Through-bond coupling mechanism

Nonphotoactive units, such as ex-TTF and Fc, have been covalently linked to spheroid by means of different methodologies. When Diels-Alder cycloaddition was used to attach exTTF moieties to the fullerene, efficient electron and energy transfer took place by a through-bond coupling mechanism (Figure 2.27a). ... 

The algebraic increase from -7.0 Hz in CDCl to -3.2 Hz in DMSO -d corroborates the existence of a through space coupling mechanism (F 2) In fact, inhibition of this contribution due to the rupture of intramolecular hydrogen bonds between fluorine and the N-H proton is produced by DMSO and a concomitant decrease in the absolute value of... 

As with the COSY experiment, the sequence starts with a pulse followed by an evolution period, but now the mechanism that couples the two spins (which must be in close proximity, typically <6 A) is the Nuclear Overhauser Effect (NOE). The second pulse converts magnetization into population disturbances, and cross-relaxation is allowed during the mixing time. Finally, the third pulse transfers the spins back to the x-y-plane, where detection takes place. The spectrum will resemble a COSY spectrum, but the off-diagonal peaks now indicate through-space rather than through-bond interactions. 

Although the exchange mechanism was originally formulated in terms of direct orbital overlap between the donor and acceptor chromophores, it is clear that it can be extended to cover the case of through-bond mediated EET. The reason is because TB coupling provides a mechanism for spatially extending the active orbitals of the two chromo-... 

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