From an ST = 3 Single-Molecule Magnet to Diamagnetic Ground State Depending on the Molecular Packing of MnIIIsalen-type Dimers Decorated by N,N'-Dicya
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- 作者：Chihiro Kachi-Terajima ; Hitoshi Miyasaka ; Ken-ichi Sugiura ; Rodolphe Clé ; rac ; and Hiroyuki Nojiri
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：May 29, 2006
- 年：2006
- 卷：45
- 期：11
- 页码：4381 - 4390
- 全文大小：479K
- 年卷期：v.45,no.11(May 29, 2006)
- ISSN：1520-510X
文摘
Two manganese(III) tetradentate Schiff-base dimers to which N,N'-dicyano-1,4-naphthoquinonediiminate (DCNNQI)radicals are attached have been selectively synthesized by varying the solvents used in the reactions: [Mn2(5-MeOsaltmen)2(DCNNQI)2]·MeOH (1) and [Mn2(5-MeOsaltmen)2(DCNNQI)2]·2CH2Cl2·2CH3CN (2) [5-MeOsaltmen2-= N,N'-(1,1,2,2-tetramethylethylene)bis(5-methoxysalicylideneiminate)]. These two complexes share the samemolecular core, [(DCNNQI
-)-MnIII-(O)2-MnIII-(DCNNQI-)], where -(O)2- is a biphenolate bridge in the out-of-plane dimerized [Mn2(5-MeOsaltmen)2]2+ moiety. However, their packing arrangements are completely different.Whereas complex 1 is found to be relatively isolated, strong intermolecular dimerization of the DCNNQI moieties(with the nearest contact being ~3.0 Å) is observed in 2, forming a one-dimensional chain of [-MnIII-(O)2-MnIII-(DCNNQI-)2-]
. The magnetic susceptibility of 1 can be modeled with an [S = 1/2, 2, 2, 1/2] four-spin systemincluding strong antiferromagnetic MnIII/DCNNQI radical coupling (JMn/rad/kB = -23 K) and ferromagnetic MnIII/MnIIIcoupling through the biphenolate bridge (JMn/Mn/kB = +2.0 K). These interactions lead to an ST = 3 ground statethat possesses significant uniaxial anisotropy (DS=3/kB = -2.1 K). Low-temperature ac and dc magnetic data of 1reveal its single-molecule magnet behavior with quantum tunneling of the magnetization. By contrast, 2 possessesthe diamagnetic ground state induced by dominating MnIII-MnIII antiferromagnetic interactions mediated by thediamagnetic DCNNQI dimers and/or 
- contact along the b axis.
-)-MnIII-(O)2-MnIII-(DCNNQI-)], where -(O)2- is a biphenolate bridge in the out-of-plane dimerized [Mn2(5-MeOsaltmen)2]2+ moiety. However, their packing arrangements are completely different.Whereas complex 1 is found to be relatively isolated, strong intermolecular dimerization of the DCNNQI moieties(with the nearest contact being ~3.0 Å) is observed in 2, forming a one-dimensional chain of [-MnIII-(O)2-MnIII-(DCNNQI-)2-]. The magnetic susceptibility of 1 can be modeled with an [S = 1/2, 2, 2, 1/2] four-spin systemincluding strong antiferromagnetic MnIII/DCNNQI radical coupling (JMn/rad/kB = -23 K) and ferromagnetic MnIII/MnIIIcoupling through the biphenolate bridge (JMn/Mn/kB = +2.0 K). These interactions lead to an ST = 3 ground statethat possesses significant uniaxial anisotropy (DS=3/kB = -2.1 K). Low-temperature ac and dc magnetic data of 1reveal its single-molecule magnet behavior with quantum tunneling of the magnetization. By contrast, 2 possessesthe diamagnetic ground state induced by dominating MnIII-MnIII antiferromagnetic interactions mediated by thediamagnetic DCNNQI dimers and/or - contact along the b axis.