Effects of Substituent on Binaphthyl Hinge-Containing Conductive Polymers

Conductive polymers containing hinged 1,1′-binaphthyl were synthesized. Their conformational flexibility around the 1,1′ C–C bonds was found to vary with the substituents at the 2,2′-positionshydroxy, linear alkyloxy, and macrocyclic alkyloxy groups were compared. Macrocyclic alkyloxy groups appeared to immobilize the binaphthyl. The connection patterns of electroactive oligothiophenes to the binaphthyl groups were also investigated with 6,6′- and 7,7′-attachments. The substituents binaphthyl polymers were examined using cyclic voltammetry, <i>in situ</i> conductivity measurements, and spectroelectrochemistry. Their electronic properties were found to vary greatly with the substituents and their connectivity. Binaphthyl polymer with hydroxyls and 3,4-ethylenedioxythiophenes exhibited interesting charge-trapping properties. 7,7′-Substitution led to intrachain interactions, which were promoted by the presence of linear alkyl chains. The observed properties give binaphthyl hinge-containing conductive polymers potential applicability in chiral electroactive sensors, polymer actuators, and electrochromic and optoelectronic devices

Torsionally Responsive Tropone-Fused Conjugated Polymers

Torsionally responsive molecular systems can change their electronic properties according to the dihedral angles and can be utilized as sensory materials. We have designed and synthesized novel tropone-fused conjugated polymers <b>PBTr</b>, <b>PBTr-T</b>, and <b>PBTr-Tz</b> that showed interesting dihedral-angle-dependent variations in UV–vis absorptions. Tropone-fused thiophene derivatives were prepared from one-step condensation of thiophene-3,4-dialdehyde and aliphatic ketones via a modular, facile, and high-yielding method. Subsequent halogenation and Stille cross-coupling polymerization with a bis­(stannyl)­benzo­dithiophene resulted in a tropone-fused conjugated polymer <b>PBTr</b>. We were also able to prepare thiophene- and thiazole-bridged polymers, <b>PBTr-T</b> and <b>PBTr-Tz</b>, respectively, using similar synthetic methods. Electronic absorptions of the newly synthesized <b>PBTrs</b> were measured in solutions and in films states. Substantial red-shifts occurred in the case of thiophene-bridged <b>PBTr-T</b>, whereas almost no shift was observed for thiazole-bridged <b>PBTr-Tz</b>. We attributed this to the substantial change in the torsional angle between the tropone-fused thiophene moiety and thiophene, which was further supported by density functional theory (DFT) calculations. Similar spectral changes of UV–vis absorptions were observed when a poor solvent (methanol) was introduced to a chloroform solution of <b>PBTr-T</b>. Reverse torsional angle variations were realized with initially planar <b>PBTr-Tz</b> by introducing steric hindrance through protonation on the thiazole rings. We believe that torsionally responsive tropone-fused conjugated polymers are promising as novel platforms for sensory applications