N. Allen, A. Richards
1990
Citations
0
Influential Citations
7
Citations
Journal
European Polymer Journal
Abstract
Abstract The reaction between aluminium compounds and 1,4-dihydroxyanthraquinone (quinizarin QH 2 ) results in the formation of a highly fluorescent pink-red complex the properties of which are dependent upon the nature of the solvent, the mole ratio of the aluminium, the type of compound used and the pH. According to the method of continuous variation, complexes are formed with stoichiometries of 1:1 and 2:1 aluminium to quinizarin. However, using the mole ratio method, the progressive addition of aluminium results in a gradual increase in both the absorption and fluorescence quantum yield suggesting the formation of higher order complexes with polymeric characteristics. Flash photolysis studies on the aluminium complexes in nitrogen saturated 2-propanol gives rise to transient absorptions in the region 300-450 nm due to the semiquinone radical produced by the triplet-state of the complex abstracting a hydrogen atom from the solvent. The transient absorption is dependent upon the mole ratio of aluminium used to produce the complex and it is quenched with increasing aluminium concentration due to an intra-molecular triplet quenching process. Complexes of iron, cobalt and zinc were also prepared with quinizarin and found to have 1:1 stoichiometries with the latter exhibiting some polymeric properties. End-of-pulse transient absorption spectra are obtained in the region 300–650 nm and found to be dependent on the magnetic properties of the metal ions. Both the paramagnetic iron and cobalt exhibit a strong quenching effect compared with that obtained with quinizarin while the diamagnetic zinc has no such effect. The photoconductive properties of the 1:2 aluminium complex prepared with the acetylacetonate compound are examined in a single layer system in polyvinylcarbazole. Initial charge acceptance is found to be higher under positive charging and increases with increasing concentration of the complex and has maximum photoresponse at 10–20% w/w concentration. Both charge acceptance and photoresponse are more effective under positive than negative charging indicating that the complex is an effective electron-donor.