Acetato-bridged dinuclear lanthanide complexes with single molecule magnet behaviour for the Dy2 species

Article abstract of DOI:10.1039/c3dt53366b

Five dinuclear lanthanide complexes with formula [Ln₂L ₂(OAc)₄(MeOH)_a(H₂O) _b]·cMeOH·dH₂O (a = 2, b = 0, c = 2, d = 0, Ln = Sm (1), Gd (2), Dy (3); a = 0, b = 2, c = 4, d = 2, Ln = Tm (4)) and [Yb₂L₂(OAc)₄(MeOH)₂]·[Yb ₂L₂(OAc)₄(H₂O)₂] ·2H₂O (5) (HL = (E)-N′-(2-hydroxybenzylidene)-2- mercaptonicotinohydrazide), have been synthesized and their crystal structures and magnetic properties are reported. All five complexes are centrosymmetric, showing a similar dinuclear core with two lanthanide ions in each complex being bridged by acetate groups in the η¹:η²: μ₂ mode. The various coordination modes of acetate groups result in two kinds of coordination geometries for Ln ions with the ones in complexes 1-4 and the Yb2 in 5 being nine-coordinated with a mono-capped square antiprism geometry, while the Yb1 ions in the other part of complex 5 are eight-coordinated with a triangular dodecahedron geometry. Magnetic susceptibility studies reveal that complex 3 shows single molecule magnet behaviour with an energy barrier of 39.1 K. In addition, comparison of the structural parameters among the similar Dy₂ SMMs with a η¹:η²:μ₂ coordination mode of carboxylate groups reveals the significant role played by coordination geometry in modulating the relaxation dynamics of SMMs. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c3dt53366b

View Article Online
View Journal
Dalton
Transactions
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: H. Zhang, S. Lin, S.
Xue, C. Wang and J. Tang, Dalton Trans., 2014, DOI: 10.1039/C3DT53366B.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/dalton

View Article Online
DOI: 10.1039/C3DT53366B
Page 1 of 8
Dalton Transactions
Journal Name
RSCPublishing
ARTICLE
Acetato-bridged dinuclear lanthanide complexes with
single molecule magnet behaviour for the Dy2 species
Cite this: DOI: 10.1039/x0xx00000x
Haixia Zhang,a,b Shuang-Yan Lin,a,b Shufang Xue,a,b Chao Wanga and Jinkui
Tang*a
Received 00th January 2012,
Accepted 00th January 2012
Five
dinuclear
lanthanide
complexes
with
formula
), Gd ( ),
4)) and
[Ln2L2(OAc)4(MeOH)a(H2O)b]·cMeOH·dH2O (a = 2, b = 0, c = 2, d = 0, Ln = Sm (
Dy
[Yb2L2(OAc)4(MeOH)2]·[Yb2L2(OAc)4(H2O)2]·2H2O
1
(
2
DOI: 10.1039/x0xx00000x
(
3
);
a
=
0,
b
=
2,
c
=
4,
d
=
2, Ln
(HL
=
Tm
=
(
5
)
(E)-N'-(2-
www.rsc.org/
hydroxybenzylidene)-2-mercaptonicotinohydrazide), have been synthesized and their crystal
structures and magnetic properties are reported. All five complexes are centrosymmetric,
showing similar dinuclear core with two lanthanide ions in each complex being bridged by
acetate groups in the form of η1
result in two kinds coordination geometries for Ln ions with the ones in complexes
Yb2 in are nine-coordinated with mono-capped square antiprism geometry, while Yb1 ions in
the other part of complex are eight-coordinated with triangular dodecahedron geometry.
Magnetic susceptibility studies reveal that complex shows single molecule magnet behaviour
with energy barrier of 39.1 K. In addition, the comparison of the structural parameters among
the similar Dy2 SMMs with η1 η2
µ2 coordination mode of carboxylate groups reveals the
:
η2
:
µ2 mode. The various coordination modes of acetate groups
and the
1-4
5
5
3
:
:
significant role played by coordination geometry in modulating the relaxation dynamics of
SMMs.
is necessary to prepare some complexes with similar structure
by modifying functional group to probe into the structure-
property relationship.15
Introduction
Since
the
discovery
of
the
molecule
[Mn12O12(CH3COO)16(H2O)4] (Mn12OAc)1 that shows slow
relaxation of magnetization at liquid-helium temperatures, in
the early 1990s, great increments of compounds displaying this
property, known as single-molecule magnets (SMMs), have
been reported.2 The research enthusiasm of scientists promoting
the exploration of such advanced magnetic materials is due to
their various promising applications in many significant areas
It is critical to select suitable organic ligands to gain SMMs
with defined geometries and particular properties.15-16 Earlier,
various Schiff base ligands have been utilized in our group,
which exhibit excellent performance in the construction of
molecules displaying distinct anisotropic centres.17 In the
present study, we choose a new salicylaldehyde-based Schiff
base
ligand,
namely
(E)-N'-(2-hydroxybenzylidene)-2-
such as high-density data storage,1b, quantum information
3
mercaptonicotinohydrazide (HL, Scheme 1). The ligand
provides O,N,O-based multichelating sites forming a coordinate
pocket, which is especially favorable for accommodating
lanthanide ion.18 Additionally, lanthanide acetates are brought
into the systems in the view of enriching the coordination
processing systems,4 and spintronic devices.5 Initially, the
research was only limited to the field of 3d metal-based6
complexes, however, compared to 3d metal ions included in
most SMMs, lanthanide (Ln) ions are more suitable for
constructing high performance SMMs because of their inherent modes by utilizing multidentate acetate groups. Thus, a series
large unquenched orbital angular momentum,7 which may bring
significant anisotropy8 to the systems. Thus, attention has been
given to incorporate 4f ions into SMMs so as to build either
heterometallic 3d-4f9 or homometallic 4f2c, 10 clusters. Hitherto,
lanthanide SMMs continue to flourish in this domain and new
high relaxation barriers are being reached.11 At the same time, it
is responsible for researchers to search for more breakthrough
outcomes in the case of Lnn (n = 1, 2, 3, 4, 5 and so on)
complexes.2c, 10b, 10c, 11d, 12 Of particular interest are dinuclear
systems with facile control of the intradimer magnetic
interactions, especially Dy2 complexes.11b, 13 Among them, Dy2
bridged by carboxylic acid groups14 have been investigated. It
of Ln2 (Ln = Sm (1), Gd (2), Dy (3), Tm (4), Yb (5)) complexes
bridged by acetate groups in the form of η1:η2:µ2 mode were
obtained. Furthermore, the structure-property relationship was
primarily discussed through the comparison of the structural
parameters of the title Dy2 complex with that of Dy2 complex
containing n-butyric acid ligand.
