Hierarchical Assembly of a INNC0208SI320167052134nf>MnIII4} Brucite Disc: Step-by-Step Formation and Ferrimagnetism

Article abstract of DOI:10.1021/jacs.5b11736

In search of functional molecular materials and the study of their formation mechanism, we report the elucidation of a hierarchical step-by-step formation from monomer (Mn) to heptamer (Mn₇) to nonadecamer (Mn₁₉) satisfying the relation 1 + Σ_n6n, where n is the ring number of the Brucite structure using high-resolution electrospray ionization mass spectrometry (HRESI-MS). Three intermediate clusters, Mn₁₀, Mn₁₂, and Mn₁₄, were identified. Furthermore, the Mn₁₉ disc remains intact when dissolved in acetonitrile with a well-resolved general formula of [Mn₁₉(L)_x(OH)_y(N₃)_36-x-y]²⁺ (x = 18, 17, 16; y = 8, 7, 6; HL = 1-(hydroxymethyl)-3,5-dimethylpyrazole) indicating progressive exchange of N₃^- for OH^-. The high symmetry (R-3) Mn₁₉ crystal structure consists of a well-ordered discotic motif where the peripheral organic ligands form a double calix housing the anions and solvent molecules. From the formula and valence bond sums, the charge state is mixed-valent, [Mn^II₁₅Mn^III₄]. Its magnetic properties and electrochemistry have been studied. It behaves as a ferrimagnet below 40 K and has a coercive field of 2.7 kOe at 1.8 K, which can be possible by either weak exchange between clusters through the anions and solvents or through dipolar interaction through space as confirmed by the lack of ordering in frozen CH₃CN. The moment of nearly 50 N_B suggests Mn^II-Mn^II and Mn^III-Mn^III are ferromagnetically coupled while Mn^II-Mn^III is antiferromagnetic which is likely if the Mn^III are centrally placed in the cluster. This compound displays the rare occurrence of magnetic ordering from nonconnected high-spin molecules.

Full text of DOI:10.1021/jacs.5b11736

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Article
Hierarchical Assembly of a {MnII15MnIII4} Brucite
Disc: Step-by-Step Formation and Ferrimagnetism
Yong-Kai Deng, HaiFeng Su, Jia-heng Xu, Wen-Guang Wang, Mohamedally
Kurmoo, Shuichao Lin, Yuan-Zhi Tan, Jiong Jia, Di Sun, and Lan-Sun Zheng
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.5b11736 • Publication Date (Web): 18 Jan 2016
Downloaded from http://pubs.acs.org on January 23, 2016
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Hierarchical Assembly of a {Mn Mn } Brucite Disc: StepꢀbyꢀStep
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Formation and Ferrimagnetism
†, ┴
‡, ┴
†
†
§
YongꢀKai Deng, HaiꢀFeng Su, JiaꢀHeng Xu, WenꢀGuang Wang, Mohamedally Kurmoo, Shuiꢀ
‡
‡
†
*,†,‡
‡
Chao Lin, YuanꢀZhi Tan, Jiong Jia, Di Sun
and LanꢀSun Zheng
†
Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shanꢀ
dong University, Jinan, 250100, P. R. China.
‡
State Key Laboratory for Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and
Chemical Engineering, Xiamen University, Xiamen, 361005, People’s Republic of China.
§
Institut de Chimie de Strasbourg, Université de Strasbourg, CNRSꢀUMR 7177, 4 rue Blaise Pascal, 67008 Strasbourg Cedex,
France.
┴
These authors contributed equally to this work
ABSTRACT: In search of functional molecular materials and the study of their formation mechanism, we report the elucidation of
a hierarchical stepꢀbyꢀstep formation from monomer (Mn) to heptamer (Mn ) to nonadecamer (Mn ) satisfying the relation 1+Σ 6n,
where n is the ring number of the Brucite structure using highꢀresolution electrospray ionization mass spectrometry (HRESIꢀMS).
7
19
n
Three intermediate clusters, Mn , Mn and Mn , were identified. Furthermore, the Mn disc remains intact when dissolved in
10
12
14
19
2+
acetonitrile with a wellꢀresolved general formula of [Mn (L) (OH) (N ) ]
(x = 18, 17, 16; y = 8, 7, 6; HL = 1ꢀ(hydroxymethyl)ꢀ
19
x
y
3 36ꢀxꢀy
–
–
3
,5ꢀdimethylpyrazole) indicating progressive exchange of N3 for OH . The high symmetry (Rꢀ3) Mn crystal structure consists of
19
a wellꢀordered discotic motif where the peripheral organic ligands form a double calix housing the anions and solvent molecules.
