铬——稀土单分子磁体的研究进展
Research Progress in Cr-Ln SMMs Single Molecule Magnets
DOI: 10.12677/japc.2024.133044, PDF, HTML, XML, 下载: 8  浏览: 78  科研立项经费支持
作者: 王窦尊, 张腾坤, 郑 祺, 李 佳, 刘 雨, 王 金:南通大学化学化工学院,江苏 南通;崔会会*:南通大学化学化工学院,江苏 南通;南通智能与新能源材料重点实验室,江苏 南通
关键词: 铬–稀土单分子磁体结构磁性Cr-Ln Single Molecule Magnets Structure Magnetism
摘要: 铬(III)具有[Ar] 3d3的电子构型,属于d3离子类别。在八面体配位环境中,它简并的t2g轨道上只能容纳三个电子,这会使Jahn-Teller效应减弱。因此,该离子显示出相对较弱的磁各向异性,这也导致了关于利用铬(III)作为中心离子的单分子磁体(SMM)的研究报告十分缺乏。因此,本文通过对近年来典型的铬–稀土单分子磁体进行综述,以期为3d-4f单分子磁体的发展奠定一定的基础。
Abstract: Chromium(III) has an electronic configuration of [Ar] 3d3 and belongs to the d3 ion category. In an octahedral coordination environment, its degenerate t2g orbital can only accommodate three electrons, which weakens the Jahn Teller effect. Therefore, the ion exhibits relatively weak magnetic anisotropy, which also leads to a lack of research reports on single molecule magnets (SMMs) using chromium(III) as the central ion. This article reviews typical chromium lanthanide based single molecule magnets in recent years, in order to lay a certain foundation for the development of 3d-4f single molecule magnets.
文章引用:王窦尊, 张腾坤, 郑祺, 李佳, 刘雨, 王金, 崔会会. 铬——稀土单分子磁体的研究进展[J]. 物理化学进展, 2024, 13(3): 385-395. https://doi.org/10.12677/japc.2024.133044

1. 引言

在过去的十几年里,关于f元素的配合物发表数量呈指数级增长,这些化合物大多都显示出磁矩的缓慢弛豫[1]。由于强烈的自旋–轨道耦合和晶体场效应[2]。稀土离子具有显著的单离子各向异性,大的总角矩(J)使其成为SMM的优良自旋载流子。然而,由于4f轨道的有限径向伸展展现出了非常弱,甚至没有交换作用的现象。而其中一种提供强磁交换相互作用的方法是将3d离子引入4f系统,并且分子的大基态和磁各向异性可以通过控制磁交换相互作用力来引导。通过增加配合物中3d和4f离子之间的磁耦合,利用4f离子的单离子各向异性来增加Ueff [3]。因此,构建3d-4f SMM的目标是来自f元素的大磁矩和各向异性,而预期抑制不期望的量子磁化隧穿效应(QTM)的3d-4f磁耦合同样也是热点问题[4]-[10]

3d-4f系统在各个领域都有潜在的应用并被备受关注。例如发光,催化,磁热效应和单分子磁体[2] [5] [11] [12]等等。至今为止,化学家已经开发了几种合成策略,并合成了许多具有多核的和拓扑结构的3d-4f团簇,包括球,笼子,圆盘和车轮形状结构[13]-[18],并对其特性进行评估。若将3d和4f离子机械的混合,会与配体存在竞争配位,很难得到预期的混金属配合物。难点在于需要同时考虑3d和4f金属离子的不同配位几何偏好[17],例如,3d金属离子倾向于采用协调几何,这就主要受到电子构型,和配体场之间相互作用的影响[19],而本文所综述的铬(Ⅲ),具有[Ar] 3d3的电子构型,属于d3离子类别。在八面体配位环境中,它简并的t2g轨道上只能容纳三个电子,这会使Jahn-Teller效应减弱。因此,该离子显示出相对较弱的磁各向异性,同时这也导致了关于利用铬(Ⅲ)作为中心离子的单分子磁体(SMM)的研究报告十分缺乏。另一方面对于4f离子,配体场稳定往往需要静电和自旋耦合效应的平衡来引导[3] [7]。为了实现对于建立3d-4f稳定构型的控制,进行大量的实验探究是必不可少的,归根结底,如果结构能够稳定建立,应该是合成显示出某种特定属性的目标配合物,但显然,实现这一目标还是一个漫长的过程。因此,本文通过对近年来典型的铬–稀土单分子磁体进行综述,以期为3d-4f单分子磁体的发展奠定一定的基础。

2. 铬–稀土单分子磁体的研究进展

目前,已报道的铬–稀土单分子磁体如表1所示,本论文仅选其中一些具有代表性的例子进行描述,并根据其核数进行分类,以研究其结构与磁性行为之间的关系。磁交换可以利用ab从头算或者利用自旋哈密顿算符拟合变温磁化率(χT vs. T)或者磁化强度(Mvs.H)得到。对于异核体系,各向同性的哈密顿算符为 H ^ =2 i>j J ij S ^ i S ^ j ( S ^ 是每个顺磁离子的自旋算符,Jij是顺磁性离子ij之间磁相互作用的耦合常数)。在Cr-Ln单分子磁体中,有三种磁交换作用(图1),分别为过渡–过渡磁交换(JCr-Cr)、过渡–稀土磁交换(JCr-Ln)、稀土–稀土磁交换(JLn-Ln)。利用Heisenberg模型拟合磁化率的方法是存在局限性的,仅限于各向同性的离子,如GdIII离子。如果想求得JCr-LnJLn-Ln,由于复杂的晶体场分裂和各向异性LnIII离子大的轨道角动量,使各向同性的自旋哈密顿算符受到了限制。因此,对于含有各向异性离子的体系,利用Lines模型和ab从头算比较可靠。目前,在已报道的铬–稀土单分子磁体中,最简单为Cr-Ln双核体系,在这个体系中,只有一种JCr-Ln磁交换(图1(a))。在复杂的蝴蝶型[Cr2Ln2] (图1(b))、三角双锥型[Cr2Ln3] (图1(c))、[Cr4Ln4] (图1(d))单分子磁体中,存在三种磁交换(JCr-CrJCr-LnJLn-Ln)。

Table 1. The magnetic data of Cr-Ln SMMs

1. 铬–稀土单分子磁体的磁性数据

Complexes

Hdc/kOe

Ueff/K

τ0/s

v/mT/s

TB/K

Ref.

