Structural Systematics of Rare Earth Complexes. III. Structural Characterization of Lanthanoid (III) Picrate Hydrates: Gadolinium Picrate Dodecahydrate - an X-Ray-Induced Phase Modification - and Some General Aspects of the Structural Chemistry of Lanthanoid Picrates

In the course of the studies described in Parts I and II, an unusual result was observed in the case of the structure determination of hydrated gadolinium(III) picrate. Midway through data collection, the monoclinic P2(1)/c phase underwent a phase modification (X-ray-induced?) to a similar cell more nearly resembling that of the La --> Pr structure type recorded previously, with no loss of crystal integrity, and with useful data sets being obtained on both forms. Redetermination of the structure with a fresh sample yielded no reproduction of the anomaly. These results are recorded and discussed, together with an overview of the consequences of the data of Parts I-III in relation to those of other literature in the field.