Tetranuclear [MDy]2 compounds and their dinuclear [MDy] (M = Zn/Cu) building units: Their assembly, structures, and magnetic properties

Article abstract of DOI:10.1021/ic400620j

The reactions between a salen ligand N,N′-bis(3-methoxysalicylidene)- 1,2-cyclohexanediamine (H₂L) and different metal salts lead to the formation of four 3d-4f [MDy] and [MDy]₂ (M = Zn/Cu) compounds, where the [MDy]₂ can be considered as resulting from the assembly of two [MDy] building blocks. Field-induced single molecule magnet (SMM) behavior was observed in [ZnDy] and [CuDy] compounds with the effective suppression of fast quantum tunneling under a dc field. Moreover, the [ZnDy]₂ compound demonstrates typical SMM behavior, which may originate from the high axial anisotropy of Dy ions correlating to the change of coordination geometry and enhanced ferromagnetic interactions between Dy ions via the coupling of two [DyZn] units. The result suggests the positive effects of coupling blocking units to enhance their SMM behavior, presenting a promising strategy for constructing efficient heterometallic SMMs.

Full text of DOI:10.1021/ic400620j

Article
pubs.acs.org/IC
Tetranuclear [MDy] Compounds and Their Dinuclear [MDy] (M = Zn/
2
Cu) Building Units: Their Assembly, Structures, and Magnetic
Properties
Peng Zhang, Li Zhang,†,§ Shuang-Yan Lin,†,‡ and Jinkui Tang*,†
†,‡
†State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
Changchun 130022, P. R. China
‡
University of Chinese Academy of Sciences, Beijing, 100039, P. R. China
§
College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, P. R. China
*
S Supporting Information
ABSTRACT: The reactions between a salen ligand N,N′-
bis(3-methoxysalicylidene)-1,2-cyclohexanediamine (H L) and
2
different metal salts lead to the formation of four 3d-4f [MDy]
and [MDy] (M = Zn/Cu) compounds, where the [MDy]2
2
can be considered as resulting from the assembly of two
[
(
MDy] building blocks. Field-induced single molecule magnet
SMM) behavior was observed in [ZnDy] and [CuDy] compounds with the effective suppression of fast quantum tunneling
under a dc field. Moreover, the [ZnDy] compound demonstrates typical SMM behavior, which may originate from the high axial
2
anisotropy of Dy ions correlating to the change of coordination geometry and enhanced ferromagnetic interactions between Dy
ions via the coupling of two [DyZn] units. The result suggests the positive effects of coupling blocking units to enhance their
SMM behavior, presenting a promising strategy for constructing efficient heterometallic SMMs.
INTRODUCTION
To date, some empirically methodologies to obtain a variety
of heterometallic complexes have been established, such as the
employment of compartmental or multifunctional ligands.
In general, the design of ligands containing different
coordination donors and bonding modes is considered as a
■
1
Synthesis of single molecule magnets (SMMs) containing
lanthanide ions has been an important topic in the field of
molecule-based magnetic materials in recent years because of
33−35
2,3
the large inherent anisotropy of most lanthanide ions.
A
typical example is the successful enhancement of magnetic
anisotropy through the deliberate incorporation of the
anisotropic Dy ion, creating a new [Mn Dy] aggregate that
critical factor in determining crystal structure of a hetero-
19,36
metallic complex.
However it should be noted that some
1
8
4
,5
subordinate factors, such as the nature of anions, the radii of
metal ions, and the introduction of secondary ligands, also play
displays slow relaxation of magnetization. Since the first
discovery of SMM behavior in 3d-4f complex (a Cu Tb
compound), research into heterometallic complexes has been
2
2
37−40
3
a vital role in the assembly of coordination compounds.
In
developed as a significant branch in the field of SMMs with a
this context, four new compounds (ZnDy, 1; [ZnDy] , 2;
2
6
,7
8,9
flood of 3d-4f complexes, containing Mn-Ln, Cu-Ln, Fe-
CuDy, 3; [CuDy] , 4) were obtained through using a “salen”
2
1
0,11
12−14
15−17
Ln,
Ni-Ln
and Co-Ln
behaving as SMMs. In fact,
type Schiff-base ligands (H L), representing a successful
2
the magnetic investigations of 3d-4f compounds, mainly for 3d-
assembly of [MDy] compounds based on [MDy] (M = Zn/
III
2
Gd compounds, can date back to 1985, when the
−
II
Cu) units mediated by anions (ClO
4
). Here field-induced slow
ferromagnetic interaction was discovered between Cu and
III
18,19
relaxation of magnetization is observed in the ZnDy (1) and
Gd by Gatteschi et al.
Furthermore, the magnetocaloric
application has also been explored recently in multinuclear 3d-
CuDy (3) compounds. Remarkably, the [ZnDy]
(2)
2
2
0
21
2−
4
f clusters, such as [Ni Gd P ], [Gd Ni ] and other 3d-4f
compound bridged by two CO3 displays typical SMM
behavior, possibly influenced by the ferromagnetic interactions
between lanthanide ions concomitant with variation of the axial
geometry around Dy ions through the assembly of two building
6
6
6
36 12
2
2−24
complexes.
In addition, it is noted that the design of
multifunctional magnetic materials combining the magnetism
and other functions such as luminescence or chirality has
25
26−30
become an important focus of interest in this field.
Here
blocks, while no SMM behavior was observed in [CuDy] (4)
2
the heterometallic complexes have presented a great promise in
−
3
1,32
complex bridged by two OH groups.
magneto-luminescent molecular material.
Therefore, the
construction of compounds incorporating both transition metal
and lanthanide ions represents a promising field of research in
molecule-based magnetic materials.