[Cr4Dy4(μ3-OH)4(μ3-N3)4(mdea)4(piv)4]·3CH2Cl2 (1)

0

15

1.9(1) × 10−7

35

0.04

[20]

[Cr4Dy4F4(OMe)1.12(OH)2.88(O2CPh)8(mdea)4] (2)

0

78.65

6.1 × 10−8

3

3.5

[21]

[Cr2Dy2(OMe)2(O2CPh)4(mdea)2(NO3)2] (3)

0

77

5.1 × 10−8

3

3.5

[22]

[Cr2Tb2(OMe)2-x(OH)x(2-Cl-4, 5-F-benz)4(mdea)2(NO3)2] (4)

0

62.92

7.7 × 10−9

3

2.8

[23]

[Cr2Dy2(OMe)2-x(OH)x(2-Cl-4, 5-F-benz)4(mdea)2(NO3)2] (5)

0

87.23

2.1 × 10−7

3

4.4

[23]

[Cr2Ho2(OMe)2-x(OH)x(2-Cl-4, 5-F-benz)4(mdea)2(NO3)2] (6)

0

51.48

6.8 × 10−9

3

2.2

[23]

[Cr2Dy2(OMe)(OH)(4-tBu-benz)4(tBudea)2(NO3)2]MeOH·2Et2O

0

64.35

7.7 × 10−8

3

3.1

[23]

[Cr2Dy2(OMe)2(mdea)2(hfacac)6] (7)

0

41.5

1.6 × 10−7

4

2.2

[24]

[Dy(4-MMNO)(H2O)5][Cr(CN)6] (8)

0

592

1.86 × 10−11

50

25

[25]

[Cr2Dy3(PhCO2)7(OH)6(iPrO)(NO3)(H2O)3] (9)

0

30.9

4.09 × 10−10

[26]

[Dy(hfac)3(H2O)CrF2(py)4Dy(hfac)3(NO3)]

0.5

4.29

5.3(4) × 10−8

[27]

[Cr2Dy2(μ-F)4(μ-OH)2(py)4(hfac)6]

1.6

6.56

2.8(3) × 10−5

[28]

Na3[Dy3Cr2(HGly)6(μ3-OH)6(H2O)9]·(ClO4)8·Cl4·14H2O

0

12.68

1.07 × 10−7

[29]

Na3[Tb3Cr2(HGly)6(μ3-OH)6(H2O)9]·(ClO4)6·Cl6·6H2O

0

13.0

6.4 × 10−7

[29]

[Dy3Cr2(HGly)6(dpyo)2(μ3-OH)6(H2O)7]·(ClO4)9·15H2O

0

13.24

9.16 × 10−8

[29]

(pipzH2)[Cr2Dy4(μ4-O)2(μ3-OH)4(H2O)10(μ3-SO4)4(SO4)2]·2H2O

0

39.7

2.9 × 10−9

[30]

[Cr2Dy2(OMe)2(O2CPh)4(dea)2(MeOH)4](NO3)2

0

62.1

2.3 × 10−7

2

3

[31]

[Cr2Dy2(OMe)(OH)(O2CPh)4(edea)2(NO3)2] ·MeOH·Et2O

0

79.1

3.4 × 10−8

2

3.5

[31]

[Cr2Dy2 (OMe)2(O2CPh)4(bdea)2(NO3)2]

0

61.6

1.1 × 10−7

2

3

[31]

[Cr2Dy2(OMe)2 (O2CPh)4(teaH)2(NO3)2(MeOH)2]

0

63.4

8.3 × 10−7

2

3.5

[31]

[Cr2Dy2(OMe)2(mdea)2(acac)4(NO3)2]

0

34.6

1.2 × 10−7

4

1.8

[32]

[Cr2Dy2(OMe)2(edea)2(acac)4(NO3)2]

0

41.6

9.2 × 10−8

4

2.2

[32]

[Cr2Dy2(OMe)2(bdea)2(acac)4(NO3)2]

0

37.5

3.1 × 10−7

4

2.2

[32]

[CrDy2(OCH3)4(dpm)5(CH3OH)]·CH3OH

0

13.7

4.5 ± 1 × 10−8

[33]

0.8

13.4

5.0 ± 1 × 10−8

[Cr2Tb2(OMe)2(O2CPh)4(mdea)2(NO3)2]

0

62.92

1.7 × 10−9

3

2.5

[34]

[Cr2Ho2(OMe)2(O2CPh)4(mdea)2(NO3)2]

0

51.48

1.1 × 10−9

3

1.8

[34]

(pipzH2)[Cr2Tb4(μ4-O)2(μ3-OH)4(H2O)10(μ3-SO4)4(SO4)2]·2H2O

0

24.1

4.0 × 10−9

[35]

[(Tb6Cr)-(C8A)2]

0

18.13

7.5 × 10−8

[36]

[(Dy6Cr)-(C8A)2]

0

7.56

1.36 × 10−6

[36]

