A Conducting Poly(cyclophane) and Its Poly([2]-catenane).

TitleA Conducting Poly(cyclophane) and Its Poly([2]-catenane).
Publication TypeJournal Article
Year of Publication2000
AuthorsSimone, DL, Swager, TM
JournalJournal of the American Chemical Society
Keywordsband gap catenane bipyridinium placement cavity polyphenylenethiophene, catenane phenylene thiophene complex prepn crystal structure, conducting polymer polythiophene phenylene cyclophane redox potential, electron donor phenylene thiophene cyclophane charge transfer Paraquat, phenylene thiophene cyclophane fluorescent monomer prepn electropolymn

Cyclization of 1,4-Bis[2-(2-(2-(2-toluene-p-sulfonylethoxy) ethoxy) ethoxy) ethoxy]benzene with 1,4-diiodo-2,5-dihydroxybenzene, followed by coupling with (3,4-ethylenedioxy)-thiophene produced 1,4-Bis((3,4-ethylenedioxy)thiophene)-7,10,13,16,19,26,29,32,35,38-decaoxa[13.13]paracyclophane (I) a highly fluorescent electropolymerizable monomer and electron donor. Addn. of Paraquat to I in CH3CN resulted in formation of a deep-green colored soln. with a charge-transfer absorption band at $łambda$ = 589 nm ($ε$ = 204 M-1cm-1), indicative of the highly electron-donating nature of the thiophene-phenylene-thiophene arom. scaffold. The tetrakis-hexafluorophosphate I-[2]-catenane complex (II) was prepd. by reaction of I with NH4PF6 and 1,4-bis(bromomethyl)benzene. The deep-green complex II exhibits a charge-transfer absorption at $łambda$ = 626 nm ($ε$ = 1230 M-1 cm-1), which is red-shifted relative to that of Paraquat:I complex indicating greater intimacy between donor and acceptor in the [2]-catenane. The crystal structure of II indicates an interlocked $π$-stacked geometry with inner bipyridinium moieties within the cyclophane cavity and outer bipyridinium on the periphery of the cavity. Electrochem. polymn. of I and II proceeds via two propagating sites at the 5-position of 3,4-ethylenedioxythiophene and affords conducting polymers. Oxidn. and redn. potentials for poly-II are identical to those of II monomer suggesting that the neutral polymer backbone has the same electronic influence as the thiophene-phenylene-thiophene in II. For both poly-I and poly-II, the multiple redn. peaks obsd. are indicative of the energetic inequality between the inner- and outer-bipyridinium groups. The cond. of poly-II rapidly reaches a max. of 0.2 S/cm at 0.12 V vs. Fc/Fc+, which decays quickly thereafter. In contrast, the cond. profile for poly-I shows that oxidn. of the backbone occurs over a broad range of potentials without decay. The absorption spectra of both conducting polymers are similar; in the neutral (insulating) form, the $łambda$max for poly-I was 527 nm (2.35 eV) and poly-II 542 nm (2.29 eV). When oxidatively doped, both displayed a longer wavelength band at 767-796 nm (1.62-1.56 eV), indicative of new states formed within the band gap upon reaching a conductive state. Further lower energy absorptions occur at higher oxidn. potentials leading to an absorption at >1100 nm (>1.13 eV) owing to the formation of free carriers. The films differ in that poly-II requires higher oxidn. potentials to reach its conductive state than does poly-I. [on SciFinder(R)]