II
III
From the formula and valence bond sums the charge state is mixedꢀvalent, [Mn 15Mn 4]. Its magnetic properties and electrochemꢀ
istry have been studied. It behaves as a ferrimagnet below 40 K and has a coercive field of 2.7 kOe at 1.8 K, which can be possible
by either weak exchange between clusters through the anions and solvents or through dipolar interaction through space as conꢀ
II
II
III
III
firmed by the lack of ordering in frozen CH CN. The moment of nearly 50 Nµ suggests Mn ꢀMn and Mn ꢀMn are ferromagꢀ
3
B
II
III
III
netically coupled while Mn ꢀMn is antiferromagnetic which is likely if the Mn are centrally placed in the cluster. This comꢀ
pound displays the rare occurrence of magnetic ordering from nonꢀconnected highꢀspin molecules.
–
–
2–
–
happen if OH , OR or O and N3 coexist in a selfꢀassembled
system? To find an answer to this question more examples are
highly sought and different bridging ligands need to be exꢀ
plored to address this challenging issue.
INTRODUCTION
Polynuclear transition metal clusters have captured much atꢀ
tention in the field of molecular magnetism and materials
1
chemistry due to their structural aesthetics and potential apꢀ
On the other hand, the connectivity recognition in a selfꢀ
assembly process is intensively dependent on the final single
crystals obtained by trial and error as well as the Xꢀray singleꢀ
crystal diffraction technique, whereas the details of the cluster
growth and nucleation process are less known at the molecular
level. Electrospray ionization mass spectrometry (ESIꢀMS) is
a powerful tool to precisely determine the elemental composiꢀ
tion of the molecular species or assembly intermediates in
solutions by matching experimental mass spectra with calcuꢀ
2
plications in areas such as high density data storage, magnetic
3
4
cooler, and qubits for quantum computation. Since the obꢀ
servation of singleꢀmolecule magnetism (SMM) for Mn12 in
5
1
990, a whole gamut of polynuclear manganese clusters from
Mn to Mn , as well as other transition and rareꢀearth metal
3
84
ions, have been prepared using flexible organic ligands such as
6
carboxylates, βꢀdiketonates and alkoxides. Based on these
reported beautiful examples, it is regarded that the small bridgꢀ
ing ions are indispensable in aggregating metal ions into clusꢀ
ters, where suitable metalꢀmetal distances for strong magnetic
exchange interactions are guaranteed. From a magnetic point
8
lated isotope distributions. The realꢀtime monitoring of the
dynamic molecular species in solution by HRESIꢀMS could
provide rich information about bonding and the way reactions
progress, which are the deeper aim in chemistry. Cronin’s
group have exploited the electrospray and cryospray mass
spectrometry to track the formation of polyoxometalate
(POM), transition metal clusters and exploration of new POMs
–
–
2–
of view, OH , OR and O provide antiferromagnetic MꢀOꢀM
exchange paths if the angle is >98° and ferromagnetic one for
–
<98°, whereas endꢀon bridging N3 usually resulted in ferroꢀ
magnetic coupling and hence the spin ground state of a highꢀ
7
nuclearity molecule can be increased dramatically. What will
9
in solution. Following these works, in 2013, Zeng's group
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discovered a Co16 cluster and tracked its formation and comꢀ
Structural
Analysis
of
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plex elimination and substitution reactions in solution by iteraꢀ
tive ESIꢀMS and crystallography, which provided ample inꢀ
[Mn 15Mn (L) (OH) (N ) ](ClO ) ·12CH CN (1).
