Giant Dendritic Molecular Electrochrome Batteries with Ferrocenyl and Pentamethylferrocenyl Termini Catia Ornelas, Jaime Ruiz, Colette Belin, and Didier Astruc* Institut des Sciences Mole ´culaires, UMR CNRS 5255, UniVersite ´ Bordeaux 1, 351 Cours de la Libe ´ration, 33405 Talence Cedex, France Received August 7, 2008; E-mail: d.astruc@ism.u-bordeaux1.fr Abstract: Giant redox dendrimers were synthesized with ferrocenyl and pentamethylferrocenyl termini up to a theoretical number of 3 9 tethers (seventh generation). Lengthening of the tethers proved to be a reliable strategy to overcome the bulk constraint at the dendrimers periphery. These redox metallodendrimers were characterized by 1 H, 13 C, and 29 Si NMR; MALDI-TOF mass spectrometry (for the low generations); elemental analysis; UV-vis spectroscopy; dynamic light scattering (DLS); atomic force microscopy (AFM); electron-force microscopy (EFM) for half- or fully oxidized dendrimers; cyclic voltammetry; and coulometry. UV-vis spectroscopy, coulometry, and analytical data are consistent with an increasing amount of defects as the generation number increases, with this amount remaining relatively weak up to G 5 . AFM shows that the dendrimers form aggregates of discrete size on the mica surface, recalling the agglomeration of metal atoms in monodisperse nanoparticles. Cyclic voltammetry reveals full chemical and electrochemical reversibility up to G 7 , showing that electron transfer is fast among the flexible peripheral redox sites. Indeed, the redox stability of these new electrochromic dendrimers, i.e., a battery behavior, was established by complete chemical oxido-reduction cycles, and the blue 17-electron ferrocenium and deep-green mixed-valence Fe(III)/Fe(II) dendritic complexes were isolated and characterized. AFM studies also show the reversible dendrimer size changes from upon redox switching between Fe(II) and Fe(III), suggesting a breathing mechanism controlled by the redox potential. Considerable adsorption of high- generation dendrimers on Pt electrodes such as G 7 -Fc allows the easy formation of modified electrodes that sense the ATP anion only involving the electrostatic factor even in the absence of any other type of interaction with the redox tethers. 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Published on Web 12/29/2008 10.1021/ja8062343 CCC: $40.75  2009 American Chemical Society 590 9 J. AM. CHEM. SOC. 2009, 131, 590–601