Hydrothermal synthesis and characterization of three one-dimensional chain materials formed by reduced tetra-capped Keggin polyoxoanions and [M(en)2]2+ (M = Cu, Co and Ni) cations

Abstract Three compounds based on polyoxometalate building blocks, [Cu(en) 2 ]{[Cu(en) 2 ] 2 [Mo VI 5 Mo V 3 V IV 8 O 40 (PO 4 )]} · 4H 2 O ( 1 ), [Co(en) 2 ]{[Co(en) 2 ] 2 [HMo VI 4 Mo V 4 V IV 8 O 40 (PO 4 )]} · 5H 2 O ( 2 ) and [Ni(en) 2 ]{[Ni(en) 2 ] 2 [Mo VI 5 Mo V 3 V IV 8 O 40 (VO 4 )]} · 2H 2 O ( 3 ) (en = ethylenediamine), have been synthesized and characterized by elemental analysis, IR, XPS, XRD, TGA and single-crystal X-ray diffraction analysis. The result of structure determination shows that isomorphic compounds 1 , 2 and 3 feature a one-dimensional chain built from the reduced tetra-capped pseudo-Keggin polyoxoanion, which is further interconnected by [M(en) 2 ] 2+ (M = Cu, Co and Ni) groups via the terminal oxygen atoms of polyoxoanions. The crystal data for these compounds are the following: 1 , monoclinic, space group C2 / c , a  = 26.702(3) A, b  = 13.4539(14) A, c  = 19.5987(19) A, β  = 108.650(2)°, V  = 6671.0(12) A 3 , Z  = 4; 2 , monoclinic, space group C2 / c , a  = 26.244(3) A, b  = 13.5070(17) A, c  = 19.581(3) A, β  = 106.881(2)°, V  = 6641.8(15) A 3 , Z  = 4; 3 , monoclinic, space group C2 / c , a  = 26.2789(15) A, b  = 13.5408(6) A, c  = 19.6312(9) A, β  = 106.2590(10)°, V  = 6706.1(6) A 3 , Z  = 4. Variable-temperature magnetic susceptibility measurements of compounds 1 and 3 reveal the feature of antiferromagnetic exchange in these compounds.