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3 6
4 6
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The Mn19 cluster was obtained by room temperature reacꢀ
tion of Mn(ClO ·6H O, NaN , and HL in CH CN with triꢀ
ethylamine as base, and brown crystals of Mn19 were grown
over a period of one month. Despite very low yields, it can be
readily reproduced. The key feature of the singleꢀcrystal strucꢀ
ture is the stacking of the discs along the cꢀaxis with the ClO4
counter ions trapped in ellipsoidal cavities between the calix
of adjacent clusters and CH CN sharing the cavities as well as
occupying the interstitial vacancies between the discs (Figure
2a and 2b). 1 crystallized in the trigonal Rꢀ3 space group with
the Mn19 disc lying on an inversion center (Figure S1). Its
asymmetric unit is oneꢀsixth of the Mn19 disc and contains
formation to understand the complex assembly process. Deꢀ
1
1
4
)
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spite the ever increasing advances in this field, accurate deꢀ
termination of the formula and possible intermediate bridged
between initial reactants and final products still represents a
major challenge for understanding and exploiting cluster asꢀ
sembly.
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Based on the above considerations, we have recently been
experimenting with hydroxymethylꢀpyrazole ligands in polyꢀ
nuclear cluster chemistry. Such ligands have had limited reꢀ
ports in this area, in comparison to carboxylates and polyꢀ
alcohols. In this work, we report on this chemistry with Mn(II)
in air and obtained an unprecedented mixedꢀvalence hierarꢀ
3
–
–
–
four unique Mn atoms, three L ligands, two OH , one N , one
3
–
chical (1+Σ 6n, where n is the ring number) homologue of the
ClO
octahedral geometry, as reflected by the six equivalent MnꢀO
distances of 2.077(5) Å symmetryꢀimposed by the C axis and
4
and two CH CN solvents. The Mn1 is in an ideal MnO
3
6
n
12
Brucite heptanuclear cluster (Figure 1) which is the nonꢀ
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adecanuclear [Mn 15Mn 4] disc having the formula
3
II
III
[
Mn 15Mn (L) (OH) (N ) ](ClO ) ·12CH CN (1). More
the inversion center. The other three Mn atoms are in distorted
octahedral geometries and no axial JahnꢀTeller effect were
observed for all Mn atoms in this disc (MnꢀO: 2.062(5)ꢀ
2.279(5) Å; MnꢀOꢀMn: 95.67(19)ꢀ107.2(2) ; Mn···Mn:
3.2836(11)ꢀ3.3723(16) Å; MnꢀNꢀMn = 99.7(3) ). Although the
H atoms of the hydroxide were not located from ꢀEꢀmap, sevꢀ
eral hydrogen bonds were easily identified with ClO4 indicatꢀ
ing they are intrinsically hydroxide anions. The 18 L ligands
4
18
12
3 6
4 6
3
interesting, we examine the solution stability of Mn19 disc,
indicating the core integrity in acetonitrile and multistep elimꢀ
ination and substitution reaction between coexisted bridging
anions. Realꢀtime monitoring of the reaction solution using
HRESIꢀMS at room temperature provided much deeper inforꢀ
mation about the formation mechanism of this novel Mn19 disc,
o
o
–
–
that is, Mn disc is a primary species bridging between single
7
Mn atom and Mn19 disc. Surprisingly, Mn19 disc in the solid
crystalline state does not behave as a SMM as may be exꢀ
pected but displays longꢀrange magnetic ordering to a ferriꢀ
magnet at 40 K and a high coercive field of 2.7 kOe at 1.8 K.
Both the transition and the magnetic hardness are absent for
sit on the rim above and below the Mn plane, and are of two
19
–
–
types: 6 ꢁ ꢀL and 12 ꢁ ꢀL . The Mn core has S symmetry
2
3
19
6
and can be seen as a threeꢀring motif: one Mn1 is in the center,
which is connected to outer Mn ring (6 Mn2) by six symꢀ
metryꢀrelated ꢁ ꢀOH bridges. This Mn ring, in turn, connectꢀ
ed to an outermost Mn12 ring consisting of alternating Mn3
and Mn4 atoms through alternating ꢁ ꢀOH and ꢁ ꢀO (Figure
). The six endꢀon ꢁ ꢀN3 and twelve ꢁ ꢀL ligands edgeꢀ
sealed the whole disc at its periphery. Alternatively, this disc
also can be described as consisting of 24 edgeꢀsharing [Mn O]
triangles or 12 edgeꢀsharing [Mn O ] butterfly units. Two
discs, acting as calyxes, embrace six ClO4 anions, which are
hydrogenꢀbonded with the disc through OhydroxylꢀH···O hydroꢀ
gen bonds (O4ꢀH4···O7 = 2.854(12) Å and O5ꢀH5···O6 =
6
–
3
6
crystals dissolved in CH CN.