[Cr8Dy8(mdea)16(CH3COO)8(NO3)8]·6CH3CN

0

19.0

3.5 × 10−8

0.6

0.5

[37]

[Cr6Ln6(μ3-OH)8(tbdea)6(C6H5COO)16]·2H2O

0

12.8

1.8 × 10−7

[38]

[Cr2Dy4(μ4-O)23-OH)4(H2O)9(SO4)5]·3H2O

0

24.6

7.2 × 10−9

[39]

[Cr2Dy4(μ4-O)2(μ3-OH)4(H2O)5(μ4-SO4)4(μ3-SO4)]·9H2O

0

37.5

6.7(0.3) × 10−8

1.9

[40]

[Cr2Dy4(μ4-O)2(μ3-OH)4(H2O)8(μ4-SO4)2(μ3-SO4)(ter-η3-SO4)2]·2H2O

0

25.9

7.3(0.3) × 10−9

[40]

[CrTb6(OH)8(o-tol)12(NO3)(MeOH)5]∙2MeOH

3

12.3

6.3 × 10−8

[41]

[CrEr6(OH)8(o-tol)12(NO3)(MeOH)5]∙2MeOH

3

4.5

9.1 × 10−8

[41]

[Cr2Tb3(Piv)10(OH)6(H2O)2]Et3NH

0

17

7 × 10−9

[42]

[Cr2Dy3(Piv)10(OH)6(H2O)2]Et3NH

0

10

1.3 × 10−9

[42]

[Cr2Tb2(OH)2(FcCO2)4(NO3)2(Htea)2]·2MePh·2THF

0

54

2.1× 10−8

[43]

续表

[Cr2Dy2(OH)2(FcCO2)4(NO3)2(Htea)2]·2MePh·2THF

0

75

2.6× 10−8

5

4

[43]

[Cr2Ho2(OH)2(FcCO2)4(NO3)2(Htea)2]·2MePh·2THF

0

47

2 × 10−9

[43]

[Cr3Dy3(μ3-F)(μ3-OH)3(mdea)3(piv)8DMF]·H2O·CH3CN

0

17(3)

38(4)

τ1 = 3(1) × 105;

τ2 = 7(2)× 10−9

8

5

[44]

[Cr2Dy2(OCH3)2(Htea)2(piv)6]

0

71.5

1.2 × 10−7

7

2

[45]

[Cr3Dy3(mdea)3(piv)8(OH)4(H2O)]

0

3

20.0

28.6

4 × 10−10 − 3×10−8

[46]

HPiv = pivalic acid; H2mdea = methyldiethanolamine; 2-Cl-4, 5-F-benz = 2-Cl-4,5-F-benzoate; hfacacH = hexafluoroacetylacetone; 4-MMNO = 4-methylmorpholine N-oxide; iPrO = isopropoxide; Hhfac = 1, 1, 1, 5, 5, 5-hexafluoroacetylacetone; py = pyridine; dpyo = 4, 4-dipyridyl N, N-dioxide; HGly = glycine; H2pipz = piperazine; H2dea = diethanolamine; H2edea = N-ethyldiethanolamine; H2bdea = butyldiethanolamine; H3tea = triethanolamine; Hdpm = dipivaloymethane; H8C8A = p-tert-pbjutylcalix[8]arene; o-tol= o-toluate; Fc = (η5-C5H4)(η5-C5H5)Fe

Figure 1. The magnetic interaction type of Cr-Ln. Color code: Cr, bright green; Ln, sky blue

1. Cr-Ln的磁相互作用类型。颜色代码:Cr,亮绿色;Ln,天蓝色

2.1. [Cr4Dy4]型单分子磁体

2010年,Powell的研究小组成功地将Cr与高度各向异性的Dy结合在了一起,合成了第一个具有单分子磁性的Cr-Dy配合物[Cr4Dy4 (μ3-OH)4 (μ3-N3)4 (mdea)4 (piv)4]·3CH2Cl2 (1,HPiv = 新戊酸,H2mdea = 甲基二乙醇胺) [20]。在配合物1中,4个Dy离子分别与4个μ3-OH配体连接,在同一平面内形成正方形结构,并与4个叠氮配体配位。此外,4个去质子化的mdea2配体分别与1个Cr和2个Dy离子连接。四种Cr离子交替位于四种Dy离子组成的正方形的上下方。沿着配合物的四重轴方向沿着分析,观察到四个Dy离子的正方形排列嵌入四个Cr离子组成的正方形结构中(图2)。值得注意的是,1在5 K的温度,在零外磁场下表现出显著的频率依赖的异相信号。利用Arrhenius定律对数据进行拟合,得到有效能垒为15 K,τ0为1.9(1) × 107 s。

Figure 2. The molecular structure of [Cr4Dy4(μ3-OH)4(μ3-N3)4(mdea)4(piv)4]·3CH2Cl2. Color code: Cr, green; Dy, purple; O, pink; N, blue; C, gray. H atoms are omitted for clarity

2. [Cr4Dy4(μ3-OH)4(μ3-N3)4(mdea)4(piv)4]·3CH2Cl2的分子结构。颜色代码:Cr,绿色;Dy,紫色;O,粉红色;N,蓝色;C,灰色。为了清晰起见省略了H原子

