Donor-acceptor -conjugated compounds

Pai C-L, Liu C-L, Chen W-C, Jenekhe SA (2006) Electronic structiffe and properties of alternating donor-acceptor conjugated copolymers 3,4-ethylenedioxythiophene (EDOT) copolymers and model compounds. Polymer 47 699... 

Fig. 8. Examples of some of the donor-acceptor substituted TEEs prepared for the exploration of structure-property relationships in the second- and third-order nonlinear optical effects of fully two-dimensionally-conjugated chromophores. For all compounds, the second hyperpolarizability y [10 esu], measured by third harmonic generation experiments in CHCI3 solution at a laser frequency of either A = 1.9 or 2.1 (second value if shown) pm is given in parentheses. n.o. not obtained...

NHCs are often compared to phosphines and theoretical studies by Frenking et al. [211-213] showed that the substitution of the phosphines in 89 for two NHCs leads to compounds with a carbon(O) atom that is formally stabilized by two NHC C donor-acceptor bonds. The first carbodicarbene 90 was prepared by Bertrand et al. who selected benzimidazolin-2-ylidenes as carbene donors and the deprotonation of the conjugated acid of an allene as the synthetic strategy (Fig. 29)... 

FIGURE 2-16 Conjugate acid-base pairs consist of a proton donor and a proton acceptor. Some compounds, such as acetic acid and ammonium ion, are monoprotic they can give up only one proton. Others are diprotic (H2C03 (carbonic acid) and glycine) or triprotic... 

The desire to increase P values above those of molecules used in the earliest materials has led to the exploration of organic compounds as the active components of second order NLO devices. Considerable effort has been expended in the synthesis and analysis of candidate molecules, which are largely donor-acceptor substituted conjugated n systems. (2) Examples of compound classes whose members display large nonresonant P include azo dyes, stilbenes, polyenes, merocyanines, stilbazolium salts, and quinoid... 

Despite the differences between the functions implemented by hydrogen peroxide in gas, liquid and biological oxidation processes, they are united by a specific feature H202 first transforms to a higher reactive form in which the donor-acceptor properties of the original compound are preserved, and then only (in this new form) oxidizes the substrate according to the conjugated mechanism. 

A different approach must be used for the photochemical hydrophosphination of electron-poor olefins, and this involves a PET reaction. Silyl phosphites (e.g., 30) were used as electron donors, whereas conjugated ketones have the double role of electron acceptors and absorbing species. Thus, the irradiation of a mixture containing 2-cydohexenone and 30 generated an ion pair. The phosphoniumyl radical cations decomposed to give trimethylsilyl cations (which in turn were trapped by the enone radical anion) and phosphonyl radicals. A radical-radical combination afforded the 4-phosphonylated ketones in yields ranging from 78% to 92% (Scheme 3.20) [49]. This reaction was exploited for the preparation of substituted phosphonates, which serve as key intermediates in the synthesis of a class of biologically active compounds. 

---