Syntheses, structures, and magnetism of new vanadium and iron fluoride phosphates Ax(NH4)3-xM4(PO4)2F7(OH)2 (A=K, Rb, Cs, and M= V, Fe) containing novel structural motifs

Five new vanadium and iron fluoride phosphates Ax(NH4)3-xM4(PO4)2F7(OH)2 (A = K, Rb, Cs, and M = V, Fe) were prepared through hydrothermal redox reactions. All compounds crystallize in the monoclinic crystal system, space group P21/m. The crystal structure constitutes three-dimensional frameworks with channels extending along [001] where A+ or (NH4)+ ions reside in the channels. Novel structural motifs are made up of & INFIN;[M4O8F7(OH)2]10- chains formed by corner-shared cubane M4 clusters. In the isostructural series, the interconnection between these units feature corner-shared cubane M4 S = 1 spin-chains (M = V3+) and corner-shared cubane M4 S = 5/2 spin-chain (M = Fe3+), which all promote antiferromagnetic (AFM) interactions.

Automated summary

Five new vanadium and iron fluoride phosphates with the formula Ax(NH4)3-xM4(PO4)2F7(OH)2 (A = K, Rb, Cs, and M = V, Fe) were synthesized via hydrothermal redox reactions. These compounds exhibit monoclinic crystal structure with space group P21/m. The crystal structure consists of three-dimensional frameworks with channels along [001] direction, where A+ or (NH4)+ ions are located. Novel structural motifs composed of corner-shared cubane M4 clusters form & INFIN;[M4O8F7(OH)2]10- chains. In the isostructural series, the interconnection between these units involves corner-shared cubane M4 S = 1 spin-chains (M = V3+) and corner-shared cubane M4 S = 5/2 spin-chains (M = Fe3+), which promote antiferromagnetic interactions.