Received: March 13, 2013
©
XXXX American Chemical Society
A
dx.doi.org/10.1021/ic400620j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Table 1. Details of the Structure Solution and Refinement of Complexes 1−4
1
2
3
4
formula
C H DyN O Zn
C H Dy N O Zn
C H CuDyN O
C H Cl Cu Dy N O
50 78 4 2 2 4 34
2
7
34
3
12
60 94
2
4
28
2
26 30
3
11
Mr
820.44
1775.13
786.57
1873.04
color
pale-yellow
pale-yellow
dark green
brown
crystal size [mm]
crystal system
space group
T [K]
0.21 × 0.20 × 0.18
triclinic
0.20 × 0.16 × 0.15
triclinic
0.22 × 0.20 × 0.19
triclinic
0.19 × 0.17 × 0.16
triclinic
P1
̅
185(2)
P1
̅
185(2)
P1
̅
185(2)
P1
̅
185(2)
a [Å]
8.6421(5)
13.3663(7)
13.8293(8)
91.6820(10)
97.5110(10)
108.6700(10)
1496.10(15)
2
12.2311(6)
12.5430(6)
13.6239(7)
71.8110(10)
64.7270(10)
89.4210(10)
1777.06(15)
1
8.5160(5)
12.8301(8)
13.8385(9)
82.4100(10)
74.4400(10)
74.9300(10)
1403.34(15)
2
10.6912(7)
12.5528(8)
13.4070(8)
100.7830(10)
92.2780(10)
104.5300(10)
1703.85(19)
1
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
V [Å3]
Z
ρcalcd [g cm−3]
μ(Mo−Kα) [mm−1]
F (000)
1.821
1.659
1.861
1.825
3.347
2.828
3.465
3.033
818
898
780
936
reflns collected
unique reflns
Rint
8344
9904
7861
9523
5880
6977
5502
6701
0.0169
0.0200
0.0220
0.0256
parameters/restraints
GOF
403/12
446/0
383/0
440/12
1.042
1.069
1.036
1.037
R1 [I > 2σ(I)]
0.0329
0.0324
0.0288
0.0428
wR (all data)
0.0802
0.0827
0.0717
0.0977
2
largest diff. peak/hole [e Å−3]
1.375 and −0.883
1.134 and −0.944
1.063 and −1.097
1.046 and −0.631
EXPERIMENTAL SECTION
by the addition of Dy(NO
triethylamine (0.2 mmol, 0.028 mL). Then Zn(OAc) ·2H O (0.1
mmol, 0.022 g) was added after 2 h, and the resulting solution was
stirred for 3 h. Pale yellow rectangular single crystals, suitable for X-ray
diffraction analysis, were formed after one week. Yield: 30 mg (37%,
based on the metal salt). Elemental analysis (%) calcd for
) ·6H O (0.1 mmol, 0.046 g) and
3 3 2
■
2
2
General Procedures. All chemicals were of analytical reagent
grade and were used as received without any further purification.
Elemental analysis for C, H, and N were performed on a Perkin-Elmer
2
400 analyzer. IR spectra were recorded with a Perkin-Elmer Fourier
transform infrared spectrophotometer with samples prepared as KBr
C H DyN O Zn: C, 39.52, H, 4.18, N, 5.12; found: C, 39.55, H,
−1
27 34
3
12
disks in the 4000−300 cm range.
−1
4
(
1
.05, N, 5.23. IR (KBr, cm ): 3438 (br), 2943 (w), 2865 (w), 1655
m), 1631 (s), 1607 (m), 1557 (s), 1476 (s), 1455 (s), 1396 (m),
355 (w), 1305 (s), 1243 (m), 1222 (s), 1168(w), 1078 (m), 1037
X-ray Crystal Structure Determinations. Single crystal X-ray
data of the title complexes were collected at 185 (2) K on a Bruker
Apex II CCD diffractometer equipped with graphite-monochromat-
ized Mo−Kα radiation (λ = 0.71073 Å). Data processing was
completed with the SAINT processing program. The structures were
solved by direct methods and refined by full matrix least-squares
(
(
w), 1023 (m), 963 (m), 952 (m), 854 (w), 782 (w), 742 (s), 665
m), 622 (w), 566 (w), 441 (w), 424 (w).
Synthesis of [Dy Zn L (OAc) (CO ) ]·10CH OH (2). H L (0.1
2
2
2
2
3 2
3
2
mmol, 0.038 g) was dissolved in CH OH/CH Cl (10 mL/10 mL)
3
2
2
2
41
methods on F using SHELXTL-97. The locations of the heaviest
atoms (Dy, Zn, and Cu) were easily determined, and C, O, N, and Cl
atoms were determined from the difference Fourier maps. The
nonhydrogen atoms were refined anisotropically. All hydrogen atoms
were introduced in calculated positions and refined with fixed
geometry with respect to their carrier atoms. Crystallographic data
are summarized in Table 1. CCDC 905911−905914 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.
followed by the addition of Dy(ClO ) ·6H O (0.1 mmol, 0.057 g) and
triethylamine (0.2 mmol, 0.028 mL). Then Zn(OAc) ·2H O (0.1
4
3
2
2
2
mmol, 0.022 g) was added after 2 h and the resulting solution was
stirred for 3 h. Pale yellow block-shaped single crystals, suitable for X-
ray diffraction analysis, were formed after 9 days. Yield: 26 mg (29%,
based on the metal salt). Elemental analysis (%) calcd for
C H Dy N O Zn : C, 40.59, H, 5.34, N, 3.16; found: C, 40.74,
60
94
2
4
28
2
−1
H, 5.23, N, 3.32. IR (KBr, cm ): 3513 (br), 3061 (w), 2929 (m),
2
859 (w), 1660 (s), 1637 (s), 1605 (s), 1565 (s), 1471 (s), 1399(s),
1358 (m), 1307 (m), 1285 (s), 1244 (s), 1218 (s), 1167(m), 1078 (s),
1023 (m), 975 (m), 950 (m), 919 (w), 851 (m), 785 (w), 737 (s), 668
(m), 622 (s), 580 (w), 554 (w), 514 (w), 459 (w), 424 (m).
