A one dimensional coordination polymer composed of antiferromagnetically coupled disk-like [Mn7] units

Article abstract of DOI:10.1039/c8ce01374h

The synthesis, characterization by X-ray analysis and magnetic properties of a one dimensional coordination polymer {[Mn₇(OH)₂(dhap)₂(N₃)₃(MeCN)₄(ClO₄)₂]·2(MeCN)·2(ClO₄)}_∞ (1) are reported. The ligand dhapH₄ in the complex is 2,6-bis[N,N-di(hydroxyethyl)aminomethyl]pyridine. This compound crystallizes in the monoclinic space group C2/c. Each [Mn₇(OH)₂(dhap)₂(N₃)₃(MeCN)₄(ClO₄)₂] unit (abbreviated by Mn₇) is linked end-to-end by azido ligands to its neighboring units to form a one dimensional polymer. Magnetic susceptibility measurements indicate that the polymer is composed of S = 8 units with inter-Mn₇-unit antiferromagnetic coupling. The Jahn-Teller axes of the Mn₇ units are arranged in a zigzag manner along the polymer chain which induces spin canting at low temperatures. The slow magnetization relaxation at low temperatures was evidenced by observing out-of-phase signals in ac magnetic susceptibility measurements that give U_eff = 47.5 K and Δ₀ = 2.7 × 10^-13 s. This phenomenon also indicates that this one dimensional coordination polymer functions as a single-chain magnet (SCM).

Full text of DOI:10.1039/c8ce01374h

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PAPER
A one dimensional coordination polymer
composed of antiferromagnetically coupled
Cite this: CrystEngComm, 2018, 20,
963
6
disk-like [Mn ] units†
7
a
a
a
a
En-Che Yang, * Han-Sheng Huang, Shao-Yun Huang, Shi-Yi Huang,
a
b
c
c
Yu-Ying Chang, Gene-Hsiang Lee, Hwo-Shuenn Sheu and Chung-Kai Chang
The synthesis, characterization by X-ray analysis and magnetic properties of a one dimensional coordina-
tion polymer {[Mn IJOH) IJdhap) IJN IJMeCN) IJClO ]·2IJMeCN)·2IJClO )} (1) are reported. The ligand dhapH
in the complex is 2,6-bisijN,N-diIJhydroxyethyl)aminomethyl]pyridine. This compound crystallizes in the
monoclinic space group C2/c. Each [Mn IJOH) IJdhap) IJN IJMeCN) IJClO ] unit (abbreviated by Mn ) is
linked end-to-end by azido ligands to its neighboring units to form a one dimensional polymer. Magnetic
susceptibility measurements indicate that the polymer is composed of S = 8 units with inter-Mn -unit anti-
7
2
2
)
3 3
4
)
4 2
4
∞
4
7
2
2
)
3 3
4
)
4 2
7
7
Received 15th August 2018,
Accepted 5th October 2018
ferromagnetic coupling. The Jahn–Teller axes of the Mn units are arranged in a zigzag manner along the
7
polymer chain which induces spin canting at low temperatures. The slow magnetization relaxation at low
temperatures was evidenced by observing out-of-phase signals in ac magnetic susceptibility measure-
DOI: 10.1039/c8ce01374h
−13
ments that give Ueff = 47.5 K and Δ
0
= 2.7 × 10 s. This phenomenon also indicates that this one dimen-
rsc.li/crystengcomm
sional coordination polymer functions as a single-chain magnet (SCM).
magnetization relaxation. We now understand that most
Introduction
SCMs actually display slow magnetization relaxation with
both magneto anisotropy and short range interactions being
used as their driving force. Although many predictions were
made concerning this before the end of the last century, the
1
,2
Coordination polymers have attracted substantial interest,
not only due to the challenges associated with their molecular
architecture but also for their applications as catalysts and
sensors and for their luminescence properties. The magnetic
properties of these materials are also of interest. Assuming
that molecular magnets are arranged regularly in the lattice,
10
very first experimental example reported was SCMs in 2001.
Thereafter, Clérac and coworkers developed a series of
theoretical and experimental methods for modeling the mag-
3–5
11–15
they could be used in quantum computing
as well as in
netic properties of SCMs.
