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Magnetothermal studies of a series of coordination clusters built from ferromagnetically coupled {Mn~(II)_4Mn~(III)_6} supertetrahedral units

机译:铁磁耦合{Mn〜(II)_4Mn〜(III)_6}超四面体单元构建的一系列配位簇的磁热研究

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摘要

Three high-nuclearity mixed valence manganese~(II/III) coordination clusters, have been synthesised, that is, [Mn~(III)_6Mn ~(II)_4(μ_3-O)_4(HL~1) _6(μ_3-N_3)_3(μ_3-Br) (Br)](N_3)_(0.7)/(Br)_(0.3)·3-MeCN·2- MeOH (1) (H_3L~1=3-methylpentan-1,3,5-triol), [Mn ~(III)_(11)Mn~(II)_6(μ_4-O) _8(μ_3-Cl)_4(μ,μ_3-O _2CMe)_2(μ,μ-L~2)_(10)Cl _(2.34)(O_2CMe)_(0.66)(py)_3(MeCN) _2]7-MeCN (2) (H_2L~2=2,2-dimethyl-1,3-propanediol and py is pyridine), and [Mn~(III)_(12)Mn~(II)_7(μ_4-O)_8(μ_3-? ~1N_3)_8(HL~3)_(12)(MeCN) _6]Cl_2·10-MeOH ·MeCN (3) (H_3L ~3=2,6-bis(hydroxymethyl)-4-methylphenol) with high ground-spin states, S=22, 28±1, and 83/2, respectively; their magnetothermal properties have been studied. The three compounds are based on a common supertetrahedral building block as seen in the Mn_(10) cluster. This fundamental magnetic unit is made up of a tetrahedron of Mn~(II) ions with six Mn~(III) ions placed midway along each edge giving an inscribed octahedron. Thus, the fundamental building unit as represented by compound 1 can be described as a Mn_(10) supertetrahedron. Compounds 2 and 3 correspond to two such units joined by a common edge or vertex, respectively, resulting in Mn_(17) and Mn_(19) coordination clusters. Magnetothermal studies reveal that all three compounds show interesting long-range magnetic ordering at low temperature, originating from negligible magnetic anisotropy of the compounds; compound 2 shows the largest magnetocaloric effect among the three compounds. This is as expected and can be attributed to the presence of a small magnetic anisotropy, and low-lying excited states in compound 2.
机译:合成了三个高核价锰〜(II / III)配位簇,即[Mn〜(III)_6Mn〜(II)_4(μ_3-O)_4(HL〜1)_6(μ_3- N_3)_3(μ_3-Br)(Br)](N_3)_(0.7)/(Br)_(0.3)·3-MeCN·2- MeOH(1)(H_3L〜1 = 3-甲基戊烷-1,3 ,5-三醇),[Mn〜(III)_(11)Mn〜(II)_6(μ_4-O)_8(μ_3-Cl)_4(μ,μ_3-O_2CMe)_2(μ,μ-L〜 2)_(10)Cl _(2.34)(O_2CMe)_(0.66)(py)_3(MeCN)_2] 7-MeCN(2)(H_2L〜2 = 2,2-二甲基-1,3-丙二醇和py是吡啶),[Mn〜(III)_(12)Mn〜(II)_7(μ_4-O)_8(μ_3-?〜1N_3)_8(HL〜3)_(12)(MeCN)_6] Cl_2·10-MeOH·MeCN(3)(H_3L〜3 = 2,6-双(羟甲基)-4-甲基苯酚)具有高旋态,S = 22、28±1和83/2;已经研究了它们的磁热性质。如Mn_(10)簇所示,这三种化合物均基于常见的超四面体结构单元。该基本磁性单元由Mn〜(II)离子的四面体和沿每个边的中间放置六个Mn〜(III)离子的六面体组成。因此,可以将由化合物1表示的基本构建单元描述为Mn_(10)超四面体。化合物2和3分别对应于两个这样的单元,它们通过共同的边缘或顶点相连,从而导致Mn_(17)和Mn_(19)配位簇。磁热研究表明,这三种化合物在低温下均表现出有趣的远距离磁有序性,这是由于化合物的磁各向异性可忽略不计。化合物2在三种化合物中显示出最大的磁热效应。这是预料之中的,并且可以归因于化合物2中存在小的磁各向异性和低态激发态。

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