3
–
3
3
L
–
–
1
2
2
3
4
2
–
2
.854(12) Å).
Figure 2. (a) View of the structure along the cꢀaxis where the yellow
spheres highlight the cavity sandwiched between the adjacent clusters and
the grey spheres highlight the channels housing the CH CN solvents. (b)
A pair of clusters where the calyxes form the cavity (yellow) housing the
six ClO and six CH CN.
3
4
3
In the Mn19 disc, charge neutrality requires a total of +42
per 19 Mn atoms. Assuming that the disc comprises Mn atoms
in the valence states +2, +3, and +4, there are three possible
ꢀ
Figure 1. (a) The coordination modes of L ligands; (b) the structure of
a Mn19 with threeꢀring motif;. (c) the hierarchy of Brucite discs for n = 0
(green), 1 (cyan), 2 (blue) and 3 (purple).
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IV
valence distributions, Mn 15Mn 4, Mn 16Mn Mn , and
2
II
IV
Mn 17Mn 2. Bond Valence Sum (BVS) calculations suggest
RESULTS AND DISCUSSION
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that each Mn atom has a nonꢀinteger oxidation state between
+2 and +3 (Table S1). Consequently, Mn is ruled out. The
1897.080, [Mn (L) (OH) (N ) ] ), all of which correspond
19 17 7 3 12
IV
to
[Mn (L) (OH) (N ) ]
3 36ꢀx-y
a
total of nine species with the formulae
2+
consideration of overall charge of the nonadecanuclear disc
(x = 18, 17, 16; y = 8, 7, 6). Altꢀ
hough so many peaks appeared in solution, they belong to the
same Mn19 species demonstrating clearly that the core of the
disc is still intact. The few L ligands could be lost from the
disc and interesting substitution reaction of the OH by N
19
x
y
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necessitates a mixedꢀvalence Mn 15Mn description in acꢀ
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cordance with magnetic susceptibility (below). Within the
trigonal space group Mn1 has to be one of the trivalent cation
and we assume that the other three are delocalized within the
Mn2 ring. The observed solidꢀstate structure suggests rapid
intramolecular electron transfer or electron delocalization,
ꢀ
–
–
3
ions in solution was also observed, which usually occurs durꢀ
ing the ESI process as previous reports.
11a, 11b
There was no
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2+
which renders Mn and Mn indistinguishable on the Xꢀray
timeꢀscale in such highly symmetrical disc. The valence localꢀ
ization phenomenon is not at all new in mixedꢀvalence Mn
compounds, especially those with high symmetry. For examꢀ
evidence of the parent [Mn (L) (OH) (N ) ]
(m/z =
1
9
18
12
3 6
1876.099) cation resulting from 1 by losing all solvent moleꢀ
cules and ClO , which may be caused by complicated metalꢀ
ligand solution exchange between OH or L and N ions.
–
4
–
–
–
3
II
III
ple, in the oxoꢀcentered trinuclear Mn Mn cluster a C axis
2
3
As shown in Figure 3, for doubly charged species, there are
nine ion peaks, which can be divided into three subgroups and
each subgroup contains three species. Every three ion peaks
within a subgroup are formed by replacement of N3 by OH
one by one with the well matched experimental and simulated
m/z values. For ion peaks (1), (2), (3), the former one has a
weight of 25 less than the latter one, suggesting a N (m/z =
2) bridge was replaced by an OH (m/z = 17). The other two
make the different valence state of Mn atoms became symꢀ
1
3
II
III
metry equivalent. Another Mn Mn cluster with a symꢀ
3
4
14
metry imposed S has valence delocalization feature. Not
–
–
6
only limited to metalꢀorganic Mn compounds, this phenomeꢀ
non also exist in inorganic Mn minerals such as lithiophorite,
II
IV
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where Mn and Mn sites are indistinguishable.
–
3
–
4
ionic peaks in each subgroup also show similar substitution
reaction and are also unambiguously assigned to precise forꢀ
mulae. Between two adjacent subgroups, the ion peak (3)
2+
[Mn (L) (OH) (N ) ] has a weight of 83 less than that of
19
16
6
3 14
2+
ion peak (6) [Mn (L) (OH) (N ) ] , representing the reꢀ
19
17
6
3 13
–
–
placement of a L bridge by N . Similar behaviors are also
observed between ion peak (6) and (9). These results not only
clearly proved the existence and stability of the parent Mn19
3
cluster in CH CN, but also provided important chemical inꢀ
3
formation about the solution behavior such as ligand exchange
in complicated associationꢀdissociation equilibrium in the
reaction.
