Construction and magnetic properties of hemicyclic “phoenix crown” manganese clusters: Molecular assembly from {Mn5} to {Mn10} cluster

Article abstract of DOI:10.1016/j.ica.2020.119438

Two high-nuclearity manganese clusters formulated as [Mn^IIMn^III₄(L)₂(Py)₈(N₃)₂]·2Py ({Mn₅} cluster) and [Mn^III₁₀(L)₅(DMF)₆(H₂O)₄]·5DMF·9H₂O ({Mn₁₀} cluster), (H₆L = N,N'-bis(2-salicylhydrazide)isophthalohydrazide, N₃^– = azide ion, Py = pyridine, and DMF = N,N'-dimethylformamide), were synthesized and structurally characterized. The four Mn^III ions and one Mn^II ion in {Mn₅} cluster are linked by two diacylhydrazine ligands to form hemicyclic “Phoenix crown” cluster structure. The {Mn₁₀} cluster presents a deca-nuclear skeleton, which appears to be structurally equivalent to two “Phoenix crown” {Mn₅} clusters bridged by a diacylhydrazine ligand. Interestingly, the double helix structure {Mn₁₀} clusters can be also obtained via a simply dissolving and reassembling process of the “Phoenix crown” {Mn₅} clusters in the mixed solution of DMF and CH₃OH. The magnetic measurements show that {Mn₅} and {Mn₁₀} clusters reveal antiferromagnetic interactions.

Full text of DOI:10.1016/j.ica.2020.119438

Journal Pre-proofs
Construction and magnetic properties of hemicyclic “phoenix crown” manga-
nese clusters: molecular assembly from {Mn5} to {Mn10} cluster
Qun Tang, Yanli Yang, Ze Cheng, Xiuni Chen, Qingmei Lin, Zhiming Zou,
Hua-Hong Zou, Fu-Pei Liang
PII:
S0020-1693(19)31720-7
https://doi.org/10.1016/j.ica.2020.119438
ICA 119438
DOI:
Reference:
Inorganica Chimica Acta
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31 December 2019
10 January 2020
Please cite this article as: Q. Tang, Y. Yang, Z. Cheng, X. Chen, Q. Lin, Z. Zou, H-H. Zou, F-P. Liang, Construction
and magnetic properties of hemicyclic “phoenix crown” manganese clusters: molecular assembly from {Mn5} to
{Mn10} cluster, Inorganica Chimica Acta (2020), doi: https://doi.org/10.1016/j.ica.2020.119438
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Construction and magnetic properties of hemicyclic
"phoenix crown" manganese clusters: molecular assembly
from {Mn5} to {Mn10} cluster
Qun Tanga, Yanli Yanga, Ze Chenga, Xiuni Chenb, Qingmei Linb, Zhiming Zoua,
Hua-Hong Zoub, and Fu-Pei Lianga,b*
a
Guangxi Key Laboratory of Electrochemical and Magneto-chemical Functional
Materials, College of Chemistry and Bioengineering, Guilin University of Technology,
Guilin, Guangxi 541004, China
b
State Key Laboratory for Chemistry and Molecular Engineering of Medicinal
Resources, School of Chemistry & Pharmacy of Guangxi Normal University, Guilin
Guangxi 541004, China.
* Corresponding author.
E-mail addresses: fliangoffice@yahoo.com.
1

Abstract
Two
high-nuclearity
manganese
clusters
formulated
cluster)
cluster),
as
and
=
[MnIIMnIII (L)2(Py)8(N3)2]·2Py
({Mn5}
({Mn10}
4
[MnIII10(L)5(DMF)6(H2O)4]·5DMF·9H2O
(H6L
-
N,N'-bis(2-salicylhydrazide)isophthalohydrazide, N3 = azide ion, Py = pyridine, and
DMF = N,N'-dimethylformamide), were synthesized and structurally characterized.
The four MnIII ions and one MnII ion in {Mn5} cluster are linked by two
diacylhydrazine ligands to form hemicyclic "Phoenix crown" cluster structure. The
{Mn10} cluster presents a deca-nuclear skeleton, which appears to be structurally
equivalent to two "Phoenix crown" {Mn5} clusters bridged by a diacylhydrazine
ligand. Interestingly, the double helix structure {Mn10} clusters can be also obtained
via a simply dissolving and reassembling process of the "Phoenix crown" {Mn5}
clusters in the mixed solution of DMF and CH3OH. The magnetic measurements
show that {Mn5} and {Mn10} clusters reveal antiferromagnetic interactions.
Keywords: High-nuclearity clusters; Manganese; Diacylhydrazine ligand; Assembly;
Magnetic properties
2

