Laser Phenomena in Europium Chelates. III. Spectroscopic Effects of Chemical Composition and Molecular Structure

The emission spectra of the tris and tetrakis forms of four β-diketone chelates of europium were studied in the solid powder, and in alcohol solution with and without dimethylformamide added. Partial dissociation of the tetrakis form was observed in solution. Effective site symmetries, subject to steric distortion, were derived for the tetrakis-chelated europium ion in the various hosts: D2d in pure alcohol, C4v in alcohol plus dimethylformamide, and C4v in the crystal. For the tris chelates, in both their hydrated and anhydrous forms, a number of different low-symmetry species were found to exist simultaneously in each host medium. The implications of these findings to the laser capabilities of the chelates are discussed.