Synthesis of [DyCuL(OAc) (NO )] (3). A procedure similar to
Magnetic Measurements. Magnetic susceptibility measurements
were recorded on a Quantum Design MPMS-XL7 SQUID magneto-
meter equipped with a 7 T magnet. The variable-temperature
magnetization was measured with an external magnetic field of 1000
Oe in the temperature range of 1.9−300 K. Diamagnetic corrections
for the compounds were estimated from the Pascal’s constants, and
magnetic data were corrected for diamagnetic contributions of the
sample holder.
2
3
that for 1 was followed except that Zn(OAc) ·2H O and CH OH/
2
2
3
CH CN (10 mL/5 mL) were replaced by Cu(OAc) ·H O (0.1 mmol,
3
2
2
4
2
0.020 g) and CH OH/CH Cl (10 mL/10 mL), respectively. Dark
3 2 2
green rectangular single crystals, suitable for X-ray diffraction analysis,
were formed after 6 days. Yield: 32 mg (41%, based on the metal salt).
Elemental analysis (%) calcd for C H CuDyN O : C, 39.70, H,
3.84, N, 5.34; found: C, 39.42, H, 3.78, N, 5.48. IR (KBr, cm ): 3422
(br), 3071 (w), 2945 (w), 2862 (w), 1637 (s), 1608 (m), 1577 (s),
1561 (m), 1477 (s), 1459 (s), 1417 (s), 1391 (m), 1347 (m), 1307
(s), 1290 (s), 1248 (m), 1224 (s), 1165(w), 1073 (m), 1039 (w), 965
Synthesis of H L. The Schiff-base ligand was synthesized by a
2
26 30
3
11
−1
condensation reaction between 1,2-cyclohexanediamine (1.150 g, 10
4
3
mmol) and o-vanillin (3.040 g, 20 mmol) in methanol (50 mL).
Synthesis of [DyZnL(OAc) (NO )]·CH OH (1). H L (0.1 mmol,
2
3
3
2
0
.038 g) was dissolved in CH OH/CH CN (10 mL/5 mL) followed
3 3
B
dx.doi.org/10.1021/ic400620j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(
5
m), 922 (w), 855 (w), 783 (w), 742 (s), 683 (w), 650 (w), 619 (w),
65 (w), 458 (w), 427 (w).
In most examples, the perchloride anion tends not to
coordinate with lanthanide ion or provides only one
3
8,49,50
Synthesis of [Dy Cu L (μ -OH) (H O) (CH OH) ]-
2
2
2
2
2
2
2
3
2
coordinated site,
of other ligands with strong bridging ability, such as CO
from the fixation of atmospheric CO and OH from H O.
which give a chance for the introduction
(
ClO ) ·4CH OH (4). A procedure similar to that for 2 was followed
2−
4
4
3
3
except that Zn(OAc) ·2H O and CH OH/CH Cl (10 mL/10 mL)
2
2
3
2
2
¯
2
2
were replaced by Cu(ClO ) ·6H O (0.1 mmol, 0.037 g) and CH OH/
CH Cl2 (10 mL/5 mL), respectively. Brown block-shaped single
crystals, suitable for X-ray diffraction analysis, were formed after 8
days. Yield: 20 mg (21%, based on the metal salt). Elemental analysis
4
2
2
3
Subsequently, the [CuDy] (4) compound was also obtained
2
2
through the reaction between ligand H L and perchlorate salts
2
(
Cu(ClO ) and Dy(ClO ) ) under same conditions, further
4 2 4 3
(
%) calcd for C H Cl Cu Dy N O : C, 32.06, H, 4.20, N, 2.99;
confirming our deduction.
Crystal Structures. The reactions of Dy(NO ) ·6H O,
50
78
4
2
2
4
34
−1
found: C, 32.11, H, 4.07, N, 3.05. IR (KBr, cm ): 3410 (br), 2949
w), 2851 (w), 1633 (s), 1609 (m), 1558 (w), 1475 (s), 1458 (s),
3
3
2
(
Zn(OAc) ·2H O/Cu(OAc) ·H O and Et N in a 1:1:2 ratio
2 2 2 2 3
1
1
7
443 (m), 1392 (w), 1346 (w), 1308 (s), 1289 (m), 1240 (m),
222(s), 1172 (m), 1074 (s), 952 (m), 930 (w), 857 (w), 783 (w),
41 (m), 670 (w), 651 (w), 623 (m), 589 (w), 564 (w), 469 (w), 448
afford pale yellow and dark green crystals, namely, [DyML-
II
II
(
OAc) (NO )]·nCH OH [M = Zn with n = 1 (1), M = Cu
2 3 3
with n = 0 (3)]. However, the reactions of Dy(ClO ) ·6H O,
Zn(OAc) ·2H O/Cu(ClO ) ·6H O and Et N in a 1:1:2 ratio
4
3
2
(
m), 425 (w).
2
2
4 2
2
3
in mixed solvent (methanol/dichloromethane) afford pale
y e l l o w a n d b r o w n c r y s t a l s ,
Dy Zn L (OAc) (CO ) ]·10CH OH (2) and [Dy Cu L (μ -
RESULTS AND DISCUSSION
■
[
Synthetic Aspects. For o-vanillin salen ligands, it tends to
2
2
2
2
3 2
3
2
2
2
2
OH) (H O) (CH OH) ](ClO ) ·4CH OH (4). Details for
form the binuclear Ln-M complex (M = transition metal),
which is the result of the fact that the inner site (commonly of
the N O type) shows preference for transition metal ions and
2
2
2
3
2
4 4
3
the structure solution and refinement are summarized in
Table 1, and selected bond distances and angles are listed in
Supporting Information, Table S1.
