Giant Dendritic Molecular Electrochrome Batteries with Ferrocenyl and Pentamethylferrocenyl Termini

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.

Preparation and Characterization of Novel Poly(alkylidenamine) Nitrile Ruthenium Metallodendrimers

“…Also in the 1 H NMR spectrum, only one signal is present for the Cp-ring (around δ = 4.4 ppm). This confirms the equivalence of all ruthenium 2 ], as this always resulted in the formation of a mixture of unidentified impurities that was not possible to purify. For the general procedure, cores 4 or 7 and cis-[RuCl(dppe) 2 ][PF 6 ] (4.5 molar ratio) were stirred in 1,2-dichloroethane at 90°C.…”

“…In a typical experiment, a solution of core 4 or 7 (Scheme 3), [Ru(η 5 -C 5 H 5 )(PPh 3 ) 2 Cl] (4.5 molar ratio) and TlPF 6 (4.5 molar ratio) in methanol was stirred at room temperature. The resulting mixture was filtered, and the solid part was quickly extracted with dichloromethane, which upon solvent evaporation afforded tetrakis-ruthenium dendrimers 8 or 9 in the form of yellow powders (Scheme 3).…”

“…The incorporation of transition-metal complexes into dendritic molecules may lead to new and interesting materials [1] with specific and tunable properties (e.g., catalytic, [2] sensing, [3] biomedical [4] and photo-optical [5] ). Coordination chemistry, with its variety of metals and ligands, provides good and straightforward synthetic strategies for the preparation of metallodendrimers.…”

Synthetic regimes due to packing constraints in dendritic molecules confirmed by labelling experiments

“…13). Since then, the vicinity of g max and the SIS were invoked to rationalize deviations of observed MM from their ideal values 31,32 , as well as synthesis failures [33][34][35] . It was also discussed as a design guideline for controlling the accessibility of the dendritic interior to guest molecules 36,37 .…”

Organometallic rotaxane dendrimers with fourth-generation mechanically interlocked branches

“…The absence of the pillar [5]arene wheels resulted in reduced solubility of G n -c in common solvents (chloroform and THF); the third-generation model dendrimer G 3 -c was the highest-generation dendrimer that could be synthesized. We used electron microscopy methods such as atomic force microscopy (AFM) and transmission electron microscopy (TEM), to visualize individual supramolecular dendrimers as described by others (27). These methods can provide structural parameters of dendrimers such as their size, conformation, and rigidity, using direct images on a surface.…”