1. Introduction
The polynuclear metal cluster complexes synthesized by 3d metals have attracted
great interest given the structural aesthetics and their excellent applications in
molecular magnetic materials [1-6], optics [7-10], catalysts [11-14] and so on. When
such polynuclear metal clusters contain manganese(Ⅲ) ions, the high-spin ground
state and the apparent magnetic anisotropy of Mn(Ⅲ) ions (S = 2) can contribute to
unusual magnetic behavior such as single-molecule magnetism [2, 11]. During the
formation of Mn clusters, Mn ions stabilised in the formal oxidation state of trivalent,
even divalent and tetravalent states by ligand fields, which is conducive to obtaining
multinuclear Mn clusters with diverse structures and excellent properties [15-25].
For these reasons, the rational design and construction of polynuclear manganese
clusters has attracted considerable interest of many researchers.
In the synthesis of Mn clusters, there are two main types of ligands that are
classified as rigid ligands and flexible organic ligands. Usually, the ligands with
oxygen-containing groups and nitrogen-containing groups are propitious to the
construction of polynuclear metal clusters [26-34]. Some bridging atoms are
provided by these ligands to form O-bridge, N-bridge, N-N bridge, C-N bridge,
O-C-O bridge, etc., which can connect metal ions to form polynuclear metal clusters
[35-41]. The diacylhydrazine organic ligands are more flexible and possess more
coordination sites than the carboxylate ligand and nitrogen heterocyclic ring ligand, so
diacylhydrazine organic ligands contribute to the formation of multinuclear metal
3

clusters. In recent study, higher nuclear metal clusters with different nuclearities
depending on diacylhydrazine ligands have been reported [15, 17, 42-49]. The main
reasons for the formation of higher nuclear metal clusters constructed by such
diacylhydrazine ligands are due to the good bridging abilities and adequate positions
between acyl group groups and N–N bonds of diacylhydrazine ligands.
The
diacylhydrazine
organic
ligand
(N,N'-bis(2-salicylhydrazide)isophthalohydrazide, H6L) is a versatile bridging ligand,
which containing the phenyl-acylamide group, azide group and phenol hydroxy group
and providing multi-coordination sites and new coordination possibility. There are
multiple O-coordination and N-coordination sites in the diacylhydrazine H6L ligand,
which can capture many metal ions and help to form polynuclear metal clusters with
excellent properties.
Some polynuclear manganese clusters based on
diacylhydrazine ligands have been reported [46-50]. As part of our long-standing
interest, it is necessary to rationally design diacylhydrazide ligands to construct
polynuclear metal clusters, and systematically study the assembly rules and magnetic
properties of these clusters. Herein, two novel high-nuclearity manganese cluster
formuiated
as
[MnIIMnIII (L)2(Py)8(N3)2]·2Py
({Mn5}
cluster)
and
4
−
[MnIII (L)5(DMF)6(H2O)4]·5DMF·9H2O ({Mn10} cluster) (N3 = azide ion, Py =
10
pyridine, and DMF = N,N'-dimethylformamide), were constructed and synthesized
successfully
by
utilizing
diacylhydrazine
ligand
H6L
(N,N'-bis(2-salicylhydrazide)isophthalohydrazide) as a bridging ligand under different
reaction conditions.
The structures of {Mn5} and {Mn10} clusters were
4

