钴–稀土单分子磁体的研究进展
Research Progress in Co-Ln Single-Molecule Magnets
DOI: 10.12677/japc.2024.133051, PDF, HTML, XML,    科研立项经费支持
作者: 李嘉欣, 解梦婷, 韦 艺, 梁皓然, 崔会会, 郑 祺：南通大学化学化工学院，江苏 南通；朱金丽*：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: 钴–稀土单分子磁体；结构；磁性；Co-Ln Single Molecule Magnets； Structure； Magnetism
摘要: 在Co(II)离子中，d轨道上总共有7个电子，其中3个为不成对电子。由于它的轨道角动量未淬灭且自旋轨道耦合相对较强，CoⅡ表现出明显的磁各向异性，使其成为磁性材料中优良且稳定的自旋载体。同时，CoⅡ容易氧化为CoⅢ，在配位环境中通常表现出抗磁性行为。这一特性在3d-4f单分子磁体(SMMs)中被用作磁稀释剂，有效抑制QTM。研究人员利用这些特性合成了许多钴–稀土(Co-Ln)SMMs。因此，本文通过对近年来典型的钴–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: In the Co (II) ion, there are a total of 7 electrons present in the d orbitals, including 3 unpaired electrons. Due to its unquenched orbital angular momentum and relatively strong spin-orbit coupling, CoⅡ exhibits significant magnetic anisotropy, making it an excellent and stable spin carrier within magnetic materials. Simultaneously, CoⅡ readily undergoes oxidation to CoⅢ, which often exhibits diamagnetic behavior in coordination environments. This property is harnessed in 3d-4f single molecule magnets (SMMs)to serve as a magnetic diluter, effectively suppressing QTM. Researchers have exploited these characteristics to synthesize numerous Co-Ln SMMs.
文章引用：李嘉欣, 解梦婷, 韦艺, 梁皓然, 崔会会, 郑祺, 朱金丽. 钴–稀土单分子磁体的研究进展[J]. 物理化学进展, 2024, 13(3): 467-481. https://doi.org/10.12677/japc.2024.133051

1. 引言

单分子磁体领域的研究始于90年代初，意大利科学家Sessoli等[1] [2]报道了一例具有高自旋态的混合价锰的簇合物，并且发现该化合物具有磁体行为。单分子磁体(single-molecule magnets, SMMs)是一类纳米尺度的磁性材料，由于其具有特殊的量子特性，在量子比特、高密度信息存储和分子自旋电子学等方面具有潜在的应用价值而备受关注。相对于传统的磁性存储材料，单分子磁体尺寸通常小于3 nm，且每个分子高度一致，可以在性质上保证完全一致。此外，单分子磁体在化学上易于调控，且可以溶解在普通溶剂中，易于成膜，可降低成本。

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。稀土离子具有显著的单离子各向异性，大的磁矩使其成为SMMs的优良自旋载体。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有效能垒(Ueff) [3]。因此，利用f元素的大磁矩和各向异性，3d-4f磁耦合抑制量子隧穿效应(QTM)，从而获得高性能的3d-4f SMMs [4]-[10]。

在Co(II)离子中，d轨道上总共有7个电子，其中3个为不成对电子。与镧系金属离子相比，虽然3d过渡金属离子没有很强的自旋轨道耦合和磁矩，但是其受配体场的影响较大。通常，弱的配体场会导致电子基态和激发态之间的d轨道能量分裂能隙变小，进而使自旋轨道耦合最大化，从而增强磁各向异性[11]-[13]。同时，CoⅡ容易氧化为CoⅢ，在配位环境中通常表现出抗磁性行为。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钴-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. 钴–稀土单分子磁体的研究进展

目前，已报道的钴–稀土单分子磁体如表1所示，本论文仅选其中一些例子进行描述，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。

2.1. [Co2Dy]型单分子磁体

近年来，随着人们对稀土配合物的不断研究，由镧系金属与有机配体形成的多功能配合物在许多领域表现出了其特殊的应用价值。2012年唐金魁研究组利用多齿席夫碱配体成功合成了一例线性四核配合物[Co2Dy2(L1)2(CH3COO)4(OH)2(H2O)2] (ClO4)2 4CH3CN (1，H2L1 = N1，N3-双(3-甲氧基水杨亚胺)二乙烯三胺) [14] (图1)。相较于其他配合物而言，所得配合物1结构简单。磁性研究表明，在高于6 K的弛豫过程中遵循热激活Orbach弛豫。根据公式拟合，有效能垒为33.8 K，τ0为3.73 × 10−6 s。低于6 K时，数据偏离了Orbach弛豫，表明热激活弛豫过程逐渐被直接过程所取代。由于存在抗磁性CoⅢ，配合物1中的磁核可视为由四个乙酸盐配体连接的Dy2系统。抗磁部分有效降低了Dy2二聚体磁核之间的磁相互作用，从而提高了SMM的有效能垒。

Table 1. The magnetic data of Co-Ln SMMs

表1. 钴–稀土单分子磁体的磁性数据

Complexes

 Hdc/kOe

 Ueff/K

 τ0/s

 v/m T/s

 TB/K

 Ref
[Co2Dy2(L1)2(CH3COO)4(OH)2(H2O)2]·(ClO4)2·4CH3CN (1)

 0

 33.8

 3.73 × 10−6

[14]
[Co2Dy(valdien)2(OCH3)2(chp)2] (2)

 2

 71.4(4.2)

 5.6(0.3) × 10−6

[15]
[Co2Tb(valdien)2(OCH3)2(chp)2] (3)

 2

 32.3(2.6)

 2.5(1.1) × 10−10

[15]
Dy2Co2(L2)10(bipy)2 (4)

 0

 118(3)

 1.85 × 10−11

[16]
[DyCo(CN)6(hep)2(H2O)4] (5)

 2

 63

 7.1 × 10−11

[17]
[Dy2CoⅡ(C7H5O2)8]·6H2O (6)