Since that report, many SCMs
6
16–18
high-density memory devices. Single chain magnets, SCMs,
represent a type of molecule that would be intermediate be-
tween coordination polymers and molecular magnets. SCMs
are molecular magnets which also show slow magnetization
were reported in the literature.
antiferromagnetic coupled SCMs or SCMs using SMMs as
building blocks are still quite rare. It is noteworthy that, in a
Nevertheless, cases of
1
9
previous paper, we reported the preparation of disk-like Mn
7
4
,7
20
relaxation processes that would permit out-of-phase signals
from ac magnetic susceptibility measurements and even mag-
netization hysteresis loops to be observed. Certain types of
molecules have the ability to show an energy barrier for spin
SMMs. In that study, we classified all of the known Mn
7
molecules into four categories based on their oxidation states.
II
3
III 21–25
II
III 25–33
They include the following: Mn
Mn
4
,
Mn
4 3
Mn ,
II
IV 30
II
II
III 20
Mn
4
Mn
3
,
Mn
7
(ref. 34) and Mn Mn
6
.
Herein, we report
8
flip based on their magneto anisotropy. In 1963, Glauber
proposed that even a simple Ising chain can display slow
the preparation of a new ligand, dhapH , as shown in
4
9
Scheme 1. Using this ligand, we were able to prepare a new
a
Department of Chemistry, Fu Jen Catholic University, Hsinchuang, New Taipei
City, 24205, Taiwan, Republic of China. E-mail: 071549@mail.fju.edu.tw
b
Instrumentation Centre, College of Science, National Taiwan University, Taipei,
1
06, Taiwan, Republic of China
c
National Synchrotron Radiation Research Center, NSRRC, Hsinchu City 300,
Taiwan, Republic of China
†
Electronic supplementary information (ESI) available. CCDC 1496544. For ESI
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
c8ce01374h
Scheme 1 Synthesis of 2,6-bisijN,N-diIJhydroxyethyl)aminomethyl]pyridine
(dhapH ).
4
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−
1
Mn unit that could be used as a building block that was anti-
days. IR (cm ): 3383(br), 2883(s), 2092(vs), 1610(s), 1581(s),
1456(s), 1346(s), 1313(s), 1270(s), 1088(vs), 921(s), 887(s),
7
ferromagnetically coupled to give an SCM. Slow magnetiza-
tion relaxation was clearly observed as the result of a finite-
4 7 19
802(s). Elemental analysis (C38H60Cl Mn N O26): found
(calc): C: 26.45 (26.85); H: 3.51 (3.85); N: 15.42 (15.02).
2
2,35
size effect.
Experimental section
Powder X-ray diffraction patterns
General procedures and materials
Powder X-ray diffraction patterns were collected on beamline
TPS09A at the Taiwan Photon Source (TPS) of the National
Synchrotron Radiation Research Center (NSRRC). The X-ray
source of TPS09A comes from an in-vacuum undulator (IU22)
which provides an X-ray energy covering 8–25 keV. The
powder diffraction patterns were recorded by means of a
position-sensitive detector composed of 24 K MYTHEN-II
detector modules that covered a 2θ range of 120° with an
angular resolution of 0.005° and an exposure time of 30 s.
The detector was mounted on a concentric large three-circle
diffractometer with a sample to detector distance of 760 mm.
A powdered sample was produced by grinding some large
crystals together with the mother liquid and loaded into a
0.5 mm capillary for faster rotation during the data collec-
tion. The powder diffraction patterns were recorded at 15 keV
X-rays and calibrated using the Bragg peaks of the NIST LaB6
standard.
All manipulations were performed under aerobic conditions.
All the chemicals were of commercial grade and were used
without further purification.
