Linear trinuclear cobalt(ii) single molecule magnet

Article abstract of DOI:10.1039/c4dt03545c

The introduction of NaBPh₄ into a methanolic solution of CoCl₂·6H₂O and 2-[(pyridine-2-ylimine)-methyl]phenol (Hpymp) afforded {[Co^II₃(pymp)₄(MeOH)₂][BPh₄]₂

Full text of DOI:10.1039/c4dt03545c

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Linear trinuclear cobalt(II) single molecule magnet
Yuan-Zhu Zhang,*,a Andrew J Brown,b Yin-Shan Meng,a Hao-Ling Sun,c Song Gao*,a
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
DOI: 10.1039/b000000x
5
Introduction of NaBPh4 into a methanolic solution of CoCl2⋅6H2O and 2-[(pyridine-2-ylimine)-
methyl]phenol (Hpymp) afforded {[CoII3(pymp)4(MeOH)2][BPh4]2}⋅2MeOH (1) with a centro-
symmetrically linear trinuclear structure. Magnetic analysis of 1 exhibited significant intracluster
ferromagnetic exchange (2.4 cm-1) and slow relaxation of magnetization at both zero and non-zero static
fields below 5 K, giving the first [CoII ] single molecule magnet with an effective energy barrier of 17.2(3)
3
10 cm-1 under 500 Oe dc field.
cobalt ions.12,13 However, this disc-like geometry suffers from the
non-colinear alignment of magnetic anisotropies between the
surrounding cobalt(II) ions, as evidenced by the mixed
Introduction
In an Ising-like system, or when spin is a good quantum number,
the combination of a large spin ground state (S) and uniaxial
magnetic anisotropy (D < 0) can result in a single molecule
15 magnet (SMM) with an energy barrier (U) to spin reversal: U =
|D|S2 or |D|(S2-1/4) for integer and half-integer spin, respectively.
Extensive studies, both in theory and experiment, are on-going
efforts with the aim for higher energy barriers that would allow
practical applications in information storage.1,2 In well-studied
20 Mn(III)-SMMs, where the orbital contribution to magnetic
moment in the Mn(III) ion is quenched, a common magneto-
structural correlation has been documented. Namely, the parallel
alignment of Jahn-Teller (JT) axes and ferromagnetic intracluster
interactions lead to large anisotropy.3 One drawback from such
25 systems is the low magnitude of the axial zero-field splitting
parameter for the Mn(III) ion, DMn ≈ -4 cm-1.4 Thus, other metal
ions with unquenched orbital angular momentum emanating from
strong spin-orbital couplings have attracted more concerns.5,6 The
Co(II) ion has been of particular interest as a new anisotropy
30 source in recent years.7 The very recent progress on several series
of mononuclear Co(II)-SMMs demonstrated large and tunable
anisotropy with DCo varying from -115 to +13 cm-1 afforded by
deliberate modification on coordination geometry, degree of
structural distortion, and ligand field strength.8 Further
35 incorporation of these high anisotropy ions into clusters with the
potential for strong communication and favorable arrangement of
the anisotropy vectors may stand for a new challenge in this
field.9 In this regard, structurally simple molecules (low-
nuclearity) are currently of particular interest.
50 [CoII CoIII3] disc13a exhibiting improved SMM properties over the
4
[CoII CoIII] disc, which contained only one CoIII ion in the
6
center.13b
In attempts to exploit a co-linear alignment of the anisotropy
axes, we were inspired by a series of heterometallic linear
55 [CoII LnIII]14 and one linear [CoII ]15 clusters that have been
2
4
characterized as SMMs. In this regard, we targeted linear [CoII ]
3
SMMs, which hitherto remain unexplored.16 Treatment of
CoCl2⋅6H2O and 2-[(pyridine-2-ylimine)methyl]phenol (Hpymp,
Scheme 1) with NaBPh4 in a methanolic solution afforded brown
60 thin-plate crystals of {[CoII3(pymp)4(MeOH)2][BPh4]2}⋅2MeOH
(1), which consists of a centro-symmetric cationic array of three
cobalt atoms ligated by four [pymp]− ligands. For comparison,
[CoII (pymp)4(pya)2][ClO4]2 (2, pya = pridine-2-amine) was also
3
synthesized.17 Magnetic analysis revealed that
1 exhibits
65 significant intracluster ferromagnetic exchange (J = +2.4 cm-1)
and slow relaxation of magnetization at both zero and non-zero
static fields below 5 K with an effective energy barrier of 17.2(3)
cm-1 under 500 Oe dc field.