characterized and confirmed by single crystal X-ray diffraction analyses, infrared (IR)
spectroscopy, elemental analyses, and powder X-ray diffraction (PXRD) analyses.
Furthermore, magnetic properties of {Mn5} and {Mn10} clusters were investigated.
2. Experimental
2.1. Materials and general methods
All chemical reagents and solvents for the synthesis of H6L ligand and the title
complexes were purchased from commercial sources and used without further
purification. Fourier transform infrared (FT-IR) spectra data with the range of
4000–400 cm−1 were recorded on a Perkin-Elmer Spectrum. Elemental analysis of
carbon, nitrogen and hydrogen for {Mn5} and {Mn10} clusters were performed on a
Model 2400 II, Perkin-Elmer elemental analyzer. The powder X-ray diffraction
(PXRD) data were collected using a Rigaku D/max 2500v/pc diffractometer with
Cu-Kα radiation (λ = 1.5418 Å) in the 2θ range of 3–60° at 293 K. All magnetic
data of {Mn5} and {Mn10} clusters were collected using a Quantum Design MPMS
SQUID-XL-7 magnetometer furnished with a 7 T magnet and PPMS DynaCool.
The diamagnetic contribution of the sample and sample holder was taken into account
when correcting the magnetic data.
2.2. Synthesis
Synthesis of the ligand H6L
5

The ligand H6L was synthesized according to the reported literature [51], and the
sturture of H6L was presented in Supporting Information Fig. S1. In an ice bath，10
mmol (2.03 g) of isophthaloyl dichloride was added to a solution of salicyloyl
hydrazide (3.65 g, 24 mmol) and triethylamine (1.7 mL, 12 mmol) in THF (60.0 mL).
The resulting solution was stirred at 0 °C for 2 h and then at room temperature for 48
h. The resulting white precipitate was filtered, washed with acetone, water and
anhydrous ether, and then vacuum-dried to give the ligand H6L in 85% yield. Anal.
Calc. for C22H18N4O6 (434.41) (%): C, 60.83; H, 4.18; N, 12.90. Found: C, 60.74；
H, 4.15；N, 12.86. IR data (KBr pellets, cm–1): 3219(m), 2976(vs), 2930(w),
2752(m), 2683(vs), 2494(m), 1660(w), 1618(vs), 1567(vs), 1484(vs), 1364(s), 1306(s),
1237(vs), 1163(m), 1109(m), 1103(m), 851(m), 744(s), 686(m).
Synthesis of {Mn5} cluster
Added 0.05 mmol (0.0216 g) of H6L, 0.10 mmol (0.0245 g) of Mn(OAc)2·4H2O
and 0.1 mmol (0.0065 g) of NaN3 respectively into a Pyrex tube with one end sealed,
followed by dropping into 1.2 mL ethanol and 6 drops of pyridine and then shaking
well to mix. Subsequently, the Pyrex tube was frozen in liquid nitrogen, vacuumed
and sealed at another end. After thawing at room temperature, the sealed Pyrex tube
was placed in an oven at 60 °C for 2 days and then slowly cooled to room temperature.
The resulting black bulk crystals were collected, washed with ethanol, and then air
dried. Yield: 75% (based on Mn2+), Anal. calcd (%) for C84H64N22O12Mn5 ({Mn5}
cluster)：C, 56.27; H, 3.72; N, 16.75. Found: C, 55.87; H, 3.59; N, 16.65. IR (KBr
pellet, cm–1): 3436 (m), 3062 (w), 2060 (vs), 1602 (s), 1568 (s), 1516 (vs), 1442 (vs),
6

