K6Bi13(PO4)15, K5Bi(P2O7)2, A5Bi5(PO4)4(P2O7)2 (A=K, Rb): New bismuth phosphates with different condensed phosphate groups

Four new Bi(III) phosphates, K 6 Bi 13 (PO 4 ) 15 , K 5 Bi(P 2 O 7 ) 2 , and A 5 Bi 5 (PO 4 ) 4 (P 2 O 7 ) 2 (A= K, Rb) with the different condensed P-O groups have been successfully synthesized via the solid-state reactions. The single crystals X-ray diffractions show that they crystallize in the different space groups (K 6 Bi 13 (PO 4 ) 15 : C 2; K 5 Bi(P 2 O 7 ) 2 : P 1 ¯ ; K 5 Bi 5 (PO 4 ) 4 (P 2 O 7 ) 2 and Rb 5 Bi 5 (PO 4 ) 4 (P 2 O 7 ) 2 : P 2 1 / c ). The structure of K 6 Bi 13 (PO 4 ) 15 can be described as a three-dimensional (3D) network composed of the Bi-O polyhedra and PO 4 tetrahedra with K atoms filling in the space to balance the residual charges. K 5 Bi(P 2 O 7 ) 2 features 2D [BiP 4 O 14 ] ∞ layers built by the BiO 6 octahedra and P 2 O 7 dimers and the adjacent [BiP 4 O 14 ] ∞ layers are bridged by the K atoms. A 5 Bi 5 (PO 4 ) 4 (P 2 O 7 ) 2 (A = K, Rb) contain two different condensed P-O groups, PO 4 tetrahedra and P 2 O 7 dimers, which are connected by Bi-O polyhedra to construct the complicated 3D framework with K/Rb atoms located in the tunnels. Note that, the compounds that simultaneously contain two different types of P-O groups are still rare in phosphates. Detailed structural comparisons of Bi 3+ -containing phosphates indicate that the Bi/P ratios have a significant effect on the condensed degrees of PO 4 groups. Furthermore, TG-DSC, IR, UV-Vis-NIR diffuse reflectance spectra and SHG test for title compounds have also been reported.