H
H
H
H
H
H
H
N
N
H
O
H
H
40
Among the known Co(II)-SMMs, the first and most well-
studied are primarily those containing the cubane [Co4O4] motif,
in which orthogonal hard-axis alignments of four single-ion spins
(DCo > 0) were proposed to result in negative global Dmol values.10
This concept was again manifest in a [CoII7] SMM with two fused
Scheme 1 2-[(pyridine-2-ylimine)methyl]phenol (Hpymp)
Experimental Section
70 Materials and Physical Measurements.
45 cubanes.11 Another popular system is the planar [Co7] disc family
of SMMs with a central cobalt ion surrounded by a ring of six
All starting materials were commercially available, reagent grade,
and used as purchased without further purification. Elemental
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analysis of carbon, hydrogen, and nitrogen were carried out with
Table 1. Selected crystallographic data for 1 at 293(2) K.
an Elementary Vario EL. The IR spectra were recorded on a
Magna-IR 750 spectrophotometer in the 4000-500 cm–1 region.
The measurements of magnetic properties were performed on an
Oxford Maglab2000 System and a Quantum Design MPMS XL-7
SQUID magnetometer. The experimental susceptibilities were
adjusted to correct for diamagnetic contributions (Pascal’s
tables).18 All SQUID samples were immobilized in NMR tubes
with eicosane for reducing possible magnetic torqueing.
formula
formula wt
crystal system
space group
a, Å
C100H92B2Co3N8O8
1732.23
Triclinic
P ī
5
11.5855(5)
14.4488(6)
15.1235(8)
72.292(2)
67.952(2)
69.590(2)
2154.99(17)
1.335
b, Å
c, Å
α
, deg
, deg
, deg
10 Synthesis of Hpymp
β
γ
Treatment of salicylalhehyde (2.44 g, 2.00 mol) and pya (1.88 g,
2.00 mol) in methanol (20 mL) afforded a yellow solution, which
was stirred for 3 d. Yellow crystalline powder of Hpymp was
obtained after removing the methanol by rotary evaporation, and
15 drying under vacuum for 3 h. Yield: 3.60 g (90.9 %). Anal. Calcd
C12H10N2O (M.W. = 198.22 g mol−1): C, 72.71; H, 5.08; N,
14.13. Found: C, 72.58; H, 5.13; N, 14.09. IR (Nujol, cm−1): 1614
(S) for ν(C=N) stretching vibration of Schiff base. The purity
was also checked by NMR spectra (CDCl3). (Fig. S1)
V, Å3
Dc, g cm-3
Z
1
ꢀ
, mm-1
0.634
0.834
0.0484
0.0872
GOOF
R1 (I ≥ 2σ(I))
wR2 (I ≥ 2σ(I))
20 Synthesis of {[CoII3(pymp)4(MeOH)2][BPh4]2}⋅2MeOH (1)
A 5 mL methanolic solution of Hpymp (95.5 mg, 0.482 mmol)
was added to a 8 mL methanolic solution of CoCl2⋅6H2O (72.5
mg, 0.305 mmol) to afford an orange solution, which was stirred
for 2 min. NaBPh4 (99.7 mg, 0.291 mmol) in methanol (3 ml)
25 was added and the resulting solution was kept undisturbed
overnight in air. Brown thin plate-like crystals of 1 were isolated
via filtration, washed with methanol (5 mL), and dried in air.
Yield: 115 mg (65.3 %). Anal. Calcd C100H92B2Co3N8O8: C,
69.34; H, 5.35; N, 6.47. Found: C, 69.87; H, 5.23; N, 6.58. IR
30 (Nujol, cm−1): νs(C=N) 1623 (s). Powder X-ray diffraction
(PXRD) of 1 matched the simulated pattern from single crystal
data. (Fig. S2)
Table 2. Selected bond distances (Å) and angles (°) for 1
Co1-O1
2.022(3) O1-Co1-N1A
2.145(3) O3-Co2-N3
2.124(3) O3-Co2-N2
2.089(3) O3-Co2-N4
2.018(3) O3-Co2-O2
2.397(4) O3-Co2-O1A
2.137(3) N3-Co2-N4
2.038(3) N2-Co2-O2
2.118(3) Co1-O1A-Co2
180.0 (1) Co1-O2-Co2
97.91(10) Co1…Co2
82.09(10) Co2…Co2A
88.29(11)
91.71(11)
92.86(13)
90.75(13)
86.89(13)
95.76(12)
170.67(11)
59.88(14)
109.41(13)
94.30(0)
Co1-O2
Co1-N1
Co2-N2
Co2-N3
Co2-N4
Co2-O3
Co2-O2
Co2-O1A
O1-Co1-O1A
O1-Co1-O2
O1-Co1-O2A
O1-Co1-N1
93.02(0)
3.036(1)
6.072(3)
Synthesis of {[CoII3(pymp)4(pya)2][ClO4]2} (2)
Symmetry transformations used to generate equivalent
atoms: A -x,-y,-z+1;
Compound 2 was synthesized with a slightly modified procedure
35 of the reported literature.17 A 5 mL methanolic solution of Hpymp
(85.5 mg, 0.431 mmol) and pya (26.5 mg, 0.282 mmol) was
added to a 5 mL methanolic solution of Co(ClO4)2⋅6H2O (105.6
mg, 0.288 mmol). The resulting red solution was filtered and
allowed to sit undisturbed overnight. Red block-like crystals were
40 isolated via filtration, washed with methanol (5 mL), and dried in
air. Yield: 75.5 mg (58.0 %). Anal. Calcd C58H48Co3Cl2N12O12:
C, 51.50; H, 3.58; N, 12.42. Found: C, 51.65; H, 3.76; N, 12.49.
