Probe-electron donor dyads

In 2004, Leventis et al. [12] presented a study in which they demonstrated that probe-doped silica aerogels could be prepared by post-doping cationic mthenium probes and cationic probe-electron donor dyads into silica sol-gel monoliths. Ruthenium complexes have well-described properties and have been studied extensively by others (as noted in [4, 13]). 

The study of photoinduced ET in covalently linked donor-acceptor assemblies began with comparatively simple dyad systems which contain a transition metal center covalently linked to a single electron donor or acceptor unit [26]. However, work in this area has naturally progressed and in recent years complex supramolecular assemblies comprised of one or more metal complexes that are covalently linked to one or more organic electron donors or acceptors have been synthesized and studied [27-36]. Furthermore, several groups have utilized the useful photoredox properties of transition metal complexes to probe electron and energy transfer across spacers comprised of biological macromolecules such as peptides [37,38], proteins [39,40], and polynucleic acids [41]. 

Quantitative Evaluation of Arenes as Electron Donors 437 Spectral (UV/vis) Probe for the Formation of CT Complexes 438 IR Spectroscopic Studies of Charge-Transfer Complexation 442 Thermodynamics of Charge-Transfer Complexation 443 Structural Features of Arene Charge-Transfer Complexes 445 Bonding Distance of the Donor/Acceptor Dyad in Arene Complexes 446 Relationship Between Hapticity and Charge Transfer in Arene Complexes 447 Effect of Charge Transfer on the Structural Features of Coordinated Arenes 448... 

The probe ruthenium(ll) frA-(l, 10-phenanthroline) and the electron donors 4-benzoyl-A-methylpyridinium and A-benzyl-A -methyl viologen were employed by Leventis et al. [12]. A base-catalyzed TMOS precursor recipe was used to prepare silica sol-gel monoliths. The wet gels were then soaked in methanol baths containing one of the dyads, or the mthenium complex, each of which is a cationic species that was taken up by the sol-gels to such an extent that no color was observed in the remaining bath solution. The doped gels... 

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