Dendrimers charge transfer

G2, to G3, and to G4, the effective enhancement was 10%, 36%, and 35% larger than the value estimated by the simple addition of monomeric values. The enhancement included the local field effect due to the screening electric field generated by neighboring molecules. Assuming the chromophore-solvent effect on the second-order susceptibility is independent of the number of chro-mophore units in the dendrimers, p enhancement can be attributed to the inter-molecular dipole-dipole interaction of the chromophore units. Hence, such an intermolecular coupling for the p enhancement should be more effective with the dendrimers composed of the NLO chromophore, whose dipole moment and the charge transfer are unidirectional parallel to the molecular axis. 

Using chemistry similar to that just discussed for Cu +, we have shown that many other transition metal ions, including Pd +, Pt +, Ni +, and Ru +, can be extracted into the dendrimer interiors [59,83,84]. For example, a strong absorption peak at 250 nm ( =8000 cm ) arising from a ligand-to-metal-charge-transfer... 

Some of the materials highlighted in this review offer novel redox-active cavities, which are candidates for studies on chemistry within cavities, especially processes which involve molecular recognition by donor-acceptor ii-Jt interactions, or by electron transfer mechanisms, e.g. coordination of a lone pair to a metal center, or formation of radical cation/radical anion pairs by charge transfer. The attachment of redox-active dendrimers to electrode surfaces (by chemical bonding, physical deposition, or screen printing) to form modified electrodes should provide interesting novel electron relay systems. 

These results indicate that in the individual dendrimers, interactions take place both in the ground state and in the excited state between the naphthyl units and also between naphthyl and amine units of the dendrimer branches which result in dimer/excimer and charge-transfer/exciplex excited states. 

Control of self-assembly by switchable redox processes in complexes between dendrimers with re-donor and re-acceptor units permitted specific prediction of the space occupied by dendritic aggregates. Use of cucurbit[8]uril (see Fig. 6.9) as donor-host compound for viologen guests (dendronised 4,4 -bipyridines as acceptors) promotes formation of such charge-transfer complexes [24]. 

In another study also, electrochemical impedance technique has been shown to be a useful method for a DNA biosensor using a multinuclear nickel(II) salicylaldimine metallodendrimer platform [164], Both the preparation of the dendrimer-modified GCE surface and the immobilization of DNA have been effectively done by simple drop-coating procedures. The metallodendrimer is electroactive exhibiting two redox couples in phosphate buffer solution. The impedance study demonstrated that the DNA biosensor responded well to 5 nM of target DNA by displaying a decrease in charge transfer resistance in phosphate buffer solution and increase in charge transfer resistance in the presence of the [Fe(CN)6]3/4" redox probe. 

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