[Mn2(saltmen)2Ni(pao)2(L)2](A)2 with L = Pyridine, 4-Picoline, 4-tert-Butylpyridine, N-Methylimidazole and A = ClO4
详细信息 查看全文
- 作者：Hitoshi Miyasaka ; Rodolphe Clé ; rac ; Kaori Mizushima ; Ken-ichi Sugiura ; Masahiro Yamashita ; Wolfgang Wernsdorfer ; and Claude Coulon
- 刊名：Inorganic Chemistry
- 出版年：2003
- 出版时间：December 15, 2003
- 年：2003
- 卷：42
- 期：25
- 页码：8203 - 8213
- 全文大小：471K
- 年卷期：v.42,no.25(December 15, 2003)
- ISSN：1520-510X
文摘
A series of single-chain magnets, [Mn2(saltmen)2Ni(pao)2(L)2](A)2 (saltmen2- = N,N'-(1,1,2,2-tetramethylethylene) bis(salicylideneiminate), pao- = pyridine-2-aldoximate; A- = ClO4- with L = 4-picoline; 2, 4-tert-butylpyridine; 3,N-methylimidazole; 4, and L = pyridine with A- = BF4-; 5, PF6-; 6, ReO4-; 7), was prepared by reactions between MnIIIdimer units, i.e., [Mn2(saltmen)2(H2O)2](A)2 (A- = ClO4-, BF4-, PF6-) or Mn2(saltmen)2(ReO4)2, and NiII monomeric units,i.e., Ni(pao)2(L)2, in methanol/water media. The crystal structures of 4, 6, and 7 were established by single-crystal X-raycrystallography. These three compounds are isostructural with [Mn2(saltmen)2Ni(pao)2(py)2](ClO4)2 (1) (Clérac, R.; Miyasaka,H.; Yamashita, M.; Coulon, C. J. Am. Chem. Soc. 2002, 124, 12837) and crystallize in monoclinic space group C2/c. Thelinear arrangement of MnIII dimer units and NiII building blocks leads to an alternating chain having a repeating unit,[-(O)2-Mn-ON-Ni-NO-Mn-]. The chains are well separated with the nearest interchain intermetallic distance of 10.36Å for 4, 10.51 Å for 6, and 10.30 Å for 7, and there is no significant 
- interchain interaction between ligands. The voidspace between the chains is occupied by counteranions, which control the three-dimensional organization of the chains.The X-ray diffraction analysis (XRD) on a powder sample was also performed for all compounds. The XRD patterns for1, 2, and 4-7 are very similar, emphasizing the isostructural nature of these materials although they have individuallyslight different interchain distances. Inversely, the XRD pattern for 3 reveals a completely different shape being indicativeof the peculiar crystal packing compared to the others. Nevertheless, the one-dimensional nature of the structure is alsokept in 3 as indicated by magnetic measurements. The whole family of compounds exhibits quasi-identical magneticbehavior compared to that described for 1. Above 30 K, the heterometallic chain can be described as an assembly ofantiferromagnetically coupled Mn···Ni···Mn trimers (via oximate bridge, -24.2 K < JMn-Ni/kB < -20.8 K) connected throughMn···Mn ferromagnetic interaction (via the phenolate bridge, JMn-Mn/kB 
+0.7 K), assuming a ferromagnetic chain withS = 3 units. In the low temperature region, combined ac and dc magnetic measurements revealed for the whole seriesthe systematic presence of a magnet behavior exhibiting coercivity and slow relaxation of magnetization below 3.5 K. Thisbehavior was analyzed on the basis of Glauber's theory for an Ising one-dimensional system which predicts an activateddependence (Arrhenius law) of the relaxation time: 
= 0 exp(
/kBT). Similar values of 0 1 × 10-10 s and /kB 70 K have been found along the series. The described compounds constitute the first example of the rational design ofa single-chain magnet family and clearly demonstrate the unique behavior of these heterometallic chains independently oftheir interchain environments.
- interchain interaction between ligands. The voidspace between the chains is occupied by counteranions, which control the three-dimensional organization of the chains.The X-ray diffraction analysis (XRD) on a powder sample was also performed for all compounds. The XRD patterns for1, 2, and 4-7 are very similar, emphasizing the isostructural nature of these materials although they have individuallyslight different interchain distances. Inversely, the XRD pattern for 3 reveals a completely different shape being indicativeof the peculiar crystal packing compared to the others. Nevertheless, the one-dimensional nature of the structure is alsokept in 3 as indicated by magnetic measurements. The whole family of compounds exhibits quasi-identical magneticbehavior compared to that described for 1. Above 30 K, the heterometallic chain can be described as an assembly ofantiferromagnetically coupled Mn···Ni···Mn trimers (via oximate bridge, -24.2 K < JMn-Ni/kB < -20.8 K) connected throughMn···Mn ferromagnetic interaction (via the phenolate bridge, JMn-Mn/kB +0.7 K), assuming a ferromagnetic chain withS = 3 units. In the low temperature region, combined ac and dc magnetic measurements revealed for the whole seriesthe systematic presence of a magnet behavior exhibiting coercivity and slow relaxation of magnetization below 3.5 K. Thisbehavior was analyzed on the basis of Glauber's theory for an Ising one-dimensional system which predicts an activateddependence (Arrhenius law) of the relaxation time: = 0 exp(/kBT). Similar values of 0 1 × 10-10 s and /kB 70 K have been found along the series. The described compounds constitute the first example of the rational design ofa single-chain magnet family and clearly demonstrate the unique behavior of these heterometallic chains independently oftheir interchain environments.