2015年,Keith S. Murray课题组[21]报道了一种由氟桥联的[Cr4Ln4]型配合物[Cr4Dy4F4(OMe)- 1.12(OH)2.88(O2CPh)8(mdea)4] (2)。2的金属核与1的金属核相似,都具有四个Cr离子围绕四个Dy离子的正方形排列。四个Dy离子由四个无序的μ3-OH/OMe桥和四个μ-F离子桥联(图3(a))。磁性测量证实了2中Dy和Cr存在显著的磁交换作用,在零磁场下表现出SMM行为,磁翻转势垒为78.65 K。此外,在30 Oe/s的扫描速率下,2在3.5 K下显示出开口的磁滞回线,表明2具有优异的SMM性能(图3(b))。在2中观察到多个弛豫过程,这可能归因于无序的OH/OMe桥。2中的能垒要明显高于1中的能垒,关键区别在于桥联的氟离子。因此,可以推断,作为桥联单元或末端配体的电负性基团可以影响系统中的有效能垒和弛豫时间。

Figure 3. The molecular structure (a) and magnetic hysteresis (b) of [Cr4Dy4F4(OMe)1.12(OH)2.88(O2CPh)8(mdea)4]. Color code: CrIII, green; DyIII, purple; O, pink; N, blue; C, gray; F, bright green. H atoms are omitted for clarity

3. [Cr4Dy4F4(OMe)1.12(OH)2.88(O2CPh)8(mdea)4]的分子结构(a)和磁滞回线(b)。颜色代码:Cr,绿色;Dy,紫色;O,粉红色;N,蓝色;C,灰色;F,亮绿色。为了清晰起见,省略了H原子

2.2. 蝴蝶型单分子磁体

除了[Cr4Ln4]型配合物外,蝴蝶型配合物也表现出优异的磁性能。2013年,Langley研究组[22]成功合成了具有平面蝴蝶状结构的配合物[Cr2Dy2(OMe)2(O2CPh)4(mdea)2(NO3)2] (3)。在配合物3中,两个μ3-甲氧基配体分别连接两个Dy离子和一个Cr离子。Cr离子还与mdea2配体和两个苯甲酸根配体连接,形成六配位八面体构型。除了与mdea2配体和两个苯甲酸根配体连接外,单个Dy还与一个硝酸根离子配位,形成八配位反棱柱构型(图4(a))。交流磁化率测量揭示了实部(χM’)和虚部(χM”)都表现出显著温度和频率依赖性,表明配合物3具有SMM行为。通过拟合Arrhenius定律确拟合得到有效能垒为77 K。此外,在3.5 K以下磁滞回线出现开口。理论计算表明,磁滞回线中观察到大的矫顽场是由顺磁性Cr离子的存在引起(图4(b))。Cr和Dy之间的磁交换相互作用导致3中存在的多级交换型势垒,抑制了量子隧穿效应(QTM)并延长了弛豫时间。

随后,Langley研究组用2-氯-4,5-氟苯甲酸酯取代苯甲酸配体,合成了一系列铬–稀土配合物[CrIII2LnIII2(OMe)2-x(OH)x(2-Cl-4, 5-F-benz)4(mdea)2(NO3)2xMeOH (Ln = Tb (4), Dy (5) and Ho (6)) (图5(a)) [23]。研究结果表明具有较高电负性的卤素基团的引入,影响了磁交换作用的强度,导致磁滞回环的开口温度提高到4.4 K (图5(b)),并使配合物5的能垒提高到87.2 K。因此,引入吸电子配体可以有效地抑制QTM。此外,配合物46的磁滞回线测试结果显示出较大的矫顽场,为合成含Tb和Ho的蝴蝶型SMM提供了有价值的先例。

Figure 4. The molecular structure (a) and magnetic hysteresis (b) of [Cr2Dy2(OMe)2(O2CPh)4(mdea)2(NO3)2]. Color code: Cr, green; Dy, purple; O, pink; N, blue; C, gray. H atoms are omitted for clarity

4. [Cr2Dy2(OMe)2(O2CPh)4(mdea)2(NO3)2]的分子结构(a)和磁滞回线(b)。颜色代码:Cr,绿色;Dy,紫色;O,粉红色;N,蓝色;C,灰色。为了清晰起见,省略了H原子

Figure 5. The molecular structure (a) and magnetic hysteresis (b) of [CrIII2DyIII2(OMe)2-x(OH)x(2-Cl-4, 5-F-benz)4(mdea)2(NO3)2xMeOH. Color code: Cr, green; Dy, purple; O, pink; N, blue; C, gray; F, brightgreen; Cl, yellow. H atoms are omitted for clarity

5. [CrIII2DyIII2(OMe)2-x(OH)x(2-Cl-4, 5-F-benz)4(mdea)2(NO3)2xMeOH的分子结构(a)和磁滞回线(b)。颜色代码:Cr,绿色;Dy,紫色;O,粉红色;N,蓝色;C,灰色;F,亮绿色;Cl,黄色。为了清晰起见,省略了H原子

此外,Langley研究组采用多元醇胺配体H2mdea,并用hfacac取代苯甲酸根和硝酸根配体,成功合成了蝴蝶的配合物[Cr2Dy2(OMe)2(mdea)2(hfacac)6] (7,Hhfacac = 六氟乙酰丙酮) [24]。在交流磁化率测量中,7在整个频率范围内,观察到具有温度依赖性的磁弛豫,表明配合物在短时间尺度内没有跨越到纯量子状态,使其在4 K下显示出相对较长的弛豫时间,表现出SMM行为。通过拟合得到有效能垒为41.5 K (图6(a))。此外,7的磁滞回线开口温度为2.2 K (图6(b))。这是Cr和Dy离子间强磁性交换的结果。

Figure 6. Frequency dependence of the out-of-phase (χM”) susceptibilities of 7 (a) and the M-H diagram of [Cr2Dy2(OMe)2(mdea)2(hfacac)6] (b). Inset: The molecular structure of [Cr2Dy2(OMe)2(mdea)2(hfacac)6]. The M-H diagram is measured under a scanning rate of 0.004 T/s. Color code: Cr, green; Dy, purple; O, pink; N, blue; C, gray; F, brightgreen. H atoms are omitted for clarity

