New Substituted Polyacetylenes with Phenyleneethynylene Side Groups [−(C₆H₄−C⋮C)_n−SiⁱPr₃; n = 1, 2]:  Synthesis, Characterization, Spectroscopic, and Photoelectric Properties

Abstract

The selective, terminal triple bond polymerization of HC⋮C−C6H4−C⋮C−SiiPr3 (1) and HC⋮C−C6H4−C⋮C−C6H4−C⋮C−SiiPr3 (2) yields soluble, high-MW polyacetylenes P1 and P2 with phenyleneethynylene-type pendant chains. The [Rh(cod)(OCH3)]2- and MoCl5-based catalysts show 100% polymerization selectivity to terminal triple bonds and give high-cis (NMR: Rh, 94% cis; Mo, 70% cis) polymers having a medium extent of π-conjugation. WOCl4-based catalysts reacting in benzene marginally also insert internal triple bonds and give low-cis polymers (<10% cis) having a high extent of conjugation. Addition of 1,4-dioxane to the WOCl4-based catalyst considerably reduces or even eliminates the internal triple bond insertion and increases the polymer molecular weight, cis-unit content (≈35% cis) and extent of π-conjugation. The π−π* band of P1 pendant groups is closely correlated with the polymer microstructure: the cis-unit content in P1 can be reliably ascertained from the A 292/A 268 UV-absorbance ratio. Raman bands of the main-chain ν(CC) mode exhibit both frequency and intensity dispersion with extent of conjugation. On the other hand, only intensity dispersion is conclusively observed for the ν(Ph−Cchain) band at 1341 cm-1 that, upon correction to the dispersion effect, is in a good correlation with the cis-unit content obtained from NMR spectra. Xerographic and transient photoconductivity measurements have shown that the photogeneration in these polymers proceeds through the side group excited states, and the charge carrier's (holes) transport is controlled by hopping between the main chain conjugated sequences.

Electronic processes in end-functionalized oligomeric poly(diphenylvinylene)s

“…Measurements were done on several samples of thicknesses ranging from 0.5 to 2.0 lm to verify the emission-limited conditions. As can be seen, all studied PDVs show strong dependence of g on F and shapes of the dependences resemble that observed for other conjugated polymers [16,18,20,21,43,44] and for molecular crystals [45,46]. The charge carrier Positively charged surface, electric field F = 4 · 10 7 V m À1 , thickness of films varied between 1 and 2 lm, room temperature.…”

“…The effect of substituents on the functional properties of monosubstituted acetylene polymers has been mainly studied on poly(phenylacetylene) [4,5,16] and its ring-substituted derivatives [17][18][19] including those carrying phenyleneethynylene pendent chains [20], and on polymers of propynyl derivatives of heteroaromatic compounds, such as on poly[(N-2-propynyl)carbazole] and poly[(N-2-propynyl)phenothiazine] [21,22]. As to polydiphenylacetylenes (i.e., poly(diphenylvinylene)s, PDV), only a few ring-substituted PDVs have been studied [23][24][25][26] because the parent polymer, unsubstituted PDV, is infusible and insoluble in any solvent [14,15,27].…”

Synthesis of polyarylacetylenes by γ‐ray‐induced polymerization of terminal alkynes. Nanostructures of ortho‐substituted derivatives

“…In the 13 C NMR spectrum (Fig. 3, bottom trace), the signals centered at 141 (broad) and 131 ppm correspond to the vinylic carbon atoms of a polyarylacetylene main chain, (Ar C CH) and (ArC C H), respectively,31 and that at 126 ppm to the CF 3 groups. This spectrum of P4 shows better resolved signals than that of poly( o ‐CF 3 PA)s obtained by WCl 6 or MoCl 5 based catalysts which exhibited multiplet absorptions in the region 145–115 ppm 14…”

Terminal C≡C triple bond hydrogenation using immobilized Wilkinson’s catalyst

“…Besides hydrogenation, a particular Rh complex can usually catalyze a few types of other reactions such as hydrocarbonylation, isomerization, hydrosilylation and silylation [1][2][3][4][5][6], Kharash addition [7], methanation of carbon oxides [8], transformations of diazo compounds [9], and various kinds of polymerizations [2,[10][11][12]. Therefore, they can be used for the activation of various organic compounds towards a variety of chemical transformations under mild conditions (room or slightly elevated temperature, in solvents from water to hydrocarbons, and in the presence of air), which compensates for the high cost of these catalysts.…”