The compound was confirmed by single crystal X-ray diffraction.
Caution! Perchlorate salts of metal complexes with organic
45 compounds are potentially explosive. Only a small amount of
material should be prepared and handled with great care.
riding model. Weighted R factors (wR) and all the goodness-of-fit
(S) values are based on F2; conventional R factors (R) are based
60 on F, with F set to zero for negative F2.
Results and discussion
Single Crystal structural data:
The diffraction data for 1 (0.25 × 0.14 × 0.04 mm) was collected
at 293(2) K on a Nonius κ-CCD diffractometer (λ = 0.71073 Å).
50 Initial cell parameters were obtained (DENZO) from ten 1º
frames (SCALEPACK). Lorentz/polarization corrections were
applied during data reduction and the structures were solved by
the direct method (SHELXS-97). Refinements were performed by
full-matrix least squares (SHELXL-97) on F2 and empirical
55 absorption corrections (SADABS) were applied. Anisotropic
thermal parameters were used for the non-hydrogen atoms.
Hydrogen atoms were added geometrically and refined using a
Fig. 1 Ball-and-stick view of X-ray structure of 1. Counter anions of
[BPh4]-, hydrogen atoms and lattice solvents are eliminated for clarity.
2
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Description of structures
indicating significant spin-orbital couplings present.19 For 1, the
40 χmT value increases steadily upon cooling to a maximum of 14.1
cm3 mol−1 K at 6 K, suggesting significant ferromagnetic (F)
couplings between the neighbouring Co(II) ions, then slightly
decreases to 13.5 cm3 mol−1 K at 2 K, likely due to the zero-field
splitting effect and/or intermolecular antiferromagnetic (AF)
45 interactions. For 2, the χmT value decreases gradually to 7.7 cm3
mol−1 K at ca. 20 K and then increases slightly to a maximum of
8.0 cm3 mol−1 K at 9 K before dropping again. This curve
suggests much weaker couplings within 2. The data may be fit by
using the PHI program20 with the Hamiltonian as the following
50 equation (eq. 1) as well as the mean-field approximation (eq. 2):
Compounds 1 and 2 crystallize in the triclinic Pī space group and
exhibit similar structures (Figs. 1 and S3). Compound 1 consists
of a centro-symmetric cationic array of three cobalt atoms ligated
by four [pymp]− ligands with dihedral angles between their
phenyl and pyridine rings being 114.8° and 16.1° for the twisted
(pymp_O1) and flattened (pymp_O2) ligands, respectively. The
central Co1, which resides on an inversion center, displays a
compressed octahedral geometry formed by two imino N atoms
10 and four phenolate O atoms. The bond distance of the apical Co1-
O1/O1A [2.022(3) Å] is significantly shorter than the equatorial
distances [Co1-N/O = 2.124(3) – 2.145(3) Å]. The bond angles of
cis O–Co1–O/N are in the range of 82.09(10) to 97.91(10)°. The
outer cobalt atoms [Co2 and Co2A] adopt a highly distorted
5
3
2
H = −2J(S1 ⋅ S2 + S2 ⋅ S ) + {D (S 2 − Si (Si +1) / 3) + Ei (Si,x − Si,y ) +
ꢀ
B gSi B}
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ ˆ
∑
3
i
i,z
i=1
(eq. 1)
(eq. 2)
χcalc
χexp
=
15 octahedral geometry with
a [N3O3] environment due to
2zJ
1− (
)χcalc
coordination of one methanol molecule, one flat pymp ligand,
and two twisted pymp ligands. The flat pymp ligand serves as a
tridentate ligand, and the twisted ligands provide one pyridine N
and one phenolate O atom, respectively. The bond distances of