6. (a)7的频率依赖性的虚部磁化率和[Cr2Dy2(OMe)2(mdea)2(hfacac)6]的M-H图。插图:[Cr2Dy2(OMe)2(mdea)2(hfacac)6]的分子结构。M-H图是在0.004T/s的扫描速率下测量的。颜色代码:Cr,绿色;Dy,紫色;O,粉红色;N,蓝色;C,灰色;F,亮绿色。为了清晰起见,省略了H原子

从结构上看,蝴蝶型单分子磁体是指其分子结构呈现类似蝴蝶状的形态,通常由两个磁性核心通过柔性的连接基团相互连接而成,在设计和合成过程中需要考虑到分子的空间排布和化学键的稳定性。但同时,通过合理设计分子结构和调控连接基团的性质,可以实现蝴蝶型单分子磁体的磁性质可调,包括磁滞回线、磁耦合等。而[Cr4Dy4]型单分子磁体结构相对简单,通常由金属离子和有机配体构成,合成相对容易。从磁性质上看,蝴蝶型单分子磁体和[Cr4Dy4]型单分子磁体都表现出了强烈的单分子磁性,但具体表现出的磁性质有所不同。蝴蝶型单分子磁体常常表现出较强的反铁磁性质,具有较高的自旋翻转温度和磁滞回线。而方块型单分子磁体则更倾向于表现出铁磁性质,具有更高的磁矩和磁稳定性。

2.3. 其他类型的单分子磁体

除了前面提到的Cr-Ln族中的[Cr4Ln4]和[Cr2Ln2]型单分子磁体外,还有其他类型,如[Cr2Ln3] [24]、[Cr3Ln3] [24]、[Cr2Ln4] [24]、[CrLn6] [24]、[Cr6Ln6] [24]、[Cr4Ln4] [47]等。2021年,S.Gao等人使用配体4-甲基吗啉N-氧化物(4-MMNO)合成了一类新的具有离子对的稳定的3d-4f SMMs,即[Dy(4-MMNO)(H2O)5] [Cr(CN)6] (8) [25]。在该配合物中,Dy离子轴向连接到两个4-MMNO配体,赤道平面为五个水分子(图7(a))。此外,抗衡离子[CrCN6]3确保了配合物的总体电荷平衡。由于离子对结构,顺磁性Cr和Dy离子之间的磁交换作用可以忽略,主要是偶极作用,这加速了低温下的磁弛豫过程。由于8中Dy具有高对称性的D5h构型(图7(b)),因此零场时通过拟合得到有效能垒为592(5) K。

Figure 7. The molecular structure (a) and coordination geometry around the Dy ion (b). Color code: Cr, green; Dy, purple; O, pink; N, blue; C, gray. H atoms are omitted for clarity

7. Dy离子的分子结构(a)和配位几何构型(b)。颜色代码:Cr,绿色;Dy,紫色;O,粉红色;N,蓝色;C,灰色。为了清晰起见,省略了H原子

2022年,Gopalan Rajaraman等人报道了一个五核配合物[Cr2Dy3(PhCO2)7(OH)6(iPrO)(NO3)(H2O)3] (9,IPRO = 异丙醇胺) [26]。该配合物中的5个金属离子呈三角双锥构型,其中3个Dy离子位于一个三角形平面内,2个Cr离子占据三角形平面上下的轴向位置。这些金属离子由6个μ3-OH基团和7个羧酸配体桥联。直流磁化率数据显示,Dy和Cr之间存在铁磁相互作用(图8(a))。此外,在磁化率测量中,对弛豫时间使用Orbach过程和拉曼过程进行全程拟合,得到有效能垒为30.9 K,指前因子为4.09 × 1010 s (图8(b))。从头计算表明在9中存在的Dy和Cr的强铁磁相互作用抑制了量子隧穿效应,使其在零场下表现出SMM的行为。

Figure 8. The molecular structure (a) and Plots of ln(τ) vsT1 for complex 9. The blue solid line is fitting curve with the Arrhenius law (single Orbach process). The red solid lines are fitting curves using a dual-process (Orbach and Raman) model (b). Color code: Cr, green; Dy, purple; O, pink; N, blue; C, gray. H atoms are omitted for clarity

8. 配合物9的分子结构(a)和ln(τ)对T1的图。蓝色实线是Arrhenius定律(仅含Orbach过程)的拟合曲线。红色实线是使用双过程(Orbach和Raman)模型(b)的拟合曲线。颜色代码:Cr,绿色;Dy,紫色;O,粉红色;N,蓝色;C,灰色。为了清晰起见,省略了H原子

3. 结论

Cr-Ln单分子磁体作为一类具有独特磁学性质的材料,吸引了研究者们广泛的研究兴趣。目前已报道的Cr-Ln单分子磁体还相对较少,并且由于CrIII离子的自身局限使Cr-Ln单分子磁体的磁学性质并不出众,研究主要集中在理解磁体的磁学行为和性质,并改进合成和制备技术。虽然已取得了一些重要的进展,但仍面临着合成方法不成熟、磁性行为理解不够全面等问题。

综合以上研究进展,本文综述了不同结构类型且单分子磁体性能优异的Cr-Ln单分子磁体。随着科学技术的不断进步,可以将Cr-Ln单分子磁体纳入纳米技术中,实现更高级别的磁性控制,并用于纳米电子学和纳米磁性器件,为稀土–过渡异金属单分子磁体的应用和发展做出了重要贡献。