 0

 127.27(2)

 1.69 × 10−9

[18]
[Co2Dy((L3)Br)2(H2O)]NO3·3H2O (7·3H2O)

 0

 422

 2.4× 10−11

[19]
[Co2Dy((L3)Br)2(H2O)]NO3 (7)

 0

 600

 1.4× 10−11

[19]
[Co2Dy((L3)Br)2(H2O)]NO3 (7·H2O)

 0

 522

 1.8× 10−10

[19]
[Co2Dy(TTTTCl)2(MeOH)]NO3·3MeOH (8)

 0

 401(13)

 1.3(6) × 10−10

[20]
[Co2Dy(TTTTCl)2(MeOH)] [Co(HTTTTCl)] (9)

 0

 536(10)

 3.8(10) × 10−11

 20

 10

 [20]
(PPh4)[Dy2(bbpen)2{Co(CN)6}]·3.5MeCN (10)

 2

 1075(22)

 4.51 × 10−13

[21]
[L4CoYCoL4]NO3·CH3OH

 2

 53 K

 7.66 × 10−7

[22]
[L5CoYCoL5]NO3·CH3OH

 2

 51.3

 2 × 10−6

[22]
[L5CoGdCoL5]NO3

 0

 29.4

 1.47 × 10−7

 2

 1.1

 [22]
[L5CoGdCoL5]ClO4·2CHCl3

 0

 27.4

 1.50 × 10−7

 2

 1.6

 [22]
[L5CoGdCoL5](C5HF6O2)

 0

 29.5

 1.3 × 10−7

 2

 1.6

 [22]
[Co2Dy2(L1)2(pdm)2(CH3COO)2(CH3OH)2]

 0

 64.6(1)

 1.3(7) × 10−6

[23]
[Dy2CoⅢ2(OMe)2(teaH)2(O2CPh)4(MeOH)4] (NO3)2·MeOH·H2O (11)

 0

 88.8(2)

 5.64 × 10−8

[24]
[Tb2CoⅢ2(OMe)2(teaH)2(O2CPh)4(MeOH)4] (NO3)2·MeOH·H2O (12)

 1

 14.31(1)

 2.84 × 10−6

[24]
[Dy2CoⅢ2(OMe)2(dea)2(O2CPh)4(MeOH)4] (13)

 0

 102.9

 6.05 × 10−8

[25]
[Dy2CoⅢ2(OMe)2(mdea)2(O2CPh)4(NO3)2] (14)

 0

 78.6

 1.03 × 10−7

[25]
[Dy2CoⅢ2(OMe)2(bdea)2(O2CPh)4(MeOH)4] (15)

 0

 114.4

 3.38 × 10−8

[25]
[Dy2CoⅢ2(OMe)2(teaH)2(acac)4(NO3)2] (16)

 0

 27

 8.1 × 10−6

[26]
[Dy2CoⅢ2(OH)2(teaH)2(acac)4(NO3)2]·4H2O (17)

 0

 28

 7.4 × 10−6

[26]
[Dy2CoⅢ2(OMe)2(mdea)2(acac)4(NO3)2] (18)

 0

 38

 2.6 × 10−6

[26]
[CoⅢ2Dy2(OMe)2(O2CPh-2-Cl)4(bdea)2(NO3)2] (19)

 0

 114.9

 1.8 × 10−8

[27]
[CoⅢ2Dy2(OMe)2(O2CPh-4-tBu)4(bdea)2(NO3)(MeOH)3] (20)

 0

 137.3

 5.6 × 10−8

[27]
[CoⅢ2CoⅡDy(OH)(O2CPh-4-OH)(bdea)3(NO3)3(MeOH)] (21)

 1.5

 167.3

 3.4 × 10−7

[27]
[CoⅢ2Dy2(OMe)2(O2CPh-2-CF3)4(bdea)2(NO3)2] (22)

 0

 125.8

 1.4 × 10−8

[27]
[CoⅢ2Dy2(mdea)4(hfacac)3(O2CCF3)(H2O)] (23)

 0

 32.3

 1.4 × 10−6

[27]
[CoⅢ2Dy2(μ3-OH)2(o-tol)4(mdea)2(NO3)2]

 0

 116.9(2)

 9.8 × 10−9

[28]
[CoⅢ2Tb2(μ3-OH)2(o-tol)4(mdea)2(NO3)2]

 5

 49.2

 6.6 × 10−11

[28]
[Co2Dy2(L6)4(NO3)2(THF)2]·4THF (24)

 0

 117.4

 6.2 × 10−7

 235

 3

 [29]
[Co2Dy2(L6)4(NO3)2(MeOH)2]·2CH2Cl2

 0

 104.8

 9.2 × 10−7

[30]

续表

[Co2Dy2(L6)4(NO3)2(DMF)2]·2C2H6CO

 0

 94.5

 .2 × 10−6

[30]
[Dy2Co2(L5)4(NO3)2(DMF)2]·2DMF

 0

 125.1

 2.67 × 10−6

[31]
[Dy(4-MMNO)(H2O)5][Co(CN)6] (25)

 0

 595(3)

 1.29 × 10−11

 50

 25

 [32]
[CoDy3(HBpz3)6(dto)3]·4CH3CN·2CH2Cl2 (26)

 0.8

 52

 3.6 × 10−8

[33]
[Co4Dy2(μ3-O)2(μ-N3)2(OH)2(H2O)2(HL7)4]

 0

 73.5

 1.86 × 10−8

[34]
[L82CoII2GdⅢ][NO3]

 0

 27.2

 1.7 × 10−7

[35]
[Co2Dy10(L9)4(OAc)16(SCN)2(MeCN)2(H2O)4(OH)2(μ3-OH)4]·2Co(SCN)4·H2O·2MeCN·2H2O