20 Co2-N/O are in the range of 2.018(3) – 2.137(3) Å, except Co2-
N4 = 2.397(4) Å. The bond angles of cis N–Co2–O/N vary from
59.88(14) to 109.48(13)°, which deviates substantially from an
ideal octahedral geometry. Co1 and Co2 are triply connected by
2
NAꢀB g2
where ꢀB, J, zJ, Di, Ei, Si, B, NA correspond to the Bohr magneton,
the intracluster and intercluster interaction, the axial and rhombic
55 ZFS parameters, the spin operator, the magnetic field vector, and
Avogadro’s constant, respectively. The best simulations are
found: for 1, J = 2.4 cm-1, giso = 2.48, DCo = -27.0 cm-1, E = 0, and
zJ = -0.04 cm-1; for 2, J = 0.65 cm-1, giso = 2.46, DCo = -28.5 cm-1,
E = 0, and zJ = -0.14 cm-1. On the basis of the J value, the first
60 excited state (S = 7/2) may be well isolated with an approximate
energy gap of 7.2 cm-1 (3J) from the ground state (ST = 9/2) in 1;
while the states may be heavily mixed in 2 due to the weaker
couplings. To date, structure-magneto correlation for the
anisotropic Co(II) system is still not clear, because of the
65 complications arising from orbital contributions, which are highly
dependent on the coordination geometry, as well as ligand field
around the metal center.13b,21 One purported hypothesis that has
gained general acceptance suggests that larger Co-O-Co angles
would allow for antiferromagnetic (AF) exchange while smaller
70 angles correspond to ferromagnetic (F) exchange.21 As such, a
crossover angle corresponding to AF/F transfer is likely to exist,
which may explain our observed significant change on the J
two
phenolate-O
bridges
with
Co1-O1/O2-Co2
=
25 94.30(0)/93.02(0)°, respectively, and one syn-syn N–C–N bridge,
leading to Co1–Co2 distance of 3.036(1) Å- slightly shorter than
that (3.049(3) Å) in 2. It should be mentioned that the smaller
bridging angle (92.19(10)°) of Co1-O2-Co2 in 2 may be due to
H-bonding between O2 and N6. Each molecule in 1 is well
30 isolated with the nearest intermolecular neighbor giving a
Co…Co distance of 8.541(3) Å, which is significantly longer
than that of 7.351 Å in 2 (Fig. S4).
Magnetic properties
Variable-temperature direct-current (dc) magnetic susceptibility
35 measured in an applied field of 1 kOe for both 1 and 2 is shown
in Fig. 2. The χmT value of ca. 8.95 and 8.70 cm3 mol−1 K for 1
and 2, respectively, at 300 K, is much higher than the spin-only
value (5.625 cm3 mol−1 K) for three isolated HS CoII metal ions,
Fig. 3 M vs. H plot at 1.8 K for 1. The solid line represents the simulation
by PHI based on eq. 1 with J = 2.4 cm-1, giso = 2.48, DCo = -27.0 cm-1 and
E = 0. Inset: Reduced magnetization data for 1 in applied fields (30, 50
and 70 kOe) at temperatures between 1.8 and 3.0 K; the solid lines
Fig. 2 χmT vs. T in an applied field of 1 kOe for 1 and 2: the solid lines
represent the best simulations via a linear trimeric model by PHI
program.
represent the best fitting via ANISOFIT2.0
.
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values, even though only a small variation exists in the related
bridging angles [∠Co1-O1/O2-Co2 = 94.30(0)/93.02(0)° for 1
and 94.61(9)/92.19(9)° for 2]. Furthermore, the different donor
ligand strength (σ-donor (MeOH) in 1 and π-donor (pya) in 2)
may also play a vital role.22 However, our attempts on replacing
pya with methanol in 2 or methanol with pya in 1 did not succeed.
The isothermal magnetization (M) as a function of the applied
field (H) was collected at 1.8 K for both 1 and 2 (Fig.s 3 and S5).