Scheme 1 Schematic view of the proposed planar epitaxial growth
mechanism of Mn19 core in solution.
Figure 3. The HRꢀESI mass spectrum of 1 dissolved in acetonitrile.
Charge states are indicated as 2+. Experimental (black) and simulated (red)
mass spectra of the isotopic envelopes for +2 (top) and +3 (bottom) comꢀ
ponents. The formula of each species were given in the table.
Electrospray Ionization Mass Spectrometry
Although so much enthusiasm was poured on the characterꢀ
16
ization of solid state manganese coordination clusters, their
solution behavior and assembly process remains underdevelꢀ
17
After checking the solution behaviors of Mn19 disc in aceꢀ
tonitrile, we pay attention to the assembly details of such
beautiful Mn19 disc by tracking the reaction time dependence
of the different species present in solution and their abundancꢀ
es from HRESIꢀMS. The aliquots were taken from the reaction
solution at specific time intervals. Each of the aliquots was
filtrated and diluted before injecting into the instrument. As
shown in Figure 4a, a total of four intermediates and one final
product were identified with isotope resolution. The time evoꢀ
oped. Mass spectrometry has given very miscellaneous inꢀ
formation in coordination chemistry regarding the structural
1
8
19
integrity in solution, fragment composition, the degree of
2
0
protonation, even revelation of the assembly mechanism
occurring during the selfꢀassembly process. Crystals of 1
2
1
were dissolved in CH CN and probed by HRESIꢀMS at
3
2
00 °C. As shown in Figure 3, a series of double charged ion
peaks centered in the m/z range of 1840ꢀ1960 (max. m/z
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lution of HRESIꢀMS peak intensity is plotted in Figure 4b and
nearly synchronizes with their formation. It is worth noting
the detailed assignment of the main peaks of each species
based on experimental and simulated isotope is shown in Supꢀ
porting Information (Figure S2). Analysis of the HRESIꢀMS
data showed that the very strong doubleꢀcharged peaks of Mn7
species were observed in the very short reaction time (~the
first 1 min), indicating rather quick and highꢀyield formation
of this kinetic product. The most prevailing envelops in the
m/z range of 773ꢀ860 are unambiguously assigned to the
that the Mn19 species (7 species identified) appears after ~20
mins., although its abundance is very low. During the 20ꢀ90
mins., the peak intensities of Mn , Mn , Mn , and Mn speꢀ
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cies progressively increase and the maximum peak intensities
were observed for four smaller intermediates at t = 90 min. As
the assembly continued, the peak intensities of Mn , Mn ,
1
0
12
and Mn14 species are gradually decreased, whereas intensity of
Mn19 species increase further to a maximum at t = 330 min.,
which indicates these smaller intermediates gradually transꢀ
form to the larger and thermodynamically stable Mn19 disc.
Based on the realꢀtime HRESIꢀMS tracking results and the
threeꢀring motif feature of Mn19 disc, we tentatively assign its
formation to a planar epitaxial growth mechanism from single
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2+
2+
[
[
[
Mn (L) (OH) (N ) ] ,
[Mn (L) (N ) ] ,
7 8 3 4
2+
7
7
2
3 6
2+
Mn (L) (OH) (N ) ] ,
[Mn (L) (N ) ] ,
7 9 3 3
7
8
2
3 5
2+
2+
Mn (L) (OH) (N ) ] , and [Mn (L) (N ) ] by comparing
7
9
2
3 4
7
10
3 2
isotopic distributions. Within the same time window, the lowꢀ
intensity envelops of Mn10 (11 species identified), Mn12 (16
species identified) and Mn14 (14 species identified) were also
Mn atom to Mn
disc (Scheme 1).
, Mn10, Mn12, and Mn14, then to the final Mn19
7
found. This suggests that the further growth of Mn species
7
2+
Figure 4. (a) Timeꢀdependent HRESIꢀMS spectra with five representative Mn
MS signals of Mn19 species (m/z = 1850 ꢀ 2000). (b) The HRESIꢀMS spectral intensityꢀtime profiles of the Mn
x
(x =7, 10, 12, 14 and 19) species. The right panel in (a) is the magnified
2+
x
species during the selfꢀassembly.