2
2
the outer site (O ) shows preference for lanthanide ions, as
4
1
2,44−46
Single-crystal X-ray studies revealed that 1 and 3 are
indicated by many examples.
In addition, many
̅
isostructural, crystallizing in the triclinic space group P1 with
transition metal salen complexes act as highly useful building
blocks for the design of magnetic assemblies not only toward
bulk magnets but also toward molecular superparamagnets.
Very recently, a carbonate-bridged Ni Gd complex was
Z = 2. A perspective view of the molecular structures of 1 and 3
47
is presented in Figure 1. In the asymmetric molecule, M ions
II
II
III
(
M = Zn for 1 and Cu for 3) and Dy ions are located in the
2
2
2−
inner N O2 pocket and outer O4 pocket of L ligand,
2
assembled by atmospheric CO fixation, where a ferromagnetic
2
4
8
respectively and are linked by two phenol oxygen atoms (O2
interaction can be observed. Thus, we were motivated to
explore the possibility of obtaining novel heterometallic SMM
systems containing such heterometallic building blocks.
and O3) from L2 ligand and a acetate group in a η :η :μ
fashion with the Dy−O−M angles of 101.45° and 101.47° for 1
and 103.03° and 101.11° for 3. The coordination sphere of Dy1
is completed by bidentate acetate and nitrate anions, making
nine-coordinate with a distorted tricapped trigonal prismatic
−
1
1
(
TCTP) geometry. The average Dy−O distances are in the
range of 2.302(3)−2.616(3) Å and 2.257(3)−2.653(3) Å for 1
and 3, respectively, indicating a wide distribution of bond
lengths. Moreover, the bridging acetate group forces the
structure to be folded with a small hinge. The M ion is five-
coordinated with the M-O distances of 1.976(3)−2.017(3) Å
for 1 and 1.918(3)−2.242(3) Å for 3, displaying a pyramidal
geometry.
12
Both compound 2 and 4 are crystallized in the triclinic space
group P1
̅
with Z = 1, whose structures are displayed in Figures
2
and 3. In compound 2, the asymmetric unit is composed of
II
III
2−
one Zn ion, one Dy ion, one L ligand, one bidentate
acetate anion, and one carbonate anion. The carbonate anion
II
III
1
2
1
binds one Zn ion and two Dy ions in η :η :η :μ bridging
3
mode. Actually, complex 2 can be considered as the coupling of
two [ZnDy] units through the loss of terminal nitrate and
bridging acetate groups and formation of bridging carbonate
Figure 1. Molecular structures of 1 (up) and 3 (bottom). Hydrogen
atoms and solvent molecules are omitted for clarity. Color scheme:
yellow, Dy; purple, Zn; sky blue, Cu; red, O; blue, N; gray, C.
involving the fixation of atmospheric CO (Figure 2). In fact,
2
such a situation is not unprecedented, and there are many
examples of lanthanide complexes where the carbonate from
atmospheric CO fixation links several lanthanide ions into a
2
4
8,51−54
First, the [ZnDy] (1, Figure 1) and [ZnDy] (2, Figure 2)
large cluster.
Such modulation allows five oxygen atoms
2
compounds were obtained through the reactions of salen ligand
(O1, O2, O3, O4, and O6) around Dy1 being the nearly
coplanar, favoring the high axial anisotropy of Dy ion, which
III
(
(
H L) with different metal salts under the same base conditions
2
Scheme 1). A careful inspection of experimental condition
could be associated with the strong intramolecular magnetic
−
III
II
reveals that the anion (ClO ) provided by the lanthanide salt
interactions and SMM behavior. All Dy and Zn atoms
arrange in a zigzag fashion with the Dy−O and Zn−O distances
in the range of 2.292(3)−2.617(3) Å and 1.977(3)−2.027(3)
Å, respectively, and Dy−O−Zn angles of 103.61° and 102.27°,
4
may have a dominant contribution to the coupling of ZnDy (1)
units, forming [ZnDy] (2) complex, which might mainly hinge
2
¯
on the weakly coordinating ability of ClO to lanthanide ions.
4
C
dx.doi.org/10.1021/ic400620j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 2. Crystal structure of compound 2 and its assembly from [ZnDy] building blocks (1).
Scheme 1. Assembly Process for [ZnDy] and [ZnDy]2
Compounds
which are in agreement with the corresponding values of
compound 1.
In molecule 4, two μ -OH anions replace two carbonato
2
III
anions of 2, and play the role of connecting two Dy ions to
generate a structure coupling two CuDy units (Figure 3). One
water and one methanol molecules occupy the remaining
coordination sites of Dy1 instead of terminal bidentate acetate
in 2 with the Dy−O−Dy angles of 112.86(14)° and Dy−O
II
III
distances of 2.231(3) Å and 2.246(3) Å. The Cu and Dy ions
are four-coordinate and eight-coordinate, respectively. The
perchlorate connects to μ -OH and coordinated water molecule
2
#1
via intermolecular hydrogen bonds O6−H22···O15 and O5−
#1
H5A···O16 (symmetry codes: #1, −x+2,−y+1,−z+2). One
perchlorate and two methanol molecules join coordinated
water and methanol molecules from adjacent molecules via
#2
#3
#4
strong O6−H21···O8 , O9−H9A···O13 , O8−H8A···O12 ,
and O7−H7···O9 (symmetry codes: #2, x+1,y,z; #3, x,y−1,z;
#
4, −x+1,−y+1,−z+1; see Supporting Information, Table S2
for details) bonds to generate a one-dimensional chain (Figure
).
Magnetic Properties. Static susceptibility measurements
4
on polycrystalline samples of compounds 1−4 have been
measured in the temperature range of 2−300 K under a direct
current (dc) field of 1000 Oe (Figures 5 and 6). The room
temperature value of the χ T product of compound 1 is 13.8
cm K mol , comparable with the expected value of 14.17 cm
M
Figure 3. Crystal structure of compound 4.