 0

 25

 3.14 × 10−6

[36]
[CoⅢ2Dy4(OH)2(ib)8(bdea)2(NO3)4(H2O)2]·2MeCN

 0

 26.6

 2.26 × 10−5

[37]
[CoⅢ3Dy3(µ3-OH)4(O2CtBu)6(teaH)3]·(NO3)2·H2O

 2

 17.5

 2.3×10−6

[38]
[Dy2Co2(2, 3-DCB)10(2, 2’-bpy)2]

 2

 2

 7 × 10−5

[39]
[Dy2Co8(μ3-OCH3)2(L10)4(HL10)2(OAc)2(NO3)2(CH3CN)2]

 0

 14.89

 1.68 × 10−7

[40]
[Dy4Co6(L10)4(HL)2(OAc)6(OCH2CH2OH)2(HOCH2CH2OH)(H2O)]

 0

 5.49

 2.88 × 10−5

[40]
[Dy2Co4(L11)4(NO3)2(OH)4(C2H5OH)2]·2C2H5OH

 0

 27.50

 3.36×10−8

[41]
[CoII4Dy4(L12)4(μ1,3-Piv)4(μ1,1,3-Piv)2(η1-Piv)2(μ3-OH)4(MeOH)2]

 0

 12.5

 1.51×10−6

[42]
[CoⅢDy(CH3CN)0.5(L13)3(NO3)3]

 3

 2.58

 3.11×10−5

[43]
[CoⅢ2Dy4(μ3-OH)2(NO3)4(OAc)4(L32)4(DMF)2]·2C2H5OH

 0

 27.8

 1.94 × 10−7

[44]
[DyCo(CN)6(H2L14)(H2O)(DMF)]2·5H2O

 1

 11.17

 1.36 × 10−6

[45]
[CoⅢ2Dy3Na(CH3CH2COO)6(OH)6(NO3)4(H2O)2]

 0

 60.3

 9.6 × 10−8

[46]
[Dy18CoIICoⅢ6(OH)14(CO3)9(CH3CH2COO)6(dea)12(H2O)30]

 0

 3.53

 6.03 × 10−6

[47]
[Ni(L15)Dy(H2O)4][Co(CN)6]·3H2O

 0.8

 47.02

 6.7 × 10−9

[48]
[Dy(pyzic){Dy3Co2(pyzha)6(*pyzha)(NO3)2(H2O)(MeOH)2}]2

 0

 1.46

 2.4 × 10−5

[49]
Dy[CoⅢ(CN)6]

 2

 58.3(5)

 1.76(13)×10−6

[50]
[(L16)4Ru2Co2](BF4)4

 3

 12.58

 3.1 × 10−5

[51]
[Nd(18-crown-6)(H2O)4][Co(CN)6]∙2H2O

 0.8

 37.0

 2.9×10−8

[52]
[CoⅢ4Dy3(L17)4(μ4-O)2(μ-OMe)2(μ1,3-OAc)4(H2O)2(NO3)2]·NO3·3CH3OH·1.5H2O

 0

 73.5

 9.40 × 10−7

[53]
[CoⅡ4Gd(OH)2(chp)4(saloh)5(H2O)(MeCN)(Solv)]

 2

 86

 6.95 × 10−12

[54]
[CoⅡ4Dy(OH)2(chp)4(saloh)5(H2O)(MeCN)(Solv)]

 2

 66

 3.43× 10−7

[54]
[CoⅡDy (R-HL18)(hfac)5]

 1.5

 297.4

 4.7 × 10−10

[55]
[Co2Eu(NO3)(Piv)6(EtPy)2]

 1

 4

 4.7 × 10−6

[56]
Co(μ-L19)(μ-CCl3COO)Y(NO3)2]

 1.2

 8.4(6)

 3.2(4) × 10−6

[57]
[Co(μ-L19)(μ-CH3COO)Y(NO3)2]·CH3CN

 1.2

 11.0(4)

 2.5(2) × 10−6

[57]
[Co(μ-L19)(μ-PhCOO)Y(NO3)2]·3CH3CN·2H2O

 1.2

 13.7(8)

 2.6(4) × 10−6

[57]
[Co(μ-L19)-(μ-tBuCOO)Y(NO3)2]·CHCl3·2H2O

 1.2

 18.7(6)

 7.4(9) × 10−7

[57]
[Co6Dy2(O)2(dhpb)6(NO3)2(DMF)2]

 0

 11.1

 2.8 × 10−7

[58]
[Co6Ho2(O)2(dhpb)6(NO3)2(DMF)2]

 1.5

 7.3

 2 × 10−7

[58]
[CoⅢ2Dy2(HL20)L20{(py)2CO2}{(py)2C(OCH3)O}(NO3)4CH3OH]

 0.6

 59.4(9)

 3.1(1) × 10−8

[59]
[CoⅢ{(py)2C(OH)O}2][CoⅡ 2DyⅢ 4DyⅢ(HL20)4(L20)4]

 0.8

 10.9(6)

 3.5(3) × 10−8

[59]
[Co2Dy2(L21)4(Ac)2(DMF)2]·3CH3CN

 0

 15

 2.37 × 10−5

[60]
Na[CoⅢ2CoⅡCe0.65Dy0.35(H3L22)2(OAc)2(NO3)2]Cl2⋅4H2O

 1.5

 2.13

 1.03 × 10−4

[61]
[Co2La(HL42)4(NO3)] (NO3)2

 1.5

 10.65

 1.6 × 10−4

[62]
[Co2Pr(HL42)4(NO3)] (NO3)2

 2

 15.03

 2.63 × 10−7

[62]
[Co2Gd(HL24)4(NO3)](NO3)2

 0

 6.69

 3.73 × 10−8

[63]
[Co2Tb(HL24)4(NO3)](NO3)2

 0

 1.0

 3.15 × 10−5

[63]
[Co2Dy(HL24)4(NO3)](NO3)2

 0

 0.58 s

 3.86 × 10−5

[63]

