Hydrolytic products of diphthalimidodiethylamine and temperature independent sensitized luminescence of their lanthanide(III) complexes

Abstract

Syntheses and structural and luminescence studies of hydrolytic products of diphthalimidodiethylamine (DPDA) and their lanthanide(III) compounds have been undertaken in order to determine the potential for the phthalamate functionality to sensitize intense Eu³⁺ and Tb³⁺ emission via the ‘antenna effect’. Acid promoted hydrolysis of the relatively simple DPDA is efficient; hydrolysis is negligible at pH > 11. At pH 2–3, hydrolysis to phthalic acid (1) occurs which upon interaction with DPDA yields the phthalic acid–DPDA supramolecular hydrate, DPDAH–HP·1.75H₂O. With a potassium carbonate–ethanol–acetonitrile mixture containing a small amount of water, the novel phthalamate–phthalimide H2·H₂O is formed while at pH ca. 9–10 the new diphthalamate Na₂3·3H₂O is formed. These transformations have been confirmed by single crystal X-ray analyses of DPDAH–HP·1.75H₂O and H2·H₂O. The crystal structures of DPDAH–HP· 1.75H₂O and H2·H₂O reveal that the phthalamates and phthalimides are stabilized by non-covalent (e.g. π–π stacking and hydrogen bonding) interactions which are of interest as potential conduits for energy transfer and are responsible for molecular aggregations seen in FAB mass spectrometry of H2·H₂O and Na₂3·H₂O. Europium(III) compounds of 3^2– and H2 exhibit intense sensitized red emission which is, surprisingly, temperature independent.