Quasi-one-dimensional molecular magnets based on derivatives of (fluorobenzyl)pyridinium with the [M(mnt)2] monoanion (M = Ni, Pd or Pt; mnt2- = maleonitriledithiolate): syntheses, crystal structures and magnetic properties.
Quasi-one-dimensional molecular magnets based on derivatives of (fluorobenzyl)pyridinium with the [M(mnt)2] monoanion (M = Ni, Pd or Pt; mnt2- = maleonitriledithiolate): syntheses, crystal structures and magnetic properties.
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DOI：
10.1039/b514278d
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发表时间：
2006-04
影响因子：
4
通讯作者：
X. Ren;S. Nishihara;T. Akutagawa;S. Noro;Takayoshi Nakamura;W. Fujita;K. Awaga;Z. Ni;Jin Xie;Q. Meng;Reinhard K. Kremer
中科院分区：
文献类型：
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作者：
X. Ren;S. Nishihara;T. Akutagawa;S. Noro;Takayoshi Nakamura;W. Fujita;K. Awaga;Z. Ni;Jin Xie;Q. Meng;Reinhard K. Kremer
报道了三种新的配合物1-（3 '，4'，5 '-三氟苄基）吡啶[M（mnt）2]- [M = Ni（1），Pd（2）或Pt（3）]的合成、结构表征和磁性。这些配合物是类质同象的，其突出的结构特征是[M（mnt）2]-阴离子形成柱状堆叠，其中观察到二聚化。配合物2和3是抗磁性的，而配合物1具有2474 K的能隙。对于4，1-（4 '-氟苄基）吡啶[Ni（mnt）2]晶体（其结构和磁化率已在前面作过简要报道），其磁性可分为两个区域，即93 K以上的弱铁磁耦合和93 K以下的强反铁磁耦合。一个转变发生在93 K的开关的磁交换性质从铁磁性到反铁磁性。从其热容量测量中出现了与转变相关的明显的λ形热异常，表明转变是一级的。超晶格衍射的温度依赖性揭示了至少在140 K之前存在预转变现象。对4的异常磁性行为，如高温相铁磁相互作用的起源和引起自旋跃迁的原因进行了进一步的讨论。
The syntheses, structural characterizations and magnetic behaviors of three new complexes, 1-(3',4',5'-trifluorobenzyl)pyridinium [M(mnt)2]- [M = Ni (1), Pd (2) or Pt (3)], are reported. These complexes are isomorphous and their prominent structural character is that the [M(mnt)2]- anions form columnar stacks, in which the dimerization was observed. Complexes 2 and 3 are diamagnetic, while 1 possesses an energy gap of 2474 K. For crystal 4, 1-(4'-fluorobenzyl)pyridinium [Ni(mnt)2] (its structure and magnetic susceptibility were briefly reported earlier), the magnetic behavior can be divided into two regimes, namely, weakly ferromagnetic coupling above 93 K and strongly antiferromagnetic coupling below 93 K. A transition occurs at 93 K which switches the magnetic exchange nature from ferromagnetic to antiferromagnetic. A sharp thermal abnormality with lambda-shape, associated with the transition, appears from its heat capacity measurement to indicate that the transition is first order. The temperature dependences of the superlattice diffractions revealed the existence of the pretransitional phenomena up to at least 140 K. The unusual magnetic behavior of 4, such as the origin of the ferromagnetic interaction in the high temperature phase and what causes the spin transition, are discussed further.