Third conjugated compounds

In a cross-conjugated compound, three groups are present, two of which are not conjugated with each other, although each is conjugated with the third. Some... 

The C=C 7t bond in the conjugated compound produces a signal at lower wavenumber (1600 cm" ) because it has some single bond character, as seen in the third resonance structure below. This additional single bond character renders the C=C k bond weaker (relative to the C=C 7t bond of the other compound, which does not exhibit any single bond character). 

Addition polymerization requires a chain reaction in which one monomer molecule adds to a second, then a third and so on to form a macromolecule. Addition polymerization monomers are mainly low molecular-weight olefinic compounds (e.g., ethylene or styrene) or conjugated diolefins (e.g., hutadiene or isoprene). 

The physical properties of the expanded radialenes were greatly enhanced upon donor functionalization, leading to the stable derivatives 76-78 with fully planar conjugated rr-chromophores [110]. These compounds exhibit large third-order nonlinear optical coefficients, can be reversibly reduced or oxidized, and... 

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...

Julolidine (3) and benzoquinuclidine (4) can be considered as aniline derivatives with parallel and perpendicular electron lone-pairs, respectively. Relative to N,N-dimethylaniline (5), the simplest tertiary aromatic amine, the n orbital of julolidine is destabilized by 0.20 eV, while that of benzoquinuclidine is destabilized by 0.80 eV42. In the latter compound there is no n/jt conjugation while in the former it has a maximum value and, accordingly, the splitting of the first and the third IP is much smaller (0.70 eV) than in the former (2.55 eV) compound. 

Polydiacetylenes are obtained as single crystals by topochemical solid-state polymerization of the monomer single crystal. These compounds have received considerable attention because of their one-dimensionally -conjugated structure. Their unique --electron structures, and therefore superior third-order nonlinear optical properties, have been extensively investigated. 

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