3
6
2
,6-bisIJBromomethyl)pyridine . To a solution of 2,6-
pyridinedimethanol (6.96 g, 50 mmol) in 90 mL of CHCl in
an ice bath, a mixture of 14.5 mL (50 mmol) PBr and 10 mL
CHCl was added dropwise. After the completion of the addi-
3
3
3
tion, the solution was allowed to warm to room temperature
and was then refluxed for 7 hours. After cooling, 80 mL of
distilled water was added and the stirring was continued
overnight. After the solution was filtered, the product was
obtained by extraction with CH Cl . The organic layer was
2
2
then dried over anhydrous MgSO
4
. The product was obtained
1
in 70% yield as a white solid by evaporating the solvent. H-
NMR (CDCl ): δ 7.72 (t, 1H, pyridine-H), δ 7.38 (d, 2H, pyri-
3
1
3
2
dine-H), δ 4.55 (s, 4H, CH Br); C-NMR: δ 33.3, δ 123.0, δ
−
1
1
1
1
8
2
3
38.4, δ 156.7. IR (cm ): 3435(br), 3021(w), 2967(w), 1990(w),
906(w), 1821(w), 1630(m), 1590(s), 1571(s), 1452(s), 1384(w),
322(w), 1274(w), 1204(s), 1161(m), 1083(m), 993(m), 957(w),
68(w), 818(s), 747(vs), 586(vs), 553(s). HRESI-MS [M] :
63.9020. Elemental analysis (C H NBr ): found (calc): C:
1.36 (31.73); H: 2.62 (2.66); N: 5.25 (5.26).
,6-bisijN,N-diIJHydroxyethyl)aminomethyl]pyridine (dhapH4).
A mixture of NMe HCO (6.76 g, 50.0 mmol) and NMe OH
X-ray crystallography. A suitable crystal was selected for
X-ray analysis on a Bruker SMART CCD diffractometer with
Mo Kα radiation (λ = 0.71073 Å). The temperature of the crys-
tal was controlled using an Oxford Cryosystems Cryostream
Cooler. The detector distance was maintained at 5.00 cm
from the crystal. Crystallographic data were collected over a
hemisphere of reciprocal space, by a combination of four sets
of exposures. Each set had a different φ angle for the crystal
and each 5 second exposure covered 0.30° in ω. Empirical
absorption was based on symmetry-equivalent reflections,
+
7
7
2
3
7
2
4
3
4
(
4.56 g, 50.0 mmol) was stirred for 30 minutes and then
added to a solution of 2,6-bisIJbromomethyl)pyridine (6.63 g,
5.0 mmol) and diethanolamine (5.26 g, 50.0 mmol) in 100
38
2
and the data were applied using the SADABS program. The
SHELXTL program on a PC computer was used for the struc-
ture analysis. The structure was solved using the Shelxs-97
mL of isopropanol. The resulting solution was refluxed for 24
hours. The filtrate was then evaporated to dryness and
redissolved in distilled water, which was then extracted with
3
9
40
program and refined using the Shelxl-97 program by the
2
2 2
CH Cl . The organic layer was then evaporated to give a
full-matrix least squares method on F values. Non-hydrogen
1
brown solid product in 62% yield. H-NMR (CDCl ): δ 7.59 (t,
atoms were refined anisotropically. Hydrogen atoms were
fixed at the calculated positions and refined using a riding
model. Table 1 summarizes the unit cell and structure refine-
ment parameters for complex 1.
3
1
H, pyridine-H), δ 7.05 (d, 2H, pyridine-H), δ 3.73 (s, 4H,
CCH N), δ 3.58 (t, 8H, CH OH), δ 2.67 (t, 8H, NCH CH OH);
C-NMR: δ 58.5, δ 59.25, δ 121.5, δ 137.81, δ 159.69. IR
2
2
2
2
1
3
−
1
(
cm ): 3376(br), 2883(m), 1651(w), 1595(s), 1577(s), 1457(vs),
Physical property measurements. NMR spectra were
recorded on a Bruker AV-300 spectrometer. Infrared spectra
were recorded using KBr pellets on a Perkin Elmer 1600
1
363(w), 1158(w), 1075(vs), 1040(vs), 875(w), 776(w). HRESI-
+
MS [M + H] : 314.2074. Elemental analysis (C H N O ):
15
27 3 4
−
1
found (calc): C: 57.33 (57.49); H: 8.43 (8.68); N: 13.10 (13.41).
[Mn IJOH) IJdhap) IJN IJMeCN) IJClO ]·2IJClO )} (1). A
spectrometer in the 450–4000 cm range. DC magnetic sus-
ceptibility data were collected using a Quantum Design
MPMS7 system. Samples were restrained with Parafilm to
prevent torquing. Magnetic data were corrected for back-
ground caused by the gel cap and the Parafilm, and the dia-
magnetism correction was estimated from Pascal's constant.