Magnetic Properties
of 48.3 Nꢁ in 70 kOe at 1.8 K is smaller than that expected
B
II
for a ferrimagnet with the moments of 15 Mn being antiparalꢀ
lel to those of 4 Mn (15 × 5 – 4 × 4 = 59 Nꢁ ). The hystereꢀ
Magnetization data were collected in the temperature range
.8 and 300 K and field range –70 and +70 kOe (Figure 5).
III
B
1
sis loop exhibits a coercive field of 2.7 kOe, characterizing it
as a moderately hard magnet. The acꢀsusceptibilities (2 Oe
oscillating at different frequencies between 1 and 777 Hz)
exhibit peaks for both components at 38 K (Figure S7). The
peaks maxima are frequency independent confirming a LRO
The susceptibility (H = 1 kOe) behaves in a CurieꢀWeiss fashꢀ
ꢀ
1
ion with C = 78.74(4) emu K mol and
θ = –33.1(1) K in the
range 100 and 300 K. The Curie constant is close to the 77.6
ꢀ
1
II
III
emu K mol expected for 15 Mn (S = 5/2) and 4 Mn (S = 2)
and assuming g = 2. At 40 K it takes large positive deviation.
ZFCꢀFC magnetizations in 500 Oe show a bifurcation at 40 K
and become more divergent below 35 K (Figure 5a). The diꢀ
vergence of the FC magnetization from the ZFC is present for
fields of 0.5, 1, 2, and 5 kOe (Figure S3). Plotting χMT versus
(longꢀrange ordering) rather than blocking of moments akin a
SMM.
The ordering temperature (40 K) is very close to that of the
spinel Mn O (43 K) and the hysteresis is less (Figure 5b). To
3
4
ꢀ
1
T shows a minimum of 51.9 emu K mol at 48 K (Figure S4),
demonstrate the intrinsic nature of the LRO, we first confirm
the purity of the samples used by PXRD and elemental analꢀ
yses for CHN and Mn and confirm the absence of biphasic
samples using both optical and electron microscopes (Figure
S11). We then show that the LRO is absent when dissolved in
2
2
signifying ferrimagnetic behavior. Isothermal magnetizations
at 2 K exhibit an almost linear dependence with a slight curvaꢀ
ture and attaining 48.3 Nꢁ in 70 kOe (Figure S5), on which is
B
superposed a hysteresis loop. The value of the magnetization
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CH CN, reꢀiterating that it cannot be originating from an
3
In contrast the only known monovalent disc compound,
II
Mn O impurity. Finally we studied a sample of Mn O for
[Mn O (MOE) (MOEH) ]·MOEH,
(MOEH
=
3
4
3
4
19 12
14
10
comparison where we estimate that more than 10% of the latꢀ
ter is required to produce a hysteresis of the magnitude obꢀ
served for 1.
HOC H OCH ), has almost structurally identical Mn cores as
2
5
3
19
–
1 but lacks the peripheral endꢀon ꢁ ꢀN3 bridge. Its magnetism
2
is dominated by antiferromagnetic interaction and neither
LRO nor SMM blocking was observed. In the present case, we
It is interesting to note that this material is an uncommon
magnet where the moment carriers are not connected into infiꢀ
nite lattice. Thus, the ordering can be by one of two mechaꢀ
nisms; first by weak exchange between the discs though the
intervening electron densities of the counterꢀions and solvents
that are hydrogenꢀbonded and second, by purely dipolar interꢀ
II
II
argue that the J(Mn ꢀMn ) interaction is ferromagnetic as
ꢀ
III
II
expected for the endꢀon ꢁ ꢀN bridge while the J(Mn ꢀMn )
2
3
III
III
is antiferromagnetic (Figure S10). The J(Mn ꢀMn ) exchange
will also be ferromagnetic. Consequently, we have a ferrimagꢀ
netic cluster which interacts weakly with its neighbors to reꢀ
sult in a longꢀrange ordered ferrimagnet. The presence of
0
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action through space. Due to the high temperature Curie
transition, one may bow towards the first the one. In contrast,
it is also possible to be the second choice as the moment is
III
strong anisotropy originating from the Mn results in the obꢀ
served hardness with a coercive field of 2.7 kOe.
fairly high (50 Nꢁ ) per disc that are only 8.6 Å between Mn
B
Electrochemistry
atoms on the edge of adjacent discs and nearest disc to disc
distance of 13.5 Å. LRO is destroyed by extending the disꢀ
tance between molecules when the crystals are dissolving in
Cyclic voltammetric studies on 1 were studied in acetoniꢀ
n
trile solution containing 0.1 M Bu NPF as supporting elecꢀ
4
6
CH CN.
