The solid-state photoluminescence spectra of 1Dy–3Yb display their characteristic emissions of lanthanide components based on their 4f–4f transitions.
1Dy–3Yb exhibit reversible photochromism and they can change from white (for 1Dy and 3Yb) or pink (for 2Er) to blue upon UV irradiation and then their colors gradually recover in the dark for about five days. Crystal structure analyses reveal that 1Dy–3Yb are isomorphic and are all built from two mono-lanthanide substituted Keggin polyoxoanion fragments joined together by two tartaric ligands. A series of inorganic–organic hybrid double-tartaric bridging mono-lanthanide substituted phosphotungstates with a general formula of 6K 3H 7 2♲7H 2O (Ln = Dy for 1Dy, Er for 2Er, and Yb for 3Yb) have been synthesized by the reactions of K 14♲4H 2O and LnCl 3♶H 2O in the presence of tartaric acid and tetramethyl ammonium counterions in an aqueous medium.
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