Elemental analyses (C, H, and N) and dc magnetic suscepti-
bility measurements were performed by National Taiwan
University Instrument Centre, College of Science. AC mag-
netic susceptibility data were collected using the Quantum
{
7
2
2
3
)
3
4
4
)
2
4
∞
solution of dhapH4 (0.314 g, 1 mmol), NaN3 (0.065 g, 1
mmol) and Et N (0.102 g, 1 mmol) in 15 mL of MeCN was
3
4 2
stirred for 30 min. To this solution, a mixture of MnIJClO )
·
6H O (1.809 g, 5 mmol) in 10 mL of MeCN was added
2
dropwise, and the resulting solution was then stirred for an
additional hour. After filtering, diethyl ether vapor was
allowed to diffuse into the filtrate at 8 °C. Black crystals suit-
able for X-ray crystallography analysis were obtained after 5
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Table 1 Crystallographic data of complex 1
1
Formula
C
38 60 19 26
H N N21Cl14O
−
1
F
w
, g mol
1725.37
Cryst syst
Space group
a (Å)
b (Å)
c (Å)
Monoclinic
C2/c
20.8441IJ10)
16.0569(8)
23.1343IJ11)
90
114.14605IJ11)
90
7064.6(6)
4
α (deg)
β (deg)
γ (deg)
3
V (Å )
Z
−3
Fig. 1 ORTEP plot of the Mn7 of 1 at the 30% probability level. Color
scheme: Mn, purple; O, red; N, blue; C, gray; Cl, green.
D (calcd, g cm
)
1.698
1.451
3656
−1
μ (mm
F (000)
θ range for data collection (deg)
)
2
1.66 to 27.50
−27 ≤ h ≤ 25
Index ranges
4
2–45
−
20 ≤ k ≤ 20
29 ≤ l ≤ 30
coordinated polymer chain.
in an end-to-end μ1,3 form.
The azide ligand is oriented
Based on reports in the litera-
4
6,47
−
No. of measured reflns
26 970
ture, an end-to-end μ1,3 bridging form usually leads to anti-
No. of independent reflns
8104
0.0392
472
1.038
0.0527, 0.1438
0.0664, 0.1529
0.934, −0.731
48
ferromagnetic coupling. This appears to be the case for
complex 1. An inspection of the arrangement of the Mn
R
int
Refined params
7
2
Goodness-of-fit on F , S
units indicated that the molecules are not arranged in a par-
allel manner, but, rather, are arranged in a zig-zag pattern in
the direction of the one-dimensional chain which is illus-
a
b
b
R
R
1
, wR
2
[I ≥ 2σ(I)]
a
1
, wR
2
[all data]
−
3
Max, min electron density (e Å
)
= [P||F
||/P|F
= [PwIJF
P
trated in Fig. 2. This unparallel feature also leads to spin
a
b
2
0
2 2
4 1/2
R
1
0
| − |F
C
0
|]. wR
2
− F
C
) / wF
0
]
.
49–52
canting
of the antiferromagnetic chain.
Powder X-ray diffraction patterns
Design MPMS XL7 system found at the National Chiao Tung
University.
The synchrotron powder X-ray diffraction patterns of com-
pound 1 are shown in Fig. 3 (2θ in the range of 2–50° is
found in ESI† Fig. 2S). A simulated powder pattern of a single
crystal is also plotted together for comparison. The powdered
samples, while still in the mother liquid, were ground and
the resulting powder was loaded into the capillary to prevent
the crystals from collapsing due to drying and to maintain
their quality. The experimental data obtained from the syn-
chrotron X-ray powder diffraction pattern of compound 1 is
similar to that of the single crystal simulation. This result
confirms the integrity of the sample.
Results and discussion
Preparation and structure
The ligand utilized in this study, dhapH , was synthesized as
4
shown in Scheme 1. Upon combining the ligand with MnIJII)
at a 1 : 5 ratio under basic conditions, crystallization was ac-
complished by allowing ethyl ether vapor to diffuse into the
sample, which was in a refrigerator with the temperature be-
ing maintained at roughly 8 °C. Crystals of complex 1 were
isolated after 7 days.
An ORTEP plot of compound 1 is shown in Fig. 1. It can
be seen that the heptanuclear manganese Mn7 unit with
three MnIJIII) ions crossing the middle separate the other four
MnIJII) ions into two sets with two being located on each side.
