Donor organs

Whereas the electrochemical decomposition of propylene carbonate (PC) on graphite electrodes at potentials between 1 and 0.8 V vs. Li/Li was already reported in 1970 [140], it took about four years to find out that this reaction is accompanied by a partially reversible electrochemical intercalation of solvated lithium ions, Li (solv)y, into the graphite host [64], In general, the intercalation of Li (and other alkali-metal) ions from electrolytes with organic donor solvents into fairly crystalline graphitic carbons quite often yields solvated (ternary) lithiated graphites, Li r(solv)yC 1 (Fig. 8) [7,24,26,65,66,141-146],... 

Elegant evidence that free electrons can be transferred from an organic donor to a diazonium ion was found by Becker et al. (1975, 1977a see also Becker, 1978). These authors observed that diazonium salts quench the fluorescence of pyrene (and other arenes) at a rate k = 2.5 x 1010 m-1 s-1. The pyrene radical cation and the aryldiazenyl radical would appear to be the likely products of electron transfer. However, pyrene is a weak nucleophile the concentration of its covalent product with the diazonium ion is estimated to lie below 0.019o at equilibrium. If electron transfer were to proceed via this proposed intermediate present in such a low concentration, then the measured rate constant could not be so large. Nevertheless, dynamic fluorescence quenching in the excited state of the electron donor-acceptor complex preferred at equilibrium would fit the facts. Evidence supporting a diffusion-controlled electron transfer (k = 1.8 x 1010 to 2.5 X 1010 s-1) was provided by pulse radiolysis. 

Several crystal structure determinations of [AuX2l salts with different cations have been carried out for [AuC12],1823,1904,2854,3065-3068 [AuBr2],3065,3069,3070 or [AuF]-.3065 3066 3071-3074 Many other structural determinations have been reported in which [AuX2]- salts act as counterions of conducting or superconducting ion radical salts as bis-ethylenedithiotetrathiafulvalene (ET) and related organic donors. 

Electron-transfer activation of electrophilic aromatic substitution 274 Electron-transfer activation in nitrogen dioxide reactivity toward organic donors 292... 

The donor strength is quantitatively evaluated by the energetics of the oxidative conversion of an organic donor (D) to its cation radical (D+ ) as measured in solution by its reversible oxidation potential ( ox)63 (equation 28). 

Except for very electron-rich donors that yield stable, persistent radical cations, the ox values are not generally available.64 Thus the cation radicals for most organic donors are too reactive to allow the measurement of their reversible oxidation potentials in either aqueous (or most organic) solvents by the standard techniques.65 This problem is partially alleviated by the measurement of the irreversible anodic peak potentials E that are readily obtained from the linear sweep or cyclic voltammograms (CV). Since the values of E contain contributions from kinetic terms, comparison with the values of the thermodynamic E is necessarily restricted to a series of structurally related donors,66 i.e.,... 

An alternative measure of the electron-donor properties is obtained from the energetics of electron detachment in the gas phase the ionization potentials (IP) of many organic donors have been experimentally determined from the photoelectron spectra obtained by their photoionization in the gas phase. Thus, the values of the ionization potential IP differ from the oxidation potential x by solvation,66 i.e.,... 

Fig. 5 Global correlation of the oxidation potentials Eox (V versus SCE) with the vertical ionization potentials IP (eV) of various types of organic donors identified in Table 3.

New synthetic transformations are highly dependent on the dynamics of the contact ion pair, as well as reactivity of the individual radical ions. For example, the electron-transfer paradigm is most efficient with those organic donors yielding highly unstable cation radicals that undergo rapid unimolecular reactions. Thus, the hexamethyl(Dewar)benzene cation radical that is generated either via CT activation of the [D, A] complex with tropylium cation,74... 

The BFT, PFg" and SbCl salts of cation radicals are readily prepared by oxidation of organic donors with the corresponding NO+ salts in a relatively nonpolar solvent such as dichloromethane. For example, a solution of the hydroquinone ether MA in anhydrous (deaerated) dichloromethane turns purple upon the addition of crystalline NO+BFT at low temperature ( 50°C).173 The coloration is due to formation of the donor/acceptor complex [MA, NO+] (equation 34). 

The strongly oxidizing SbCl5 is an effective oxidant for the preparation of cation-radical salts of hexachloroantimonate (SbCl ) from a variety of organic donors, such as para-substituted triarylamines, fully-substituted hydroquinone ethers, tetraarylethylenes, etc.176 For example, the treatment of the hydroquinone ether EA (2 mmol) with SbCl5 (3 mmol) in anhydrous dichloromethane at — 78°C immediately results in an orange-red solution from which the crystalline cation radical salt readily precipitates in quantitative yield upon the slow addition of anhydrous diethyl ether (or hexane)173 (equation 36). 

B. Tetranitromethane. Tetranitromethane forms colored charge-transfer (CT) complexes with a variety of organic donors such as substituted benzenes, naphthalenes, anthracenes, enol silyl ethers, olefins, etc. For example, an orange solution is instantaneously obtained upon exposure of a colorless solution of methoxytoluene (MT) to tetranitromethane (TNM),237 i.e.,... 

ELECTRON-TRANSFER ACTIVATION IN NITROGEN DIOXIDE REACTIVITY TOWARD ORGANIC DONORS... 

Hepatocytes are a cell-type, of particular interest in tissue engineering due to the regenerative capacity of the liver and the quantity of waiting liver transplant recipients, for which there are too few available organ donors. While the asialoglycoprotein receptor on hepatocytes does not... 

Compared with the conducting anion radical salts of metal complexes, the number of molecular conductors based on cationic metal complexes is still limited. Donor type complexes M(dddt)2 (M = Ni, Pd, Pt Fig. 1) are the most studied system. The M(dddt)2 molecule is a metal complex analogue of the organic donor BEDTTTF. Formally, the central C=C bond of BEDT-TTF is substituted by a metal ion. The HOMO and LUMO of the M(dddt)2 molecule are very similar in orbital character to those of the M(dmit)2 molecule. In addition, the HOMO of the M(dddt)2 molecule is also very similar to that of BEDT-TTF. More than ten cation radical salts of M(dddt)2 with a cation (monovalent) anion ratio of 2 1 or 3 2 are reported [7]. A few of them exhibit metallic behavior down to low temperatures. The HOMO-LUMO band inversion can also occur in the donor system depending on the degree of dimerization. In contrast to the acceptor system, however, the HOMO-LUMO band inversion in the donor system leads a LUMO band with the one-dimensional character to the conduction band. 

Fig. 1 Molecular structure of organic donor molecules that appear in this chapter...

Surface complexation of Ti02 with fluoride also shows a relevant effect on dioxygen reduction. Over illuminated Ti02/F in the presence of dioxygen and an organic donor a sustained production of H202 is observed, with steady state concentration levels of 1-1.3 ulm - nearly 100 x the levels reported for naked... 

It is interesting that X values in modified proteins are comparable to those values (0.9-1.25 eV) extracted from studies of organic donor-acceptor complexes [3, 30], The electronic couplings estimated for close contact, however, are dramatically smaller than typical values ( 300 to 1900 cm obtained from experiments on donor(spacer)acceptor molecules [3]. The intrinsic (close contact) electronic coupling also varies significantly from protein to protein. 

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