The magnetization did not saturate up to 7.0 T and the values of
5
10 6.9 Nβ and 6.5 Nβ for 1 and 2, respectively, are substantially
smaller than the expected value (> 9.0 Nβ) when g > 2.0 for an ST
= 9/2 magnetic ground state. This behaviour indicated strong
magnetic anisotropy, which was further confirmed by the reduced
magnetizations measured in the range of 1.8 to 3.0 K at applied
15 fields of 3, 5 and 7 T, where the isofield lines are non-
superimposable (Inset of Fig.s 3 and S5). The best fit to the data
by using Anisofit 2.023 for a ST = 9/2 spin model gave: for 1, D =
−6.5 cm−1, E = 0.009 cm-1, and giso = 2.56 with R = 9.4 × 10-5; for
2, D = -2.3 cm-1, E = 0.016 cm-1, and giso = 2.05 with R = 1.1 ×
20 10-3 {R = ∑(Mexp-Mfit)2/∑(Mexp2)}. The resulting smaller giso
value for 2 demonstrated that the spin model (ST = 9/2) may not
be suitable due to the weaker intracluster interactions. It should
be mentioned that the D value for 1 is among the largest for all
cluster-based SMMs,9a,24 and may lead to an energy barrier of U
25 = 130 cm-1. Additionally, the simulation by using the same set of
parameters (vide supra) for M-T data roughly matches with the
M-H data for 1, however, the effort to extract reasonable
parameters for 2 did not succeed. Interestingly, the extracted
global molecular D (-6.5 cm-1) and the single ion DCo (-27.0 cm-1)
30 for 1 follows the calculated expression of D(9/2) ≈ 0.25DCo.25 It
may be mentioned that no hysteresis loop of magnetization was
observed for 1 at 1.9 K (Fig. S6).
To probe the magnetization dynamics of 1 and 2, ac
susceptibility data was collected at different frequencies and
35 under zero and nonzero static fields below 5 K. Frequency
dependent ac susceptibility for 1 at zero dc field reveal the
beginning of out-of-phase signals, although no maxima are
observed (Fig. S7). As Co(II)-SMMs are known to show a high
prevalence of fast quantum tunnelling at zero field, applied dc
40 fields could efficiently reduce this probability.8 Additional ac
measurements were collected under small dc fields (Hdc ≤ 1500
Oe) at 1.8 K (Fig. S8). As expected, the relaxation in
magnetization was dramatically decreased even under a very
small dc field with the characteristic frequency (maximum in the
45 χm″ vs v plot) appearing at ~110 Hz (300 Oe), and 65 Hz (500
Oe), etc. The Cole−Cole plots fitted by the generalized Debye
model26 gave α parameters of 0.14-0.19 and relaxation times from
1.2 × 10-3 to 1.3 × 10-3 s (Fig. S9, Table S1).
Fig. 4 (a) Variable-temperature and (b) variable-frequency in-phase and
out-of-phase components of the ac magnetic susceptibility data for 1,
collected at temperatures of 1.8 – 2.6 K with a dc applied field of 500 Oe
and ac field of 3 Oe; (c) Arrhenius plot of relaxation time, as determined
through variable temperature (black) and variable-frequency (blue) ac
susceptibilities.
frequency data collected in the temperatures 1.8 – 2.6 K show
60 highly frequency dependent peaks (Fig. 4b). The relaxation time
follows an Arrhenius law: τ = τ0 exp(Ueff/kBT) with an energy
gap, Ueff = 17.2(3) cm-1 and τ0 = 6.6(7) × 10−9 s (Fig. 4c). The
energy barrier and pre-exponential constant are comparable with
those of previously reported Co(II)-SMMs as well as [CoII2GdIII]
65 SMM under an applied dc field.14b The significant increase for
the characteristic frequency-dependence under dc fields confirms
the presence of strong quantum tunnelling at zero field. However,
the effective barrier height is still far lower than the calculated
value (-130 cm-1, vide supra), indicating that the quantum
70 tunnelling effect is the predominant relaxation mode. The
Cole−Cole plots (Fig. S10) of 1 at temperatures between 1.80 and
2.60 K exhibit a symmetric shape and can be fit to the
generalized Debye model, with α parameters of 0.08-0.18 (Table
S2), which supports a relative narrow distribution of relaxation
75 times.26
For compound 2, in the absence of an applied dc field, no out-
of-phase (χ″) signals were observed at frequencies up to 9999 Hz
and temperatures down to 1.8 K. However, under a 1 kOe applied
field, strong frequency-dependent tails of χ″ appear, suggesting
80 SMM behaviour with fast quantum tunnelling (Fig. S11).
For comparison, rough estimations of Ueff and τ0 for both 1
and 2 by fitting the experimental data at 4111 Hz based on a
relative expression suitable for cluster compounds with only one
characteristic relaxation process:28 ln(χ″/χ′) = ln(ωτ0)+Ueff/(kBT),
85 gave Ueff (1 kOe) = 18.0(2) cm-1 and τ0 = 1.9 × 10-8 s for 1 and
Ueff (1kOe) = 7.9(1) cm-1 and τ0 = 8.5 × 10-8 s for 2 (Fig. S12).