The three MnIJIII) ions are arranged in a linear manner with
the two on the ends chelated by the heptadentate ligand
dhap with all four alcohol groups being deprotonated. Hence,
these two MnIJIII) units are seven coordinated but all of the
other manganese ions, irrespective of whether they carry a
Magnetic property measurements
To explore the magnetic properties of this one dimensional
chain, DC magnetic susceptibility measurements of complex
1 were carried out for a polycrystalline sample under a 1000
G magnetic field in the temperature range of 2–300 K. Fig. 4
shows the χ T vs. T plot of complex 1. The χ T value is 23.6
M
M
3
−1
cm K mol at 300 K which is quite close to the spin-only
value of 26.5 cm K mol for three uncoupled MnIJIII) ions
3
−1
plus four uncoupled MnIJII) ions in a Mn7 unit. The χ T
values were then maintained at about 23.5(3) cm K mol be-
tween 250–25 K and then dropped to 15.0 cm K mol at 2
K. A small shoulder was observed at around 5 K. This charac-
teristic suggests the possibility of spin canting in this
M
3
−1
charge of 2+ or 3+, are six coordinated. The Mn
7
unit of com-
3
−1
pound 1 has an inversion center. The two MnIJIII) ions on the
4
1
peripheral possess Jahn–Teller compression axes and the
middle MnIJIII) ion has a Jahn–Teller elongation axis. Selected
metal–ligand distances are listed in Table 2. The Mn units
complex. The χ T curve was then simulated using the intra-
7
M
in 1 are bridged by azide units and form a one-dimensional
molecular coupling pattern shown in Scheme 2 with the
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Table 2 Comparison of the structural parameters of the [Mn
CrystEngComm
7
] cores in compound 1
MnIJ1)–OIJ1)
MnIJ1)–OIJ2)
MnIJ1)–OIJ4)
MnIJ2)–OIJ2)
MnIJ2)–OIJ3)
MnIJ2)–OIJ4)
MnIJ2)–OIJ5)
MnIJ3)–OIJ3)
MnIJ3)–OIJ4)
1.9416(20)
1.9627(26)
2.1967(27)
2.3368(26)
1.8667(23)
2.1429(28)
1.8761(22)
2.1032(29)
2.2101(20)
MnIJ4)–OIJ1)
MnIJ4)–OIJ2)
MnIJ4)–OIJ5)
MnIJ2)⋯MnIJ1)
MnIJ3)⋯MnIJ1)
MnIJ4)⋯MnIJ1)
MnIJ4)⋯MnIJ2)
OIJ4)–MnIJ1)–OIJ4)A
OIJ3)–MnIJ2)–OIJ5)
2.2110(25)
MnIJ1)–OIJ1)–MnIJ3)
MnIJ1)–OIJ4)–MnIJ3)
MnIJ1)–OIJ2)–MnIJ2)
MnIJ1)–OIJ4)–MnIJ2)
MnIJ4)–OIJ2)–MnIJ2)
MnIJ4)–OIJ5)–MnIJ2)
MnIJ4)–NIJ4)–MnIJ3)
102.347IJ96)
97.614(97)
104.114IJ103)
103.088IJ107)
93.256(88)
2.2849(20)
2.1010(28)
3.3985(5)
3.3161(5)
3.2600(4)
3.3598(7)
180
115.18(13)
101.723IJ132)
178.637IJ124)
Fig. 2 One-dimensional chain of 1. Skeleton: Mn, green; O, red; N,
blue. C atoms were omitted for clarity.
Hamiltonian in eqn (1). The obtained magnetic susceptibili-
ties were treated by the inter-cluster interaction −2 J′S ·S .
2
2′
The simulations were obtained with the above patterns using
M
Fig. 4 Plot of χ T versus T of complexes measured in a 1 kG magnetic
5
3,54
the MAGPACK
program. The resulting simulation is then
field. The solid red line represents a theoretical simulation of the
experimental data.
presented as a red solid line in Fig. 4 with the parameters:
−
1
−1
−1
−1
J
1
= −3.5 cm , J
2
= −0.2 cm , J
3
= −0.15 cm , J
4
= +1.5 cm ,
−
1
J′ = −0.35 cm , and g = 1.9.
cates that the energy barrier for spin flipping cannot simply
be an appropriate model for a simple antiferromagnetic
chain with Mn repeating units. Nonetheless, even given this
7
deviation, the kinetic barrier for the spin-flip still follows the
Arrhenius law reasonably well.
