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7456 Chem. Commun., 2012, 48, 7456–7458 This journal is c The Royal Society of Chemistry 2012
Cite this: Chem. Commun., 2012, 48, 7456–7458
Heterometallic thiacalix[4]arene-supported Na2NiII12LnIII
2 clusters with
vertex-fused tricubane cores (Ln = Dy and Tb)w
Kecai Xiong,ac
Xinyi Wang,bFeilong Jiang,
aYanli Gai,
acWentao Xu,
acKongzhao Su,
ac
Xingjun Li,ac
Daqiang Yuanaand Maochun Hong*
a
Received 1st April 2012, Accepted 15th May 2012
DOI: 10.1039/c2cc32360e
Two heterometallic thiacalix[4]arene-supported complexes
possess a trinary-cubane core composed of one [Ni2Ln2] cubane
unit and two [NaNi2Ln] cubane units sharing one LnIII
ion
(Ln = Dy and Tb). Only the DyIII
complex exhibits slow
magnetic relaxation behaviour of single molecule magnet nature.
The design and construction of transition-lanthanide (3d–4f)
heterometallic complexes has attracted considerable attention
in the past two decades because of their fascinating architectures1
and their potential applications as functional materials in
magnetism,2–4 luminescent materials,5 absorption materials6
and bimetal catalysts.7 As a result of the cooperativity between
the 3d–4f metal ions, significant magnetic behaviors have been
documented such as single molecule magnets (SMMs),2 single
chain magnets (SCMs)3 and magnetic refrigerants.4 However, the
preparation of designed heterometallic aggregates is still a formid-
able challenge owing to the variable and versatile coordination
behaviour of lanthanide ions and other factors. As is widely
known, the critical factor for the construction of heterometallic
3d–4f complexes is the rational choice of organic building block.
On the other hand, calix[4]arene derivatives and thiacalix[4]-
arene derivatives with functional groups and molecular back-
bones are most pivotal in the structural regulation of resultant
crystalline materials.8–10 In particular, thiacalix[4]arene deri-
vatives with four additional bridging sulfur atoms can bind to
up to four metal ions simultaneously forming metal4-
thiacalix[4]arene building blocks to support various polynuclear
clusters. To date, several homometallic thiacalix[4]arene-
supported complexes have been obtained.9,10 However, few 3d–4f
mixed-metal complexes involving (thia)calix[4]arenes have
been reported.8a–c,9a,b To the best of our knowledge,
MnIII4LnIII
4 are the largest 3d–4f aggregates sustained by
(thia)calix[4]arenes so far.8b For the reasons above and along
the line of our previous research on creating thiacalix[4]arene-
based complexes with interesting magnetic properties, we have
tried to expand the uses of carbonato anion in synthesizing
thiacalix[4]arene-supported 3d and/or 4f heterometallic
clusters employing sodium carbonate as a reactant. In the
present work, we have successfully obtained two new high nucle-
arity 3d–4f heterometallic clusters with vertex-fused tricubane
cores: [Na2NiII12LnIII
2(BTC4A)3(m7-CO3)3(m3-OH)4(m3-Cl)2-(OAc)6(dma)4]�2OAc�0.5dma�3MeCN�8DMA (Ln = Dy for
1, and Tb for 2; H4BTC4A = p-tert-butylthiacalix[4]arene;
dma= dimethylamine and DMA= N,N0-dimethylacetamide).
Herein the syntheses, structures and magnetic properties of
complexes 1 and 2 are presented.
X-Ray analysis reveals that both 1 and 2 crystallize in the
monoclinic system with space group P21/c.z The two
thiacalix[4]arene-supported clusters are isomorphous. Taking
complex 1 as representative, the structure possesses a hetero-
metallic Na2NiII12DyIII2 core capped by three BTC4A4� ligands
(Fig. 1). Within complex 1, both sodium ions are five-coordinated
in a distorted square-pyramidal geometry, while each NiII ion is
six-coordinated with distorted octahedral geometry. In addition,
Fig. 1 Molecular structure of complexes 1 (Ln=Dy) and 2 (Ln=Tb);
hydrogen atoms are omitted for clarity.