Experimental Section
General
This journal is © The Royal Society of Chemistry 2013
J. Name., 2013, 00, 1-3 | 1

View Article Online
Dalton Transactions
DOI: 10.1039/C3DT53P36a6gBe 2 of 8
ARTICLE
Journal Name
All chemicals were of reagent grade and used without further 1235 (w), 1205 (w), 1150 (m), 1124 (m),1075 (w), 1020 (w),
purification. Elemental analysis for C, H, and N were carried 974 (w), 937 (w), 888 (m), 852 (w), 804 (w), 759 (m), 750 (w),
out on a Perkin-Elmer 2400 analyzer. FTIR spectra were 736 (w), 708 (w), 673 (s).
recorded with a Perkin-Elmer Fourier transform infrared
[Gd2L2(OAc)4(MeOH)2]·2MeOH (2)
spectrophotometer using the reflectance technique (4000-300 Gd(OAc)3·6H2O (0.1 mmol, 44.24 mg) was reacted with HL
cm-1). Samples were prepared as KBr disks. Magnetic (0.1 mmol, 25.93 mg) in MeOH/DMF (15 mL/2 mL) in the
susceptibility measurements were performed in the temperature presence of Et3N (0.1 mmol, 0.1 mL). The ensuing yellow
range 1.9-300 K, using a Quantum Design MPMS XL-7 solution was stirred for 5 h and subsequently filtered. The
SQUID magnetometer equipped with a 7 T magnet. The filtrate was left undisturbed to allow the slow volatilization of
magnetisation isotherm was collected between 0 and 7 T. The the solvent. Yellow block-shaped single crystals of complex 2,
diamagnetic corrections for the complexes were estimated suitable for X-ray diffraction analysis, formed after one week.
using Pascal’s constants,19 and magnetic data were corrected Yield: 15 mg (24%, based on the metal salt). Elemental analysis
for diamagnetic contributions of the sample holder.
(%) calcd for C38H48Gd2N6O16S2: C 37.02, H 3.99, N 6.87;
found C 37.30, H 4.02, N 6.81. IR (KBr, cm-1): 3114 (w), 1608
(m), 1584 (m), 1537 (s), 1431 (s), 1380 (m), 1339 (m), 1310
(m), 1232 (m), 1185 (m), 1150 (m), 1127 (m), 1083 (w), 1064
(w), 1037 (w), 1019 (w), 967 (w), 932 (w), 890 (m), 863 (w),
799 (w), 761 (m), 745 (s), 698 (s), 666 (s), 630 (m), 610 (w),
588 (s), 542 (w).
X-Ray crystal structure determinations
Suitable single crystals for complexes 1-5 were selected for
single-crystal X-ray diffraction analysis. Crystallographic data
were collected at a temperature of 293(2) K on a Bruker Apex
II CCD diffractometer with graphite monochromated Mo-Ka
radiation (λ = 0.71073 Å). Data processing was accomplished
with the SAINT processing program. The structure was solved
by direct methods and refined on F2 by full-matrix least squares
[Dy2L2(OAc)4(MeOH)2]·2MeOH (3)
Dy(OAc)3·6H2O (0.1 mmol, 44.77 mg) was reacted with HL
(0.1 mmol, 25.93 mg) in MeOH/DMF (20 mL/2 mL) in the
presence of Et3N (0.15 mmol, 0.15 mL). The ensuing yellow
solution was stirred for 5 h and subsequently filtered. The
using SHELXTL97.20 The location of Ln (Ln = Sm, Gd, Dy, filtrate was left undisturbed to allow the slow volatilization of
the solvent. Yellow block-shaped single crystals of complex 3,
Tm, Yb) atom was easily determined, and S, O, N, and C atoms
were subsequently determined from the difference Fourier
maps. The non-hydrogen atoms were refined anisotropically.
suitable for X-ray diffraction analysis, formed after two weeks.