续表

[CoⅢ2Dy4(μ3- OH)2(NO3)4(OAc)4(L25)4(DMF)2]·2C2H5OH

 0

 31.6

 5.66 × 10−6

[64]
[Dy2Co(2, 3-pzdc)4(H2O)4]·4H2O

 2

 5

 10−5

[65]
[L26CoⅢBr2Dy(acac)2]·CH2Cl2

 0

 167.66(0.03)

 8.28(5) × 10−8

 5

 3.5

 [66]
[L27CoⅢCl2Dy(acac)Cl(MeO)]

 0

 118.72(4.27)

 4.76(2) × 10−7

 5

 3

 [66]
[L27CoⅢCl2Dy(acac)Cl(H2O)]

 0

 75.28(13.02)

 3.47(1) × 10−6

 5

 3

 [66]
[L27CoⅢCl2 Dy0.05Y0.95 (acac)Cl(H2O)]

 0

 128.27(9.61)

 4.51(1) × 10−7

 5

 4

 [66]
[CoⅡ5EuⅢ4(OMe)8(OAc)12(NO3)2(MeOH)6]·4MeOH

 2

 16.4

[67]
[CoⅡ5DyⅢ4(OH)2(OMe)6(OAc)10(NO3)4(MeOH)6]·4MeOH

 0

 7.4

[67]
[(μ3-CO3){CoⅡDyⅢL28(μ3-OH)(OH2)}3](ClO4)·3H2O

 1

 9.2

 1.0 × 10−7

[68]
[Co(H0.5L29)Dy(DBM)2(H2O)](ClO4)0.5·3H2O

 2

 88.9

 1.34 × 10−10

[69]
[Tb2Co2(hfac)10(NITPhPybis)2]

 0

 7.98

 5.4 × 10−6

[70]
[Dy2Co2(hfac)10(NITPhPybis)2]

 1

 6.03

 5.2 × 10−5

[70]
[Dy45Co7(OH)68(CO3)12(CH3COO)26(CH3CH2COO)6(H2O)70]

 0

 4.34

 3.25 × 10−7

[71]
[CoⅢ6DyⅢ6(μ3-OH)8(nbdea)6(m-CH3C6H4COO)16]·2H2O·2CH3CN

 1

 20.8

 8.5 × 10−7

[72]
[CoⅡ2Dy2(Hhms)2(CH3COO)6(CH3OH)2(H2O)2]·(NO3)2

 0.8

 13.8

 3.2 × 10−6

[73]
[CoⅢ4Dy4(μ-F)4(μ3-OH)4(o-tol)8(mdea)4]3H2O∙EtOH∙MeOH

 0

 55.77

 1.0 × 10−6

[74]
[Co(μ-L30)(μ-NO3)Y(NO3)2]

 1

 23.9(8)

 1.5 × 10−6

[75]
[Zn0.9Co0.1(μ-L30)(μ-NO3)Y(NO3)2]

 1

 24.8(1)

 1.4 × 10−6

[75]
[Zn0.9Co0.1(μ-L30)(μ-benzoate)Y(NO3)2]

 1

 33.2(4)

 2.5 × 10−7

[75]
[Zn0.9Co0.1(μ-L30)(μ-9-anthracenecarboxylato)Y(NO3)2]

 1

 34.6(9)

 2.3 × 10−7

[75]
[CoⅢ2Yb2(OCH3)2(teaH)2(Piv)6]

 1.5

 32.89

 2.1 × 10−6

[76]
[CoⅢ2Ho2(OCH3)2(teaH)2(Piv)6]

 3

 42.9

 6.2 × 10−9

[76]
[CoⅢ2Dy2(OCH3)2(teaH)2(Piv)6]

 0

 51

 6.1 × 10−7

[77]
[Dy4Co2(μ3-OH)2(NO3)4(CH3COO)4(L31)4(DMF)2]

 0

 41.9

 1.21×10−7

[78]
[(vdpyCH2O)2Co2Dy2ac8]

 2.4

 15.9

 2.5 × 10−6

 140

 0.5

 [79]
[CoⅢ2Tb(L32)2(μ-O2CCH3)2(H2O)3]

 1.5

 15.6(4)

 1 × 10−7

[80]
[CoⅢ2Er(L32)2(μ-O2CCH3)2(H2O)3]

 1

 9.9(8)

 8 × 10−7

[80]
[Dy2CoⅢ2(OH)2(teaH)2(acac)6]·MeCN

 0

 71

 2.7 × 10−7

[81]
[Dy2CoⅢ2(OH)2(bdea)2(acac)6]·2H2O

 0.5

 38

 2.7 × 10−7

[81]
[Dy2CoⅢ2(OH)2(edea)2(acac)6]·2H2O·4MeCN

 1

 16

 1.3 × 10−6

[81]
[CoⅢ2Dy(L33)2(μ-O2CCH3)2(H2O)3]·NO3·MeOH·4H2O

 1

 88(8)

 1.0 × 10−8

[82]
[CoⅡY(L34)(DBM)3]

 2

 8.56

 1.01× 10−4

[83]
[Co2Dy4(μ3-OH)2(piv)4(hmmp)4(ae)2]·(NO3)2·2H2O

 0.8

 32.4

 4.2 × 10−7

[84]
[(CoⅡ)3(CoⅢ)2Dy3(μ3-OH)5(O2CtBu)12(L35)2]·2H2O

 0

 3.8

 1.5 × 10−6

[85]
[(CoⅢ)3Dy3(μ3-OH)4(O2CtBu)6(L35)3](NO3)2·2CH3CN·2H2O

 2

 17.4

 2.5 × 10−6

[85]
[Co(3-MeOsaltn)(MeOH)x(ac)Tb(hfac)2]

 1

 17.0(4)

 6.1(10) × 10−8

[86]
[CoⅢ2Dy2(OH)2(bdea)2(acac)2(NO3)4]