a State Key Laboratory of Structure Chemistry, Fujian Institute ofResearch on the Structure of Matter, Chinese Academy of Sciences,Fuzhou, 350002, China. E-mail: [email protected];Fax: +86-591-83794946; Tel: +86-591-83714605
b State Key Laboratory of Coordination Chemistry, School ofChemistry and Chemical Engineering, Nanjing University, Nanjing,210093, China
c Graduate School of the Chinese Academy of Sciences, Beijing,100049, Chinaw Electronic supplementary information (ESI) available: Syntheses,crystallographic information, supplementary figures, PXRD of com-plexes 1 and 2. CCDC 874210 and 874211. For ESI and crystallo-graphic data in CIF or other electronic format see DOI: 10.1039/c2cc32360e
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This journal is c The Royal Society of Chemistry 2012 Chem. Commun., 2012, 48, 7456–7458 7457
Dy1 and Dy2 are ten-coordinated with a distorted bicapped
square-antiprism geometry and eight-coordinated with a dis-
torted square-antiprism geometry, respectively. The two DyIII
centers are connected by two carbonato and one acetate
anions. Every four NiII ions simultaneously bond to the lower-
rim phenoxy oxygens and bridge sulfur atoms of one fully
deprotonated BTC4A4� ligand leading to a shuttlecock-like build-
ing block of NiII4-BTC4A, in which one carbonato anion acts as
the cork base. Three subunits are linked together in an up-to-up
fashion through four cations (two Na+ ions and two DyIII ions)
along with other anions (including two Cl� anions, four OH�
anions and three OAc� anions), leading to a pseudo-trigonal
planar entity with heterometallic Na2NiII12DyIII2 cluster. All
carbonato anions bind to seven metal centres with the same
chelating and bridging configurations, which can be represented
as [7.21233453567] according to Harris notation (Fig. 2a),11 different
from the reported [6.222]10b or [5.212234245]10c within the
thiacalix[4]arene-supported complexes. It is noteworthy that this
coordination mode has not been reported heretofore.
Further analysis shows that there is an unprecedented
trinary-cubane core composed of one [Ni2Dy2] cubane unit
and two [NaNi2Dy] cubane units, which share one DyIII ion at
the center of the Na2NiII12DyIII2 cluster (Fig. 2b and c). To the
best of our knowledge, the discrete cubane-like heterometallic
systems reported so far are restricted to a few 3d–4f systems.
This [NaNi2Dy] cubane core presents the first example which
consists of more than two metal elements. In addition, the
vertex-fused tricubane topology is a very rare structural type.
There is no previous example of such a discrete unit in
heterometallic chemistry, but two 3d–4f examples with tricubane
cores have been reported: three [Ce2Mn2] cubanes sharing a
trigonal-bipyramidal unit {Ce2(OH)3} in the centre12 or three
[Gd2Cu2] cubanes sharing three GdIII ions in a triangular way.13
The heterometallic cluster of 1 can be viewed as a tricubane
connects to six peripheral NiII ions through three m7-carbonatoanions (Fig. 2c). Three BTC4A4� ligands are located on the
trigonal plane of the tricubane core. Although there has been a
report with three calixarenes bonded to one CuII9 cluster, those
three p-tert-butylcalix[4]arene ligands lie on the trigonal plane.14
All the Ni–N, Ni–O, Ni–Cl, Ni-S, Na–N, Na–O, Na–Cl and
Dy–O bond distances are located in the normal bond length
range.1d,10b,15 The dma molecules were generated through the
decarbonylation of DMA.10b The Ni� � �Ni distances are
3.07–3.73 A, while the Ni� � �Dy distances are 3.46–3.69 A
within 1. Analysis of the bond lengths, charge balance and
bond valence sum calculations (BVS) suggests all Ni and Ln ions
of complexes 1 and 2 to be NiII and LnIII.16 Two CH3CN and
one DMA molecules penetrate slantwise into three
thiacalix[4]arene cavities stabilized by C–H� � �p interactions. In
addition, one acetate counter anion locates above the afore-
mentioned tricubane core via hydrogen bonds (Fig. S1w). Upon
crystal packing, complex 1 exhibits a bilayer structure in which
the pseudo-trigonal planar entities sit in an up–down fashion.
The interstices of the lattice are occupied by the solvent molecules
and acetate counter anions (Fig. S2w).The temperature dependent of magnetic susceptibilities
measured on the polycrystalline samples of 1 and 2 under
Hdc = 1000 Oe were displayed in Fig. 3a. At 300 K, the wmTvalues (40.53 and 36.48 cm3 K mol�1 for 1 and 2) are in
good agreement with the theoretical values of 40.34 and
35.64 cm3 K mol�1 for the two non-interacting LnIII ions
(Dy: 6H15/2, gJ = 4/3; Tb: 7F6, gJ = 3/2) and twelve NiII ions
(S= 1, g= 2).17 As the temperature is lowered, the wmT value
decreases continuously and falls rapidly in the lower tempera-
ture region, reaching 16.89 and 13.54 cm3 K mol�1 for 1 and 2
at 2 K, respectively. The Curie–Weiss fit of the data above
50 K give the Weiss constants y = �13.52 and �16.09 K for
complexes 1 and 2, respectively (Fig. 3a). The negative y valuesand the decrease of the wmT values at high temperature could
be ascribed to two sources, the antiferromagnetic interaction
between the spin carriers and the thermal depopulation of the
Stark levels of the DyIII and TbIII centers.