We presumptively attribute the slow relaxation in 2 to single-ion
behavior instead of cluster behavior due to the weak couplings.
As a result, the effective energy barrier for 1 is two times higher
90 than that for 2. Overall, this work gives evidence for the potential
co-alignment of the anisotropy tensors in linear trinuclear systems
- making them an ideal target for large global anisotropy.29
Detailed ac magnetic susceptibility for 1 was measured as a
50 function of both temperature (1.8 – 4.0 K) and frequency (1-1500
Hz) in an applied dc field of 500 Oe. Remarkably, strong
frequency-dependent peaks in both in-phase and out-of-phase
components of the susceptibility appear below 4 K with the peaks
for 1400 Hz occurring at ∼2.5 K and 100 Hz at ∼1.9 K (Fig. 4a).
55 The ratio (χm′:χm″ ≈ 3:1) is in agreement with other well-
established SMMs.7 The shift of peak temperature (Tp) in χm′′ is
measured by the parameter φ = (ꢁTp/Tp)/ꢁ(logf) ≈ 0.20, which
also confirms super paramagnetic behaviour.27 Variable-
Conclusions
4
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In summary, we characterized the first linear trinuclear [CoII ]
11290; (l) J. M. Zadrozny, J. J. Liu, N. A. Piro, C. J. Chang, S. Hill
and J. R. Long, Chem. Commun. 2012, 48, 3927; (m) J. Vallejo, I.
Castro, R. Ruiz-García, J. Cano, M. Julve, F. Lloret, G. De Munno,
W. Wernsdorfer and E. Pardo, J. Am. Chem. Soc. 2012, 134, 15704;
(n) S. A. Cantalupo, S. R. Fiedler, M. P. Shores, A. L. Rheingold and
L. H. Doerrer, Angew. Chem. Int. Ed. 2012, 51, 1000; (o) J. M.
Zadrozny and J. R. Long, J. Am. Chem. Soc. 2011, 133, 20732; (p) D.
Weismann, Y. Sun, Y. Lan, G. Wolmershäuser, A. K. Powell and H.
Sitzmann, Chem. – Eur. J., 2011, 17, 4700; (q) T. Jurca, A. Farghal,
P. H. Lin, I. Korobkov, M. Murugesu and D. S. Richeson, J. Am.
Chem. Soc. 2011, 133, 15814.
(a) I.-R. Jeon, J. G. Park, D. J. Xiao and T. D. Harris, J Am Chem
Soc, 2013, 135, 16845; (b) S. Fortier, J. J. Le Roy, C.-H. Chen, V.
Vieru, M. Murugesu, L. F. Chibotaru, D. J. Mindiola and K. G.
Caulton, J. Am. Chem. Soc. 2013, 135, 14670; (c) S. Demir, J. M.
Zadrozny, M. Nippe and J. R. Long, J. Am. Chem. Soc. 2012, 134,
18546.
3
SMM with an effective energy barrier of 17.2(3) cm-1 under 500
Oe dc field and found significant ferromagnetic couplings (J =
+2.4 cm-1) in 1. Our result suggests that even a slight change in
the coordination environments of the cobalt centers have a
distinct influence on the magnetic properties.
70
75
80
5
Acknowledgments
This work was supported by NSFC (21321001) and the National
Basic Research Program of China (2013CB933400).
9
10 Notes and references
a Beijing National Laboratory for Molecular Sciences, State Key
Laboratory of Rare Earth Materials Chemistry and Applications, College
of Chemistry and Molecular Engineering, Peking University, 100871
Beijing, China. E-mail: gaosong@pku.edu.cn; yuanzhuzhang@gmail.com.
15 b Department of Chemistry, Texas A & M University, College Station, TX
77842-3012 (USA).
c Department of Chemistry, Beijing Normal University, Beijing 100875,
P. R. China
† Electronic Supplementary Information (ESI) available: additional
85 10 (a) E.-C. Yang, D. N. Hendrickson, W. Wernsdorfer, M. Nakano, L.
N. Zakharov, R. D. Sommer, A. L. Rheingold, M. Ledezma-Gairaud
and G. Christou, J. Appl. Phys. 2002, 91, 7382; (b) K. W. Galloway,
A. M. Whyte, W. Wernsdorfer, J. Sanchez-Benitez, K. V. Kamenev,
A. Parkin, R. D. Peacock and M. Murrie, Inorg. Chem. 2008, 47,
90
7438.
