Synthesis and ring-opening metathesis polymerisation of o-alkoxy benzothiadiazole paracyclophane-1,9-dienes.

ortho-Diethylhexyloxyphenylene benzothiadiazole paracyclophane-1,9-diene as a mixture of diastereomers was synthesized by a sequential benzyne-induced Stevens rearrangement, oxidation and pyrolysis of a dithia[3.3]paracyclophane. Reaction of these highly strained cyclophanedienes with the second generation Grubbs catalyst showed that they can be ring opened to alternating cis,trans-phenylenevinylene polymers. In situ NMR experiments showed that one isomer 8a polymerised to 90% conversion, whereas the other 8b gave only 9% conversion due to steric hindrance on both faces of the alkene bridges of this isomer. The resulting polymers can be readily isomerized in dilute solution using visible light to the all-trans isomer and the optical and electrochemical properties of these polymers were examined by theory and experiment.

Modular synthesis of unsymmetrical [1]benzothieno[3,2-b][1]benzothiophene molecular semiconductors for organic transistors.

A modular approach to underexplored, unsymmetrical [1]benzothieno[3,2-b][1]benzothiophene (BTBT) scaffolds delivers a library of BTBT materials from readily available coupling partners by combining a transition-metal free Pummerer CH-CH-type cross-coupling and a Newman-Kwart reaction. This effective approach to unsymmetrical BTBT materials has allowed their properties to be studied. In particular, tuning the functional groups on the BTBT scaffold allows the solid-state assembly and molecular orbital energy levels to be modulated. Investigation of the charge transport properties of BTBT-containing small-molecule:polymer blends revealed the importance of molecular ordering during phase segregation and matching the highest occupied molecular orbital energy level with that of the semiconducting polymer binder, polyindacenodithiophene-benzothiadiazole (PIDTBT). The hole mobilities extracted from transistors fabricated using blends of PIDTBT with phenyl or methoxy functionalized unsymmetrical BTBTs were double those measured for devices fabricated using pristine PIDTBT. This study underscores the value of the synthetic methodology in providing a platform from which to study structure-property relationships in an underrepresented family of unsymmetrical BTBT molecular semiconductors.

Synthesis and Ring-Opening Metathesis Polymerization of o-Dialkoxy Paracyclophanedienes.

The highly strained ortho-diethylhexyloxy [2.2]paracyclophane-1,9-diene (M1) can be synthesized by ring contraction of a dithia[3.3]paracyclophane using a benzyne-induced Stevens rearrangement. This paracyclophanediene undergoes ring-opening metathesis polymerization to give well-defined 2,3-dialkoxyphenylenevinylene polymers with an alternating cis/trans alkene stereochemistry and controllable molecular weight. Fully conjugated block copolymers with electron-rich and electron-deficient phenylene vinylene polymer segments can be prepared by sequential monomer additions. These polymers can be readily isomerized to the all-trans stereochemistry polymer. The optical and electrochemical properties of these polymers were investigated by theory and experiment.