1391 (m), 1357 (w), 1243 (m), 1162 (m), 1106 (w), 1037 (m), 1008 (w), 849 (w), 757
(vs), 700 (vs).
Synthesis of {Mn10} cluster
0.10 mmol (0.0245 g) of Mn(OAc)2·4H2O and 0.05 mmol (0.0216 g) of H6L were
respectively added into a mixed solvent of DMF (5.0 mL) and CH3OH (6.0 mL),
followed by gently stirring for 10 minutes at 30 ºC. Then added 1.0 mL pyrazine
aqueous solution (0.01 mol/L) into the above mixture solution with magnetic stirring
for 1 h. Subsequently, 4 drops of pyridine were added to the above solution with
further stirring for 8 h. The resulting mixture was then filtered to get brown and black
filtrate, which was keep at room temperature for six weeks to evaporate the solvent.
The obtained black crystals were collected, washed with CH3OH, and then air-dried.
Yield: 38% (based on Mn2+), Anal. calcd (%) for C143H163N31O54Mn10 ({Mn10}
cluster): C, 46.05; H, 4.41; N, 11.64. Found: C, 45.93; H, 4.38; N, 11.66. IR (KBr
pellet, cm–1): 3400(m, br), 1659(vs), 1603(s), 1573(s), 1523(w), 1499(s), 1431(m),
1394(m), 1357(m), 1234(vs), 1154(m), 1111(vs), 1037(w), 846(m), 767(m), 674(w).
Reassembling from {Mn5} to {Mn10} Cluster. Ca. 30 mg of the as-synthesized
{Mn5} cluster (single crystals) and 1.0 mL of pyrazine (0.01 mol/L) were respectively
added into a mixed solvent of DMF (4.0 mL) and CH3OH (8.0 mL), followed by
gently stirring for 1 h. Then the mixed solution was filtered, and the filtrate was
allowed to evaporate the solvent at room temperature for three weeks. The resulting
dark block crystals of {Mn10} cluster were collected in yields of about 67%.
7

2.3. X–ray crystallographic study
All the data for {Mn5} and {Mn10} clusters were collected with a Bruker SMART
CCD instrument by using graphite monochromatic Mo-Kα radiation (λ = 0.71073 Å).
The data of {Mn5} cluster were collected at 293(2) K. The data of {Mn10} cluster
were collected at 173(2) K. Absorption effects were corrected by semi-empirical
methods. The structures were solved by direct methods with the program
SHELX-2014 [52]. The non-hydrogen atoms (Mn, O, N, C) in {Mn5} and {Mn10}
clusters were refined anisotropically by full-matrix leastsquares procedure based on
F2 values. The aromatic hydrogen atoms were placed in calculated positions and
refined using a riding model, but those of phenolic groups were located in the last
final difference Fourier map. The hydrogen atom positions of disordered solvent
molecules were fixed geometrically at calculated distances and allowed to ride on the
parent atoms. The final cycle of full-matrix least-squares refinement was based on
observed reflections and variable parameters. The B level alerts (in CHECK CIF
reports) are likely due to the weak diffractions of the compounds and the large
number of solvent molecules in {Mn5} and {Mn10} structures, many of which being
severely disordered. Efforts were made to deal with these problems, including
adding additional constraints and applying additional restraints to the displacement
coefficients. The CCDC numbers of {Mn5} and {Mn10} cluster are 1883911 and
1883912, respectively. The crystallographic data for {Mn5} and {Mn10} cluster is
summarized in Table 1.
8

Table 1. Crystal data and structure refinements for {Mn5} and {Mn10} clusters.
Compounds
{Mn5}
{Mn10}
Empirical formula
Formula weight
Temperature/K
Crystal system
Space group
a/Å
C94H74N24O12Mn5 C143H163N31O54Mn10
2006.47
293.00(10)
monoclinic
I 2/a
3729.45
173.00
monoclinic
P 21/c
22.7117(15)
14.5551(10)
27.400(3)
90
30.019(3)
19.632(2)
28.964(3)
90
b/Å
c/Å
α/°
β/°
91.973(7)
90
111.683(2)
90
γ/°
Volume/Å3
9052.3(13)
4
15861(3)
4
Z
Dcalcm/g mm-3
μ/mm-1
1.472
1.562
0.755
0.865
F(000)
4108.0
7680.0
Crystal size/mm3
0.19 × 0.15 × 0.13
0.71073
0.3 × 0.25 × 0.19
0.71073
Wavelength/Å
θ Range (°)
Rint
3.02 to 25.01
0.0540
0.73 to 25.009
0.0838
Reflns coll./unique
GOF on F2
20317 / 7980
1.065
137522 / 27973
1.063
R1 [I>=2σ (I)]a
R1 = 0.0637
R1 = 0.0711
wR2 = 0.1936
2.63/-1.87
R2 [all data]b
wR2 = 0.1894
Largest diff. peak/hole / e Å-3
0.53/-0.51
2
a R1 = ∑| |Fo|–|Fc| |/∑|Fo|, b wR2 = {∑[w(Fo – Fc2)2]/∑[w(Fo2)2]}1/2
.
9

