%0 Journal Article %A Xu, Haisheng %A Li, Lili %A Liu, Bin %A Xue, Ganglin %A Hu, Huaiming %A Fu, Feng %A Wang, Jiwu %D 2009 %T AsMo7O27-Bridged Dinuclear Sandwich-Type Heteropolymolybdates of Cr(III) and Fe(III): Magnetism of [MM′(AsMo7O27)2]12− with MM′ = FeFe, CrFe, and CrCr %U https://acs.figshare.com/articles/journal_contribution/AsMo_sub_7_sub_O_sub_27_sub_Bridged_Dinuclear_Sandwich_Type_Heteropolymolybdates_of_Cr_III_and_Fe_III_Magnetism_of_MM_AsMo_sub_7_sub_O_sub_27_sub_sub_2_sub_sup_12_sup_with_MM_FeFe_CrFe_and_CrCr/2817079 %R 10.1021/ic901416m.s001 %2 https://ndownloader.figshare.com/files/4514665 %K compound 2 %K homometallic sandwich polyoxometalate %K χ MT values %K MM %K cm %K 300 K %K NH %K antiferromagnetic exchange %K Fe %K homometallic sandwich POM %K χ MT values decline monotonously %K Cr %K AsMo 7O %K homometallic species %K 2.0 K %X Two new dinuclear sandwich-type heteropolymolybdates based on the mulitidendate inorganic fragment [AsMo7O27] and Cr(III) and Fe(III) ions, namely, the homometallic sandwich polyoxometalate (POM) (NH4)12[Fe2(AsMo7O27)2]·12H2O (1) and the first example of the “symmetrical” heterometallic Cr(III)−Fe(III) sandwich POM, (NH4)12[FeCr(AsMo7O27)2]·13H2O (2), were simultaneously synthesized in high yield. Their magnetic properties are thoroughly investigated together with the homometallic sandwich POM (NH4)12[Cr2(AsMo7O27)2]·11H2O (3). The χMT values for compounds 13 at 300 K correspond well to the calculated spin-only values for FeIII (S = 5/2) and CrIII (S = 3/2) with gFe = gCr = 2. Upon cooling, the χMT values decline monotonously and reach 0.14, 1.00, and 0.11 cm3 K mol−1 at 2.0 K for 1, 2, and 3, respectively, indicating a significant antiferromagnetic exchange between the magnetic centers with J = −2.09, −4.09, and −6.26 cm−1, respectively, for 1, 2, and 3. The magnetic results clearly establish that compound 2 is formed by bimetallic Cr(III)−Fe(III) units and not by a mixture of the two antiferromagnetically coupled homometallic species. Their thermal properties are also characterized. %I ACS Publications