3
−1
3
Figure 4. 1D chain of compound 4 through intermolecular hydrogen bonding.
D
dx.doi.org/10.1021/ic400620j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
mol− at 45 K before it increases to a value of 44.0 cm K mol
at 2.0 K, indicating the presence of intramolecular ferromag-
netic interactions. Such strong ferromagnetic interactions are
rare in lanthanide-based compounds, and here its occurrence
may be as a result of the connecting of two [DyZn] building
1
3
−1
2−
blocks through two CO
with high negative charge. The
3
CO32 in one building block is coordinated to the Zn atom in
the other building block, making the O atoms (O1, O2, O3,
O4, O6) almost planar, which therefore may lead to the strong
−
unaxial anisotropy of the Dy ion. For 4, the χ T vs T curve
M
demonstrates a decrease, then a little increase, and finally an
abrupt drop. The decrease of χ T value at the higher
M
Figure 5. Plots of χ T vs T for complexes 1 and 3 and the difference
temperature region is associated with crystal field effects of
the Dy ion, while the magnetic behavior at low temperature
M
III
of Δχ T.
M
should be ascribed to the competitions of magnetic interactions
(
JDy−Dy, JDy−Cu and intermolecular interactions).
The M-H plots measured at an applied field of 0−70 kOe for
K mol−1 for one Dy ion (6H15/2, g = 4/3) (Figure 5). With
decreasing temperature, the χ T product displays a typical
M
compounds 1−4 reveal the stronger field dependence of
magnetization in compounds 2 and 3 (the initial rapid increase)
than that in compounds 1 and 4 (Supporting Information,
Figures S1, S2, and S3) at low field, which is in agreement with
the presence of intramolecular ferromagnetic interactions in
complexes 2 and 3. Especially for compound 2, the value of
magnetization reaches 10.1 μ under a small dc field of 5 kOe at
1.9 K. At high field, the magnetization for compound 1−4
shows a linear increase with field, finally reaching values of 6.3
decrease, induced by the depopulation of the Stark sublevels of
5
5
3
the Dy ion. For compound 3, the χ T value of 15.2 cm K
M
−1
mol at 300 K is compatible with the theoretical value of 14.53
3
−1
cm K mol for the uncoupled Cu and Dy ion (Figure 5). The3
value decreases slightly down to a minimum value of 14.7 cm
57
K mol−1 with decreasing temperature, which is ascribed to the
B
depopulation of the Stark sublevels of Dy ion, and then shows
3
an obvious increase, reaching a maximum value of 15.6 cm K
−1
mol at 3.5 K, indicating the occurrence of intramolecular
(
1), 11.8 (2), 7.1 (3), and 15.1 (4) μ at 70 kOe and 1.9 K, but
B
ferromagnetic interactions. Finally, the χ T value displays a
M
without clear saturation. Furthermore, the nonsuperimposition
of the M vs H/T data on a single master curve (Figure 6 inset
and Supporting Information, Figures S1, S2, S3) suggests the
presence of low lying energy states and/or anisotropy in the
sharp decrease below 3.5 K, probably resulting from the
presence of weak intermolecular antiferromagnetic interactions.
Strikingly, because compound 1 and 3 are isostructural only
with some slight differences in bond lengths and angles, we can
1
2,14
II
system for compounds 1−4.
probe the nature of the magnetic interaction between Cu and
III
Variable-temperature ac susceptibility measurements as a
function of temperature or frequency were carried out under
zero dc field. Here only compound 2 exhibits the strong
frequency-dependence of both in-phase (χ′) and out-of-phase
Dy in compound 3 by extracting the Δχ T vs T curve from
M
the experimental χ T data of compound 1 and 3, Δχ T = χ T
M
M
M
56
(
3) − χ T (1) (Figure 5), which removes the influence of the
M
crystal-field effects of the Dy ion on dc magnetic susceptibility.
(
χ″) susceptibilities with maxima below 13 K (Figure 7),
Here the Δχ T value demonstrates a constant increase with
M
suggesting a typical SMM behavior, which is possibly associated
with the strong axial anisotropy induced by coplanar
coordinated O atoms around Dy ions. For compound 4,
although Dy ions show the similarly coplanar geometries, no
out-of-phase signals were observed above 1.8 K (Supporting
Information, Figure S4) probably because of the subtle
differences in coordination environment at Dy ions or the
interaction between Dy and Cu ions which might split further
decreasing temperature in the whole temperature region,
II
III
confirming a ferromagnetic interaction between Cu and Dy
1
2
ions.
The χ T value of 30.7 cm K mol at 300 K for compound
3
−1
M
3
−1
2
is a little larger than the calculated value (28.34 cm K mol ),
while compound 4 shows a relatively reasonable value of 29.9
3
−1
compared with the theoretical value of 29.06 cm K mol
Figure 6). Upon cooling, the χ T value of compound 2
(
M
3
III
44,45
displays a very slightly decrease to a minimum of 30.27 cm K
the ground sublevel of the Dy ion.
In addition,
Figure 6. Temperature dependence of the χ T product at 1000 Oe and field dependence of the magnetization at low temperatures (inset) for
M
complexes 2 (left) and 4. The solid lines are a guide for the eyes.
E
dx.doi.org/10.1021/ic400620j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 8. Temperature dependence of the in-phase (top) and out-of
phase (bottom) ac susceptibility signals for 1 (left) and 3 under the
optimal dc field. The solid lines are a guide for the eyes.
the out-of-phase component (χ″) of ac susceptibility showing
the maximum at the frequency of 300 and 1200 Hz (Figure 8).