Yield: 18 mg (30%, based on the metal salt). Elemental analysis
(%) calcd for C38H48Dy2N6O16S2: C 36.99, H 3.92, N 6.81;
found C 36.72, H 3.84, N 6.79. IR (KBr, cm-1): 1609 (w), 1530
(s), 1432 (s), 1339 (w), 1309 (w), 1232 (m), 1187 (m), 1150
(m), 1126 (m), 1019 (w), 933 (w), 890 (m), 843 (w), 799 (m),
761 (m), 746 (m), 655 (s).
CCDC
972393−972397
contain
the
supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[Tm2L2(OAc)4(H2O)2]·4MeOH·2H2O (4)
Tm(OAc)3·6H2O (0.1 mmol, 45.mg) was reacted with HL (0.1
mmol, 25.93 mg) in MeOH/DMF (20 mL/2 mL) in the presence
of Et3N (0.15 mmol, 0.15 mL). The ensuing yellow solution
was stirred for 5 h and subsequently filtered. The filtrate was
left undisturbed to allow the slow volatilization of the solvent.
Synthesis of the ligand HL
The Schiff-base ligand HL was synthesized by a condensation
reaction
mercaptonicotinohydrazide. The crude product was obtained as
pale yellow powder in 75%. Recrystallisation from
between
salicylaldehyde
and
2-
a
Yellow block-shaped single crystals of complex 4, suitable for
dimethylformamide and ethanol gave the purified product.
Elemental analysis (%) calcd for C13H11N2O2S: C 60.16, H
4.24, N 10.80; found C 59.66, H 4.19, N 10.71. IR (KBr, cm-1):
3185 (w), 3078 (w), 3008 (w), 2793 (w), 1662 (s), 1621 (m),
1608 (w), 1574 (m), 1545 (s), 1482 (m), 1442 (w), 1357 (w),
1332 (w), 1311 (s), 1278 (m), 1228 (s), 1190 (w), 1155 (m),
1129 (w), 1117 (w), 1082 (m), 1061 (w), 1031 (w), 999 (w),
943 (w), 886 (m), 876 (s), 850 (w), 812 (s), 783 (w), 754 (s),
720 (m), 706 (m), 678 (s), 662 (s), 635 (w), 565 (m), 529 (m).
X-ray diffraction analysis, formed after ten days. Yield: 17 mg
(26%, based on the metal salt). Elemental analysis (%) calcd for
C38H56Tm2N6O20S2: C 34.61, H 4.28, N 6.37; found C 34.45, H
4.16, N 6.64. IR (KBr, cm-1): 1619(m), 1542(s), 1434(s), 1395
(m), 1329 (m), 1304 (m), 1231 (m), 1204(w), 1149 (m), 1126
(m), 1077 (w), 1043(m), 1018 (m), 980 (w), 960 (w), 941 (w),
890 (m), 855(w), 794 (w), 760(m), 749 (m), 737 (m), 701(w),
676 (m), 649 (m), 633 (w), 590 (w).
[Yb2L2(OAc)4(MeOH)2]·[Yb2L2(OAc)4(H2O)2]·4H2O (5)
Yb(OAc)3·6H2O (0.1 mmol, 90.83 mg) was reacted with HL (0.1
mmol, 25.93 mg) in MeOH/DMF (20 mL/2 mL) in the presence of
Et3N (0.15 mmol, 0.15 mL). The ensuing yellow solution was
stirred for 5 h and subsequently filtered. The filtrate was left
undisturbed to allow the slow volatilization of the solvent.
Synthesis of the complexes
[Sm2L2(OAc)4(MeOH)2]·2MeOH (1)
Sm(OAc)3·6H2O (0.1 mmol, 43.56 mg) was reacted with HL
(0.1 mmol, 25.93 mg) in MeOH/CH3CN (15 mL/10 mL) in the
presence of triethylamine (abbreviated as Et3N, 0.15 mmol,
0.15 mL). The ensuing yellow solution was stirred for 5 h and
subsequently filtered. The filtrate was left undisturbed to allow
the slow volatilization of the solvent. Yellow block-shaped
Yellow block-shaped single crystals of complex 5, suitable for
X-ray diffraction analysis, formed after two weeks. Yield: 23
mg (18%, based on the metal salt). Elemental analysis (%) calcd
for C70H84Yb4N12O28S4: C 34.66, H 3.49, N 6.93; found C 34.42, H
3.36, N 6.98. IR (KBr, cm-1): 1615 (m), 1534 (s), 1477 (w), 1442
(m), 1386 (m), 1346 (w), 1329 (m), 1232 (m), 1203 (m), 1153 (m),
1126 (m), 1079 (w), 1026 (w), 958 (w), 893 (m), 848 (w), 807 (w),
750 (m), 697 (w), 674 (m).
single crystals of complex
1, suitable for X-ray diffraction
analysis, formed after ten days. Yield: 25 mg (41%, based on
the metal salt). Elemental analysis (%) calcd for
C38H48Sm2N6O16S2: C 37.73, H 4.00, N 6.95; found C 37.52, H
3.92, N 6.86. IR (KBr, cm-1): 1610 (m), 1575 (w), 1536 (s),
1470 (w), 1434 (s), 1405 (w),1382 (m), 1328 (m), 1305 (m),
Results and discussion
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

View Article Online
DOI: 10.1039/C3DT53366B
Page 3 of 8
Journal Name
Dalton Transactions
ARTICLE
A dinuclear Dy2 complex bridged by n-butyric acid groups in geometry, while the eight-coordinated Yb1 in
triangular dodecahedron (Fig. S1 in ESI). In complexes
coordination sphere of Ln is completed by two acetate ions and
two methanol molecules (Fig. 1a), while the Ln ion in is
5
exhibits
the form of η1:η2:µ2 has been previously reported by S. K.
