Syntheses and characterizations of Cs2Cr3(BP4O14)(P4O13) and CsFe(BP3O11) compounds with novel borophosphate anionic partial structures.

Explorations of the A(I)-M(III)-B(III)-P(V)-O quinary system under solid-state reactions led to an anhydrous cesium-chromium borophosphate-phosphate and an anhydrous cesium-iron borophosphate, namely, Cs(2)Cr(3)(BP(4)O(14))(P(4)O(13)) (1) and CsFe(BP(3)O(11)) (2). They both feature complicated three-dimensional (3D) frameworks and represent the first examples of borophosphate frameworks with a P-O-P connection. Compound 1 contains a novel anionic borophosphate partial structure [B(P(2)O(7))(2)](5-) with B:P = 1:4 besides an isolated [P(4)O(13)](6-) anion. Its 3D structure is composed of a layer of [CrB(P(2)O(7))(2)](n)(2n-) and a neutral layer of [Cr(2)(P(4)O(13))](n) interconnected with the linking of P-O-Cr, and the Cs ions are located at the space. Compound 2 contains another novel borophosphate anionic unit of [B(PO(4))(P(2)O(7))](4-) with B:P = 1:3, which further bridges the Fe cations to constitute the whole structure. Both compounds are of high thermal stable and transparent in the range of 0.75-7.1 microm. Magnetic measurements indicate that there exist antiferromagnetic interactions in both compounds.