In situ EPR and UV-vis spectroelectrochemistry of hole-transporting organic substrates

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2000-02, Vol.56 (2), p.357-362
• Main Authors: Rapta, Peter, Fáber, René, Dunsch, Lothar, Neudeck, Andreas, Nuyken, Oskar
• Format: Article
• Language: English
• Subjects: Benzidines - chemistry; bis-anilines; Conducting polymers; Cyclic voltammetry; Electrochemistry; Electrodes; Electron Spin Resonance Spectroscopy - instrumentation; EPR/UV-vis spectroelectrochemistry; Hole-transporting materials; Oxidation-Reduction; Polymers - chemistry; Pyrroles - chemistry; Spectrophotometry - instrumentation; Spectrophotometry, Ultraviolet - instrumentation; Thiophenes - chemistry
• ISSN: 1386-1425
• DOI: 10.1016/S1386-1425(99)00246-2

A newly developed in situ electron paramagnetic resonance (EPR)/ultraviolet-visible (UV-vis) spectroelectrochemical cell equipped with a laminated indium-tin oxide (ITO) working electrode was used in the investigation of various organic substrates which are potential hole-transporting materials. The experiment demonstrated the possibility of using such a technique for examining redox behavior of conducting polymers (polypyrrole, PPy), oligomers (thiophene dimmer and quarterthiophene) and bis-anilines (N,N,N′,N′-tetraphenylbenzidine, TPB). All investigated structures formed stable paramagnetic intermediates in the first oxidation step characterised with UV-vis spectra in the region 400–600 nm. In the second oxidation step EPR-silent di-cationic structures are formed with broad vis bands in the region 600–1000 nm. The measurement of the reference UV-vis spectra direct in the EPR cavity was possible using a specially-constructed non-contacted ITO plate in the spectroelectrochemical cell in the case of polypyrrole.