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Characterization of Isomers in Solid Aluminum tris-(Quinoline-8-olate) by 27Al NMR

Published online by Cambridge University Press:  15 February 2011

Magesh Nandagopal ,
Mathew Mathai ,
Fotios Papadimitrakopoulos  and
Marcel Utz
Magesh Nandagopal
Affiliation:
Institute of Materials Science, University of Connecticut, Storrs CT 06269, USA
Mathew Mathai
Affiliation:
Institute of Materials Science, University of Connecticut, Storrs CT 06269, USA
Fotios Papadimitrakopoulos
Affiliation:
Institute of Materials Science, University of Connecticut, Storrs CT 06269, USA Department of Chemistry, University of Connecticut, Storrs CT 06269, USA
Marcel Utz
Affiliation:
Institute of Materials Science, University of Connecticut, Storrs CT 06269, USA Department of Physics, University of Connecticut, Storrs CT 06269, USA
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Abstract

Aluminum tris-(quinoline-8-olate) (Alq3) is the most widely used electron transport material for organic light emitting diodes. The Alq3 molecule exists as two different isomers: meridianal and facial, which differ by the symmetry of the arrangement of ligands around the aluminum ion. Various crystalline polymorphs of Alq3 have been identified to contain one of these isomers. In this paper we present experimental results that show that the facial and meridianal isomers of Alq3 can be distinguished in the solid state by 27Al nuclear magnetic resonance (NMR) spectroscopy under magic angle spinning (MAS). Our results prove that the recently discovered δ-phase of Alq3 exclusively contains the facial isomer. The same technique is also used to characterize the amorphous deposit of Alq3 showing that it is the meridianal isomer that predominantly exists in the amorphous state.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 771: Symposium L – Organic and Polymeric Materials and Devices , 2003 , L7.42
Copyright
Copyright © Materials Research Society 2003

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