Novel 4s–4f heterometallic cluster substituted polyoxometalates based on mixed dilacunary Keggin/open Wells-Dawson units: Syntheses, crystal structure and luminescent study

A series of novel 4s–4f heterometallic cluster substituted polyoxometalates (POMs) with formula of H9Na12K2[K3Ln4(NO3)2(GeW10O37)2(Ge2W18O66)]·34H2O (1-Ln) (Ln = Dy, Ho, Er) have been hydrothermally made by adopting a trilacunary [A-α-GeW9O34]10− as a precursor. 1-Ln represent the first examples of metal-substituted POM clusters based on mixed POM fragments including dilacunary [α-GeW10O37]10− and multilacunary open Well-Dawson [Ge2W18O66]16− fragments. [Display omitted] •Novel 4s–4f heterometallic substituted POMs have been prepared and characterized.•The compounds contain mixed Keggin/ open Well-Dawson POM fragments.•The Luminescent properties of these compounds were systematically studied.•The work enriches the diversity of heterometallic metal cluster substituted POMs.•This work provides a new route for making new POMs based on mixed POM units. By adopting a trilacunary [A-α-GeW9O34]10− as a precursor under hydrothermal conditions, a series of novel 4s–4f cluster substituted polyoxometalates (POMs) containing two types of in situ generated lacunary POM fragments have been made. These compounds were characterized by single-crystal X-ray diffractions, powder X-ray diffractions, infrared spectroscopy, thermogravimetric analyses, respectively. Structural analyses indicate that these compounds constructed from a seven-nuclearity K-O-Ln (Ln = Dy, Ho, Er) heterometallic cluster stabilized by mixed dilacunary Keggin [α-GeW10O37]10−/multilacunary open Wells-Dawson [Ge2W18O66]16− fragments. Furthermore, the solid luminescent properties of the compounds at room temperature were studied.