Electron donor/acceptor complexation

Wynne K, Galli C and Hochstrasser R M 1994 Ultrafast charge transfer in an electron donor-acceptor complex J. Cham. Phys. 100 4796-810... 

Morokuma K 1977. Why Do Molecules Interact The Origin of Electron Donor-Acceptor Complexes, Hydrogen Bonding, and Proton Affinity. Accounts of Chemical Research 10 294-300. 

Catalysis by Electron Donor-Acceptor Complexes Kenzi TAMARU... 

The UV spectra suggest that the equilibrium between the diazonium ion and the solvent, on the one hand, and an electron donor-acceptor complex (8.58) on the other, lies on the side of the complex. The latter may possibly exist also as a radical pair (8.60) or a covalent compound (8.59). Dissociation of this complex within a cage to form an aryl radical, a nitrogen molecule, and the radical cation of DMSO is slow and rate-determining. Fast subsequent steps lead to the products observed. 

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. 

When the reaction of two compounds results in a product that contains all the mass of the two compounds, the product is called an addition compound. There are several kinds. In the rest of this chapter, we will discuss addition compounds in which the molecules of the starting materials remain more or less intact and weak bonds hold two or more molecules together. We can divide them into four broad classes electron donor-acceptor complexes, complexes formed by crown ethers and similar compounds, inclusion compounds, and catenanes. 

Hajjaj, H. et ah. Production and identification of N-glucosylrubropunctamine and N-glucosyhnonascorubramine from Monascus ruber and occurrence of electron donor-acceptor complexes in these pigments, Appl Environ. Microbiol, 63, 2671, 1997. Jung, H. et ah. Color characteristics of Monascus pigments derived by fermentation with various amino acids, J. Agric. Food Chem., 51, 1302, 2003. 

Mulliken [3] presented a classification of electron donor-acceptor complexes based on the extent of intermolecular charge transfer that accompanies complex formation. An outer complex is one in which the intermolecular interaction B- XY is weak and there is little intra- or intermolecular electric charge redistribution, while an inner complex is one in which there is extensive electric charge (electrons or nuclei) redistribution to give [BX] + - -Y . Inner complexes are presumably more strongly bound in general than outer complexes. 

Prout CK, Kamenar B (1973) Crystal structures of electron-donor-acceptor complexes. In Foster R (ed) Molecular complexes. Elek, London, pp 151-207... 

In a similar way, the formation of halide complexes with other jt-acceptors in Fig. 3 are revealed by the appearance of new absorption bands in the electronic spectra to reflect the yellow to red colorations of the mixtures. The spectral data thus indicate that halide salts form well-defined electron donor/acceptor complexes with organic jt-acceptors, as typified by Eq. 2 ... 

The scope of the Patemo-Buchi cycloaddition has been widely expanded for the oxetane synthesis from enone and quinone acceptors with a variety of olefins, stilbenes, acetylenes, etc. For example, an intense dark-red solution is obtained from an equimolar solution of tetrachlorobenzoquinone (CA) and stilbene owing to the spontaneous formation of 1 1 electron donor/acceptor complexes.55 A selective photoirradiation of either the charge-transfer absorption band of the [D, A] complex or the specific irradiation of the carbonyl acceptor (i.e., CA) leads to the formation of the same oxetane regioisomers in identical molar ratios56 (equation 27). 

Electron donor-acceptor complexes, electron transfer in the thermal and photochemical activation of, in organic and organometallic reactions, 29, 185 Electron spin resonance, identification of organic free radicals, 1, 284 Electron spin resonance, studies of short-lived organic radicals, 5, 23 Electron storage and transfer in organic redox systems with multiple electrophores, 28, 1... 

Electron transfer, in thermal and photochemical activation of electron donor-acceptor complexes in organic and organometallic reactions, 29,185 Electron-transfer, single, and nucleophilic substitution, 26,1 Electron-transfer, spin trapping and, 31,91 Electron-transfer paradigm for organic reactivity, 35, 193... 

We now return to the thermal electron transfer reaction in eq 20, in which the rate-limiting activation process has been shown to proceed from the electron donor acceptor complex (23), i.e.,... 

Electron Transfer in the Thermal and Photochemical Activation of Electron Donor-Acceptor Complexes in Organic and Organometallic Reactions... 

The counterpart to the photo-induced electron transfer is the corresponding thermal transformation of the electron donor-acceptor complex the barrier to such an adiabatic electron transfer is included in Fig. 18 as T, with the implicit understanding that solvation is an intrinsic part of the activation process (Fukuzumi and Kochi, 1983). When the rate of back electron transfer is diminished (e.g. by a reduced driving force), the dynamics for the contact ion pair must also include diffusive separation to solvent-separated ion pairs and to free D+- and A-- (Masnovi and Kochi, 1985a,b Yabe et al., 1991). 

The long known132 electron donor-acceptor complexes between tertiary amines and carbon tetrahahdes are simple systems. Thus, l,4-diaza[2,2,2]bicyclooctane (DABCO) or quinuclidine afford solid complexes with carbon tetrabromide142. 

The electron donor-acceptor complex trimethylamine/dibromine shows a structure151 (by electron diffraction in the gas phase) with an N—Br—Br angle of 112°. On the contrary, the structures of solid152 (CH3N)3/I2 [or (CH3N)3/IC1153] show linear N—I—I (or N-I-Cl) axes. 

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