一种新颖的六帽Keggin型钼钒砷酸盐——(H_3O)_3[AsMo_(12)O_(40)(VO)_6]·6H_2O的水热合成和晶体结构

Hydrothermal Synthesis and Crystal Structure of a Novel Hexacapped Keggin-type Molybdovanadoarsenate (H_3O)_3[AsMo_(12)O_(40)(VO)_6]·6H_2O

近年来, 含有Keggin结构的杂多酸以其优异的结构可修饰性及其在催化、功能材料和医药等方面的潜在应用而引起人们广泛的研究兴趣[1～3]. 在这一领域中, 众多过渡金属取代的Keggin型杂多化合物, 尤其是含有钒和钼的多金属氧酸盐由于其独特的电磁特性及结构特点而倍受关注[4,5]. 但迄今为止, 只有少数带帽Keggin型结构的杂多阴离子被报道[6～13]. 这些Keggin阴离子通常具有低的V/Mo物质的量比, 且单帽、双帽及四帽的Keggin结构多阴离子多以磷(P)作为中心杂原子, 由Mo/V混合组成, 其中的钒通常以混合价态存在. 具有六帽Keggin型结构的多酸化合物极为少见, 仅有[V18O42(PO4)]11-一例报道[14].

A novel molybdovanadoarsenate(H3O)3[AsMo12O4o(VO)6] · 6H2O has been hydrothermally synthesized and structurally characterized by elemental analyses, cerimetric titration, EPR, and single crystal X-ray diffraction. The compound crystallizes in the triclinic system, space group PI with a = 1. 262 9(3) nm, b=1. 263 5(3) nm, c=l. 767 2(4) nm, a=91. 01(3)°, β=89. 98(3)°, 7=90. 00(3)°, V=2. 819 8(10) nm3, Z=2, R1 = 0. 095 5, wR2=0. 178 8. The polyoxoanion exhibits a hexacapped a-Keggin-type structure, in which six (VO5) square pyramids were distributed on the surface of (AsMo12O40) unit and made the bridge-oxygen (Ob, Oc) atoms of the a-Keggin-type polyoxoanion occupied.