Oligomeric bis(1,3-indandiylidene)azines: preparation, electrochemical and spectroscopic properties, and implications for the use of polyazines as conducting materials

Abstract

Four oligomeric azines of the general structure FlN(NC₉H₄N)_nNFl, where Fl represents the 9-fluorenylidene group, C₉H₄ the 1,3-indandiylidene unit, and n has the values 1 to 4, have been prepared and characterised. Their electrochemical reduction has been studied by cyclic voltammetry and the results compared with the behaviour of fluorenone azine. Two reversible peaks have been observed for each of the compounds and the peak potentials observed show an unusual alternation in their values as n increases. Vibrational spectra have been recorded for all five compounds. The strong Raman lines associated with the collective stretching of the C–C bonds involved in π-delocalisation [[graphic omitted](ya) modes] have been studied. The effect of chain length on the frequency and intensity of this mode is the reverse of that found, for example, with polyacetylene. This suggests that, while polyazines are unlikely to produce materials of very high electrical conductivity, they may be candidates as materials for electroluminescence purposes in the fabrication of organic light-emitting diodes.