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A glow in the dark: synthesis and electropolymerization of chemiluminescent thiophene derivatives

Asil, Demet
Two novel chemiluminescent monomers, 2,3-dihydrothieno(3,4-d)pyridazine-1,4-dione (T-Lum) and 5,7-di-thiophen-2-yl-2,3-dihydro-thieno[3,4-d]pyridazine-1,4-dione (TTT-Lum), were synthesized. The reaction between T-Lum and TTT-Lum in alkaline solution with H2O2 gave chemiluminescence which can be catalyzed using Fe(III) ion. Owing to its sensitivitiy towards Fe(III) ion; T-Lum and TTT-Lum can be promising materials to detect bloodstains in the application of forensic science instead of luminol which gave response to a large family of metallic cations beside Fe(III). Also, TTT-Lum, which is based on a terthienyl system, was electropolymerized and its corresponding polymer (PTTT-Lum) was obtained via repetitive cycling or constant potential electrolysis in both 0.1 M LiClO4 dissolved in acetonitrile containing 5% of BF3-Et2O by volume and neat BF3- Et2O solution. In addition, PTTT-Lum, soluble in alkaline water, was synthesized successfully without breaking the pyridazinedione unit (chemiluminescent unit), as proved by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Electrochemical Luminescence (ECL) measurements. Thus, PTTT-Lum, bearing chemiluminescent unit, can be a good candidate to be used as a sensor in near future. Furthermore, the PTTT-Lum film has a very stable and well-defined reversible redox couple as well as electrochromic behavior during p-doping process. The polymer film has also a band gap of 1.74 eV with an absorption band in its neutral state at 536 nm. Finally, PTTT-Lum film was found to be electrochemiluminescence active, maintaining its activitiy over 1000 cycles.