3. Results and discussion
3.1. Syntheses
The {Mn5} and {Mn10} clusters with different structures were obtained by H6L
ligand with Mn(OAc)2∙4H2O at different reaction conditions. Based on the good
bridging and magnetic transfer effects of azide ion, sodium azide was selected as an
auxiliary ligand and the penta-nuclear {Mn5} clusters were successfully synthesized
using pyridine as base and ethanol as solvent. When no sodium azide was added and
other conditions were not changed, the synthesis of {Mn5} clusters was attempted to
give only brown solution. In addition, the target product was also not obtained when
sodium azide was replaced by other auxiliary ligands. These results suggest that
azide ions play an important role in the synthesis of {Mn5} cluster. Using pyrazine
as auxiliary ligand, pyridine as base and DMF and CH3OH as mixed-solvent,
deca-nuclear {Mn10} clusters were successfully synthesized by a conventional
solution method. Notably, the deca-nuclear {Mn10} cluster can be also obtained via
a simply dissolving and reassembling process of penta-nuclear {Mn5} cluster under
solution conditions (DMF and CH3OH, VDMF /VCH3OH = 1:2). For the dissolving and
reassembling process of {Mn5} cluster, we also attempted to change the solvent
without DMF or reduce the amount of DMF, and no crystalline samples of {Mn10}
cluster were obtained. These phenomena indicate that the amount of DMF solvent is
very important for the assembly of {Mn5} cluster to {Mn10} cluster.
10

3.2. Description of crystal structures
Fig. 1. Hemicyclic "Phoenix crown" penta-nuclear structure of {Mn5} cluster with
selected atoms labeled. Hydrogen atoms are omitted for clarity. Symmetry code: a)
−x+1/2, y, −z+1.
Single-crystal X-ray studies revealed that {Mn5} cluster crystallized in the
monoclinic space group I 2/a, with the asymmetric unit containing two L6– ligands
chelating five manganese ions to form hemicyclic "Phoenix crown" structure clusters,
and as well as eight pyridine molecules, one azide anion and two pyridine solvent
molecules (Fig. 1). Bond valence sum (BVS) calculations (1.90 for Mn1, 3.20 for
Mn2 and 3.10 for Mn3) and charge balance consideration established that Mn1 ion is
divalent, Mn2 and Mn3 ions are trivalent, respectively. The five Mn ions in {Mn5}
cluster are all six-coordinated, the MnIII3 and MnIII3a , MnIII2 and MnIII2a ions were
found to be located at symmetrical positions. The six atoms coordinated with MnIII3
are O4 atom in the phenyl-acylamide group, a phenol hydroxy O6 atom, N4 atom in
the NH-NH group of acylhydrazine and N9 atom of azide group; and pyridine N7 and
11