11 Q. Chen, M.-H. Zeng, Y.-L. Zhou, H.-H. Zou and M. Kurmoo, Chem.
Mater. 2010, 22, 2114.
12 (a) Y. Z. Zhang, W. Wernsdorfer, F. Pan, Z. M. Wang and S. Gao,
Chem. Commun. 2006, 3302; (b) X.-T. Wang, B.-W. Wang, Z.-M.
Wang, W. Zhang and S. Gao, Inorg. Chim. Acta, 2008, 361, 3895.
13 (a) A. Ferguson, A. Parkin, J. Sanchez-Benitez, K. Kamenev, W.
Wernsdorfer and M. Murrie, Chem. Commun. 2007, 3473; (b) M.
Moragues-Canovás, C. E. Talbot-Eeckelaers, L. Catala, F. Lloret, W.
Wernsdorfer, E. K. Brechin and T. Mallah, Inorg. Chem. 2006, 45,
7038.
14 (a) V. Chandrasekhar, B. M. Pandian, J. J. Vittal and R. Clérac, Inorg.
Chem. 2009, 48, 1148; (b) V. Chandrasekhar, B. M. Pandian, R.
Azhakar, J. J. Vittal and R. Clérac, Inorg. Chem. 2007, 46, 5140.
15 Y.-Z. Zheng, M. Speldrich, H. Schilder, X.-M. Chen and P. Kogerler,
Dalton Trans, 2010, 39, 10827.
20 magnetic data of
supplementary crystallographic data can be also obtained free of charge at
www.ccdc.cam.ac.uk/data_request/cif.
1 and 2. CCDC-823183 for 1 contains the
95
1
2
D. Gatteschi and R. Sessoli, Angew. Chem. Int. Ed. 2003, 42, 268.
(a) O. Waldmann, Inorg. Chem. 2007, 46, 10035; (b) F. Neese and D.
A. Pantazis, Dalton Trans. 2011, 148, 229.
25
30
35
40
45
50
55
60
65
3
4
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.
J. Vallejo, A. Pascual-Alvarez, J. Cano, I. Castro, M. Julve, F. Lloret,
J. Krzystek, G. De Munno, D. Armentano, W. Wernsdorfer, R. Ruiz-
Garcia and E. Pardo, Angew. Chem. Int. Ed. 2013, 52, 14075.
D. N. Woodruff, R. E. P. Winpenny and R. A. Layfield, Chem. Rev.
2013, 113, 5110.
100
105
5
6
16 X. Lin, J. Tao, R.-B. Huang and L.-S. Zheng, Inorg. Chem. Commun.
2009, 12, 154.
17 H. L. Zhu and X. Y. Liu, Syn. React. Inorg. Met.-Org, Nano-Met.
Chem. 2005, 35, 193.
(a) J. M. Zadrozny, D. J. Xiao, M. Atanasov, G. J. Long, F.
Grandjean, F. Neese and J. R. Long, Nat. Chem. 2013, 5, 577; (b) P.
H. Lin, N. C. Smythe, S. I. Gorelsky, S. Maguire, N. J. Henson, I.
Korobkov, B. L. Scott, J. C. Gordon, R. T. Baker and M. Murugesu,
J. Am. Chem. Soc. 2011, 133, 15806; (c) D. E. Freedman, W. H.
Harman, T. D. Harris, G. J. Long, C. J. Chang and J. R. Long, J. Am.
Chem. Soc. 2010, 132, 1224; (d) S. Mossin, B. L. Tran, D. Adhikari,
M. Pink, F. W. Heinemann, J. Sutter, R. K. Szilagyi, K. Meyer and
D. J. Mindiola, J. Am. Chem. Soc. 2012, 134, 13651; (e) R. Ruamps,
R. Maurice, L. Batchelor, M. Boggio-Pasqua, R. Guillot, A. L. Barra,
J. J. Liu, E. Bendeif, S. Pillet, S. Hill, T. Mallah and N. Guihery, J.
Am. Chem. Soc. 2013, 135, 3017; (f) R. C. Poulten, M. J. Page, A. G.
Algarra, J. J. Le Roy, I. López, E. Carter, A. Llobet, S. A. Macgregor,
M. F. Mahon, D. M. Murphy, M. Murugesu and M. K. Whittlesey, J.
Am. Chem. Soc. 2013, 135, 13640.
