Molecular battery

Multielectron storage devices can be used as (i) redox catalysts, also called electron mediators, for multielectron processes, (ii) electrochemical sensors with signal amplification, and (iii) molecular batteries that can be foreseen to power molecular machines in the future or that can be used to construct flexible rechargeable batteries.10... 

Because of all the described properties, these dendrimers behave as molecular batteries that might find applications in molecular-electronic devices. 

Fullerene is an ideal candidate as a component of molecular batteries because it shows six chemically and electrochemically reversible, one-electron reduction70 and one oxidation process.71 In particular, the first reduction process occurs at easy accessible potentials (—0.98 V versus Fc +/Fc in MeCN/toluene solution at 263 K)70 and it is thus the most suitable process to exploit in charge storing devices. To covalently append fullerene to the dendritic structure, chemical functionalization of the bucky-ball is necessary. Fortunately, most of its derivatives keep the reversible electrochemical properties of Ceo, at least for the first reduction process, which usually occurs at more negative potentials than that of fullerene. 

Systems presenting many identical redox-active components bound to a central core or assembled by specific interactions represent approaches towards molecular batteries, i.e., molecular devices capable of performing the reversible exchange (storage and release) of many electrons at the same potential. 

Some researchers see a bright future for dendrimers in many different industrial, medical, research, and consumer applications. One company that produces dendrimers lists applications in drug delivery systems, gene transfection, biotechnology, sensors for diagnostics and detection systems, carbon fiber coatings, microcontact printing, adhesion, molecular batteries, catalysis, separation systems, lasers, composites, and ultrathin films used in optics. 

In the above two independent studies, the feasibility of CPMV as a nanobuilding block for chemical conjugation with redox-active compounds was demonstrated. The resulting robust, and monodisperse particles could serve as a multielectron reservoir that might lead to the development of nanoscale electron transfer mediators in redox catalysis, molecular recognition, and amperometric biosensors and to nanoelectronic devices such as molecular batteries or capacitors. 

I have reviewed, in Chapter No. 12, the activation of arenes by the strongly electron-withdrawing 12-electron fragment CpFe+, isolobal to Cr(CO)3 and Mn(CO)3+, and its application to the synthesis of dendritic cores, dendrons, dendrimers, and metallodendrimers, including molecular batteries. 

Activation of Simple Arenes by the CpFe+ Croup and Applications to the Synthesis of Dendritic Molecular Batteries... 

Chart 1. Third-generation polyallyl dendrimer with was hydrosilylated using dimethylferrocenylsilane a theoretical number of 243 allyl branches syn- Fc(Me)2SiH to 243-Fc , a molecular battery thesized according to Scheme 20. This 243-allyl dendrimer with a theoretical number of 243 dendrimer (like the 9-allyl, 27-allyl, and 81 -allyl peripheral ferrocenyl units,... 

Large Dendrimers Functionalized on their Branches by the Electron-Reservoir [FeCp(i/6-C6Me6)]+ Groups A Molecular Battery in Action... 

S. Nlate, J. Ruiz, V. Sartor, R. Navarro, J.-C. Blais, and D. Astruc, Molecular Batteries Ferrocenylsilylation of Dendrons, Dendritic Cores, and Dendrimers New Convergent and Divergent Routes to Ferrocenyl Dendrimers with Stable Redox Activity, Chem. Eur. J. 6, 2544-2553 (2000). 

A dendrimer consisting of multiple identical and non-interacting redox units, able to reversibly exchange electrons with another molecular substrate or an electrode, can perform as a molecular battery [64, 65]. The redox-active units should exhibit chemically reversible and fast electron transfer processes at easily accessible potential difference and chemical robustness under the working conditions. 

We briefly mention here the use of the ferrocene/ferrocenium redox couple to mediate electron transfer on the oxidation (anodic) side, especially in derivatized electrode. This broad area has been reviewed [349]. For instance, polymers and dendrimers containing ferrocene units have been used to derivatize electrodes and mediate electron transfer between a substrate and the anode. Recently, ferrocene dendrimers up to a theoretical number of 243 ferrocene units were synthesized, reversibly oxidized, and shown to make stable derivatized electrodes. Thus, these polyferrocene dendrimers behave as molecular batteries (Scheme 42). These modified electrodes are characterized by the identical potential for the anodic and cathodic peak in cyclic voltammetry and by a linear relationship between the sweep rate and the intensity [134, 135]. Electrodes modified with ferrocene dendrimers were shown to be efficient mediators [357-359]. For the sake of convenience, the redox process of a smaller ferrocene dendrimer is represented below. 

IV. METALLODENDRIMERSWITH REDOX-STABLE METALLOCENE TERMINALS TOWARD MOLECULAR BATTERIES... 

The design of molecular batteries for molecular electronics will also allow engineering nanoprocesses, and this aspect has a promising future, as do optical and magnetic nanodevices.2c... 

Bioelectrocatalysis-based fuel cells operate under mild conditions and are able to use as fuels many kinds of organic compounds such as carbohydrates and alcohols. They may be constructed in a variety of sizes ranging from a conventional type of fuel cell down to cells of nanometer seale. Therefore, bioelectrocatalysis-based fuel cells are expected to find a variety of applied fields molecular batteries, implantable batteries, disposable-type batteries, eonventional type of fuel cells, etc. 

Ruiz, J. Pradet. C. Varret. F. Astruc. D. Molecular batteries Synthesis and characterisation of a dendritic 19-electron Fe complex that reduces C60 to its mono-anion. 28. Chem. Commun. 2002. 1108-1109. 

Dendrimers and star polymers containing redox active sites have been utilized in the design of new types of catalysts, sensors, bioelectronic devices, and molecular batteries. Highly branched polymers containing arenes coordinated to oiganometallic moieties have been prepared witii chromium tricarbonyl, cyclopenta-dienyliron, " and pentamethylcyclopentadienylrutheniiun moieties. Astruc and... 

Dendrimers have attracted considerable attention since their discovery three decades ago [1 3], Potential applications involve supramolecular properties [11] in the fields of nanomedicine [29], materials science [4-13] and catalysis [16, 30, 38 3], Since the late 1980s, we have focused our attention on metallodendrimers [14, 44] with the aim to develop knowledge concerning redox properties that are useful for redox sensing and catalysis as well as for the design of molecular batteries. In this microreview article, we will illustrate the design of our recent smes of metallodendrimers and some of their properties and applications. 

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