Upon increasing the applied external magnetic field, the
magnetizations of 1 and 2 increase to 15.7 and 16.0 Nb at
60 kOe, far below the saturation values of 44 and 42 Nb(Fig. S3w).17a No obvious hysteresis loop could be observed
for either complex at 2 K (Fig. S3w). In addition, temperature
dependent ac susceptibilities were measured under zero dc field
for 1 and 2; and slow relaxation of magnetization was
observed only in 1 (Fig. S4 and S5w). The frequency dependentac susceptibilities under zero dc field were also measured for 1
(Fig. S6w), from which the relaxation time at different temp-
eratures were evaluated. An estimation of the energy barrier
Ueff = 8.4 K and the pre-exponential factor t0 = 6.8 � 10�7 s
can be obtained from the Arrhenius fit of the t values (Fig. S6winset). Furthermore, Cole–Cole plots (Fig. S7w) have also been
obtained. The analyses of the plots according to the generalized
Debye functions give a values of 0.18–0.31 above 2.2 K,
indicating the presence of a relatively narrow width of the
Fig. 2 (a) Coordination modes of carbonato anions within 1 and 2
indicated by the Harris notation [7.21233453567]. (b) [NaNi2Ln] cubane
unit and [Ni2Ln2] cubane unit of 1 and 2. (c) The heterometallic
Na2NiII12LnIII
2 cluster possessing vertex-fused tricubane core and six
peripheral NiII ions connected through three m7-carbonato anions.
Fig. 3 (a) Temperature dependence of magnetic susceptibilities of 1 (Dy)
and 2 (Tb) in a 1000 Oe field. The solid lines are the best fitting to the
Curie–Weiss Law. (b) Temperature dependence of the in-phase (top) and
out-of phase (bottom) components of the ac magnetic susceptibility for
complex 1 in a static applied dc field of 2000 Oe and an ac field of 3 Oe.
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7458 Chem. Commun., 2012, 48, 7456–7458 This journal is c The Royal Society of Chemistry 2012
distribution of slow relaxation. However, the a value at 2 K
increases sharply to about 0.75, indicating the presence of
quantum tunnelling at lower temperature. The quantum
tunnelling could be partly suppressed by the application of
an external dc field, as can be seen from the shift of the peaks
of the ac signals toward higher temperatures measured under a
2000 Oe dc field (Fig. 3b). All these magnetic parameters
clearly evidence the SMM nature of this Dy-containing
complex 1. Given that 1 and 2 are isomorphous, it appears
that the necessary magnetic anisotropy is contributed by the
DyIII ions.17b One possible reason might be the fact that the
ground state of the Kramers ion DyIII is always degenerate
while this is not the case for TbIII ion.
In conclusion, two isomorphous heterometallic complexes 1
and 2 have been synthesized and structurally characterized. In
the presented structures, three shuttlecock-like NiII4-BTC4A
subunits are linked together in an up-to-up fashion through
two Na+ ions and two LnIII ions, along with other anions,
leading to a pseudo-trigonal planar entity. Within this entity,
there is a trinary-cubane core composed of one [Ni2Ln2] cubane
unit and two [NaNi2Ln] cubane units sharing one LnIII ion. It
should be noted that a cubane unit possessing more than two
metal elements has not been reported to date. Magnetic studies
reveal that only the DyIII complex shows the slow relaxation of
the magnetization expected for SMM behaviour. This work
shows that thiacalix[4]arenes can indeed lead to high-nuclearity
heterometallic clusters with intriguing structure and interesting
magnetic properties in the presence of ancillary anions. Our
efforts to prepare isotypic heterometallic complexes are ongoing.
We thank 973 Program (2011CBA00507, 2011CB932504),
National Natural Science Foundation of China (21131006,
20231020, 20971121, 21101093) and the Natural Science
Foundation of Fujian Province for funding this research.
The authors are grateful to Prof. Xiaoying Huang for assis-
tance with the crystallographic studies and Prof. Zhangzhen
He for valuable advice and discussions.
Notes and references
z Crystal data for complexes 1/2: C186H272.5N15.5O49Cl2S12Na2Ni12-Dy2/Tb2, M = 5040.73/5033.58, monoclinic, space group P21/c, a =21.546(2)/21.608(5), b = 30.412(3)/30.507(7), c = 36.028(4)/36.110(9) A,b = 99.774(2)/99.870(5)1, V = 23265(4)/23451(10) A3, Z = 4, Dc =1.439/1.437 g cm�3, F000 = 9496/9488, l = 0.71073 A, T = 120(2) K,2ymax = 52.0/52.01, 191383/183986 reflections collected, 45039/45032unique (Rint = 0.0420/0.0604). Final GooF = 1.076/1.077, R1 =0.0814/0.0938, wR2 = 0.2348/0.2446, R indices based on 41840/37462 reflections with I > 2s(I) (refinement on F2). The diffractiondata were treated by the ‘‘SQUEEZE’’ method as implemented inPLATON18 to remove diffuse electron density associated with thebadly disordered solvent molecules. This had the effect of dramaticallyimproving the agreement indices.
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