Giant Clusters with Unusual Electronic and Magnetic Structures Due to Open Shell Metal Centers Embedded Far Apart from Each Other: Spin Frustration and Antisymmetric Exchange
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- 作者：Dante Gatteschi ; Roberta Sessoli ; Winfried Plass ; Achim Mü ; ller ; Erich Krickemeyer ; Jochen Meyer ; Dirk Sö ; lter ; and Peter Adler
- 刊名：Inorganic Chemistry
- 出版年：1996
- 出版时间：March 27, 1996
- 年：1996
- 卷：35
- 期：7
- 页码：1926 - 1934
- 全文大小：311K
- 年卷期：v.35,no.7(March 27, 1996)
- ISSN：1520-510X
文摘
The magnetic properties of the compounds(NH4)21[{VO(H2O)}6{Mo(
-H2O)2(-OH)Mo}3{Mo15(MoNO)2O58(H2O)2}3]·65H2O,1a,(NH2Me2)18(NH4)6[{VO(H2O)}6{Mo(-H2O)2(-O)Mo}3{Mo15(MoNO)2O58(H2O)2}3]·14H2O, 1b, andNa3(NH4)12[{Fe(H2O)2}6{Mo(-H2O)2(-OH)Mo}3{Mo15(MoNO)2O58(H2O)2}3]·76H2O,2, havebeen investigated. 1a, 1b, and 2contain giant cluster anions composed of three transferableMo17 ligands bridgedby cationic centers which can be exchanged for other metal centers(this means that metal centers can be placeddeliberately on the surface of large clusters serving as models formetal oxides). Six of these paramagneticcenters (V(IV) in 1a/1b and Fe(III) in2) are arranged to form a trigonal prism. The analysisof the magneticsusceptibility data reveals an efficient exchange pathway between thecenters located within the trigonal face ofthis prism mediated by the large and electronically unusualMo17 ligands. In the case of thevanadium(IV)compounds a remarkably strong antiferromagnetic coupling within thetriangles (V···V distances > 650 pm) isobserved, ca. 190 cm-1 for 1a and ca. 160cm-1 for 1b, with the Hamiltonian defined as
=J
i<jSi·Sj.Themeasurement of the anisotropic susceptibility of compound 1aallowed us to determine for the first time theelusive antisymmetric exchange parameter G, expected to begenerally operative in spin frustrated systems. Theelectronic structure of the giant cluster anions of 1a,1b, and 2 as well as, for the purpose ofcomparison, thoseof the compounds(NH4)12[{MoO2}2{H12Mo15(MoNO)2O58(H2O)2}2]·33H2O,3,Na8[{MoO2}2{H12Mo15(MoO)2O58(H2O)2}2]·58H2O,4, and(NH2Me2)6[H2H12(MoVIO3)4MoV12O40],5, have been investigated by photoelectronspectroscopy and extended Hückel calculations.
-H2O)2(-OH)Mo}3{Mo15(MoNO)2O58(H2O)2}3]·65H2O,1a,(NH2Me2)18(NH4)6[{VO(H2O)}6{Mo(-H2O)2(-O)Mo}3{Mo15(MoNO)2O58(H2O)2}3]·14H2O, 1b, andNa3(NH4)12[{Fe(H2O)2}6{Mo(-H2O)2(-OH)Mo}3{Mo15(MoNO)2O58(H2O)2}3]·76H2O,2, havebeen investigated. 1a, 1b, and 2contain giant cluster anions composed of three transferableMo17 ligands bridgedby cationic centers which can be exchanged for other metal centers(this means that metal centers can be placeddeliberately on the surface of large clusters serving as models formetal oxides). Six of these paramagneticcenters (V(IV) in 1a/1b and Fe(III) in2) are arranged to form a trigonal prism. The analysisof the magneticsusceptibility data reveals an efficient exchange pathway between thecenters located within the trigonal face ofthis prism mediated by the large and electronically unusualMo17 ligands. In the case of thevanadium(IV)compounds a remarkably strong antiferromagnetic coupling within thetriangles (V···V distances > 650 pm) isobserved, ca. 190 cm-1 for 1a and ca. 160cm-1 for 1b, with the Hamiltonian defined as =Ji<jSi·Sj.Themeasurement of the anisotropic susceptibility of compound 1aallowed us to determine for the first time theelusive antisymmetric exchange parameter G, expected to begenerally operative in spin frustrated systems. Theelectronic structure of the giant cluster anions of 1a,1b, and 2 as well as, for the purpose ofcomparison, thoseof the compounds(NH4)12[{MoO2}2{H12Mo15(MoNO)2O58(H2O)2}2]·33H2O,3,Na8[{MoO2}2{H12Mo15(MoO)2O58(H2O)2}2]·58H2O,4, and(NH2Me2)6[H2H12(MoVIO3)4MoV12O40],5, have been investigated by photoelectronspectroscopy and extended Hückel calculations.