyrazolino [60] fullerene core is followed by an electron transfer involving the fullerene moiety and the pyrazoHne N atom. 

Dendrimers with a polyphenyl core around a central biphenyl unit decorated at the rim with peryleneimide chromophores have been investigated both in bulk and at the single-molecule level in order to understand their time and space-resolved behavior [28]. The results obtained have shown that the conformational distribution plays an important role in the dynamics of the photophysical processes. Energy transfer in a series of shape-persistent polyphenylene dendrimers substituted with peryleneimide and terryleneimide chro-mophoric units (4-7) has been investigated in toluene solution [29]. 

That dendrimers are unique when compared with other architectures is confirmed by an investigation on porphyrin core dendrimers and their isomeric linear analogues [63]. The isomers displayed dramatically different hydrodynamic properties, crystallinity, and solubility characteristics when compared to those of their dendritic analogues, and photophysical studies showed that energy transfer from the poly(benzylether) backbone to the core was more efficient in the dendrimer because of the shorter distance between the donor units and the acceptor core. 

Photophysical studies have been performed on dendrimers 41 [49], built around a [Ru(bpm)3]2+ core (bpm=2,2 -bipyrimidine),and42 [59],built around a [Ru(QP)3]2+ core (QP = 2,2 3, 2" 6",2" -quaterpyridine). In both compounds energy transfer from the peripheral Re(I)-based chromophores to the central Ru(II)-based unit occurs with unitary efficiency. 

Jiao, G., Thoresen, L., Kim, T., Haaland, W., Gao, F., Topp, M., Hochstrasser, R., Metzker, M. and Burgess, K. (2006). Syntheses, photophysical properties, and application of through-bond energy-transfer cassettes for biotechnology. Chemistry 12, 7816-26. 

This chapter describes the characteristics of the fluorescence emission of an excited molecule in solution. We do not consider here the photophysical processes involving interactions with other molecules (electron transfer, proton transfer, energy transfer, excimer or exciplex formation, etc.). These processes will be examined in Chapter 4. 

Class 3 fluorophores linked, via a spacer or not, to a receptor. The design of such sensors, which are based on molecule or ion recognition by a receptor, requires special care in order to fulfil the criteria of affinity and selectivity. These aspects are relevant to the field of supramolecular chemistry. The changes in photophysical properties of the fluorophore upon interaction with the bound analyte are due to the perturbation by the latter of photoinduced processes such as electron transfer, charge transfer, energy transfer, excimer or exciplex formation or disappearance, etc. These aspects are relevant to the field of photophysics. In the case of ion recognition, the receptor is called an ionophore, and the whole molecular sensor is... 

The effects of photophysical intermolecular processes on fluorescence emission are described in Chapter 4, which starts with an overview of the de-excitation processes leading to fluorescence quenching of excited molecules. The main excited-state processes are then presented electron transfer, excimer formation or exciplex formation, proton transfer and energy transfer. 

The basic principle of this method of recognition is a cation-induced conformational change bringing closer together (or moving away) two moieties able to interact and induce photophysical effects excimer or exciplex formation (or disappearance), electronic energy transfer and quenching. 

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