Flux synthesis, crystal structures, and physical properties of new lanthanum vanadium oxyselenidesElectronic supplementary information (ESI) available. CCDC 1535833-1535837. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7dt00779e

The new lanthanum vanadium oxyselenides LaVSe 2 O, La 5 V 3 Se 6 O 7 , La 5 V 3 Se 7 O 5 , La 7 VSe 5 O 7 , and La 13 V 7 Se 16 O 15 were synthesized in eutectic NaI/KI fluxes, and their crystal structures were determined using single-crystal and powder X-ray diffraction experiments. LaVSe 2 O and La 5 V 3 Se 6 O 7 adopt known structure types, whereas La 5 V 3 Se 7 O 5 , La 7 VSe 5 O 7 , and La 13 V 7 Se 16 O 15 crystallize in hitherto unknown structure types. The main building blocks of these compounds are chains of edge-sharing VSe 6 , VSe 5 O, and/or VSe 4 O 2 octahedra, linked together by edge-sharing OLa 4 and/or OLa 3 V tetrahedra forming fluorite-like ribbons. LaVSe 2 O, La 5 V 3 Se 7 O 5 , and La 7 VSe 5 O 7 contain only V( iii ) ions, whereby La 5 V 3 Se 6 O 7 and La 13 V 7 Se 16 O 15 contain mixtures of either V( iii )/V( iv ) or V( iii )/V( v ) cations. Magnetic measurements indicate Curie-Weiss paramagnetism and magnetic ordering of the vanadium moments at low temperatures. More precisely, we observe antiferromagnetism for La 5 V 3 Se 6 O 7 , metamagnetism for La 5 V 3 Se 7 O 5 , ferromagnetism for La 7 VSe 5 O 7 and a complex magnetic structure for La 13 V 7 Se 16 O 15 . New vanadium-oxyselenides exhibit increasing structural complexity, mixed-valent vanadium and antiferromagnetism or metamagnetic transitions.