基金项目

江苏省研究生科研与实践创新计划项目(KYCX24_3546、SJCX24_1995、SJCX24_1992)资助。感谢南通大学分析测试中心。

NOTES

*通讯作者。

参考文献

[1] Ling, S., Wang, Y., Qin, X., Chen, C., Lu, C., Chen, J., et al. (2024) Design of Eu3+-Doped Fluoride Phosphor with Zero Thermal Quenching Property Based on Density Functional Theory. Inorganic Chemistry, 63, 6660-6673.
https://doi.org/10.1021/acs.inorgchem.3c04524
[2] Dey, A., Acharya, J. and Chandrasekhar, V. (2019) Heterometallic 3d-4f Complexes as Single‐Molecule Magnets. ChemistryAn Asian Journal, 14, 4433-4453.
https://doi.org/10.1002/asia.201900897
[3] Rinehart, J.D. and Long, J.R. (2011) Exploiting Single-Ion Anisotropy in the Design of F-Element Single-Molecule Magnets. Chemical Science, 2, 2078-2085.
https://doi.org/10.1039/c1sc00513h
[4] Liu, K., Shi, W. and Cheng, P. (2015) Toward Heterometallic Single-Molecule Magnets: Synthetic Strategy, Structures and Properties of 3d-4f Discrete Complexes. Coordination Chemistry Reviews, 289, 74-122.
https://doi.org/10.1016/j.ccr.2014.10.004
[5] Chakraborty, A., Goura, J., Kalita, P., Swain, A., Rajaraman, G. and Chandrasekhar, V. (2018) Heterometallic 3d-4f Single Molecule Magnets Containing Diamagnetic Metal Ions. Dalton Transactions, 47, 8841-8864.
https://doi.org/10.1039/c8dt01883a
[6] Li, G., Tang, H., Gao, R., Wang, Y., Sun, X. and Zhang, K. (2023) Tuning Quantum Tunneling in Isomorphic {mII2dyIII2} “Butterfly” System via 3d-4f Magnetic Interaction. Crystal Growth & Design, 23, 1575-1580.
https://doi.org/10.1021/acs.cgd.2c01198
[7] Peng, Y. and Powell, A.K. (2021) What Do 3d-4f Butterflies Tell Us? Coordination Chemistry Reviews, 426, Article ID: 213490.
https://doi.org/10.1016/j.ccr.2020.213490
[8] Oyarzabal, I., Echenique-Errandonea, E., San Sebastián, E., Rodríguez-Diéguez, A., Seco, J.M. and Colacio, E. (2021) Synthesis, Structural Features and Physical Properties of a Family of Triply Bridged Dinuclear 3d-4f Complexes. Magnetochemistry, 7, Article No. 22.
https://doi.org/10.3390/magnetochemistry7020022
[9] Yin, J., Chen, C., Zhuang, G., Zheng, J., Zheng, X. and Kong, X. (2020) Anion-dependent Assembly of 3d-4f Heterometallic Clusters Ln5Cr2 and Ln8Cr4. Inorganic Chemistry, 59, 1959-1966.
https://doi.org/10.1021/acs.inorgchem.9b03308
[10] Salerno, E.V., Kampf, J.W., Pecoraro, V.L. and Mallah, T. (2021) Magnetic Properties of Two GdIIIFeIII4 Metallacrowns and Strategies for Optimizing the Magnetocaloric Effect of This Topology. Inorganic Chemistry Frontiers, 8, 2611-2623.
https://doi.org/10.1039/d1qi00207d
[11] Rosado Piquer, L. and Sañudo, E.C. (2015) Heterometallic 3d-4f Single-Molecule Magnets. Dalton Transactions, 44, 8771-8780.
https://doi.org/10.1039/c5dt00549c
[12] Ghosh, A., Roy, R., Sahoo, R.C., Sarangi, S.N., Ghosh, M., Mazumdar, D., et al. (2023) Magnetic Anisotropy and Magnetocaloric Effect in Gd2NiMnO6 Thin Films. Physical Review B, 108, Article ID: 214423.
https://doi.org/10.1103/physrevb.108.214423
[13] Wang, J., Sun, C., Zheng, Q., Wang, D., Chen, Y., Ju, J., et al. (2023) Lanthanide Single‐Molecule Magnets: Synthetic Strategy, Structures, Properties and Recent Advances. ChemistryAn Asian Journal, 18, e202201297.
https://doi.org/10.1002/asia.202201297
[14] Shukla, P., Das, S., Bag, P. and Dey, A. (2023) Magnetic Materials Based on Heterometallic CrII/Iii-Lniii Complexes. Inorganic Chemistry Frontiers, 10, 4322-4357.
https://doi.org/10.1039/d3qi00193h
[15] Wang, H., Zhang, K., Song, Y. and Pan, Z. (2021) Recent Advances in 3d-4f Magnetic Complexes with Several Types of Non-Carboxylate Organic Ligands. Inorganica Chimica Acta, 521, Article ID: 120318.
https://doi.org/10.1016/j.ica.2021.120318
[16] Wang, H., Zhu, Z., Peng, J. and Zou, H. (2021) Heterometallic 3d/4f-Metal Complexes: Structure and Magnetism. Journal of Cluster Science, 33, 1299-1325.
https://doi.org/10.1007/s10876-021-02084-7
[17] Wang, J., Li, Q., Wu, S., Chen, Y., Wan, R., Huang, G., et al. (2021) Opening Magnetic Hysteresis by Axial Ferromagnetic Coupling: From Mono‐Decker to Double‐Decker Metallacrown. Angewandte Chemie International Edition, 60, 5299-5306.
https://doi.org/10.1002/anie.202014993