Ĥ = −2J
1
(S
1
·S
4
+ S
1
·S
4
′
) −2J
2
(S
2
·S
4
+ S
2
′
·S
4
′
+ S
3
·S
3′
4
+ S
3
′
·S
4
′
)
−
2J (S ·S + S ·S + S ·S + S ·S ) −2J (S ·S + S ·S2′) (1)
2′
3′
3
1
2
1
1
3
1
4
2
3
Two conclusions can be drawn from this result. First, the
The overall energy barrier for spin flipping can be evalu-
ated by ac magnetic susceptibility measurements. In the case
of complex 1, the ac magnetic susceptibility measurements
were quite successful. The experimental results obtained for
the frequencies in the range of 10–1000 Hz and in the
temperature range of 1.9–3.5 K are shown in Fig. 5(a).
intracluster coupling can result in a Mn unit with S = 8. Nev-
7
−
1
ertheless, the inter-cluster coupling value (J′ = −0.35 cm ) is
stronger than the intra-cluster coupling (J and J ). This indi-
2
3
Scheme 2 Plot showing a simplified magnetic exchange coupling
Fig. 3 Synchrotron powder X-ray diffraction patterns of experimental
scheme for complex 1, where J
1 2 3
= Mn1–Mn4, J = Mn2IJ3)–Mn4, J =
data (top) and simulation (bottom).
Mn1–Mn2IJ3), and J = Mn2–Mn3 exchange pathways.
4
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7
Table 3 Comparison of disk-like Mn complexes
D
U
eff
−
1
Complex
S
(cm ) (K)
II
3
III
[
[
{
[
[
[
[
{
(
(
{
(
[
Mn
Mn
Mn
Mn
4
IJOMe)12IJdbm)
6
] CHCl
] 5C
]} 2CHCl
] CH OH
Cl ]IJCl)IJClO
]IJClO 3MeOH
]}
IJmda)
3
14MeOH
Cl
2
17/2 −0.27
II
3
III
4
IJ5-NO
2
-hbide)
6
2
H
4
19/2 −0.20 18.1
27/2 −0.05 10
31/2
II
II
2
III
3
Mn [Mn
Mn
IJnmdea)
IJOH)
4
Cl
6
IJL )
IJN
IJhmp)
IJteaH) IJtea)
6
3
II
3
III
Mn
Mn
Mn
Mn
4
6
)
3 6
3
II
4
III
3
Mn
Mn
3
9
3
4
)
11
11
−0.11
II
4
III
3
3
3
4
)
2
−0.08 19.5
II
II
3
III
4
NEt ]{Mn ijMn
Mn
3
Cl
6
IJmda)
6
II
III
3
[NaIJMeOH)
NHEt
NHEt
3
]ijMn
4
Mn
IJN
3
)
6
6 n
]}
11
11
11
16
16
−0.15
−0.13
II
4
III
3
)[Mn
Mn
Mn
3
Cl
6
IJmda)
IJmda)
IJteaH) ]}
6
IJteaH) ]
6
]
II
4
III
3
3
)[Mn
IJN
3
)
6
6
]
II
III
3
Na[Mn
4
Mn
IJN
3
)
3
6
6
n
−0.02
II
III
NHEt
3
) [Mn
4
Mn
IJN
3
)
6
II
4
III
3
Mn
Mn
3
F IJtea)IJteaH)IJteaH
2 2 4
) IJpiv) IJHpiv)IJchp)
3
]
0
.5MeCN
II
[
[
[
[
Mn
Mn
Mn Mn
Mn
7
IJpppd)
6
IJtea)IJOH)
IJOMe) ]ijNO
IJheamp) ]IJClO
IJpeolH)
IJdhap) IJN IJMeCN)
)}
3
]ijBF
·6MeOH
·4CH Cl
]IJBF
4
]
2
·2MeOH·2CH
2
Cl
2
5/2
5/2
II
7
IJpaa)
6
6
3 2
]
II
III
6
6
4
)
2
2
2
·H
·solv
IJClO
2
O
19/2 −0.16 14.4
II
4
IV
3
Mn
IJtea)IJteaH
IJOH)
2
)
3
4
4
)
2
23/2
II
III
3
{
[Mn
4
Mn
2
2
)
3 3
4
4
2
) ]
8
47.5
·2IJMeCN)·2IJClO
4 ∞
Ligand
hmpH
2-Hydroxymethylpyridine
Triethanolaminate
N-Methyldiethanolamine
teaH
mdaH
3
2
pppdH
paaH
Hdbm
1-Phenyl-3-(2-pyridyl)propane-1,3-dione
N-(2-Pyridinyl)acetoacetamide
Dibenzoylmethane
N-(2-Hydroxy-5-nitrobenzyl)
iminodiethanol
Fig. 5 (a) AC magnetic susceptibility out-of-phase signal (  ) data
M
for complex 1 collected in a 3.5 G oscillating field with frequencies of
1
0–1000 Hz in the temperature range of 1.9–3.5 K. The inset shows the