N8 atoms in the axis position, respectively. MnIII2 and MnIII2a ions are also in
symmetrical positions of hemicyclic "Phoenix crown" structure. The
six-coordinated environment of the distorted octahedron MnIII2 ion is composed of
O5 atom in the phenyl-acylamide group on the equatorial plane, O3 atom of the
salicylic acid group, a phenolic hydroxyl O1 atom, N1 atom in the NH-NH group of
acylhydrazine, hydrazide N3 atom and pyridine N6 atom. MnII1 ion is located at the
top of the hemicyclic cluster, and in a six-coordinated deformed octahedron
environment, which is coordinated by two nacylhydrazine (N2, N2a), two npyridine
(N5, N5a), and two ophenyl-acylamide (O2, O2a), respectively. The bond length of
Mn–O falls into the range from 1.856(3) to 2.139(3) Å, and the bond length of Mn–N
falls into the range from 1.924(4) to 2.390(6) Å. Two L6– ligands in the {Mn5}
cluster adopt the same coordination patterns, as shown Fig. 2. Each L6- ligand has
ten atoms involved in the coordination, namely, four acylhydrazine N (N1, N2, N3,
N4), two phenolic hydroxyl O (O1, O6) and four carbonyl groups (O2, O3, O4, O5).
Five Mn ions of hemicyclic "Phoenix crown" {Mn5} cluster are linked together in a
quasi-linear fashion by four N–N single bonds of two L6– ligands, which are
completely deprotonated and displays the μ4-η10 mode. The angle of Mn1/Mn2/Mn3
is 128.94º, indicating that three manganese ion centres are not arranged in a straight
line, but remain a considerable bent angle. The torsion angles of Mn1–N–N–Mn2
and Mn3–N–N–Mn2 are 174.57 and 161.40°, respectively, and the distances of
Mn1∙∙∙Mn2 and Mn3∙∙∙Mn2 are 4.893 and 4.849 Å. By the π-π stacking interaction
12

of conjugate rings, the adjacent clusters are further constructed into 3D network (Fig.
S4).
Fig. 2. The coordination modes of the ligands in {Mn5} cluster.
The X-ray single crystal structure analysis shows that the {Mn10} cluster
crystallizes in monoclinic space group P 21/c, and with the double helix structure
cluster formed by five ligand chelating ten MnIII ions. As shown in Fig. 3, ten MnIII
ions are all hexa-coordinate with four different coordination environments. The
atoms Mn1, Mn5 are bound by two phenolic hydroxyl O atoms, two benzamide O
atoms, and two acylhydrazine N atoms. The coordination atoms of Mn3, Mn6, Mn7,
and Mn9 ions are a phenolic hydroxyl O atom, two benzamide O atoms, two
acylhydrazine N atoms and a carbonyl O atom of DMF molecule. The Mn2, Mn4,
and Mn10 are different from Mn3 in that the carbonyl O atom of DMF molecule is
replaced by an O atom in coordination water. Whereas, Mn8 ion is coordinated by
two benzamide O atoms, two acylhydrazine N atoms and two carbonyl O atoms of
DMF molecule. The Mn–O bond lengths range from 1.847(4) to 2.259(4) Å and the
Mn–N bond lengths range from 1.920(5) to 2.428(5) Å, which are similar to those
observed in many Mn clusters [17, 18]. The torsion angles of Mn–N–N–Mn' range
from 153.55 to 179.29°, and the corresponding distances range of Mn∙∙∙Mn' from
13

4.837 to 5.023 Å. Five MnIII ions of semicircular "Phoenix crown" structure in
{Mn10} clusters were chelated by two L6– ligands, and further interweaved to double
helix cluster structure by a bridged L6– ligand. The coordination modes of five L6–
ligands in {Mn10} clusters are identical to those of the two L6– ligands in {Mn5}
clusters, showing a μ4-η10 coordination pattern, in which the coordination atoms are
two phenolic hydroxyl O atoms, four N atoms and four benzamide oxygen atoms (Fig.
S5). The different coordination environments of the five L6– ligands in the {Mn10}
clusters are the angles of the three aromatic rings plane of L6– ligands, among which
the angle of chelating L6– ligands is smaller (100.61-107.56º) and the angle of
bridging L6– ligand is larger (142.81º) and close to 180º.
Fig. 3. The double helix deca-nuclear structure of {Mn10} cluster with selected atoms
labeled. Hydrogen atoms are omitted for clarity.
Notably, the double helix structure of {Mn10} clusters can be considered as a
double "Phoenix crown" structure containing two semicircular {Mn5} clusters
14

