Metallodendritic iron complexes: design, catalysis, and molecular recognition.

A review. Metallodendrimers can be assembled in a no. of ways (covalent, ionic, hydrogen-bonding, coordination), wherein the metal plays key roles: sensor, catalyst, electronic, magnetic, or optical device. The mol. engineering pertaining to the metallodendritic design is relevant to multiple aspects of nanoscience from fundamental to societal research. In the present chapter, we have emphasized the problems encountered in dendritic construction (i.e., surface vs. vol. limit), including synthetic strategies offered by simple organometallic activation and modem methods of characterization. Nanoparticle-cored dendrimers pioneered in 2001 are a particularly attractive category insofar as they facilitate rapid, yet relatively robust constructions. Dendritic catalysts offer the possibility of recovery due to their size, but dendritic effects are neg., that is the kinetics drops when the dendritic generation increases due to the bulk problem (access to the metal center). Recognition and sensing with dendritic exoreceptors benefits from pos. dendritic effects, because the channels become narrower, and thus better suited for interaction with the substrate when the dendritic generation increases. It is also interesting to note that metallodendritic assembly by triple H-bonding between phenols and primary amines is sufficient for recognition on the electrochem. timescale (i.e., 0.1 s), which can be a clear advantage over tedious covalent dendrimer construction. One significant advantage of robust dendrimers for sensing, however, is the size providing adsorption on solids. Thus, the larger the metallodendrimer, the better it adsorbs on electrodes for recycling the dendrimer-modified electrode sensor. The bonding interaction leading to sensing must also be strong enough to offer a significant shift in the sensing parameter (El/2), and yet be modest enough to allow easy removal of the sensed substrate for recycling and reuse. This is the case with the hypervalent Si...O bond when the Si atom is directly attached to the silylferocenyl group in ferrocenyl dendrimers. The design of mol. batteries for mol. electronics will also allow engineering nanoprocesses, and this aspect has a promising future, as do optical and magnetic nanodevices. [on SciFinder(R)]