Reduction with Organic Donor Molecules

The first chemical transformations carried out with Cjq were reductions. After the pronounced electrophilicity of the fullerenes was recognized, electron transfer reactions with electropositive metals, organometallic compounds, strong organic donor molecules as well as electrochemical and photochemical reductions have been used to prepare fulleride salts respectively fulleride anions. Functionalized fulleride anions and salts have been mostly prepared by reactions with carbanions or by removing the proton from hydrofullerenes. Some of these systems, either functionalized or derived from pristine Cjq, exhibit extraordinary solid-state properties such as superconductivity and molecular ferromagnetism. Fullerides are promising candidates for nonlinear optical materials and may be used for enhanced photoluminescence material. 

Neutral organic molecules can also be one-electron donors. For example, tetracyano-quinodimethane gives rise to anion-radical on reduction with 10-vinylphenothiazine or N,N,N, N -tetramethyl-p-phenylenediamine. Sometimes, alkoxide or phenoxide anions hnd their applications as one-electron donors. There is a certain dependence between carbanion basicity and their ability to be one-electron donors (Bordwell and Clemens 1981). 

Although the phenomenon is more common in organic photochemistry, a coordination entity can also act in the process of excimer or exciplex formation as an excited molecule AB or quencher (Q).The second-sphere donor-acceptor interaction with an acceptor quencher causes oxidative quenching of AB, whereas interaction with a donor quencher yields reductive quenching. 

Photoinduced electron transfer (PET) processes can be used to bringing about one-electron oxidation and reduction of organic molecules [115-118]. In these processes, photoexcitation of an electron acceptor or donor leads to enhancement of their electron-aceepting and -donating properties, respectively. When the excited state molecule comes into contact with a ground-state electron donor or acceptor within the exeited state lifetime, electron transfer can occur. The feasibility of producing radical ions via these processes ean be predicted by use of the Rehm-Weller equation [119], which is given in Eq. 6 [120[ ... 

When metallo-enzymes effect the oxidation or reduction of organic substrates or simple molecules such as H2O, N2 or O2, they often function as multielectron donors or acceptors with two or more metals at the active site. The electronic coupling between the metals is often accompanied by unique spectroscopic features such as electron spin-spin coupling. The metal-metal electronic coupling may facilitate the multi-electron-transfer reactions with the substrates. In simpler molecular systems, two electron-transfer processes most often require substrate binding , as in an inner-sphere, group (or atom ) transfer process. ... 

In heterogeneous catalysts, the tailored and pillared cavity is an essential property as it enables the movement of reactants to inner catalytic sites. The mass transfer of reactants and products inside the pores is mainly influenced by the interaction of the internal walls of the channel with organic molecules, and can consequently be controlled by the difference in polarities. To ensure such properties, anchored ruthenium hybrid zirconium phosphate-phosphonates coated with hydrophobic linear double-stranded polystyrene over the inner surface of the Zr layers were prepared by the first complexation of Ru and then molding of inorganic backbone method, and used as the catalyst in the ATH of o-, m- and p-substituted acetophenones (Fig. 42) [121]. This catalyst showed good catalytic activity and enantioselectivity (73.6-95.6 % ees) in the aqueous reduction with FA-TEA as the hydrogen donor, and could retain its catalytic properties after five runs in the case of acetophenone. 

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