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

A newly developed in situ electron paramagnetic resonance (EPR)/ultraviolet -visible (UV-vis) spectroelectrochemical cell equipped with a laminated ind ium-tin oxide (ITO)I working electrode was used in the investigation of var ious organic substrates which are potential hole-transporting materials. Th e experiment demonstrated the possibility of using such a technique for exa mining redox behavior of conducting polymers (polypyrrole, PPy), oligomers (thiophene dimmer and quarterthiophene) and bis-anilines (N,N,N',N'-tetraph enylbenzidine, TPB). All investigated structures formed stable paramagnetic intermediates in the first oxidation step characterised with UV-vis spectr a in the region 400-600 nm. In the second oxidation step EPR-silent di-cati onic 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 wa s possible using a specially-constructed non-contacted ITO plate in the spe ctroelectrochemical cell in the case of polypyrrole. (C) 2000 Elsevier Scie nce B.V. All rights reserved.