Ghosh and coworkers.14b Both complex
and this reported
complex are bridged by bidentate carboxylate groups, as shown
in Scheme 1. However, different from complex with
observable relaxation maxima, only temperature dependence
was observed in the reported structure, which is probably due to
1-3
, the
3
4
coordinated by two acetate groups and two H2O molecules (Fig.
1b).
3
There are three coordination modes of the acetate groups in
the differences in coordination geometry of the dysprosium complexes
1-5
, as η1:η2:µ2, η2 and η1, which are shown in Fig.
centre in respective structures.
2b. Furthermore, examinations of the crystal packing (Fig. S2
in ESI)) reveal that the molecules are stacked in a parallel
manner, producing
a
framework where the shortest
intermolecular Ln-Ln distances for in and between the parallel
lines are summarized in Table S2 (see ESI).
In contrast, the two metal centres are bridged by two
carboxylate oxygens from two different ligands in an anti-
parallel way with Dy-Dy separation distance of 4.074 Å and
Dy-O-Dy angle of 113.1o in the previously reported Dy2
complex.14b Though the Dy ions are nine-coordinated and
reside in the symmetrical coordination environment like that in
Scheme 1 Schematic diagram of ligands used in complexes 1-5 (left) and Dy2
(right, ref. 14b).
3
, each Dy centre is filled by a purely O9 donor set. Close
analysis of the resulting data utilizing SHAPE 2.1 software
reveals that the values obtained are 2.097 and 1.197 (Table S1
Crystal Structures of 1-5
in ESI) for complex Dy2 in ref. 14b and
3 respectively, both
deviating from zero (zero represents the case of the ideal
geometry considered). The coordination geometry of Dy ion in
The single-crystal X-ray diffraction studies revealed that all
complexes are crystallized in the triclinic space group P-1 with
Z = 1. The molecular structures of 3-5 are depicted in Fig. 1.
complex
3 is more closed to ideal monocapped square
antiprism, which may afford stronger magnetic anisotropy. The
molecular structures of two complexes are shown in Fig. S3
(see ESI) with the main bond lengths and bond angles are
labeled.
Crystal data and structure refinement details are summarized in
Table 1 and selected bond lengths and bond angles are listed in
Table 2.
Fig. 2 (a) Connection mode of HL ligand and (b) three specific coordinate
modes of acetate groups: η1:η2:µ2, η2 and η1.
Fig. 1 Partially labeled centrosymmetric units of complexes 3 (a), 4 (b), and 5
(c) with solvents and hydrogen atoms omitted for clarity.
Magnetic properties
As shown in Fig. 1, all five complexes are centrosymmetric
and share the similar dinuclear core structure, where each metal
ion is located in the chelating pocket formed by the carboxyl-O,
phenol-O, and hydrazide-N from the HL (Fig. 2a). The metal
centres are bridged by the acetate groups (O6 and O6A) in the
form of η1:η2 :µ2 , with the Ln-Ln distance being 4.0128(12) to
4.1802(10) Å and the Ln1-O6-Ln1A angles between 111.2(2)o
and 113.52(12)o. For all complexes, the coordination geometry
of Ln ions was calculated by utilizing the SHAPE 2.1
software21 (Table S1 in ESI) and the representative
coordination polyhedra are shown in Fig. S1 (see ESI). The Ln
Magnetic measurements were performed on polycrystalline
samples of
2-5. The phase purity of the bulk samples is
confirmed by XRD analyses as shown in Fig. S4. Direct current
(dc) magnetic susceptibility studies of the samples in an applied
magnetic field of 1000 Oe between 300 and 1.9 K are shown in
Fig. 3 in the form of χMT versus T, where χM is the molar
magnetic susceptibility. Partial of the dc magnetic data of 2-5
are summarized in Table 3. The observed χMT products at room
temperature (300 K) are in good agreement with the expected
values for two non-interacting two Ln ions.
ions in complexes 1-4 and the Yb2 in 5 are nine-coordinated
and exhibit distorted mono-capped square antiprismatic
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 3

View Article Online
Dalton Transactions
DOI: 10.1039/C3DT53P36a6gBe 4 of 8
ARTICLE
Journal Name
Firstly, we focus on complex 2
, as the isotropic f7 Gd ion has
no orbital contribution. The χMT value of
2 at 300 K is 16.62
cm3 K mol-1, which is consistent with the spin only value of
15.75 cm3 K mol-1 expected for two non-interacting Gd ions (S
8
= 7/2, L = 0, S7/2, g = 2: C = 7.875 cm3 K mol-1).7a As
temperature decreased, the χMT values are almost constant to
14 K, and decrease to reach 15.66 cm3 K mol-1 at 2 K. This
behaviour is indicative of the presence of very weak
antiferromagnetic interactions between the Gd ions within the
Gd2 complex. The χMT versus T data were simulated using
MAGPACK
Hamiltonian
program22
based
on
spin-only
ˆ
ˆˆ
(solid line), giving the best-fit
H = −2JSGd1 ⋅ SGd1A
parameters J = -0.01 cm-1, g = 2.06, which is consistent with the
results that very weak magnetic interactions is operating in Gd
complex.23
Fig. 3 Plots of χMT versus T for 2-5 (with χM being the molar susceptibility
defined as M/H) in a dc field of 1000 Oe (1.9-300 K). The light-blue solid
line corresponds to the best fit using MAGPACK program.
