Energy transfer photoinduced

Chiral recognition of A-[Co(phen)3]3+ has been observed in a modified /3-cyclodextrin.772 Chiral discrimination has also been seen in photoinduced energy transfer from luminescent chiral lanthanoid complexes773 to [Co(phen)3]3+ and between photoexcited [Ru(bpy)3]2+ and [Co(phen)3]3+ co-adsorbed on smectite clays.774 The [Co(bpy)3]3+ ion has been incorporated into clays to generate ordered assemblies and also functional catalysts. When adsorbed onto hectorite, [Co(bpy)3]3+ catalyzes the reduction of nitrobenzene to aniline.775 The ability of [Co(phen)3]3+ to bind to DNA has been intensively studied, and discussion of this feature is deferred until Section 6.1.3.1.4. 

PHOTOINDUCED ENERGY TRANSFER THROUGH DENDRIMER ARCHITECTURE... 

Use simple molecular orbital diagrams to show the various processes of photoinduced energy transfer and photoinduced electron transfer. 

Figure 12.13 Photoinduced energy transfer and electron transfer over long distances...

Fig. 9 Schematic representation of the self-assembled 2 Nd3+ [Ru(bpy)2(CN)2]. Curved arrows represent photoinduced energy transfer processes. For more details, see text...

Bifluorophores consisting of two different fluorescent dyes linked by a flexible spacer containing heteroatoms (oxygen, nitrogen or sulfur atoms) can bind cations. This results in a decrease of the distance between the two fluorophores and, consequently, to an increase in efficiency of photoinduced energy transfer between the two moieties (Figure 2.13) provided that the emission spectrum of the donor (D) overlaps the absorption spectrum of the acceptor (A).(36) The transfer efficiency depends on the distance according to Forster s theory ... 

B. Valeur, J. Pouget, J. Bourson, M. Kaschke, and N. P. Ernsting, Tuning of photoinduced energy transfer in a bichromophoric coumarin supermolecule by cation binding, J. Phys. Chem. 96, 6545-6549 (1992). 

Fig. 16. Representation of photoinduced energy transfer and electron transfer processes involved in supramolecular photochemistry. Generation of R S, RS, R+S", or R-S+ may be followed by a chemical reaction.

The study of photoinduced processes in Ir(III)-based arrays has been exploited since facile synthetic methods for the preparation of Ir(III)-polyimine complexes became available. Polynuclear complexes containing, in addition to Ir(III) centers, either Os(II)-, Ru(II)-, Re(II) or Cu(I)-polyimine units linked by different bridging ligands, displayed a rich variety of photoinduced energy transfer processes. In Fig. 22 are reported some representative cases of early studies. 

Characterization of photoinduced energy-transfer processes and mechanisms (Chap. 8). 

Energy transfer reactions in systems containing the herein investigated molecular wire structures have already been investigated in Erlangen. Two well-characterized examples, which were investigated within the scope of this thesis will be presented in more detail. This lines out the characteristic features of photoinduced energy transfer reactions. 

Apart from electron transfer, photoinduced energy transfer processes are widely observed within both natural and artificial systems and play a particularly important role at surfaces. 

Photoinduced energy transfer occurs when the excitation energy from a donor species is transferred to an acceptor species, typically resulting in the generation... 

Lammi RK, Ambroise A, Balasubramanian T, et al. Structural control of photoinduced energy transfer between adjacent and distant sites in multiporphyrin arrays. J Am Chem Soc 2000 122 7579-91. 

P-Cyclodextrines, appended to a ruthenium complex, have been employed as hosts for iridium and osmium complexes bearing adamantyl or biphenyl moieties, which form strong host-guest complexes with P-cyclodextrines (see Fig. 3). In such systems, photoinduced energy transfer can occur from the periphery, upon complexation of the iridium units, toward the central ruthenium acceptor, or switched in the other direction, from the ruthenium to the periphery when the osmium moieties are assembled (see Fig. 3) 42). The lowest excited state is in fact localized on the osmium center, while the highest luminescent excited state belongs to the iridium complex (see Fig. 3 right). 

In order to have a rod-type system where photoinduced energy transfer or electron transfer processes can occur, great attention must be devoted to the separated components and to the way they are connected [24, 26-29]. The simplest system conceivable for the occurrence of a photoinduced process, a dyad, is depicted in Figure 1. 

Figure 3. Schematic energy level diagrams for photoinduced energy transfer (left) and electron transfer (right) processes.

Figure 9. Schematic energy level diagram(left) for Ru230s compounds. Evidence for the photoinduced energy transfer process can be obtained from a) the emission spectrum (quenching of the ruthenium emission and sensitization of the osmium) and b) the rise time.

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