A series of thiophene-based π-conjugated chromophores: synthesis, photophysical properties and electrochemiluminescence applications

Abstract

Herein, we report the synthesis of a series of homologous thiophene-based π-conjugated chromophores, DTC, TTC, and HTC, in which different numbers of thiophene moieties were connected with aryl polyyne bridges. Their structures were confirmed by ¹H NMR and ¹³C NMR spectroscopies and HRMS, and the corresponding absorption spectra and luminescence behaviors in 1,4-dioxane were further investigated. The observations disclosed that the absorption intensities mainly depend on the number of thiophene groups. However, in addition to the number of thiophene groups, both the rigidity of molecular structures and interactions among intramolecular functional groups have a significant impact on the fluorescence emission of these thiophene-based chromophores. Intriguingly, all three chromophores DTC, TTC, and HTC exhibited stunning and stable cathode electrochemiluminescence (ECL), and then HTC was selected to construct an ECL sensor, which achieved sensitive monitoring of dopamine (DA). The DA was detected in the concentration range from 100 fM to 1 μM, with the detection limit reaching 33 fM. The research disclosed herein enriched the existing knowledge on the optical properties of thiophene-based oligomers and will contribute to the future construction of organic small molecule luminescent devices.