M. Murrie, Chem. Soc. Rev. 2010, 39, 1986 and references therein.
(a) M. R. Saber and K. R. Dunbar, Chem. Commun. 2014; (b) R.
Ruamps, L. J. Batchelor, R. Guillot, G. Zakhia, A.-L. Barra, W.
Wernsdorfer, N. Guihery and T. Mallah, Chem. Sci. 2014, 5, 3418;
(c) R. Herchel, L. Váhovská, I. Potočňák and Z. Trávníček, Inorg.
Chem. 2014, 53, 5896; (d) R. Boča, J. Miklovič and J. Titiš, Inorg.
Chem. 2014, 53, 2367; (e) Y. Y. Zhu, C. Cui, Y. Q. Zhang, J. H. Jia,
X. Guo, C. Gao, K. Qian, S. D. Jiang, B. W. Wang, Z. M. Wang and
S. Gao, Chem. Sci. 2013, 4, 1802; (f) J. M. Zadrozny, J. Telser and J.
R. Long, Polyhedron, 2013, 64, 209; (g) F. Yang, Q. Zhou, Y. Zhang,
G. Zeng, G. Li, Z. Shi, B. Wang and S. Feng, Chem. Commun. 2013,
49, 5289; (h) R. Ruamps, L. J. Batchelor, R. Maurice, N. Gogoi, P.
Jimenez-Lozano, N. Guihery, C. de Graaf, A. L. Barra, J. P. Sutter
and T. Mallah, Chem-Eur J, 2013, 19, 950; (i) M. Idešicová, J. Titiš,
J. Krzystek and R. Boča, Inorg. Chem. 2013, 52, 9409; (j) W. Huang,
T. Liu, D. Wu, J. Cheng, Z. W. Ouyang and C. Duan, Dalton Trans,
2013, 42, 15326; (k) F. Habib, O. R. Luca, V. Vieru, M. Shiddiq, I.
Korobkov, S. I. Gorelsky, M. K. Takase, L. F. Chibotaru, S. Hill, R.
H. Crabtree and M. Murugesu, Angew. Chem. Int. Ed. 2013, 52,
110 18 G. A. Bain and J. F. Berry, J. Chem. Edu., 2008, 85, 532.
19 O. Kahn, Molecular Magnetism, VCH: New York, NY, 1993.
20 N. F. Chilton, R. P. Anderson, L. D. Turner, A. Soncini and K. S.
Murray, J. Comput. Chem. 2013, 34, 1164.
21 (a) G. A. Seisenbaeva, M. Kritikos and V. G. Kessler, Polyhedron,
115
2003, 22, 2581; (b) G. A. Seisenbaeva, T. Mallah and V. G. Kessler,
Dalton Trans. 2010, 39, 7774; (c) D. Aguila, L. A. Barrios, O.
Roubeau, S. J. Teat and G. Aromi, Chem. Commun. 2011, 47, 707.
22 H. I. Karunadasa, K. D. Arquero, L. A. Berben and J. R. Long, Inorg.
Chem. 2010, 49, 4738.
120 23 M. P. Shores, J. J. Sokol and J. R. Long, J. Am. Chem. Soc. 2002,
124, 2279.
24 C. F. Wang, J. L. Zuo, B. M. Bartlett, Y. Song, J. R. Long and X. Z.
7
8
You, J. Am. Chem. Soc. 2006, 128, 7162.
25 O. Waldmann, Inorg. Chem., 2007, 46, 10035.
125 26 R. Schenker, M. N. Leuenberger, G. Chaboussant, D. Loss and H. U.
Gudel, Phys. Rev. B, 2005, 72.
27 S. M. J. Aubin, Z. Sun, L. Pardi, J. Krzystek, K. Folting, L.-C.
Brunel, A. L. Rheingold, G. Christou and D. N. Hendrickson, Inorg.
Chem. 1999, 38, 5329.
130 28 J. Bartolome, G. Filoti, V. Kuncser, G. Schinteie, V. Mereacre, C. E.
Anson, A. K. Powell, D. Prodius and C. Turta, Phys. Rev. B. 2009, 80,
014430.
29 Y. Z. Zhang, U. P. Mallik, N. P. Rath, R. Clerac and S. M. Holmes,
Inorg. Chem. 2011, 50, 10537.
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Dalton Transactions
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DOI: 10.1039/C4DT03545C
The first linear trinuclear [CoII ] SMM is achieved due to
3
significant intracluster ferromagnetic couplings. This study
highlights that miniscule changes in the coordination
environment of the cobalt centers in this structural
archetype can have a drastic effect on the observation of
SMM behavior.
5
6
|
Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]