Synthesis and structure–property investigation of multi-arm oligothiophenes

Abstract

Oligothiophenes are used in many applications owing to their easy accessibility in high purity, tunable electron density, high chemical stability and desired processability in solution and in the solid state. In this work, a series of soluble branched oligothiophenes have been synthesized and fully characterized. The target molecules (SCT-1 to SCT-4) are soluble in common organic solvents. Full characterization of optical and electrochemical properties indicated that the extended π-conjugation led to red-shifts in the absorption maximum (λ_max) from 360 nm (SCT-1) to 440 nm (SCT-4). Fluorescence quantum yields were in the range of 6–45% for the SCTs. The observed properties of the target molecules are better than the corresponding linear oligothiophenes. Electron deficient Hg(II) cations interact with electron rich SCT-4 to form a charge-transfer complex which led to significant quenching of photoluminescence in solution. Moreover, an electron deficient molecule, 7,7,8,8-tetracyanoquinodimethane (TCNQ), also interacts with electron rich SCTs to form a TCNQ dianion (TCNQ²⁻). Such conjugated optical materials could be used for developing potential applications in the near future.