Table 1 Crystallographic data and structure refinement for complexes 1-5.
Complex
Formula
Mr
1
2
3
4
5
C38H48Sm2N6O16S2
1209.64
yellow blocks
triclinic
P-1
C38H48Gd2N6O16S2
1223.44
yellow blocks
triclinic
P-1
C38H48Dy2N6O16S2
1233.96
yellow blocks
triclinic
P-1
C38H56Tm2N6O20S2
1318.87
yellow blocks
triclinic
P-1
C70H84Yb4N12O28S4
2425.89
yellow blocks
triclinic
P-1
Colour
Crystal system
Space group
T [K]
293(2)
293(2)
293(2)
293(2)
293(2)
a [Å]
10.447(3)
10.886(3)
11.875(3)
69.437(5)
84.878(5)
79.669(5)
1243.4(6)
1
10.198(11)
10.642(11)
11.568(12)
69.60(2)
85.69(2)
81.48(2)
1163(2)
1
10.310(5)
10.622(5)
11.674(6)
69.650(9)
85.710(8)
81.099(8)
1183.9(10)
1
9.3882(12)
10.9654(14)
13.1679(16)
111.464(2)
92.422(2)
91.767(2)
1258.9(3)
1
10.885(4)
12.424 (4)
17.847(7)
70.887(6)
73.303(6)
89.712(6)
2173.8(14)
1
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
V [Å3]
Z
ρcalcd [g cm-3]
μ[mm-1]
F(000)
1.615
1.746
1.731
1.740
1.853
2.491
2.989
3.291
3.662
4.447
602
606
610
656
1188
Rint
0.0360
0.0938
0.0277
0.0209
0.0198
GOF
1.052
0.956
1.024
1.053
1.036
R1 [I > 2σ(I)]
wR2 (all data)
0.0520
0.0922
0.0405
0.0310
0.0302
0.1432
0.2195
0.0982
0.0765
0.0751
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

View Article Online
DOI: 10.1039/C3DT53366B
Page 5 of 8
Journal Name
Dalton Transactions
ARTICLE
Table 2 Selected bond lengths (Å) and bond angles (°) for complexes 1-5.
Complex
1
2
3
4
5
Ln(1)-O(6)
2.624(5)
2.440(5)
2.482(6)
2.465(6)
2.328(5)
2.463(6)
2.501(6)
2.501(6)
2.622(7)
4.1802(10)
111.2(2)
68.8 (2)
2.602(11)
2.340(10)
2.444(12)
2.385(13)
2.246(10)
2.399(11)
2.415(11)
2.420(12)
2.553(16)
4.0992(35)
112.0(4)
68.0(4)
2.628(4)
2.348(4)
2.411(5)
2.378(5)
2.254(4)
2.380(4)
2.419(4)
2.434(4)
2.538(5)
4.1245(16)
111.86(16)
68.14(16)
2.649(3)
2.306(3)
2.441(3)
2.332(3)
2.220(3)
2.328(3)
2.411(4)
2.528(3)
2.490(3)
4.1486(5)
113.52(12)
66.48(12)
2.342(3)
2.477(4)
2.246(4)
#
Ln(1)-O(6A)
Ln(1)-O(5)
Ln(1)-O(7)
Ln(1)-O(2)
2.211(4)
2.324(4)
2.322(4)
2.388(4)
2.476(4)
4.0128(12)
112.71(14)
67.29(14)
Ln(1)-O(1)
Ln(1)-O(4)
Ln(1)-O(3)
Ln(1)-N(3)
Ln(1)-Ln(1A)
Ln(1)-O(6)-Ln(1A)
O6-Ln(1)-O6A
Symmetry codes: for 1, A: -x+1, -y, -z+1; for 2, A,-x+1, -y, -z+1; for 3, A, -x+1, -y+1, -z+2; for 4, A, -x+2, -y+2, -z+1; for 5, 1A, -x+1, -y, -z+1.
Table 3 Summary of direct current (dc) magnetic data for 2-5.
complex
2
3
4
5
ground state term of Ln ion
8S7/2
7.875
6H15/2
14.17
3H6
7.15
2F7/2
2.57
5.14
C (cm3 K mol-1) for each Ln ion
χT (cm3 K mol-1) expected value for Ln2 at RT
15.75
16.62
28.34
28.13
14.30
14.22
χT (cm3 K mol-1) experimental value for Ln2 at RT
χT (cm3 K mol-1) experimental value for Ln2 at 2.0 K
4.84
2.78
15.66
17.40
7.79
The temperature dependence of the magnetic susceptibilities saturation even at 7 T (Fig. S5 in ESI), which is most likely due
for complexes show similar thermal evolution at high to anisotropy and important crystal-field effect at the metal ions.
Furthermore, the absence of a superposition of the M versus
3-5
temperature region. For
3 and 4, the χMT product at 1000 Oe is
H/T data on a single master-curve for and (Fig. 4),
3
5
essentially temperature independent over the range 300-100 K,
followed by a slightly decrease on lowering the temperature
from 100 to 20 K and then rapidly decreases to reach a
minimum of 17.50 cm3 K mol-1 and 7.79 cm3 K mol-1 at about 2
suggesting the presence of significant magnetic anisotropy
and/or low-lying excited states in the systems. In addition, the
absence of the hysteresis loop above 1.9 K (Fig. S6 in ESI) in
the complex
fast zero-field relaxation.