[18] Dey, A., Bag, P., Kalita, P. and Chandrasekhar, V. (2021) Heterometallic CuII-Lniii Complexes: Single Molecule Magnets and Magnetic Refrigerants. Coordination Chemistry Reviews, 432, Article ID: 213707.
https://doi.org/10.1016/j.ccr.2020.213707
[19] An, Z., Gao, Y., Xu, S., Zhang, W. and Yao, M. (2023) 3d Ion-Driven Hexanuclear Heterometallic Clusters with Amazing Structures and Magnetic Properties. Crystal Growth & Design, 23, 1412-1421.
https://doi.org/10.1021/acs.cgd.2c00940
[20] Rinck, J., Novitchi, G., Van den Heuvel, W., Ungur, L., Lan, Y., Wernsdorfer, W., et al. (2010) An Octanuclear [CrIII4DyIII4] 3d-4f Single‐Molecule Magnet. Angewandte Chemie International Edition, 49, 7583-7587.
https://doi.org/10.1002/anie.201002690
[21] Langley, S.K., Forsyth, C.M., Moubaraki, B. and Murray, K.S. (2015) A Fluoride Bridged {CrIII4DyIII4} Single Molecule Magnet. Dalton Transactions, 44, 912-915.
https://doi.org/10.1039/c4dt03100h
[22] Langley, S.K., Wielechowski, D.P., Vieru, V., Chilton, N.F., Moubaraki, B., Abrahams, B.F., et al. (2013) A {CrIII2DyIII2} Single‐Molecule Magnet: Enhancing the Blocking Temperature through 3d Magnetic Exchange. Angewandte Chemie International Edition, 52, 12014-12019.
https://doi.org/10.1002/anie.201306329
[23] Langley, S.K., Wielechowski, D.P., Moubaraki, B. and Murray, K.S. (2016) Enhancing the Magnetic Blocking Temperature and Magnetic Coercivity of {CrIII2DyIII2} Single-Molecule Magnets via Bridging Ligand Modification. Chemical Communications, 52, 10976-10979.
https://doi.org/10.1039/c6cc06152d
[24] Langley, S.K., Le, C., Ungur, L., Moubaraki, B., Abrahams, B.F., Chibotaru, L.F., et al. (2015) Heterometallic 3d-4f Single-Molecule Magnets: Ligand and Metal Ion Influences on the Magnetic Relaxation. Inorganic Chemistry, 54, 3631-3642.
https://doi.org/10.1021/acs.inorgchem.5b00219
[25] Li, S., Xiong, J., Yuan, Q., Zhu, W., Gong, H., Wang, F., et al. (2021) Effect of the Transition Metal Ions on the Single-Molecule Magnet Properties in a Family of Air-Stable 3d-4f Ion-Pair Compounds with Pentagonal Bipyramidal Ln(III) Ions. Inorganic Chemistry, 60, 18990-19000.
https://doi.org/10.1021/acs.inorgchem.1c02828
[26] Chauhan, D., Vignesh, K.R., Swain, A., et al. (2022) Exploiting Strong {CrIII-DyIII} Ferromagnetic Exchange Coupling to Quench Quantum Tunneling of Magnetization in a Novel {CrIII2DyIII3} Single-Molecule Magnet. Crystal Growth & Design, 23, 197-206.
[27] Dreiser, J., Pedersen, K.S., Piamonteze, C., Rusponi, S., Salman, Z., Ali, M.E., et al. (2012) Direct Observation of a Ferri-to-Ferromagnetic Transition in a Fluoride-Bridged 3d-4f Molecular Cluster. Chemical Science, 3, 1024-1032.
https://doi.org/10.1039/c2sc00794k
[28] Thuesen, C.A., Pedersen, K.S., Schau-Magnussen, M., Evangelisti, M., Vibenholt, J., Piligkos, S., et al. (2012) Fluoride-Bridged {Ln2Cr2} Polynuclear Complexes from Semi-Labile Mer-[CrF3(py)3] and [Ln(hfac)3(H2O)2]. Dalton Transactions, 41, 11284-11292.
https://doi.org/10.1039/c2dt31302b
[29] Wang, X., Li, Z., Zhu, Z., Zhu, J., Liu, S., Ni, J., et al. (2013) Pentanuclear {Cr2Ln3} (Ln = Dy, Tb) Heterometallic Clusters Based on an Amino Acid Ligand: Slow Relaxation of Magnetization and Substitution Reactions. European Journal of Inorganic Chemistry, 2013, 5153-5160.
https://doi.org/10.1002/ejic.201300665
[30] Xiang, H., Lu, W., Zhang, W. and Jiang, L. (2013) A {Cr2Dy4} Compressed Octahedron: The First Sulfate-Based Single-Molecule Magnet. Dalton Transactions, 42, 867-870.
https://doi.org/10.1039/c2dt32651e
[31] Langley, S.K., Wielechowski, D.P., Moubaraki, B., Abrahams, B.F. and Murray, K.S. (2014) Magnetic Exchange Effects in {CrIII2DyIII2} Single Molecule Magnets Containing Alcoholamine Ligands. Australian Journal of Chemistry, 67, 1581-1587.
https://doi.org/10.1071/ch14207
[32] Langley, S.K., Wielechowski, D.P., Vieru, V., Chilton, N.F., Moubaraki, B., Chibotaru, L.F., et al. (2014) Modulation of Slow Magnetic Relaxation by Tuning Magnetic Exchange in {Cr2Dy2} Single Molecule Magnets. Chemical Science, 5, 3246-3256.
https://doi.org/10.1039/c4sc01239a
[33] Car, P., Favre, A., Caneschi, A. and Sessoli, R. (2015) Single Molecule Magnet Behaviour in a Rare Trinuclear {CrIIIDyIII2} Methoxo-Bridged Complex. Dalton Transactions, 44, 15769-15773.