In fact, a number of Ln-Zn complexes, including
1
2,31,44
55,59
60,61
62,63
[
[
DyZn],
[LnZn3],
[LnZn2],
[Dy Zn ],
and
2
2
32
Dy Zn ], have been reported recently. We summarized those
3
2
Ln-Zn complexes showing SMM behavior in Supporting
Information, Table S3. Herein some complexes exhibit not
only strong SMM behavior but also characteristic luminescent
Figure 7. Temperature dependence of the in-phase (χ′) and out-of
phase (χ″) ac susceptibility signals for 2 under zero dc field (up). The
solid lines are a guide for the eyes; Cole−Cole plots under zero-dc
field for compound 2 (bottom). The solid lines indicate the fits using a
generalized Debye model.
31
features. It is noteworthy that the [CeZn ] with a salen-type
2
ligand is the first example of slow magnetic relaxation observed
III
61
for Ce ion. In addition, we can see that the SMMs in a zero-
dc field are rare in those Ln-Zn complexes. In this regard, the
Dy Zn compound reported in this paper behaves as a typical
compounds 1 and 3 also show the absence of SMM behavior
under zero dc field, as indicated by the temperature
dependence of the ac susceptibility (Supporting Information,
Figure S5), which may be attributed to the fast quantum
tunneling relaxation induced by the large transverse anisotropy
at local Dy sites.
2
2
SMM as evidenced by the ac susceptibility data under a zero-dc
field.
CONCLUSION
■
4
From frequency dependencies of the ac susceptibility, the
magnetization relaxation times (τ) were deduced in the
temperature range of 1.9−11 K for compound 2. Through
the ln τ vs T− plots (Supporting Information, Figure S6), an
Four new compounds, [Zn/CuDy] (1, 3) and [Zn/CuDy] (2,
), have been obtained successfully through the reactions
2
1
between salen ligand (H L) and different metal salts. Both 1
2
−
6
and 3 demonstrate the field-induced slow relaxation of
magnetization. Since compounds 1 and 3 are isostructural, an
energy barrier (U ) of 34 K with τ = 2.9 × 10 s can be
eff
0
obtained based on an Arrhenius law (τ = τ exp (U /T)) above
0
eff
56
empirical approach developed by Costes et al. was applied to
study the nature of the magnetic interaction between Cu and
Dy ion, confirming the presence of ferromagnetic interaction
5
K, indicating a thermally activated mechanism at high
temperature. Below 5 K, the plots show a departure from the
Arrhenius behavior, which could be as a result of the quantum
tunneling of magnetization (QTM). The Cole−Cole diagram
between them. The [MDy]
structure can be considered as
2
(
χ″ vs χ′) was plotted in the temperature range of 1.9−8 K
resulting from the linkage of two [MDy] units. The
2−
(Figure 7, bottom), displaying a relatively symmetrical shape.
introduction of CO
3
leads to the transformation of highly
The plots can be fitted to the generalized Debye model, with
small α parameters (0.14−0.22), indicating a narrow
distribution of τ.
axial coordinating geometry of Dy ion, resulting in the
ferromagnetic interactions between Dy ions and SMM behavior
of the compound. The results described here suggest that the
assembly of multinuclear 3d-4f complexes from suitable
building blocks is a promising strategy for the design of novel
molecular magnetic architectures.
To reduce quantum tunneling of magnetization (QTM), the
optimal dc fields of 1000 and 1750 Oe according to the field
dependence of ac susceptibility were applied in compound 1
58
and 3, respectively (Supporting Information, Figure S7). The
application of dc field has a substantial influence on their
dynamic behavior of magnetization, as seen in ac susceptibility
signals. Compound 1 shows the clearly frequency-dependent
signals, but no maximum in out-of-phase component (χ″) of ac
susceptibility below 6 K (Figure 8), indicating the field-induced
slow magnetic relaxation behavior. In particular, the typical
SMM behavior was observed below 12 K in compound 3 with
ASSOCIATED CONTENT
■
*
S
Supporting Information
Table of selected bond distances (Å) and angles (deg) and
hydrogen bond parameters (Tables S1 and S2), and magnetic
measurement (Figures S1−S7). This material is available free of
charge via the Internet at http://pubs.acs.org.
F
dx.doi.org/10.1021/ic400620j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(
26) Ruiz, J.; Mota, A. J.; Rodriguez-Dieguez, A.; Titos, S.; Herrera, J.
AUTHOR INFORMATION
■
*
M.; Ruiz, E.; Cremades, E.; Costes, J. P.; Colacio, E. Chem. Commun.
012, 48, 7916.
Corresponding Author
E-mail: tang@ciac.jl.cn.
2
(27) Liu, C.-S.; Du, M.; Sanudo, E. C.; Echeverria, J.; Hu, M.; Zhang,
Q.; Zhou, L.-M.; Fang, S.-M. Dalton Trans. 2011, 40, 9366.
Notes
(
28) Bi, Y.; Wang, X.-T.; Liao, W.; Wang, X.; Deng, R.; Zhang, H.;
Gao, S. Inorg. Chem. 2009, 48, 11743.
29) Barron, L. D. Nat. Mater. 2008, 7, 691.
The authors declare no competing financial interest.
(
ACKNOWLEDGMENTS
(30) Li, X.-L.; Chen, C.-L.; Gao, Y.-L.; Liu, C.-M.; Feng, X.-L.; Gui,
■
Y.-H.; Fang, S.-M. Chem.Eur. J. 2012, 18, 14632.
We thank the National Natural Science Foundation of China
Grants 91022009, 21241006, and 21221061) for financial
support.
(31) Long, J.; Vallat, R.; Ferreira, R. A. S.; Carlos, L. D.; Almeida Paz,
(
F. A.; Guari, Y.; Larionova, J. Chem. Commun. 2012, 48, 9974.
32) Burrow, C. E.; Burchell, T. J.; Lin, P.-H.; Habib, F.;
Wernsdorfer, W.; Clerac, R.; Murugesu, M. Inorg. Chem. 2009, 48,
051.