bridged by a diacylhydrazine ligand. Based on the structural characteristics of
{Mn5} and {Mn10} clusters, the transformation from {Mn5} clusters to {Mn10}
clusters was realized by dissolving and reassembling of {Mn5} clusters (Fig. 4).
Furthermore, these double helix {Mn10} clusters are further constructed into 3D
network by the π-π stacking interaction of conjugate rings (Fig. S6). Both {Mn5} and
{Mn10} clusters are N–N single bond bridged polynuclear manganese clusters.
Literatures have reported many N–N single bond bridged polynuclear metal clusters,
including chain like clusters of {Mn3} [48], {Co3} [41], {Ni3} [48], {Cu3} [39], {Cu6}
[48], and ring like clusters of {Mn4} [40]. Remarkably, the hemicyclic {Mn5}
cluster with "Phoenix crown" structure has not been described in the previous
literature.
Fig. 4. Schematic illustration of the synthetic procedure of the transformation from
{Mn5} clusters to {Mn10} clusters.
3.2. Magnetic properties
Owing to the presence of polynuclear manganese cluster, magnetic properties could
be estimated for the as-synthesised samples of {Mn5} cluster and {Mn10} cluster.
15

The solid-state, variable-temperature dc magnetic susceptibility data of {Mn5} cluster
and {Mn10} cluster were measured in the 2–300 K temperature range with an applied
field of 1000 Oe. The plots of χMT vs. T are shown in Fig. 5 and Fig. 6. At 300 K,
the χMT value of 18.26 cm3 K mol–1 for {Mn5} cluster is slightly above the spin-only
value of 16.375 cm3 K mol–1 based on the uncoupled {MnIIMnIII } system with
4
S(Mn2+) = 5/2 and S(Mn3+) = 2 assuming g = 2.00 [53]. Upon cooling, the χMT value
for {Mn5} cluster drops gradually in the temperature range of 300−50 K, and then
decreases abruptly and reaches a value of 3.46 cm3 K mol–1 at 2 K. The shape of the
variable-temperature magnetic susceptibility plot indicates the presence of the
antiferromagnetic interactions in the {Mn5} cluster centers. The Curie–Weiss fitting
for the 1/χM –T data in the temperature range of 300–20 K gave Curie constants (C) =
19.36 cm3 mol−1 K and Weiss constant (θ) = –15.73 K (Fig. S7). The negative Weiss
constant together with the trend of χMT vs. T plot, reveals the presence of the
antiferromagnetic interaction in {Mn5} cluster [54]. There are N–N single bonds
bridged {MnIIMnIII } units in the structure of {Mn5} cluster. In our previous work,
2
similar N–N single bond bridged {Mn3} clusters have been reported, but they exhibit
ferromagnetic interactions between MnII and MnIII ions [48]. The difference of
magnetic properties between {Mn5} and {Mn3} clusters is mainly due to the
arrangement of mixed-valence Mn centers.
16

Fig. 5. Plots of χM and χMT versus T for {Mn5} cluster at 2-300 K with a dc magnetic
field of 1000 Oe.
The χMT value at 300 K is 30.33 cm3 K mol−1 for {Mn10} cluster (Fig. 6), which is
close to the calculated values of 30.00 cm3 mol−1 K for ten noninteracting high-spin
MnIII spin carrier (S = 2) [55]. As the temperature is decreased, the χMT value
continuously decreases to 4.3 cm3 K mol−1 until the lowest temperature 2 K for {Mn10}
cluster. The 1/χM data above 30 K obey the Curie–Weiss Law with C = 31.95 cm3
mol−1 K and θ = –17.28 K (Fig. S8). The overall profile of χMT vs. T curve and the
positive θ are characteristic of antiferromagnetic coupling between Mn3+ centers of
{Mn10} cluster. While for the faster decrease of χMT value in the low temperature
region, it may be ascribed to the presence of magnetic anisotropy zero field splitting
for Mn3+ centers [56].
17