3
trolyte. 1 is only slightly soluble in the electrochemical solvent,
and the solution reached saturation at less than the intended 1
mM. The voltammogram of 1 at different scan rates is disꢀ
played in Figure 6. For the same solution sample, consecutive
scans at different rates between ꢀ2 V and 1 V show the approxꢀ
imately same patterns without other peaks, indicating the abꢀ
sence of any chemical decomposition of 1. There are threeꢀ
peak and twoꢀpeak patterns for reduction and oxidization sides,
ꢀ
1
respectively. At scan rate of 100 mV s , the CV shows two
one electron quasiꢀreversible redox couples at E1/2 = 0.43 V
(
ꢀE = 0.24 V) and E = ꢀ0.17 V (ꢀE = 0.34 V), and a third
p
1/2
p
irreversible reduction at E = ꢀ1.28 V (all potentials are referꢀ
p
+
enced to the Fc /Fc couple). The profile of the CV traces corꢀ
III
II
24
respond to multiple Mn /Mn couples, which suggests the
consecutive electron transfer process occurred in disc core of 1
as summarized in Equation a.
0.43 V
MnIII MnII
ꢀ
0.17 V
MnIII MnII
ꢀ1.28 V
MnIII MnII (a)
1 18
MnIII MnII
4
15
3
16
2
17
Figure 5. (a) Compared zeroꢀfield cooled (hollow circle) and fieldꢀcool
Figure 6. Cyclic voltammogram at different scan rates for 1 in MeCN
(
solid circle) magnetizations normalized by the field (M/H) in a field of
500 Oe between 1 in solid state, 1 dissolved in CH CN and commercial
Mn . (b) Isothermal magnetization for a polycrystalline 1 in solid state,
dissolved in CH CN and commercial Mn at 1.8 K.
n
ꢀ1
containing 0.1 M NBu
labeled potentials.
4 6
PF . Inserted: CV at scan rate of 100 mV s with
3
3
O
4
1
3
3 4
O
CONCLUSIONS
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ꢀ
In this work, we discovered with the assistance of OH and
1896ꢀ1897. (c) Tasiopoulos, A. J.; Vinslava, A.; Wernsdorfer,
W.; Abboud, K. A.; Christou, G. Angew. Chem. Int. Ed. 2004, 43,
117ꢀ2121. (d) Zaleski, C. M.; Depperman, E. C.; Dendrinouꢀ
Samara, C.; Alexiou. M.; Kampf, J. W.; Kessissoglou, D. P.;
Kirk, M. L.; Pecoraro, V. L. J. Am. Chem. Soc. 2005, 127,
ꢀ
N bridges, the record size of a mixedꢀvalent Mn disc of Mn ,
3
19
2
which exhibits a [1+6+12] hierarchical arrangement of Mn
atoms in a plane. The HRESIꢀMS results show that 1 mainꢀ
tains the disc integrity in acetonitrile with very complex coorꢀ
dinationꢀdissociation equilibrium. The formation of this novel
Mn19 disc in solution was also monitored by HRESIꢀMS,
which suggests that the Mn disc is a stable and predominant
intermediate in solution prior to the stepꢀbyꢀstep formation of
the Mn19 disc, via Mn , Mn and Mn . The magnetism studꢀ
ies indicated Mn19 disc reaches a ferrimagnetic order at a high
Curie temperature of 40 K and a coercive field of 2.7 kOe.
Current studies not only pave an avenue to such fascinating
polynuclear manganese disc but also firstly discover the asꢀ
semble intermediates bridged from single Mn atom to the ulꢀ
timate Mn19 disc.
1
2862ꢀ12872. (e) Soler, M.; Wernsdorfer, W.; Folting, K.; Pink
M.; Christou, G. J. Am. Chem. Soc. 2004, 126, 2156ꢀ2165. (f)
Murugesu, M.; Habrych, M.; Wernsdorfer, W.; Abboud K. A.;
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swaran, S.; Chastanet, G.; Teat, S. J.; Mallah, T.; Sessoli, R.;
Wernsdorfer W.; Winpenny, R. E. P. Angew. Chem. Int. Ed.