 0

 169

 1.47 × 10−7

[87]
[Co(μ-L36)(μ-OAc)Y(NO3)2

 1

 22.6

 8.9 × 10−7

[88]
[Dy42CoⅡ9CoⅢ(μ3-OH)68(CO3)12(CH3COO)30(H2O)70]

 0

 3.67

 9.78 × 10−7

[89]
[L37CoGdCoL37]NO3

 0

 21.3

 1.52 × 10−7

 2

 1.1

 [90]
[L37CoTbCoL37]NO3

 0

 14.5

 3.0 × 10−6

 140

 1.1

 [90]
[{(S)P[N(Me)N=CH-C6H3-2-O-3-OMe]3}2Co2Tb]

 1.5

 25.8

 3.7 × 10−6

[91]
[{(S)P[N(Me)N=CH-C6H3-2-O-3-OMe]3}2Co2Dy]

 0

 14.2

 5.1 × 10−6

[91]
[{(S)P[N(Me)N=CH-C6H3-2-O-3-OMe]3}2Co2Ho]

 0

 8

 13 × 10−5

[91]
[Dy4Co2(HL38)2(μ3-OH)2(piv)10(OH2)2]

 0

 26.3

 8.7 × 10−6

[92]

续表

H2L1 = N1, N3-bis(3-methoxysalicylidene)diethylenetriamine; H2valdien = N1, N3-bis(3-methoxysalicylidene)diethylenetriamine; Hchp = 6-chloro-2-hydroxypyridine; HL2 = 3, 5-dichlorobenzoic acid; bipy = 2, 2’-bipyridine; hep = 1-(2-hydroxyethyl)-2-pyrrolidinone; C7H6O2 = salicylic aldehyde; (L3)Br = 2, 2’, 2”-(((nitrilotris(ethane-2, 1-diyl))tris(azanediyl))tris(methylene))tris-(4-bromophenol); H3TTTTCl = 2, 2’, 2”-(((nitrilotris(ethane-2, 1-diyl)) tris(azanediyl)) tris(methylene))tris-(4-chlorophenol); H2bbpen = N, N’-bis(2-hydroxybenzyl)-N, N’-bis(2- picolyl)ethylene diamine; H2L4 = 2-hydroxy-3-methoxybenzaldehyde with 1, 1, 1-tris(aminomethyl)ethane, Me-C(CH2NH2)3; H2L5 = 2-hydroxy-3-methoxybenzaldehyde with N, N’, N”-trimethylphosphorothioic trihydrazide, P(S)[NMe-NH2]3; H2L1 = N1, N3-bis(3-methoxysalicylidene)diethylenetriamine; pdmH2 = 2, 6-pyridinedimethanol; teaH3 = triethanolamine; H3dea = diethanolamine; H2mdea = N-methydiethanolamine; H2bdea = N-n-butyldiethanolamine; acac = acetylacetonate; hfacacH = hexafluoroacetylacetone; o-tol = o-toluate; H2L6 = o-vanillin with 2-aminophenol; H2L5 = (E)-2-ethoxy-6-(((2-hydroxyphenyl)imino)methyl)phenol; 4-MMNO = 4- methylmorpholine N-oxide; dto2- = dithiooxalato dianion; HBpz3- = hydrotris(pyrazolyl)borate; H3L7 = 2-[Bis(pyridin-2-ylmethyl)amino]-2-(hydroxymethyl)propane-1, 3-diol; H3L8 = (S)P[N(Me)NH2]3 with o-vanillin; H2L9 = 2-Bis(2-hydroxy-3-methoxybenzylidene) hydrazine; Hib = isobutyric acid; 2, 3-HDCB = 2, 3-dichlorobenzoic acid; H3L10= 3-amino-1,2-propanediol with 2-hydroxy-1-naphthaldehyde; H2L11 = 2-(((2-hydroxy-3-methoxybenzyl) imino)methyl)-4-methoxyphenol; H2L12 = 2-((2-hydroxy-3-methoxybenzylidene)amino)benzoic acid; Piv = (μ-OH2)(O2CCMe3)4(HO2CCMe3)4; HL13 = 8-hydroxyquinoline; H2L32 = (E)-1-(((2-(hydroxymethyl)phenyl)imino)methyl)nap- hthalen-2-ol; H2L14 = 2,6-diylbis(ethan-1-yl-1-ylidene)-di(isonicotinohydrazide); H2L15 = N, N-ethylenebis(3-methoxysalicylaldiimine); H2pyzha = pyrazinehydroxamic acid; Hpyzic = pyrazinic acid; HL16 = bis(tridentate) pyrazolate-bridged ligand; H2L17 = 3-methoxysalicyl-aldehyde with 2-amino-2-methyl-1-propanol; Hchp = deprotonated 6‐chloro‐2‐ hydroxypyridine; H2saloh = 3,5‐ditert‐butylsalicylic acid; HL18 = chiral nitronyl-nitroxide ligands; H2L19 = Fe[(C5H4){-C(Me)=N−N=CH-C6H3-2-OH-3- OCH3}]2; H2dhpb = 6, 6’-dihydroxyl-2, 2’-bipyridine; H3L20 = 2-((2-hydroxy-benzylidene)amino)propane-1, 3-diol; (py)2C(OH)2 = the gem-diol form of di-2-pyridyl ketone (dpk); (py)2C(OCH3)OH = the hemiacetal form of dpk; H2L21 = (E)-2-((2-hydroxy-3-methoxybenzylidene)amino)-4-methylphenol; H6L22 = bis-tris propane; H2L23 = 2-methoxy-6-[(E)-2’-hydroxymethyl-phenyliminomethyl]-phenol; H2L24 = 2-[(2-hydroxymethyl-phenylimino)-methyl]-6-methoxy-phenol; H2L25 = (E)-4-chloro-2-(((2-(hydroxymethyl) phenyl)imino)methyl)phenol; 2, 3-H2pzdc = pyrazine-2, 3-dicarboxylic acid; H2L26 = N, N’-bis(2-oxy-3-methoxybenzylidene)-1,2-phenyl-enediamine; H2L27 = N, N’-bis(2-oxy-3-methoxybenzylidene)-1, 2-diaminocyclohexane); H3L28 = 6, 6’, 6”-(nitrilotris(methylene))tris(2-methoxy-4-methylphenol); H4L29 = 2, 2’-[1, 2-ethanediylbis[(hydroxyethylimino)methylene]]bis[6-methoxy-4-methyl-phenol]; HDBM = dibenzoylmethane; NITPhPybis = 5-(4-pyridyl)-1, 3-bis(1’-oxyl-3’-oxido-4’, 4’, 5’, 5’-tetramethyl-4, 5-hydro-1H-imidazol-2-yl)benzene; H2hms = 1-(2-hydroxy-3-methoxybenzy-lidene)-semicarbazide; H2L30 = N, N’, N”-trimethyl-N, N”-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine; H2L31 = 2-((2-(hydroxymethyl)phenylimino)methyl)-6-methoxyphenol; H3vdpyCH2OH = 1, 5-dimethyl-3-[3’- (hydroxymethyl)-2’-pyridine]-6-oxotetrazane; H3L32 = 2-methoxy-6-[{2-(2-hydroxyethylamino)ethyl-imino}methyl]phenol; edeaH2 = N-ethyldiethanolamine; H3L33 = 2-methoxy-6-[{2-(2-hydroxyethylamino)ethylimino}methyl]phenol; H2L34 = N, N’-dimethyl-N, N’-(2- hydroxy-3-methoxy-5-methyl-benzyl)ethylenediamine; H2hmmp = 2-[(2- hydroxyethylimino)methyl]-6-methoxyphenol; Hae = 2-aminoethanol; H2L35 = n-N-butyldiethanolamine; 3MeOsaltn = N, N’Bis(3-methoxy-2-oxybenzylidene)-1, 3-propanediaminato; H2L36 = N, N’, N”-trimethyl-N, N”-bis(2-hydroxy-3-methoxy-5-methylbenzyl)-diethylenetriamine; H3L37 = N, N’, N”-tris(2-hydroxy-3-methoxybenzilidene)-2- (aminomethyl)-2-methyl-1, 3-propanediamine; H3L38 = 2-(2, 3-dihydroxpropyliminomethyl)-6-methoxyphenol.

