Synthesis, structure and magnetism of a S-shaped multi-iron substituted arsenotungstate containing a trivacant Keggin [B- α-As VW 9O 34] 9− and a hexavacant Keggin [ α-As VW 6O 26] 11− fragments

Abstract

A S-shaped multi-iron substituted arsenotungstate [enH 2] 2[( α-H 2As VW 6O 26)Fe 3(H 2O)(B- α-H 4As VW 9O 34)] 2[Fe] 2·8H 2O ( 1) (en=ethylenediamine) has been prepared by reaction of K 14[As 2 IIIW 19O 67(H 2O)]· nH 2O with Fe 2(SO 4) 3· xH 2O under hydrothermal conditions and structurally characterized by elemental analyses, IR spectra, UV spectra, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. The skeleton of 1 consists of two asymmetric sandwich-type subunits [( α-H 2As VW 6O 26)Fe 3(H 2O)(B- α-H 4As VW 9O 34)] 5− linked by a di-Fe III cluster. Moreover, magnetic susceptibility measurements demonstrate that 1 indicates the antiferromagnetic coupling interactions within Fe III centers with the best-fitting set of parameters of J 1=−7.07 cm −1, J 2=−0.45 cm −1 and g=2.05, which are generated by the addition of the expressions of the molar susceptibilities of two tri-Fe III clusters and one di-Fe III cluster derived from for spin pairs coupled through the isotropic exchange interactions.