The effects of double-bond twisting on the photoionization energies of push-pull ethylenes

Abstract

The U.V. photoelectron spectra of a number of push-pull substituted ethylenes with two donor groups and with planar or twisted double bonds have been interpreted by the aid of perturbational arguments, CN D0/2 calculations, and comparison with published spectra of similar compounds. The highest bonding molecular orbital in all cases is of x-type, and its energy is raised with increasing twist about the double bond, whereas the orbital formed by antisymmetric combination of the donor atom pz orbitals is unchanged or lowered by increased twist. Through-bond interaction splits the ' non-bonding ' oxygen orbitals by 0 . 6 4 . 7 eV in 1.1 -diacetyl-2,2-diaminoethylenes, in which the carbonyl groups are €,Z oriented with respect to the C=C double bond. When Z,Z orientation is enforced by ring closure, the splitting is only 0.38 eV, in agreement with calculations. In the 2.2-dithio-analogues, interaction with the C-S bond orbitals leads to a more complex splitting pattern.

CS2 insertion into a gold–carbon bond. First syntheses and characterization of 2,2-diacetylethylene-1,1-dithiolato complexes. Crystal structure of [N(PPh3)2][Au{η2-S2CC(COMe)2}2]†

“…On the other hand, the interest in ketene dithioacetals with electron-withdrawing substituents stems from some of their physical properties as push-pull polarized ethylenes. Thus, the effect of chiral substituents or hydrogen bonding on second-order non-linearity, 19 the free energy of activation for rotation around the carbon-carbon double bond, 15,20 or the influence of the double bond twisting on the position of the IR n CNC stretching band 21 or on the photoionization energy 22 have been studied. Our synthesis opens a new access for such studies.…”

Preparation and characterization of novel optically active polyurethanes containing 1,1′‐binaphthol

“…The monomer (S)-1,1 0 -binaphthol and (R)-1,1 0binaphthol were synthesized as previously reported. [18][19][20] Toluene diisocyanate (TDI, mixture of 80% 2,4 and 20% 2,6 isomers, Merck was purchased from Lingfeng Chemical Reagent and distilled before used. Polyethylene glycol 400 was dried under vacuum at 80 C for 6 h, DMF was purified, dried, and stored under nitrogen.…”

Phase Transfer Catalysis and Selectivity in Organic Synthesis

“…have been obtained in Michael reactions «20%) [85,86] . Optical yields in addition reactions of nitro alkanes on trans chalcones and other polarized double bonds have been studied in detail [87]. The following observations can be made: a OH functionality {3 to the nitrogen in the catalyst is necessary; S configuration at C ll and R configuration at C 9 in QUIBEC is preferred; ephredinium salts are more efficient with chalcone than with cyclohexenone; chiral ammonium fluorides formed in situ are a source of chirality.…”