Fig. 6. Plots of χM and χMT versus T for {Mn10} cluster at 2-300 K with a dc magnetic
field of 1000 Oe.
The field dependence of magnetization (M) versus field (H) data for the
as-prepared sample of {Mn5} and {Mn10} clusters were measured at 2 K (Fig. S9 and
S11, respectively), which shows a steady increase with increasing H and no saturation
at 5 T and 2 K. This behavior also supports the strong antiferromagnetic coupling in
penta-nuclear {Mn5} cluster and deca-nuclear {Mn10} cluster. The real, χ′, and
imaginary (out-of-phase), χ″, parts of the ac susceptibility were measured between 2
K and 10 K in an alternating magnetic field with the different frequencies ranging
from 17 Hz up to 997 Hz. There are no frequency-dependent behavior in the
in-phase signals χ′ and the out-of-phase signals χ″ for both clusters (Fig. S10 and S12,
respectively). Hence, both {Mn5} cluster and {Mn10} cluster display no slow
magnetization relaxation process and SMM behavior, which may be due to their small
magnetic anisotropy and low ground state.
18

4. Conclusions
In summary, the {Mn5} and {Mn10} clusters were successfully constructed from
MnII ions and diacylhydrazine ligands under mild reaction conditions. The {Mn5}
cluster has a penta-nuclear structure with four MnIII ions and one MnII ion, which are
linked by two diacylhydrazine ligands to form hemicyclic "Phoenix crown" structure.
The {Mn10} cluster possesses a double helix deca-nuclear skeleton, which can be
considered as a double "Phoenix crown" structure containing two {Mn5} clusters
bridged by a diacylhydrazine ligand. Through dissolving and reassembling under
solution conditions, the penta-nuclear {Mn5} cluster can be converted to the
deca-nuclear {Mn10} cluster. Systematic magnetic studies for {Mn5} and {Mn10}
clusters show the antiferromagnetic interactions.
Acknowledgments
This work was supported by the National Natural Science Foundation of China
(21771043, 21501033, and 51572050), the National Natural Science Foundation of
Guangxi Province of China (2018GXNSFAA281131 and 2016GXNSFBA380162),
Guangxi Key Laboratory of Electrochemical and Magneto-chemical Functional
Materials (EMFM20181118), and the Program of the Collaborative Innovation Center
for Exploration of Hidden Nonferrous Metal Deposits and Development of New
Materials in Guangxi (No. GXYSXTZX2017-II-3).
19

Appendix A. Supplementary material
CCDC 1883911 and 1883912 contain the supplementary crystallographic data for
{Mn5} and {Mn10} clusters. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary material associated with this article can be found in the online version
at doi:
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23

Highlights:

Two high-nuclearity manganese clusters based on manganese ion and
diacylhydrazine ligands were synthesized.

{Mn5} clusters possess hemicyclic "Phoenix crown" cluster structure, and {Mn10}
clusters appear to be structurally equivalent to two "Phoenix crown" {Mn5}
clusters.


The double helix structure {Mn10} clusters can be also obtained via the simply
dissolving and reassembling process of the "Phoenix crown" {Mn5} clusters.
The magnetic studies indicate that {Mn5} clusters and {Mn10} clusters exhibit
antiferromagnetic interactions.
24

Graphical Abstract
Hemicyclic "Phoenix crown" {Mn5} clusters and double helix structure {Mn10}
clusters have been assembled by using a diacylhydrazine ligand and characterized
structurally and magnetically. Magnetic studies reveal that these high-nuclearity
manganese clusters exhibit antiferromagnetic interactions.
25

Author statement
Qun Tang: Writing-Original Draft, Conceptualization, Validation.
Yanli Yang: Methodology, Investigation.
Ze Cheng: Investigation, Formal analysis.
Xiuni Chen: Methodology, Software.
Qingmei Lin: Methodology, Software.
Zhiming Zou: Conceptualization, Validation.
Hua-Hong Zou: Data Curation, Resources.
Fu-Pei Liang: Writing-Review & Editing, Supervision, Funding acquisition.
26