3
H (5-NO -hbide)
2
Arrhenius plot; the solid red line in the inset represents the least-
3
2
H L
N-n-Butyldiethanolamine
2-[N,N-di(2-Hydroxyethyl)
aminomethyl]phenol
squares fit. (b) AC magnetic susceptibility out-of-phase signal (  )
M
heampH
3
data for complex 2 collected in a 3.5 G oscillating field with frequen-
2
−
cies of 1–1000 Hz in the temperature range of 1.9–2.4 K.
nmdea
3 2 2 2
CH N(CH CH O)
dhapH
4
2,6-bis[N,N-di(Hydroxyethyl)
aminomethyl]pyridine
Frequency-dependent phenomena were clearly observed, thus
confirming that this 1D polymer is an SCM with an energy
barrier calculated from the Arrhenius plot (inset of Fig. 5(a))
II
III
states. The second category also has a Mn
3
Mn
4
oxidation
−
13 48
of Δeff = 47.5 K and τ = 2.7 × 10
s. Similar results were
state but the atoms are arranged in a quite different way
0
obtained in a second experiment where different frequencies
were scanned at a fixed temperature. These results are shown
in Fig. 5(b). The clear linear behaviour in the Arrhenius plot
implies that, although it cannot be explained by a simple
model composed of a weakly linked Mn unit SCM, the possi-
7
bility that it is an antiferromagnetic Ising SCM by an alter-
nate partition cannot be completely excluded.
(see Fig. 5S(b)†). The molecule also has a half-integer spin.
7
Most of the Mn members possess the third type of configu-
II
4
III
3
ration, Mn Mn . There are eight compounds that belong to
this category. Most compounds have S = 11. Nevertheless,
two S = 16 cases were also reported in the literature. The
II
III
different arrangement of Mn Mn in Fig. 5S(d)† is a spe-
4 3
cial case which belongs to the fourth category. The fifth
class has all the seven Mn centers possessing a charge of
2
+. Two complexes were reported in this class. They all ex-
Comparison of disk-like Mn
7
complexes
hibit antiferromagnetic coupling possessing S = 5/2. The
sixth kind, Mn Mn , has one MnIJII) ion sitting at the cen-
6
tre which is surrounded by six MnIJIII) ions that
ferromagnetically give S = 19/2. The seventh class has a
4 3
Mn Mn configuration. A large molecular spin of S = 23/2
II
III
In our previous study, we compared 14 different disk-like
2
0
Mn compounds. Since the appearance of that report, four
7
more compounds have been reported. Currently, there are 18
such compounds known, which are listed in Table 3. They
can be classified into eight categories according to their oxi-
II
IV
is obtained. The eighth type of disk-like Mn is obtained in
7
II
III 21–25
II
III 25–33
3
II
IV 30
II
dation states: Mn Mn ,
Mn Mn ,
Mn Mn , Mn7
the current work. This compound has three MnIJIII) ions
straddling the middle of the disk. Single chain magnetic
(SCM) behaviour was observed in this one dimensional co-
ordination polymer.
