.pi.-Conjugated Soluble Poly(aryleneethynylene) Type Polymers. Preparation by Palladium-Catalyzed Coupling Reaction, Nonlinear Optical Properties, Doping, and Chemical Reactivity

Abstract

Palladium-catalyzed polycondensation between dihalo aromatic compounds X-Ar-X (3hexyl-2,5-diiodothiophene, 2,5-dibromoselenophene, and 3,4-dinitro-2,5-dibromothiophene) and diethynyl aromatic compounds HC=C-Ar'-C=CH (2,5-diethynylpyridine, 3-hexyl-2,5-diethynylthiophene, and p-diethynylbenzene) in the presence of triethylamine gives soluble -conjugated poly(aryleneethynylene) (PAE) type polymers (-Ar-C=C-Ar'-C=C-)" when Ar and/or Ar' contains the long alkyl substituent and/or pyridine ring. The PAE type polymers are obtained in high yields (86-100 %), have molecular weights of 9.6 X 10 59 X 104 and pv (degree of depolarization) values of 0.005-0.034 as determined by the light scattering method, and show absorption bands in the range 350-462 nm, which are shifted from the absorption bands of the corresponding aromatic units (HArH and HAr'H), indicating the occurrence of -conjugation along the polymer chain. The polymers exhibit fluorescence in solutions, and the position of the fluorescence is shifted to a longer wavelength in films of the polymers, suggesting the formation of excimer-like adducts in the solid state. The polymer films give a (3) (third-order nonlinear optical susceptibility) value of about 5 x 10"u esu when the Ar group has the hexyl group. Cyclic voltammetry of the PAE type polymers indicates that they receive reduction (n-doping) at about -2 V vs Ag/Ag+ whereas oxidation (p-doping) of the polymer is difficult presumably due to the electron-withdrawing effect of the -C=Cgroup. HBr addition to the -C=Cgroup of the polymer gives a polymer having a -CH=CH(Br)group, which can be further converted into ester and amide groups.

Synthesis of some novel heteroarylene ethynylene polymers containing 1,10-phenanthroline in the polymer backbone

“…mp: 222-223°C. 1 Ϫ2 mmol, 2 mol %) were dissolved into a degassed solution of 8 mL of diisopropylamine and 20 mL of toluene under an argon atmosphere. The mixture was heated at 70 to 80°C for 24 h. After cooling to room temperature, it was added dropwise to 300 mL of vigorously stirred methanol.…”

“…It has been reported recently that -conjugated poly(arylene ethynylene)s whose arylene unit has an alkyl or alkoxy substituent exhibit large third-order nonlinear optical susceptibilities, (3) . 1 Additionally, metal complexation might enlarge these promising nonlinear optical properties. 6 The synthetic access of the heteroarylene ethynylene polymers is possible due to the development of palladium-catalyzed cross-coupling of 1,4-diethinyl-benzene with dibromopyridine or dibromobipyridine.…”

π-Conjugated Copolymers of Electron-Withdrawing Pyridine and Electron-Donating Selenophene

“…A considerably stronger interaction between thiophene and pyridine units than that between selenophene and pyridine units is reported in relation to exicimer formation of poly(aryleneethynylene) type polymers. 8 The UV-vis data of PPy, PSe and the copolymers are summarized in Table I. If the PNSe type copolymers take such a block copolymer structure, they may serve to design interesting optical devices utilizing such unique structure having electron withdrawing poly- Wave Number/ cm-1 Figure 1.…”

Synthesis and nonlinear optical properties of 1,3- and 1,4-disubstituted type of poly(phenyleneethynylene)s containing electron-donor and acceptor group

“…A variety of poly(aryleneethynylene) polymers have been synthesized for the study of their nonlinear optical properties [1][2][3] . Particularly, poly(phenyleneethynylene)s containing electron-donor and acceptor groups have attracted attention to concerning the unique structure of a linear rod like p-conjugated system leading to the enhancement of the nonlinear optical properties 4) .…”