Rigid dendrimers

Significantly, the more rigid dendrimers 53-54 and 11-14 (described in Section II) prepared by Sato 45) and Kolner 29) showed no drop in enantioselectivity for higher generations of the dendrimer for the addition of to N-... 

A. K. Diallo, J.-C. Daran, F. Varret, J. Ruiz, D. Astruc, Fast electron transfer has been recently observed also for rigid dendrimers containing ferrocene units at the periphery, Angew. Chem., Int. Ed. 2009, 48, 3141. 

Gd(III) chelates, the relatively low relaxivity is the consequence of the flexibility of the linker group between the Gd(III) chelate and the rigid dendrimer molecule (slow water exchange is also limitative). Internal flexibility has been also proved for certain non-covalently bound Gd(III) chelate - protein adducts. The tr value determined for MP-2269 bound to bovine serum albumin is 1.0 ns, one order of magnitude lower than the rotational correlation time of the protein molecule [50]. 

Structurally, dendrimers of type 5 are best compared with rigid dendrimers made up of tolan building blocks. However, neither the form of aggregation observed in stilbenoid dendrimers, nor the phase behaviour or the photochemistry of these compounds have so far been found to occur in similar form in tolan systems. 

Fig. 23. Changing the branch cell reagent size as a function of generation which could allow rigid dendrimers to be grown indefinitely even in a plane...

Gorman and coworkers have prepared five generations of dendrimers with cores composed of iron-sulfur clusters and with dendritic branches of varying flex-ibihty[44, 45]. Electrochemical measurements were carried out to determine diffusion coefficients as well as heterogeneous electron-transfer rates. The rate of electron transfer decreased monotonically with increasing dendrimer size, and the rigid dendrimers exhibited a much larger attenuation of the rate of electron transfer than the flexible ones [45]. 

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