33) Novitchi, G.; Wernsdorfer, W.; Chibotaru, L. F.; Costes, J.-P.;
Anson, C. E.; Powell, A. K. Angew. Chem., Int. Ed. 2009, 48, 1614.
34) Wu, G.; Hewitt, I. J.; Mameri, S.; Lan, Y.; Clerac, R.; Anson, C.
E.; Qiu, S.; Powell, A. K. Inorg. Chem. 2007, 46, 7229.
35) Hosoi, A.; Yukawa, Y.; Igarashi, S.; Teat, S. J.; Roubeau, O.;
(
́
8
REFERENCES
■
(
(
1) Christou, G.; Gatteschi, D.; Hendrickson, D. N.; Sessoli, R. MRS
Bull. 2000, 25, 66.
(
́
(
2) Ishikawa, N.; Sugita, M.; Ishikawa, T.; Koshihara, S.; Kaizu, Y. J.
Am. Chem. Soc. 2003, 125, 8694.
3) Osa, S.; Kido, T.; Matsumoto, N.; Re, N.; Pochaba, A.; Mrozinski,
J. J. Am. Chem. Soc. 2004, 126, 420.
4) Ako, A. M.; Hewitt, I. J.; Mereacre, V.; Cler
W.; Anson, C. E.; Powell, A. K. Angew. Chem., Int. Ed. 2006, 118, 5048.
5) Ako, A. M.; Mereacre, V.; Clerac, R.; Wernsdorfer, W.; Hewitt, I.
J.; Anson, C. E.; Powell, A. K. Chem. Commun. 2009, 544.
6) Zaleski, C. M.; Depperman, E. C.; Kampf, J. W.; Kirk, M. L.;
Pecoraro, V. L. Angew. Chem., Int. Ed. 2004, 43, 3912.
7) Karotsis, G.; Kennedy, S.; Teat, S. J.; Beavers, C. M.; Fowler, D.
(
(
Evangelisti, M.; Cremades, E.; Ruiz, E.; Barrios, L. A.; Aromí, G.
Chem.Eur. J. 2011, 17, 8264.
(
́
ac, R.; Wernsdorfer,
(
(
36) Sessoli, R.; Powell, A. K. Coord. Chem. Rev. 2009, 253, 2328.
37) Yang, X.; Chan, C.; Lam, D.; Schipper, D.; Stanley, J. M.; Chen,
(
X.; Jones, R. A.; Holliday, B. J.; Wong, W.-K.; Chen, S.; Chen, Q.
Dalton Trans. 2012, 41, 11449.
(
(
38) Peng, J.-B.; Ren, Y.-P.; Kong, X.-J.; Long, L.-S.; Huang, R.-B.;
Zheng, L.-S. CrystEngComm 2011, 13, 2084.
39) Tanase, S.; Sottini, S.; Marvaud, V.; Groenen, E. J. J.;
Chamoreau, L.-M. Eur. J. Inorg. Chem. 2010, 2010, 3478.
40) Yan, P.-F.; Lin, P.-H.; Habib, F.; Aharen, T.; Murugesu, M.;
Deng, Z.-P.; Li, G.-M.; Sun, W.-B. Inorg. Chem. 2011, 50, 7059.
41) Sheldrick, G. M. Acta Crystallogr. Sect. A: Found. Crystallogr.
008, 64, 112.
42) Boudreaux, E. A.; Mulay, L. N. Theory and Applications of
Molecular Paramagnetism; John Wiley & Sons: New York, 1976.
43) Feng, W.; Zhang, Y.; Lu, X.; Hui, Y.; Shi, G.; Zou, D.; Song, J.;
Fan, D.; Wong, W.-K.; Jones, R. A. CrystEngComm 2012, 14, 3456.
44) Watanabe, A.; Yamashita, A.; Nakano, M.; Yamamura, T.;
Kajiwara, T. Chem.Eur. J. 2011, 17, 7428.
45) Kajiwara, T.; Nakano, M.; Takahashi, K.; Takaishi, S.;
Yamashita, M. Chem.Eur. J. 2011, 17, 196.
46) Gao, T.; Xu, L.-L.; Zhang, Q.; Li, G.-M.; Yan, P.-F. Inorg. Chem.
Commun. 2012, 26, 60.
47) Miyasaka, H.; Saitoh, A.; Abe, S. Coord. Chem. Rev. 2007, 251,
622.
48) Sakamoto, S.; Yamauchi, S.; Hagiwara, H.; Matsumoto, N.;
Sunatsuki, Y.; Re, N. Inorg. Chem. Commun. 2012, 26, 20.
49) Gao, Y. J.; Xu, G. F.; Zhao, L.; Tang, J.; Liu, Z. L. Inorg. Chem.
009, 48, 11495.
50) Xue, S.; Zhao, L.; Guo, Y.-N.; Chen, X.-H.; Tang, J. Chem.
Commun. 2012, 48, 7031.
51) Gass, I. A.; Moubaraki, B.; Langley, S. K.; Batten, S. R.; Murray,
K. S. Chem. Commun. 2012, 48, 2089.
52) Langley, S. K.; Moubaraki, B.; Murray, K. S. Inorg. Chem. 2012,
(
(
A.; Morales, J. J.; Evangelisti, M.; Dalgarno, S. J.; Brechin, E. K. J. Am.
Chem. Soc. 2010, 132, 12983.
(
(
8) Aronica, C.; Pilet, G.; Chastanet, G.; Wernsdorfer, W.; Jacquot, J.-
F.; Luneau, D. Angew. Chem., Int. Ed. 2006, 45, 4659.