Figure 1. The molecular structure of 1 (a) and structure of ligand H2L1 with two types of coordination sites (b). Color code: Co, green; Dy, purple; O, pink; N, blue; C, gray. H atoms are omitted for clarity

图1. 1的分子结构和配体H2L1具有两种配位位点的结构(b)。颜色代码：Co，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

2014年，研究小组利用邻香兰素衍生的席夫碱配体成功合成了一个三核CoIII-DyIII SMM [Co2Ln(valdien)2(OCH3)2(chp)2] ClO4 5H2O (Ln = Dy (2)，Tb (3)，H2valdien = N1，N3-双(3-甲氧基水杨亚胺)二乙基三胺，Hchp = 6-氯-2-羟基吡啶[15]。在零场交流磁化率测试中，配合物2和3均显示出与频率相关的虚部信号，但没有观察到完整的峰值。然而，在施加2 kOe的外部场后，这两种配合物的交流磁化率实部和虚部均表现出明显的峰值。利用Arrhenius定律拟合，分别得到配合物2和3的有效能垒为71.4 (4.2) K和32.3 (2.6) K，τ0分别为5.6(3) × 10−6 s和2.5(1) × 10−10 s。因此，与双核4f金属的配合物1相比，单核配合物2在调控磁各向异性方面更容易实现。

2014年，研究团队利用3, 5-二氯苯甲酸(HL2)作为桥联配体和2, 2'-联吡啶(bipy)作为末端双齿配体，合成了一种四核链状阳离子团簇Dy2Co2(L2)10(bipy)2 (4) [16]。DyⅢ与七个L2-的氧原子配位，采用单帽三角棱柱配位结构。在磁性方面，配合物4在交流磁化率测量中表现出缓慢的磁弛豫行为。通过拉曼过程、量子隧穿和奥巴赫过程拟合，分别在零磁场和1 kOe外磁场下得到有效能垒为118 (3) K和114.2 (7) K，有效能垒相差不大。

2015年，Powell等人通过将配合物中的FeⅢ替换为CoⅢ，合成了配合物[DyCo(CN)6(hep)2(H2O)4] (5) [17]。在结构上，与其原来的相似。在磁性方面，直流磁化率测试表明，配合物5内通过二聚体偶极-偶极相互作用表现出弱的铁磁耦合。在2 kOe直流场下进行的交流磁化率试验中，拟合数据得到的有效能垒为63 K，指数前因子(τ0)为7.1 × 10−11 s，与配合物2相关数据相差不大。由于CoⅢ的抗磁性和较长的Dy-Dy距离，表明配合物5的磁弛豫行为可能是由单离子DyⅢ主导的。

2015年，唐金魁研究组成功地将配合物中的MnⅡ替换为CoⅡ，合成了配合物[Ln2CoⅡ(C7H5O2)8] 6H2O [18]。直流磁化测量结果显示，在配合物自旋载体之间存在显著的磁相互作用。在1.9 K至16 K的温度范围内，配合物6表现出两个独立的弛豫过程。利用Arrhenius定律拟合，当温度低于5 K时，能垒为16.77 (4) K，其前指数因子τ0为3.55 × 10−5 s。在高于5 K的情况下，获得了能量壁垒为127.27 (2) K，其前指数因子τ0为1.69 × 10−9 s，说明温度对其离子之间的作用产生了巨大的影响。在较高温度下，单个DyⅢ离子与激发Kramers双稳态弛豫有关，而在较低温度下，DyⅢ和CoⅢ离子之间的弱耦合占主导地位。因此，通过引入具有基态双稳态和各向异性的4f金属离子或选择合适的顺磁性3d金属离子，利用d和f自旋产生的强磁相互作用，可以提高SMMs的性能。

