Synthesis, structural and spectroscopic studies on the lanthanoid p-aminobenzoates and derived optically functional polyurethane composites

Aromatic carboxylates of the rare earths are known for highly efficient luminescence, thus holding the promise of applicability in optical devices, but may be problematic to apply as such due to their structure, which is polymeric in nature. Therefore, means of conversion into molecular species or eventually polymer embeddings are sought, while at the same time maintaining their advantageous optical features. For these purposes, co-ligations of rare earth p-aminobenzoates with bidentate bipyridine and phenanthroline, tridentate terpyridine and polyurethanes, which may also be perceived as polydentate ligands, have been carried out. The materials were characterised with focus on their structure and optical performance. Brightly luminescing composites were obtained from reactions with aromatic and aliphatic diisocyanates. Prolonged UV-irradiation of the materials proved hexamethylene diisocyanates to be superior with regard to photodegradation. Transparent polyurethane monoliths with emission quantum yields between 40% and 55% were eventually prepared from covalent attachement of Tb(p-aminobenzoate)3 and its bipyridine co-ligated complexes to a hexamethylene diisocyanate/polyol system. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007.