2005, 44, 5044ꢀ5048. (h) Moushi, E. E.; Lampropoulos, C.;
Wernsdorfer, W.; Nastopoulos, V.; Christou G.; Tasiopoulos, A.
J. J. Am. Chem. Soc. 2010, 132, 16146ꢀ16155.
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7) Papaefstathiou, G. S.; Perlepes, S. P.; Escuer, A.; Vicente, R.;
FontꢀBardia M.; Solans, X. Angew. Chem. Int. Ed. 2001, 40,
8
84ꢀ886.
(a) Miras, H. N.; Wilson, E. F; Cronin, L. Chem. Comm., 2009,
297ꢀ1311. (b) Rood, J. A.; Boggess, W. C.; Noll, B. C.; Henꢀ
8
)
1
ASSOCIATED CONTENT
derson, K. W. J. Am. Chem. Soc. 2007, 129, 13675ꢀ13682. (c)
Lim, I. H.; Schrader, W.; Schüth, F. Chem. Mater. 2015, 27,
3088−3095.
(a) Miras, H. N.; Yan, J.; Long, D. L.; Cronin, L. Angew. Chem.
Int. Ed.2008, 47, 8420ꢀ8423. (b) Miras, H. N.; Cooper, G. J. T.;
Long, D. L.; Bogge, H.; Muller, A.; Streb, C.; Cronin, L. Science
Supporting Information. Detailed synthesis procedure, crystal
data in CIF files, IR, TGA, magnetic plots, BVS calculation and
powder Xꢀray diffractogram. This information is available free of
charge via the Internet at http://pubs.acs.org.
9
)
2
010, 327, 72ꢀ74. (c) Wilson, E. F.; Miras, H. N.; Rosnes, M. H.;
AUTHOR INFORMATION
Cronin, L. Angew. Chem. Int. Ed. 2011, 50, 3720ꢀ3724. (d) Yan,
J.; Long, D. L.; Wilson, E. F.; Cronin, L. Angew. Chem. Int. Ed.
2009, 48, 4376ꢀ4380. (e) Seeber, G.; Cooper, G. J. T.; Newton,
G. N.; Rosnes, M. H.; Long, D. L.; Kariuki, B. M.; Kogerler, P.;
Cronin, L. Chem. Sci., 2010, 1, 62ꢀ67. (f) Long, D. L.; Streb, C.;
Song, Y. F.; Mitchell, S.; Cronin, L. J. Am. Chem. Soc. 2008,
Corresponding Author
Email: dsun@sdu.edu.cn
ACKNOWLEDGMENT
1
30, 1830ꢀ1832. (g) Newton, G. N.; Cooper, G. J. T.; Kogerler,
This work was supported by the NSFC (Grant Nos. 21201110,
1227001 and 21571115), Young Scholars Program of Shanꢀ
dong University (2015WLJH24), and The Fundamental Reꢀ
search Funds of Shandong University (2015JC045). MK is
funded by the CNRS, France.
P.; Long, D. L.; Cronin, L. J. Am. Chem. Soc., 2008, 130, 790ꢀ
791.
2
10) Zhang, K.; Kurmoo, M.; Wei, L.Q.; Zeng, M. H. Sci. Rep., 2013,
, 3516ꢀ3521.
1) (a) Chen, Q.; Zeng, M.ꢀH.; Wei, L.ꢀQ.; Kurmoo, M. Chem Mater
010, 22, 4328ꢀ4334. (b) Zhou, Y.L.; Zeng, M.ꢀH.; Wei, L. Q.;
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Li, B. W.; Kurmoo, M. Chem Mater 2010, 22, 4295ꢀ4303. (c)
Wei, L. Q.; Zhang, K.; Feng, Y. C.; Wang, Y. H.; Zeng, M. H.;
Kurmoo, M.; Inorg. Chem., 2011, 50, 7274ꢀ7283. (d) Zhou, Y.
L.; Zeng, M. H.; Liu, X. C.; Liang, H.; Kurmoo, M. Chem-Eur J.
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3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
ꢀ 8 ꢀ
ACS Paragon Plus Environment