3 may be caused by the presence of a relatively
K. For
5 the χMT product begins a very slow decrease at higher
temperature like other complexes, but without abrupt decrease
below 100 K. The Stark sublevels of the anisotropic Ln (Dy,
Tm and Yb) ions are thermally depopulated when the
temperature is lowered, resulting in a decrease of the χMT
product. Therefore, the decrease is most likely ascribed to the
progressive depopulation of excited Stark sublevels, significant
magnetic anisotropy and/or weak antiferromagnetic interactions
present in these systems.24
The field dependence of the magnetization of complexes
3
and at low temperatures shows that the magnetization
5
increases smoothly with increasing applied dc field without
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 5

View Article Online
Dalton Transactions
DOI: 10.1039/C3DT53P36a6gBe 6 of 8
ARTICLE
Journal Name
Fig. 6 Frequency dependence of the in-phase (χ′) and out-of-phase (χ″) of the
ac susceptibility for 3 under zero-dc field. The solid lines are guides for the
eyes.
Fig. 4 Field dependence of magnetizations of 3 (left) and 5 (right) at different
temperatures below 5 K.
To probe the dynamics of the magnetization, alternating
current susceptibility measurements were carried out under zero
field. Both in-phase (χ′) and out-of-phase (χ″) alternating
current (ac) susceptibilities for the complex
3 exhibit
temperature and frequency dependences. The slow relaxation of
the magnetization signals typical features associated with SMM
behaviour. As shown in Fig. 5 and Fig. S7 in ESI, χ′ shows the
maxima in the 7-13 K, while the
(50 Hz) and 13 K(1500 Hz). Unlike most Ln-SMM, the absence
of another increase in the low-temperature in both χ′ and
χ″ define maxima between 5 K
χ″
compounds for
3 indicates the efficient suppression of zero-
field tunneling of magnetization.25 In contrast, Dy2 in ref. 14b
complex only shows temperature dependence but without
observable maxima (Fig. 5, right). Thus complex
3 show
Fig. 7 Cole-Cole plots measured at 1.9 K-14 K under zero-dc field for 3. The
solid lines are the best fits to the experimental data, obtained with the
generalized Debye model2a, 26 with α parameters below 0.30.
prominent SMM behaviour. The obvious disparity in magnetic
dynamics should mainly result from the more distorted
coordination geometry in the Dy2 in ref. 14b, thus leading to the
fast quantum tunneling from more transverse anisotropy.
For complex 3, Cole-Cole plots plotted as the in-phase vs.
out-of-phase ac susceptibility data show an asymmetrical semi-
circular shape (Fig. 7), which can be fitted by the generalized
Debye model, with α parameters below 0.30 from 1.9 to 13.0 K
(Table S4 in ESI), indicating a narrow distribution of relaxation
time.26a
Fig.
5 Temperature dependence of the out-of-phase (χ″) of the ac
susceptibility for 3 (left) and Dy2 (right, ref. 14b) under zero-dc field. The
solid lines are guides for the eyes.
As shown in Fig. 6, in the range of 1.9 K to 10 K, we can
observe the peaks of χ′′, and these peaks move gradually to
high frequencies with the increase of temperature. Besides, ac
susceptibilities were also measured under various magnetic
field at 9 K, as shown in Fig.S8 in ESI. The maxima of the
frequency-dependent ac signals shift negligibly under various
dc fields, which indicates that dc field has insignificant effect
on the relaxation and suggests that tunneling in zero field is not
an efficient pathway at 9 K.
Fig. 8 Magnetization relaxation time, lnτ, versus T-1 plot for 3 under zero-dc
field. The solid line is fitted with the Arrhenius law.
The magnetization relaxation time (τ) has been extracted
from frequency dependencies of the ac susceptibility between
1.9 and 13 K (Fig. 8). Above 7 K, the relaxation follows a
thermally activated mechanism and the Arrhenius plot of lnτ
versus 1/T, where τ is the relaxation time constant, is linear
(Fig.8). The plot can be fitted by the Arrhenius law [τ = τ0
exp(Ueff/kBT)] and afford an anisotropic energy barrier (Ueff) of
39.1 K and a pre-exponential factor (τ0) of 6.4×10-7 s. These
parameters are comparable to those reported for other SMMs.13
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

View Article Online
DOI: 10.1039/C3DT53366B
Page 7 of 8
Journal Name
Dalton Transactions
ARTICLE
Below 7 K, τ becomes weakly dependent on T as the
temperature decreases, indicating a gradual crossover from a
thermally activated Orbach mechanism that is predominant at
higher temperatures (red line), to a direct or phonon induced
tunnelling process at lower temperatures.
P. Bergerat, O. Kahn, E. Bakalbassis, K. Boubekeur, P. Batail and M.
Guillot, Inorg. Chem., 1992, 31, 110-114.
8. C. Benelli, A. Caneschi, D. Gatteschi and R. Sessoli, Adv. Mater.,
1992, 4, 504-505.
9. (a) R. Sessoli and A. K. Powell, Coord. Chem. Rev., 2009, 253, 2328-
2341; (b) L. F. Zou, L. Zhao, Y. N. Guo, G. M. Yu, Y. Guo, J. K.
Tang and Y. H. Li, Chem. Commun., 2011, 47, 8659-8661.