在2015年，由童明良团队合成了一系列线性型SMMs，[Co2Dy((L3)Br)2(H2O)] NO3 3H2O(7 3H2O)，[Co2Dy((L3)Br)2(H2O)] NO3 H2O (7 H2O)，以及[Co2Dy((L3)Br)2(H2O)]NO3 (7) [19]，形成了一种新的配合物结构。在此系列中，三个配合物中DyⅢ离子具有压扁的五角双锥形(D5h)配位几何结构。随着水分子损失，沿赤道方向与DyⅢ键合的五个氧原子的共面性变得更加明显，将配合物的能量壁垒从422 K提高到600 K(7)。这项工作还强调了在合成SMMs时，在晶体结构中避免配合物之间的分子间接触的必要性，因为溶剂或水分子可以与磁性单元形成氢键，从而增强晶体中不同[CoDyCo]单元之间的振动耦合，并导致更快的磁性弛豫。

2018年，该研究团队合成了一个线性三核配合物，[Co2Dy(TTTTCl)2(MeOH)]NO3·3MeOH (8) [20]。此外，通过[CoⅢ(TTTTCl)]+与[Co2Dy(TTTTCl)2(MeOH)]+的共结晶，形成了配合物9 (图2)，从而显著提高了单分子磁体的性能。在交流磁化率测试中，两种配合物均表现出频率依赖性的虚部交流磁化率信号。然而，在较低温度下，温度依赖性的虚部信号显示出长尾现象，这表明两种配合物中都存在量子隧穿或更快的弛豫过程。分析Cole-Cole图发现两种情况下都存在多个弛豫过程。通过公式拟合，确定配合物8和9的有效能垒分别为401 K和536 K，其前指数因子分别为1.3 (6) × 10−10 s和3.8 (10) × 10−11 s，有效能垒相差不大，但前指数因子有较大差距。配合物9中的能垒比配合物8中的高，这可能是由于DyⅢ的配位环境更接近五角双锥，并加入了抗磁性CoⅢ，稀释了磁性相互作用。

Figure 2. Molecular structures of the complexes [Co2Dy(TTTTCl)2(MeOH)]NO3·3MeOH (a) and [Co2Dy(TTTTCl)2(MeOH)] [Co(HTTTTCl)] (b). Color code: Co, green; Dy, purple; O, pink; N, blue; Cl, orange; C, gray. H atoms are omitted for clarity

图2. 配合物[Co2Dy(TTTTCl)2(MeOH)]NO3·3MeOH (a)和[Co2Dy(TTTTCl)2(MeOH)] [Co(HTTTTCl)] (b)的分子结构。颜色代码：Co，绿色；Dy，紫色；O，粉红色；N，蓝色；Cl，橙色；C，灰色。为了清晰起见，省略了H原子

随后该团队用顺磁低自旋的[Co(CN)6]3−取代了[Fe(CN)6]3−部分，从而合成了配合物{Dy2Co}(10) [21]，该类型的配合物的结构与其他配合物相比，比较复杂。这种改变导致零直流场下的有效能垒显著增加，达到975 K，磁化磁滞回线的开口温度也上升到15 K。此外，当施加2 kOe的外部磁场时，有效能势垒进一步增强至1075 (22) K。本研究采用在两个DyⅢ离子之间进行顺磁性或抗磁性六氰基金属配合物的选择性整合，以有效调节磁滞。因此，在合成具有高各向异性的3d-4f SMMs时，应避免类顺磁离子的并排排列。

2.2. 蝴蝶型单分子磁体

除了[Co2Dy]型配合物外，[Co2Ln2]型SMMs也是Co-Ln SMMs领域的重要组成部分。值得注意的是，Langley研究组合成了一系列[CoⅢ2Ln2]型单分子磁体。尽管有机配体有所不同，但这些配合物都保持着类似蝴蝶的核结构，表现出非凡的性能。2012年报道了三种结构相同的3d-4f配合物中，每个晶体结构都包含一个不对称单元中的两种不同分子：[LnⅢ2CoⅢ2(OMe)2(teaH)2(O2CPh)4(MeOH)4](NO3)2 MeOH H2O (Ln = Gd, Tb (11a)和Dy (12a)，teaH3 = 三乙醇胺)和[LnⅢ2CoⅢ2(OMe)2(teaH)2(O2CPh)4(MeOH)2(NO3)2] MeOH H2O (Ln = Gd，Tb (11b)和Dy (12b) [24]。在低于20 K的条件下，配合物12的交流磁化率表现出频率和温度依赖性。理论计算表明，由于存在抗磁性的CoⅢ离子，配合物12的弛豫行为受DyⅢ单离子性质的控制。此外，配合物12中Dy离子之间的弱分子内反铁磁交换相互作用抑制了零场下的QTM。另一方面，在配合物11中，在零场下的虚部交流磁化率信号中未观察到的峰值，可见[Co2Dy]型单分子磁体和蝴蝶型单分子磁体在性质上有某些相同之处。然而，在1 kOe的外部磁场下，有效能垒上升到14.3 K，与配合物4相差较大。

2014年，他们用二乙醇胺(H3dea)、N-甲基二乙醇胺(H2mdea)和N-正丁基二乙醇胺)取代了H3tea (图3(a))，从而形成配合物13 (图3(b))、14 (图3(c))和15 (图3(d)) [25]。这些配合物的主体核心结构与仍然与配合物3相似。其主要区别在于，在配合物13-15中，配体采用不同的配位模式，导致金属离子的配位环境发生细微变化。配合物12-15均表现出SMM行为，在零场下能垒分别为102.9 K、78.6 K和114.4 K。这项工作表明，通过简单地调整磁性中心周围的配体以及化学修饰与磁性中心无关的周围配体，可以增强SMMs的性能。

