Synthetic Routes to Solution-Processable Polycyclopentadithiophenes

Abstract

Three synthetic protocols have been employed to prepare solution-processable poly (4,4dialkylcyclopentadithiophenes). These polymers are fused-ring analogues of poly(3-alkylthiophenes) and structural analogues of the polyfluorenes. Oxidative polymerization of 4,4-dialkylcyclopenta[2,1-b;3,4-b′]dithiophenes using iron (III) chloride gave high-molecular-weight polymers, whereas nickel-catalyzed polymerization of the 2,6-dibromo derivatives via in situ-generated thienylmagnesium and thienylzinc reagents gave moderate-molecular-weight polymers. The structures of the polymers were confirmed by NMR spectroscopy and MALDI-TOF mass spectrometry. In the polymerization using organomagnesium intermediates, some chain capping by methyl end groups was observed. This side reaction can be avoided by polymerization of the organozinc reagents. Post-functionalization of the halogen termini of these polymers can be readily achieved using a cross-coupling with an aryl Grignard reagent. The main chain conjugation in these polymers can be directly correlated to the length of the polymer backbone because the UV-vis spectra of fractionated samples show absorption maxima that increase with the average degree of polymerization as determined by GPC, up to a limiting value of ∼20. UV-vis spectroscopy suggests that poly(4,4-dialkylcyclopentadithiophenes) do not self-assemble in the solid state, as has been previously observed for regioregular poly-3-alkylthiophenes.

The Controlled Polymerization of Poly(cyclopentadithiophene)s and Their All-Conjugated Block Copolymers

“…68 In this work, the controlled nature of the Kumada catalyst transfer polycondensation (KCTP) mechanism, applied on these CPDTmolecules is investigated in detail. Furthermore, the possibilities towards all-conjugated 3-hexylthiophene-CPDT block-copolymers are explored.…”

Conjugated Copolymers Containing Low Bandgap Rhenium(I) Complexes

“…Column chromatography was performed using Merck 9385 silica gel 60 (0.040-0.063 mm). 2,7-Di (4,4,5,5-tetramethyl-1,3,2-dioxaboralane)-9,9-diethylhexylfluorene [1a] and 2,6-di(tributyltin) -4,4-dioctylcyclopenta[2,1-b:3,4-b']dithiophene [4] were synthesized according to the literature procedures.…”

Electrosynthesis and characterization of a novel electrochromic copolymer of N-methylpyrrole with cyclopenta[2,1-b:3,4-b′]dithiophene

“…Using these compounds as building blocks offers the possibility of forming homopolymers, copolymers with narrower band gaps and, thus, broader light-absorption properties for applications in electronic devices. [20][21][22][23] Because of the fully coplanar structure, the intrinsic properties based on dithiophene can be altered, leading to further extended conjugation, lower HOMO-LUMO energy band-gap and stronger intermolecular interaction. 22 Therefore, it is expected that the introduction of CPDT units into the main chain of PNMPy might produce a tunable band-gap polymer, which could be an ideal characteristic for electronic materials used in ECDs.…”