Conclusion
In summary, we described here a new family of dinuclear Ln
complexes obtained by the reaction of Ln(OAc)3·6H2O with
Schiff base ligands. The two metals in the dinuclear core in
each compound are bridged by acetate groups in the form of
η1:η2:µ2. These complexes were investigated by SHAPE 2.1
software and magnetic studies. Compared with Dy2 in ref. 14b,
10. (a) S. Y. Lin, L. Zhao, Y. N. Guo, P. Zhang, Y. Guo and J. K. Tang,
Inorg. Chem., 2012, 51, 10522-10528; (b) L. Sorace, C. Benelli and
D. Gatteschi, Chem. Soc. Rev., 2011, 40, 3092-3104; (c) J. K. Tang, I.
Hewitt, N. T. Madhu, G. Chastanet, W. Wernsdorfer, C. E. Anson, C.
Benelli, R. Sessoli and A. K. Powell, Angew. Chem., Int. Ed., 2006,
45, 1729-1733.
complex
3 exhibits SMM behaviour with energy barrier of 39.1
K due to its less distorted coordination geometry around Dy.
The simple comparative investigations may get insight into the
structure-property relationship of lanthanide-based SMMs,
which is crucial to the advancement of single-molecule data
storage and processing technologies.
11. (a) J. Long, F. Habib, P.-H. Lin, I. Korobkov, G. Enright, L. Ungur,
W. Wernsdorfer, L. F. Chibotaru and M. Murugesu, J. Am. Chem.
Soc., 2011, 133, 5319-5328; (b) J. D. Rinehart, M. Fang, W. J. Evans
and J. R. Long, Nat. Chem., 2011,
Fang, W. J. Evans and J. R. Long, J. Am. Chem. Soc., 2011, 133
14236-14239; (d) R. J. Blagg, C. A. Muryn, E. J. L. McInnes, F.
Tuna and R. E. P. Winpenny, Angew. Chem., Int. Ed., 2011, 50
3, 538-542; (c) J. D. Rinehart, M.
,
Acknowledgements
,
We thank the National Natural Science Foundation of China
(21241006, 21221061 and 21371166) for financial support.
6530-6533; (e) N. Ishikawa, M. Sugita, T. Ishikawa, S. Koshihara
and Y. Kaizu, J. Am. Chem. Soc., 2003, 125, 8694-8695; (f) M.
Gonidec, R. Biagi, V. Corradini, F. Moro, V. De Renzi, U. del
Pennino, D. Summa, L. Muccioli, C. Zannoni, D. B. Amabilino and
J. Veciana, J. Am. Chem. Soc., 2011, 133, 6603-6612; (g) R. J. Blagg,
L. Ungur, F. Tuna, J. Speak, P. Comar, D. Collison, W. Wernsdorfer,
E. J. L. McInnes, L. F. Chibotaru and R. E. P. Winpenny, Nat. Chem.,
Notes and references
a State Key Laboratory of Rare Earth Resource Utilization, Changchun
Institute of Applied Chemistry, Chinese Academy of Sciences,
Changchun, 130022, China. E-mail: tang@ciac.ac.cn; Fax: +86 431
85262878; Tel: +86 431 85262878
2013, 5, 673-678.
b University of Chinese Academy of Sciences, Beijing 100049, China
1. (a) R. Sessoli, H. L. Tsai, A. R. Schake, S. Y. Wang, J. B. Vincent,
K. Folting, D. Gatteschi, G. Christou and D. N. Hendrickson, J. Am.
Chem. Soc., 1993, 115, 1804-1816; (b) R. Sessoli, D. Gatteschi, A.
Caneschi and M. A. Novak, Nature, 1993, 365, 141-143.
12. (a) L. E. Roy and T. Hughbanks, J. Am. Chem. Soc., 2006, 128, 568-
575; (b) J.-B. Peng, X.-J. Kong, Y.-P. Ren, L.-S. Long, R.-B. Huang
and L.-S. Zheng, Inorg. Chem., 2012, 51, 2186-2190; (c) S.
Mukherjee, A. K. Chaudhari, S. Xue, J. Tang and S. K. Ghosh, Inorg.
Chem. Commun., 2013, 35, 144-148.
13. F. Tuna, C. A. Smith, M. Bodensteiner, L. Ungur, L. F. Chibotaru, E.
J. L. McInnes, R. E. P. Winpenny, D. Collison and R. A. Layfield,
Angew. Chem., Int. Ed., 2012, 51, 6976-6980.
2. (a) D. Gatteschi, R. Sessoli and J. Villain, Oxford University
Press:Oxford, U.K., 2006; (b) D. Gatteschi and R. Sessoli, Angew.
Chem., Int. Ed., 2003, 42, 268-297; (c) Y. N. Guo, G. F. Xu, P.
Gamez, L. Zhao, S. Y. Lin, R. P. Deng, J. K. Tang and H. J. Zhang, J.
Am. Chem. Soc., 2010, 132, 8538-8539; (d) M. N. Leuenberger and
D. Loss, Nature, 2001, 410, 789-793.
14. (a) Y. Z. Zheng, Y. Lan, W. Wernsdorfer, C. E. Anson and A. K.
Powell, Chem.- Eur. J., 2009, 15, 12566-12570; (b) S. K. Ghosh, B.
Joarder, A. K. Chaudhari and G. Rogez, Dalton Trans., 2012, 41
,
7695; (c) L. Liang, G. Peng, G. Li, Y. Lan, A. K. Powell and H.
