Diacetylene groups

Similar systems to those mentioned above exist where the constituent monomer contains the diacetylene group. 

A summary of the studies perfonned on symmetrical compounds having a diacetylene group at the centre is given in [94]. Most of the materials studied in the context of LB films have been diyonic acids (figure C2.4.8). 

Figure 58 The carboranylenesiloxane (95) containing the cross-linking diacetylene group. (Adapted from ref. 125.)... 

Figure 62 The unreacted (100), partially reacted (101), and completely reacted (102) diacetylene group-containing oligomers in the product from the reaction between 95 and Cp2Mo2(CO)6 (top). The X-ray diffraction spectrum (middle, left), TEM micrographs (middle, right), and conductivity plots (bottom) of the product from the reaction between 95 and Cp2Mo2(CO)6 after pyrolysis to 1000°C. (Adapted from ref. 130.)...

Polymerization of diacetylene (Fig. 8.13) is one of the most elegant examples of the topochemical principle. Wegner (1971, 1979) showed that diacetylene monomers, R—C = C—C = C— R, polymerize in the solid state by a 1,4-addition reaction at the diacetylene group to produce a polymer that can be represented by the mesomeric structures ... 

The extensive studies of the behavior of mixed monolayers or bilayers of di-acetylenic lipids and other amphiphiles parallel to some degree the studies of dienoyl-substituted amphiphiles. Since the dienoyl lipids do not contain a rigid diacetylenic group in the middle of the hydrophobic chains, they tend to be miscible with other lipids over a wide range of temperatures and compositions. In order to decrease the lipid miscibility of certain dienoyl amphiphiles, Ringsdorf and coworkers utilized the well-known insolubility of hydrocarbons and fluorocarbons. Thus two amphiphiles were prepared, one with hydrocarbon chains and the other with fluorocarbon chains, in order to reduce their ability to mix with one another in the bilayer. Of course it is necessary to demonstrate that the lipids form a mixed lipid bilayer rather than independent structures. Elbert et al. used freeze fracture electron microscopy to demonstrate that a molar mixture of 95% DM PC and 5% of a fluorinated amphiphile formed phase-separated mixed bilayers [39]. Electron micrographs showed extensive regions of the ripple phase (Pb phase) of the DM PC and occasional smooth patches that were attributed to the fluorinated lipid. In some instances it is possible to... 

Systems similar to the above but in which the constituent monomers contain the diacetylene group. 

Two diacetylene-bridged triptycenes, 19 and 20, were prepared in order to study the insertion effect of the diacetylene group on the circular electronic interaction of their parent compound, triptycene. Compared with the corresponding dimethyl-triptycenes, 19 shows a red-shift of the longest wavelength maximum by 10 nm, whereas there is no sign of the band-shift in the 1,4-bridged 20. These results may be... 

The absorption spectra of the charge transfer complexes of 1,3-diacetyIenes were recently measured. Table 1 shows maxima of one-to-one tetracyanoethylene (TCNE) complexes of dialkyl-1,3-diacetylene and related compounds. The cyclic tetrayne (8b)-TCNE complex shows a normal absorption spectrum regardless of the closed, parallel conformation of the two diacetylene groups in 8b. This is in striking contrast... 

The one-to-one TCNE complexes of a series of [w.njparacyclophadiynes (12), where m and are the numbers of methylene groups inserted between the benzene and diacetylene groups, were investigated for the —transannular interaction between the diacetylene and an aromatic ring (Table 2). Each of these complexes shows an absorption maximum in the narrow region of 425-431 nm, except for the 12c (m = H = 3) complex which exhibits a distinct additional maximum at 555 nm . Curve analyses of these spectra indicated that the spectrum of the lid complex also... 

For larger rings, 8c and 8d, the differences in chemical shifts of jp-carbons are about 1 p.p.m. The larger deshielding of the jp-carbons of 8b can be explained in terms of the diamagnetic anisotropy effect of the transannularly positioned diacetylene group, which was estimated by Roberts and coworkers , in addition to the ring strain effect. 

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