9) Langley, S. K.; Ungur, L.; Chilton, N. F.; Moubaraki, B.;
Chibotaru, L. F.; Murray, K. S. Chem.Eur. J. 2011, 17, 9209.
10) Ferbinteanu, M.; Kajiwara, T.; Choi, K.-Y.; Nojiri, H.;
Nakamoto, A.; Kojima, N.; Cimpoesu, F.; Fujimura, Y.; Takaishi, S.;
Yamashita, M. J. Am. Chem. Soc. 2006, 128, 9008.
11) Xu, G.-F.; Gamez, P.; Tang, J.; Cler
Inorg. Chem. 2012, 51, 5693.
12) Colacio, E.; Ruiz-Sanchez, J.; White, F. J.; Brechin, E. K. Inorg.
Chem. 2011, 50, 7268.
13) Ke, H.; Zhao, L.; Guo, Y.; Tang, J. Inorg. Chem. 2012, 51, 2699.
14) Mondal, K. C.; Kostakis, G. E.; Lan, Y.; Wernsdorfer, W.;
Anson, C. E.; Powell, A. K. Inorg. Chem. 2011, 50, 11604.
15) Chandrasekhar, V.; Pandian, B. M.; Vittal, J. J.; Clerac, R. Inorg.
Chem. 2009, 48, 1148.
16) Mondal, K. C.; Sundt, A.; Lan, Y.; Kostakis, G. E.; Waldmann,
O.; Ungur, L.; Chibotaru, L. F.; Anson, C. E.; Powell, A. K. Angew.
Chem., Int. Ed. 2012, 51, 7550.
17) Langley, S. K.; Chilton, N. F.; Ungur, L.; Moubaraki, B.;
Chibotaru, L. F.; Murray, K. S. Inorg. Chem. 2012, 51, 11873.
18) Bencini, A.; Benelli, C.; Caneschi, A.; Carlin, R. L.; Dei, A.;
Gatteschi, D. J. Am. Chem. Soc. 1985, 107, 8128.
19) Andruh, M.; Costes, J.-P.; Diaz, C.; Gao, S. Inorg. Chem. 2009,
8, 3342.
20) Zheng, Y.-Z.; Evangelisti, M.; Winpenny, R. E. P. Angew. Chem.,
Int. Ed. 2011, 50, 3692.
21) Peng, J.-B.; Zhang, Q.-C.; Kong, X.-J.; Ren, Y.-P.; Long, L.-S.;
Huang, R.-B.; Zheng, L.-S.; Zheng, Z. Angew. Chem., Int. Ed. 2011, 50,
0649.
22) Zheng, Y.-Z.; Evangelisti, M.; Tuna, F.; Winpenny, R. E. P. J.
Am. Chem. Soc. 2011, 134, 1057.
23) Peng, J.-B.; Zhang, Q.-C.; Kong, X.-J.; Zheng, Y.-Z.; Ren, Y.-P.;
Long, L.-S.; Huang, R.-B.; Zheng, L.-S.; Zheng, Z. J. Am. Chem. Soc.
012, 134, 3314.
24) Dinca, A. S.; Ghirri, A.; Madalan, A. M.; Affronte, M.; Andruh,
M. Inorg. Chem. 2012, 51, 3935.
25) Dunbar, K. R. Inorg. Chem. 2012, 51, 12055.
(
2
(
(
(
(
(
́
ac, R.; Guo, Y.-N.; Guo, Y.
(
(
(
(
(
(
(
2
(
(
́
(
(
2
(
(
(
(
(
4
(
(
51, 3947.
(53) Vallejo, J.; Cano, J.; Castro, I.; Julve, M.; Lloret, F.; Fabelo, O.;
Canadillas-Delgado, L.; Pardo, E. Chem. Commun. 2012, 48, 7726.
(54) Guo, Y.-N.; Chen, X.-H.; Xue, S.; Tang, J. Inorg. Chem. 2012, 51,
4035.
(
1
(
̈
(55) Feltham, H. L. C.; Lan, Y.; Klower, F.; Ungur, L.; Chibotaru, L.
F.; Powell, A. K.; Brooker, S. Chem.Eur. J. 2011, 17, 4362.
(56) Costes, J.-P.; Dahan, F.; Dupuis, A.; Laurent, J.-P. Chem.Eur.
J. 1998, 4, 1616.
(
2
(
(57) Lin, P.-H.; Burchell, T. J.; Cler
Chem., Int. Ed. 2008, 47, 8848.
́
ac, R.; Murugesu, M. Angew.
(58) Xue, S.; Zhao, L.; Guo, Y.-N.; Deng, R.; Guo, Y.; Tang, J. Dalton
Trans. 2011, 40, 8347.
(
G
dx.doi.org/10.1021/ic400620j | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(
59) Yamashita, A.; Watanabe, A.; Akine, S.; Nabeshima, T.; Nakano,
M.; Yamamura, T.; Kajiwara, T. Angew. Chem., Int. Ed. 2011, 50, 4016.
60) Maeda, M.; Hino, S.; Yamashita, K.; Kataoka, Y.; Nakano, M.;
Yamamura, T.; Kajiwara, T. Dalton Trans. 2012, 41, 13640.
61) Hino, S.; Maeda, M.; Yamashita, K.; Kataoka, Y.; Nakano, M.;
(
(
Yamamura, T.; Nojiri, H.; Kofu, M.; Yamamuro, O.; Kajiwara, T.
Dalton Trans. 2013, 42, 2683.
(
62) Meng, Z.-S.; Guo, F.-S.; Liu, J.-L.; Leng, J.-D.; Tong, M.-L.
Dalton Trans. 2012, 41, 2320.
63) Yu, W.-R.; Lee, G.-H.; Yang, E.-C. Dalton Trans. 2013, 42, 3941.
(
H
dx.doi.org/10.1021/ic400620j | Inorg. Chem. XXXX, XXX, XXX−XXX