3
4
III
6
4
4
3
II
(
ref. 34) and Mn Mn
(ref. 20) (also see ESI† Fig. 5S). The
II
III
4
first class, Mn Mn , has three members. The odd number of
3
valence electrons causes them to exhibit half-integer spin
This journal is © The Royal Society of Chemistry 2018
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Conclusions
10 A. Caneschi, D. Gatteschi, N. Lalioti, C. Sangregorio, R.
Sessoli, G. Venturi, A. Vindigni, A. Rettori, M. G. Pini and
M. A. Novak, Angew. Chem., Int. Ed., 2001, 40, 1760–1763.
Herein, we report the preparation of a single-chain magnet
composed of disk-like Mn units, where the Mn unit was
7 7
prepared by a new procedure. The chain is composed of
MnIJII) ions that are connected by azido ligands in an end-to-
end manner, which leads to antiferromagnetic coupling
1
1 R. Clérac, H. Miyasaka, M. Yamashita and C. Coulon, J. Am.
Chem. Soc., 2002, 124, 12837–12844.
1
2 H. Miyasaka, R. Clérac, K. Mizushima, K.-i. Sugiura, M.
Yamashita, W. Wernsdorfer and C. Coulon, Inorg. Chem.,
7
between the Mn units. Upon examining the magnetic cou-
2
003, 42, 8203–8213.
pling strength between metal ions, we found that the inter-
cluster magnetic couplings are stronger than some of the
intra-cluster ones. This characteristic rules out the possible
1
3 H. Miyasaka, T. Nezu, K. Sugimoto, K.-i. Sugiura, M.
Yamashita and R. Clérac, Inorg. Chem., 2004, 43, 5486–5488.
4 C. Coulon, R. Clérac, L. Lecren, W. Wernsdorfer and H.
Miyasaka, Phys. Rev. B: Condens. Matter Mater. Phys.,
1
“weak link of the Mn7 unit” analysis. Upon checking the
magnetic coupling between MnIJII)–MnIJIII), the coupling
strength was found to be quite small which can potentially
break down the strong exchange limit, resulting in a giant
spin picture failure. It is quite obvious that this case can-
2
004, 69, 132408.
1
5 M. Ferbinteanu, H. Miyasaka, W. Wernsdorfer, K. Nakata,
K.-i. Sugiura, M. Yamashita, C. Coulon and R. Clérac, J. Am.
Chem. Soc., 2005, 127, 3090–3099.
7
not be explained by a weakly linked Mn chain. Based on
1
1
1
6 N. E. Chakov, W. Wernsdorfer, K. A. Abboud and G.
Christou, Inorg. Chem., 2004, 43, 5919–5930.
7 A. Escuer, G. Vlahopoulou and F. A. Mautner, Inorg. Chem.,
ac susceptibility measurements, however, the clear linearity
of the Arrhenius plots suggests that this complex still fol-
lows a one-dimensional Ising chain, but that the partition
is different. Overall, we have successfully synthesized a
SCM complex and determined that the energy barrier for
spin-flipping is 47.5 K.
2
011, 50, 2717–2719.
8 H.-L. Tsai, C.-I. Yang, W. Wernsdorfer, S.-H. Huang, S.-Y.
Jhan, M.-H. Liu and G.-H. Lee, Inorg. Chem., 2012, 51,
1
3171–13180.
1
2
2
2
9 M. Murugesu, M. Habrych, W. Wernsdorfer, K. A. Abboud
and G. Christou, J. Am. Chem. Soc., 2004, 126, 4766–4767.
0 S.-Y. Chen, C. C. Beedle, P.-R. Gan, G.-H. Lee, S. Hill and
E.-C. Yang, Inorg. Chem., 2012, 51, 4448–4457.
1 G. L. Abbati, A. Cornia, A. C. Fabretti, A. Caneschi and D.
Gatteschi, Inorg. Chem., 1998, 37, 3759–3766.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
2 S. Koizumi, M. Nihei, M. Nakano and H. Oshio, Inorg.
Chem., 2005, 44, 1208.
This work was supported by the Ministry of Science and Tech-
nology of Taiwan, R.O.C. (MOST106-2113-M-030-008).
23 S. Koizumi, M. Nihei, T. Shiga, M. Nakano, H. Nojiri, R. Bircher,
O. Waldmann, S. T. Ochsenbein, H. U. Gudel, F. Fernandez-
Alonso and H. Oshio, Chemistry, 2007, 13, 8445–8453.
2
4 T. Liu, B.-W. Wang, Y.-H. Chen, Z.-M. Wang and S. Gao, Z.
Anorg. Allg. Chem., 2008, 634, 778–783.
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