Donor-acceptor complexes interactions

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. 

The chemistry of Lewis acid-base adducts (electron-pair donor-acceptor complexes) has stimulated the development of measures of the Lewis basicity of solvents. Jensen and Persson have reviewed these. Gutmann defined the donor number (DN) as the negative of the enthalpy change (in kcal moL ) for the interaction of an electron-pair donor with SbCls in a dilute solution in dichloroethane. DN has been widely used to correlate complexing data, but side reactions can lead to inaccurate DN values for some solvents. Maria and Gal measured the enthalpy change of this reaction... 

We have also used poly(propynoic acid) in our studies of the photochemical interaction of PCSs with dienophiles, such as maleic anhydride, tetracyanoethylene, and styrene. This photochemical reaction of Diels-Alder type is accompanied by the breakdown of the conjugation system and the formation of slightly colored adducts266. Together with the cycloaddition reaction, photodegradation of PPA and its adducts takes place. A cycloaddition reaction is always preceded by the formation of a donor-acceptor complex of a PCS with a dienophile. 

Since intermediates usually cannot be observed directly, the exact nature of the donor-acceptor complex and the mechanisms for their interaction with radicals are speculative. At least three ways may be envisaged whereby complex formation may affect the course of polymerization ... 

The donor-acceptor formation can be considered by transfer of electrons from the donor to the acceptor. In principle one can assume donor-acceptor interaction from A (donor) to B (acceptor) or alternatively, since B (A) has also occupied (unoccupied) orbitals, the opposite charge transfer, from B to A. Such a view refers to mutual electron transfer and has been commonly estabUshed for the analysis of charge transfer spectra of n-complexes [12]. A classical example for a donor-acceptor complex, 2, involving a cationic phosphorus species has been reported by Parry et al. [13]. It is considered that the triaminophosphines act as donor as well as an acceptor towards the phosphenium cation. While 2 refers to a P-donor, M-donors are in general more common, as for example amines, 3a, pyridines, 3b, or the very nucleophilic dimethylaminopyridine (DMAP) [ 14], 3c. It is even a strong donor towards phosphorus trichloride [15]. 

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. 

Blackstock, S. C., J. P. Lorand, and J. K. Kochi. 1987. Charge Transfer Interactions of Amines with Tetrahalomethanes. X-ray Crystal Structures of the Donor-Acceptor Complexes of Quinuclidine and Diazabicyclo-[2.2.2]octane with Carbon Tetrabromide. J. Qrg. Chem. 52,1451. 

A prominent feature of this mechanism is that the growing polymer chain alternately swings between two r/.v-disposed coordination sites during each monomer insertion. General mechanistic outlines of this reaction have been extensively examined by large-scale computations and confirmed by experimental means.59 Our present goal is to clarify the localized donor-acceptor-orbital interactions that underlie (4.106), particularly the nature of the alkyl-alkene complex II. 

Finally, Figure 5.40 displays the surprising structure of the (PtH2)2 dimer, an anti-H-bond n—a donor-acceptor complex. As expected, the leading NBO donor-acceptor interaction is of npt crptH type, but the attack by npt is now on the backside of the cjrh NBO, leading to unusual Pt - -Pt—H coordination to the hydride antibond as depicted in Fig. 5.40b. 

Electron transfer, in thermal and photochemical activation of electron donor-acceptor complexes in organic and organometallic reactions, 29, 185 Electron transfer, long range and orbital interactions, 38, 1... 

Weak nucleophile-electrophile interactions (and the donor-acceptor complexes) are considered precursors in aromatic electrophilic substitutions133 and in additions of electrophiles to C=C double bond of olefins the first step (the addition of the electrophile to an electron-rich substrate) is probably the same for both reactions. 

Attack on the aromatic ring and formation a n-complex or electron donor-acceptor complex N02 + ArH —> ArH N02. This complex involves high electrostatic and charge-transfer interactions between the n-aromatics and nitroninm ion. 

This exciton diffuses to the donor/acceptor interface via an energy-transfer mechanism (i.e., no net transport of mass or charge occurs). (3) Charge-transfer quenching of the exciton at the D/A interface produces a charge- transfer (CT) state, in the form of a coulombically interacting donor/acceptor complex (D A ). The nomenclature used to describe this species has been relatively imprecise, and has... 

The term charge tranter refers to a succession of interactions between two molecules, ranging from very weak donor-acceptor dipolar interactions to interactions that result in the formation of an ion pair, depending on the extent of electron delocalization. Charge transfer (CT) complexes are formed between electron-rich donor molecules and electron-deficient acceptors. Typically, donor molecules are p-electron-rich heterocycles (e.g., furan, pyrrole, thiophene), aromatics with electron-donating substiments, or compounds... 

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