Donor-acceptor complex formation

Donor-acceptor compounds have been known for a long time [1] and their understanding has existed long on the basis of the acid-basis theory [2]. The appearance of a standard textbook in 1961 by Briegleb [3] had a great impact in this field, since it was a comprehensive review at this time. The modern understanding of donor-acceptor complex formation [4] or more general the nature of... 

Absorption studies of 2-cyclohexenone-ethoxylethylene solutions failed to reveal evidence of donor-acceptor complex formation. It should be noted, however, that photocycloaddition from ground state 7r-complexes (such as would be observed from absorption studies) does not correctly predict the observed orientational effects. 

Poly(4-vinylpyridine) was used also as a template for polymerization of maleic anhydride. Maleic anhydride is very difficult to polymerize by conventional radical polymerization, but in the presence of poly(4-vinylpyridine) in chloroform or in nitromethane, polymerization proceeds at room temperature just after mixing 0.5% solution of poly(4-vinylpyridine) with 1% solution of maleic anhydride. A yellow precipitate is obtained. The precipitate is a mixture of poly(maleic anhydride), poly(4-vinylpyridine), and unreacted maleic anhydride. In the absence of oxygen, polymerization is much slower. The reaction stops on the stage of donor-acceptor complex formation. 

Analytical Properties Separation of polynuclear aromatic hydrocarbons (of the type often encountered in petroleum residue work) by donor-acceptor complex formation Reference 5, 6... 

While considering the rate-enhancing effect of bromobenzene in MMA polymerization initiated by AIBN, Henrici-Olive and Olive (19) noted that the effect can be explained as the consequence of electron donor—acceptor complex formation between polymer radicals and monomer or solvent molecules. Based on this view, these authors have shown that in polymerization in active solvents (which enhance the rate), the degree of polymerization Pn appears as a linear function of M2/Rp with... 

Zentel R, Wu J, Cantow HJ. (1985) Influence of electron-donor-acceptor complex formation on the melt viscosity of some poly(dimethylsiloxane)s. Makromol. Chem. 186 1763-1772. 

In a more recent study. Nelson and Yang [494] pre.sented a surface complex-ation model to describe the effect of pH on adsorption equilibria of chlorophe-nols, i.e., the electrostatic effect they also discussed the potential importance of 7t-7t interactions and donor-acceptor complex formation but could not distinguish between the two and concluded, somewhat vaguely, that [t]hese proposed mechanisms provide plausible explanations for the surface complexation reactions between chlorophenols (neutral or anionic forms) and the surface of activated carbon (acidic or basic sites). ... 

Quantum chemical computations of H complexes heats formation in case of interaction of large organic molecules lead to high errors. A more perspective way is the use of well known relations of physical organic chemistry for this purpose. These equations allow to predict the heats of hydrogen-bonded or donor-acceptor complexes formation on the basis of donor (base) and acceptor (acid) empirical parameters. There are Drago and Weyland s equation [71]... 

St/CMI TEMPO Controlled, fast rate of polymerization due to donor/acceptor complex formation Schmidt-Naake and Butz [102]... 

Ultem on the other hand has the imide groups attached to different phenyl rings in the repeat unit, so the charge separation in Ultem is lower than in Kapton. In addition, because of the kinked nature of the repeat units in Ultem, adjacent chains are unable to approach one another as closely as they can in Kapton. So in Ultem donor-acceptor complex formation is not as efficient as in Kapton, and Ultem absorbs less strongly in the visible region, as can be seen in Figure 2. 

The compact size and strong polarity of the nitrile groups make them very interactive with their surroundings. The lone pair orbital on nitrogen is suitable for hydrogen bonding, as well as for electron-donor-acceptor complex formation. In addition, the electrons in the -orbitals of the nitrile triple bond are available for interactions, for example, with transition-metal ions. 

THE KINETICS OF DONOR-ACCEPTOR COMPLEX FORMATION, STUDIED BY A MICROWAVE TEMPERATURE-JUMP METHOD. 

Molybdenum.— An oxidative-elimination reaction takes place when the complexes [Mo(CO)4(5-X-phen)] (X = H, Me, Cl, or NO2) are treated with mercuric chloride in acetone. The products are [MoCl(HgCl)(CO)3(5-X-phen)). Kinetic studies, using stopped-flow techniques, indicate that the reactions proceed via initial formation of adducts of stoicheiometry [Mo(CO)4(5-X-phen)],-HgCla and [Mo(CO)4(5-X-phen)],2HgCla. These adducts are of the metal donor-metal acceptor type which were first characterized for some iron(0) and cobalt(i) complexes. - Consistent with this formulation, the rate of initial attack of HgCla on the molybdenum complexes increases as the substituent X becomes more electron-releasing. Donor-acceptor complex formation is also apparent in the reactions of iodine with the compounds [FeCCOsP and [R(acac)a]. ... 

---