Dendritic antenna

Fig. 4.12 Dansyl-decorated oligo-lysine dendrimer (2nd generation) as dendritic antenna with sensor properties towards metal ions (according to Balzani, Vogtle et al)...

Fig. 5.10 Light-harvesting dendritic antenna (according to Frechet et al.)...

Aida T, Jiang D L, Yashima E, Okamoto Y. 1998. A new approach to light harvesting with dendritic antenna. Thin Solid Films 331(1 2) 254 258. 

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. 

Methanofullerene 20 with phenylacetylene dendrimer addends has also been reported [45] (Fig. 10). The UV absorption of fullerodendrimer 20 is particularly strong and is mainly attributed to transitions located on the two dendritic branches of the molecule. The photophysical investigations revealed that the large poly(aryl)acetylene branches act as photon antennae [46]. 

The properties of these rotaxane dendrimers are quite different from those of the individual rotaxanes or dendrimers and often a blend of both. In view of the versatile characteristics that a dendron or dendrimer can manifest, several new properties can be imparted to the rotaxanes. For example, the solubility of rotaxanes in organic solvents as well as in water can be significantly improved when large dendrimer units are appended enhancing the prospects of their use as molecular machines. The dendritic units can also influence the photo/electro-chemical properties of the rotaxanes. Employing photo-receptive dendron units, photo chemically driven molecular machines may be developed, where the dendrons act as antenna for photo-harvesting [62]. 

Very interesting antenna systems have been constructed by functionalizing the chain ends of a poly(arylether) convergent dendritic backbone with cou-marin-2 A =435 nm) and its focal point with coumarin-343 X =49Q nm) [33] dendrimer 8 represents the fourth generation. 

Remarkable concentration of the photon energy absorbed by aromatic dendritic scaffold toward the focal point (herein called antenna effects ) is one of the most distinct features of the dendritic macromolecules. Poly(benzyl ether) (PBE) dendron [1] has been studied most extensively as an efficient antenna dendron. Careful studies have revealed the crucial role of the symmetric dendritic structure for the antenna effect. 

Brinas RP, Troxler T, Hochstrasser RM, Vinogradov SA (2005) Phosphorescent oxygen sensor with dendritic protection and two-photon absorbing antenna. J Am Chem Soc 127 11851-11862... 

---