https://doi.org/10.1039/c5dt02459e
[34] Langley, S.K., Wielechowski, D.P., Chilton, N.F., Moubaraki, B. and Murray, K.S. (2015) A Family of {CrIII2LnIII2} Butterfly Complexes: Effect of the Lanthanide Ion on the Single-Molecule Magnet Properties. Inorganic Chemistry, 54, 10497-10503.
https://doi.org/10.1021/acs.inorgchem.5b01999
[35] Xiang, H., Lu, W., Jiang, L., Zhang, W. and Lan, Y. (2016) A Family of Double Cubanes {CrIII2LnIII4O6} (Ln = Tb, Ho, Er, Yb, Y) Based on Sulfate: Single‐molecule Magnet Behavior in the Terbium and Erbium Analogues. European Journal of Inorganic Chemistry, 2016, 907-912.
https://doi.org/10.1002/ejic.201501285
[36] Han, H., Li, X., Zhu, X., Zhang, G., Wang, S., Hang, X., et al. (2017) Single‐Molecule‐Magnet Behavior in a Calix[8]arene‐capped {Tb6IIICrIII} Cluster. European Journal of Inorganic Chemistry, 2017, 2088-2093.
https://doi.org/10.1002/ejic.201700013
[37] Qin, L., Singleton, J., Chen, W., Nojiri, H., Engelhardt, L., Winpenny, R.E.P., et al. (2017) Quantum Monte Carlo Simulations and High‐Field Magnetization Studies of Antiferromagnetic Interactions in a Giant Hetero‐Spin Ring. Angewandte Chemie International Edition, 56, 16571-16574.
https://doi.org/10.1002/anie.201709650
[38] Chen, S., Mereacre, V., Zhao, Z., Zhang, W., Zhang, M. and He, Z. (2018) Targeted Replacement: Systematic Studies of Dodecanuclear {MIII6LnIII6} Coordination Clusters (M = Cr, Co; Ln = Dy, Y). Dalton Transactions, 47, 7456-7462.
https://doi.org/10.1039/c8dt01289j
[39] Li, Z., Zhang, J., Liu, S., Zhang, H., Sun, Y., Liu, X., et al. (2018) Heterometallic Hexanuclear [Ln4Cr2] Cluster-Based Three-Dimensional Sulfate Frameworks as a Magnetic Refrigerant and Single Molecular Magnet. Crystal Growth & Design, 18, 7335-7342.
https://doi.org/10.1021/acs.cgd.8b00966
[40] Liu, C., Zhang, D., Hao, X. and Zhu, D. (2018) Arraying Octahedral {Cr2Dy4} Units into 3D Single-Molecule-Magnet-Like Inorganic Compounds with Sulfate Bridges. Inorganic Chemistry, 57, 6803-6806.
https://doi.org/10.1021/acs.inorgchem.8b01210
[41] Vignesh, K.R., Langley, S.K., Swain, A., Moubaraki, B., Damjanović, M., Wernsdorfer, W., et al. (2017) Slow Magnetic Relaxation and Single‐molecule Toroidal Behaviour in a Family of Heptanuclear {CrIIILnIII6} (Ln = Tb, Ho, Er) Complexes. Angewandte Chemie International Edition, 57, 779-784.
https://doi.org/10.1002/anie.201711844
[42] Zhao, X., Xiang, S., Wang, J., Bao, D. and Li, Y. (2018) Magnetic Nature of the CrIII-LnIII Interactions in [CrIII2LnIII3] Clusters with Slow Magnetic Relaxation. ChemistryOpen, 7, 192-200.
https://doi.org/10.1002/open.201700165
[43] Koroteev, P.S., Dobrokhotova, Z.V., Ilyukhin, A.B., Belova, E.V., Yapryntsev, A.D., Rouzières, M., et al. (2021) Tetranuclear Cr-Ln Ferrocenecarboxylate Complexes with a Defect-Dicubane Structure: Synthesis, Magnetism, and Thermolysis. Dalton Transactions, 50, 16990-16999.
https://doi.org/10.1039/d1dt02562g
[44] Ling, B., Zhai, Y., Jin, P., Ding, H., Zhang, X., Lv, Y., et al. (2022) Suppression of Zero-Field Quantum Tunneling of Magnetization by a Fluorido Bridge for a “Very Hard” 3d-4f Single-Molecule Magnet. Matter, 5, 3485-3498.
https://doi.org/10.1016/j.matt.2022.07.009
[45] Mecchia Ortiz, J.H., Cabrosi, D., Carrella, L.M., Rentschler, E. and Alborés, P. (2022) SMM Behaviour of the Butterfly {CrIII2DyIII2} Pivalate Complex and Magneto‐Structurally Correlated Relaxation Thermal Barrier. ChemistryA European Journal, 28, e202201450.
https://doi.org/10.1002/chem.202201450
[46] Mecchia Ortiz, J.H., Cabrosi, D., Cruz, C., Paredes-García, V. and Alborés, P. (2022) Synthesis, Structural Characterization, and Magnetic Property Study of {Cr3Ln3}, Ln = Gd and Dy Complexes. Dalton Transactions, 51, 624-637.
https://doi.org/10.1039/d1dt03176g
[47] Gu, Y., Zhao, D., Yu, H., Ge, R., Li, Z., Tian, C., et al. (2019) Incorporating Polyoxometalates and Organic Ligands to Pursue 3d-4f Heterometallic Clusters: A Series of {Cr4Ln4} Clusters Stabilized by Phthalic Acid and [SiW12O40]4−. RSC Advances, 9, 13543-13549.
https://doi.org/10.1039/c9ra01731c