Figure 3. (a) Proligands used towards the synthesis of complexes 13-15. The molecular structure of 13 (b), 14 (c), 15 (d). Color code: Co, green; Dy, purple; O, pink; N, blue; C, gray. H atoms are omitted for clarity

图3. (a) 用于合成配合物13-15的前配体。配合物13 (b)，14 (c)，15 (d)的分子结构。颜色代码：Co，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

此外，他们利用乙酰乙酸(acac)取代苯甲酸配体，得到了三个蝴蝶状的异金属配合物，分别为[Dy2CoⅢ2(OMe)2(teaH)2(acac)4(NO3)2] (16), [Dy2CoⅢ2(OH)2(teaH)2(acac)4(NO3)2]·4H2O (17)和[Dy2CoⅢ2(Om- e)2(mdea)2(acac)4(NO3)2] (18) [26]。配合物16-18的结构核心与12有相似之处。随后，使用胺–多元醇配体H2bdea和四种羧酸配体：2-氯苯甲酸、4-叔丁基苯甲酸、4-羟基苯甲酸和2-(三氟甲基)苯甲酸合成了配合物19-22。配合物19、20和22均呈现出与12相似的蝴蝶状结构。除此之外，Langley研究组还成功合成了以先前用于配合体7的H2mdea和Hhfacac为配体的蝴蝶状配合物23 [27]。在变温和变频交流磁化率测试中，配合物19-23表现出频率依赖性和温度依赖性的虚部磁化率信号，与配合物6相似，其中配合物21在零场下没有完整的峰值。配合物19-22分别显示出显著的各向异性能垒为114.9 K、(110.1 K和137.3 K)、167.3 K和125.8 K，虽然配合物12-15也表现出了较强的频率依赖性的实部和虚部信号，但有效能垒没有19-22的高。在这些配合物中，19和22中存在的电子吸引基团有助于提高它们的各向异性能垒，而20则表现出双重弛豫现象。配合物19-22在1.8 K以上没有表现出磁滞现象，而配合物7的阻塞温度被确定为2.2 K。这再次证实了在设计3d-4f SMMs时，加入吸电子基团和选择具有强交换作用的3d和4f金属的重要性。

除了上述含有CoⅢ的蝴蝶型3d-4f SMMs外，含有CoⅡ的SMMs也表现出非凡的特性。2012年，Powell研究组合成了一种配合物[Co2Dy2(L6)4(NO3)2(THF)2] 4THF(24，H2L6为邻香草醛和2-氨基酚缩合得到的席夫碱)，其显示出中心对称的排列，其中四个金属离子通过(L6)2−配体连接，形成蝴蝶状(或缺陷立方烷)拓扑结构[29]。直流磁化测量表明，在配合物24中存在铁磁交换相互作用。在零直流场下，交流磁化率的实部和虚部均表现出温度和频率依赖性，可能是由于配合物24内单离子DyⅢ的贡献所致，而较低温度下的能垒则与DyⅢ和CoⅡ之间的耦合有关。配合物24中可观察到双弛豫现象，与配合物20类似，可能是由于CoⅡ的存在所致，这导致低能级交换分裂比纯{Dy2}配合物大十倍。

2.3. 其他类型的单分子磁体

除了线性结构和蝴蝶型配合物外，研究人员还合成了具有其他结构的Co-Ln SMMs。基于配合物8，高松等人用CoⅢ代替CrⅢ合成了化合物{DyCo}(25) [32]。虽然与配合物8的结构相似，但25在磁性方面却存在显著差异。在20 K时，配合物25的磁滞回线仍然开口，而低于10 K时，与配合物8相比，其矫顽力和剩余磁化强度显著提高。此外，由于CoⅢ的抗磁性，在配合物25中，弱DyⅢ-DyⅢ偶极相互作用占主导地位。因此，与配合物12类似，QTM效应被DyⅢ的D5h高对称性所抑制。通过对各种弛豫过程的数据拟合，在零直流场下得到595 (3) K的有效能垒。

2012年，唐金魁等人使用二硫代氧杂环二阴离子(dto2−)将[DyⅢ(HBpz3)2]2+单元(HBpz3− = 三(吡唑基)硼酸盐)与过渡金属CoⅢ组装在一起，从而合成了具有三叶螺旋桨状结构的配合物[CoDy3(HBpz3)6(dto)3] 4CH3CN 2CH2Cl2(26) [33]。在零场条件下，配合物26表现出频率和温度依赖的交流磁化率，没有明显的峰值，与配合物11相似，表明存在QTM现象。即使在800 Oe的最优场下，QTM仍然很明显。通过拟合得到的配合物26的有效能垒为52 K。

3. 结论

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Co单分子磁体还相对较少，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。通过研究发现，对Co-SMMs的调控归根到底是对其磁各向异性的调控，而其磁各向异性主要来源于基态的零场分裂，还受耦合作用的影响。现阶段已取得了一些重要的进展，但显然，我们对单分子磁体的了解还远不够，有关Co-Ln单分子磁体的研究报告没有非常全面，并且大部分Co-Ln配合物在奥巴赫、拉曼、量子隧穿这些弛豫过程中的参数(Ueff、τ0、QTM)普遍是利用理性数据拟合所得，并非确切真实数据，其可靠度需要评估。

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Co-Ln单分子磁体。随着科学技术的不断进步，相信这些磁构关系不明朗、磁性行为理解片面、工业化生产困难、研究方向单一等一系列问题会被逐个解决。如果可以得到解决，相信对单分子磁体的应用会有更好的指导意义，可以将Co-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，南通大学大学生创新创业训练计划项目(2024116)，南通大学大型仪器开放基金资助(KFJN2471、KFJN2437)，感谢南通大学分析测试中心。

NOTES

*通讯作者Email: jinlizhu@ntu.edu.cn

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