Deng, Dalton Trans., 2012, 41, 5816-5823; (d) Y. M. Song, F. Luo,
M. B. Luo, Z. W. Liao, G. M. Sun, X. Z. Tian, Y. Zhu, Z. J. Yuan, S.
J. Liu, W. Y. Xu and X. F. Feng, Chem Commun., 2012, 48, 1006-
1008.
3. D. Gatteschi, A. Caneschi, L. Pardi and R. Sessoli, Science, 1994,
265, 1054-1058.
4. N. Roch, S. Florens, V. Bouchiat, W. Wernsdorfer and F. Balestro,
Nature, 2008, 453, 633-U633.
5. E. Coronado and P. Day, Chem. Rev., 2004, 104, 5419-5448.
6. (a) G. Aromi and E. K. Brechin, in Single-Molecule Magnets and
Related Phenomena, ed. R. Winpenny, 2006, pp. 1-67; (b) C. J.
Milios, A. Vinslava, W. Wernsdorfer, S. Moggach, S. Parsons, S. P.
Perlepes, G. Christou and E. K. Brechin, J. Am. Chem. Soc., 2007,
129, 2754-2755; (c) H. Miyasaka, R. Clerac, W. Wernsdorfer, L.
Lecren, C. Bonhomme, K. Sugiura and M. Yamashita, Angew. Chem.,
Int. Ed., 2004, 43, 2801-2805.
15. P. Zhang, L. Zhang, S. Y. Lin, S. F. Xue and J. K. Tang, Inorg.
Chem., 2013, 52, 4587-4592.
16. B. Hussain, D. Savard, T. J. Burchell, W. Wernsdorfer and M.
Murugesu, Chem. Commun., 2009, 1100-1102.
17. (a) S. Xue, L. Zhao, Y.-N. Guo, X.-H. Chen and J. Tang, Chem
Commun., 2012 48, 7031-7033; (b) Y. N. Guo, G. F. Xu, W.
Wernsdorfer, L. Ungur, Y. Guo, J. K. Tang, H. J. Zhang, L. F.
Chibotaru and A. K. Powell, J. Am. Chem. Soc., 2011, 133, 11948-
11951; (c) S.-Y. Lin, W. Wernsdorfer, L. Ungur, A. K. Powell, Y.-N.
Guo, J. Tang, L. Zhao, L. F. Chibotaru and H.-J. Zhang, Angew.
Chem., Int. Ed., 2012, 51, 12767-12771.
7. (a) C. Benelli and D. Gatteschi, Chem. Rev., 2002, 102, 2369-2387;
(b) A. Bencini, C. Benelli, A. Caneschi, R. L. Carlin, A. Dei and D.
Gatteschi, J. Am. Chem. Soc., 1985, 107, 8128-8136; (c) O. Guillou,
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 7

View Article Online
Dalton Transactions
DOI: 10.1039/C3DT53P36a6gBe 8 of 8
ARTICLE
Journal Name
18. (a) M. Diop, F. B. Tamboura, M. Gaye, A. S. Sall, A. H. Barry and T. 23. Y. Wang, X.-L. Li, T.-W. Wang, Y. Song and X.-Z. You, Inorg.
Jouini, B. Chem. Soc. Ethiopia, 2003, 17, 167-172; (b) X. H. Bu, M. Chem, 2010, 49, 969-976.
Du, L. Zhang, X. B. Song, R. H. Zhang and T. Clifford, Inorg Chim 24. (a) M. L. Kahn, R. Ballou, P. Porcher, O. Kahn and J. P. Sutter,
Acta, 2000, 308, 143-149.
Chem.-Eur. J., 2002, 8, 525-531; (b) M. L. Kahn, J. P. Sutter, S.
19. E. A. Boudreaux and L. N. Mulay, John Wiley & Sons, New York,
Golhen, P. Guionneau, L. Ouahab, O. Kahn and D. Chasseau, J. Am.
Chem. Soc., 2000, 122, 3413-3421.
1976.
20. (a) G. M. Sheldrick, SHELXS-97, Program for Crystal Structure 25. (a) P. H. Lin, T. J. Burchell, R. Clérac and M. Murugesu, Angew.
Solution, University of Göttingen, Germany, 1997; (b) G. M.
Sheldrick, SHELXL-97. Program for Crystal Structure Refinement,
University of Göttingen, Germany, 1997.
Chem., Int. Ed., 2008, 47, 8848-8851; (b) G. F. Xu, Q. L. Wang, P.
Gamez, Y. Ma, R. Clerac, J. K. Tang, S. P. Yan, P. Cheng and D. Z.
Liao, Chem. Commun., 2010, 46, 1506-1508.
21. D. Casanova, M. Llunell, P. Alemany and S. Alvarez, Chem.-Eur. J., 26. (a) K. S. Cole and R. H. Cole, J. Chem. Phys., 1941,
9
, 341-351; (b)
2005, 11, 1479-1494.
S. M. J. Aubin, Z. M. Sun, L. Pardi, J. Krzystek, K. Folting, L. C.
22. J. J. Borras-Almenar, J. M. Clemente-Juan, E. Coronado and B. S.
Tsukerblat, Inorg. Chem., 1999, 38, 6081-6088.
Brunel, A. L. Rheingold, G. Christou and D. N. Hendrickson,
Inorg.Chem., 1999, 38, 5329-5340.
Graphical Abstract
: :µ2 mode were reported with the Dy2
Five dinuclear Ln complexes bridged by acetate groups in the form of η1 η2
analogue behaves as SMM.
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012