Three 3-amino-1, 2, 4-triazole-based magnetic complexes incorporated with different carboxylate-containing coligands: Synthesis, structures, and magnetic properties

Article abstract of DOI:10.1002/zaac.201300033

Three 3-amino-1, 2, 4-triazole (atz)-based paramagnetic complexes, [Mn(atz)(pa)]_n (1), {[Mn(atz)_1.5(hip)]·H ₂O}_n (2), and [Mn(H₂O)₂(atz) ₂(nb)₂] (3) (H₂pa = o-phthalic acid, H ₂hip = 5-hydroxylisophthalic acid, and Hnb = p-nitrobenzoic acid) were prepared by introducing different carboxylate-containing aromatic coligands, and structurally and magnetically characterized. Helical Mn ^II-atz and bent Mn^II-pa^2- chains are crosslinked by sharing the same metal sites to generate a honeycomb-shaped framework of 1. The undulated Mn^II-atz layers constructed from 22-member metallomacrocycles are periodically supported by ditopic hip ^2- ligands to lead to a pillared-layer structure of 2. In contrast, complex 3 is a centrosymmetric mononuclear entity, which is assembled into a three-dimensional supramolecular network by abundant hydrogen-bonding interactions. The structural difference of 1-3 is significantly due to the combinations of the flexible coordination modes adopted by the mixed atz and carboxylate groups. Weak and comparable antiferromagnetic couplings are observed in the nearest neighbors of 1-3, which are cooperatively transmitted either by short carboxylate and/or atz heterobridges or by weak non-covalent interactions. Copyright

Full text of DOI:10.1002/zaac.201300033

ARTICLE
DOI: 10.1002/zaac.201300033
Three 3-Amino-1,2,4-Triazole-Based Magnetic Complexes Incorporated with
Different Carboxylate-Containing Coligands: Synthesis, Structures, and
Magnetic Properties
Xi-Ying Zhang,[a] Zheng-Yu Liu,[a] Zhong-Yi Liu,[a] En-Cui Yang,*[a] and Xiao-
Jun Zhao*[a]
Keywords: 3-Amino-1,2,4-triazole; Manganese; Paramagnetic metal complex; Pillared-layer framework; Magnetic properties
Abstract. Three 3-amino-1,2,4-triazole (atz)-based paramagnetic pillared-layer structure of 2. In contrast, complex 3 is a centrosymmet-
complexes, [Mn(atz)(pa)]n (1), {[Mn(atz)1.5(hip)]·H2O}n (2), and
[Mn(H2O)2(atz)2(nb)2] (3) (H2pa o-phthalic acid, H2hip
5-hydroxylisophthalic acid, and Hnb = p-nitrobenzoic acid) were pre-
ric mononuclear entity, which is assembled into a three-dimensional
supramolecular network by abundant hydrogen-bonding interactions.
The structural difference of 1–3 is significantly due to the combina-
tions of the flexible coordination modes adopted by the mixed atz and
=
=
pared by introducing different carboxylate-containing aromatic co-
ligands, and structurally and magnetically characterized. Helical carboxylate groups. Weak and comparable antiferromagnetic couplings
MnII-atz and bent MnII-pa2– chains are crosslinked by sharing the same are observed in the nearest neighbors of 1–3, which are cooperatively
metal sites to generate a honeycomb-shaped framework of 1. The un-
dulated MnII-atz layers constructed from 22-member metallomacro-
cycles are periodically supported by ditopic hip2– ligands to lead to a
transmitted either by short carboxylate and/or atz heterobridges or by
weak non-covalent interactions.
tives with end-on coordination capacity, such as mono- and/or
di-amino, carboxylato, as well as mercapto groups, can also
synergically assist the structural diversity and magnetic inter-
actions either by coordination with spin carriers or by weak
non-covalent interactions.[5,17] Additionally, polycarboxylate
moiety coming from the separate coligand can not only modify
the magnetic phenomena by conformation-dependent magnetic
couplings but also essentially govern the overall connectivity
of the targeted three-dimensional (3D) frameworks by the
number and position effects.[7,8]
On the other hand, different transition metal ions with di-
verse magnetic nature also play important roles for the re-
sulting interesting magnetic behavior, in which the variable co-
ordination polyhedra, the spin-orbit coupling, as well as the
single-ion anisotropy of the paramagnetic centers have become
the most important factors. Up to date, lots of 3D robust CoII-
and CuII-containing magnetic frameworks with mixed triazol-
ate and polycarboxylate mediators have been investigated by
changing different paramagnetic centers or by subtle combina-
tion of mixed heterobridges, which exhibit interesting second-
ary building units, framework connectivity and promising
spin-glassy, spin-flop, as well as spin-frustration phenom-
ena.[6–8,13] However, to the best of our knowledge, only a few
3-amino-1,2,4-triazole (atz)-based manganese(II) complexes
have been investigated by far.[14,18–20]
Introduction
Recently, the design and assembly of molecule-based mag-
netic materials built from suitable organic magnetic bridges
and inorganic paramagnetic metal ions are of intense interest
in the fields of coordination and material chemistry.[1–3] Acting
as a large family of five-member aza-heterocyclic organics,
triazole and the diverse derivatives have gradually becoming
one of the superior mediators, because lots of binary transition
metal ion-triazolate and ternary paramagnetic ion-triazolate-
carboxylate magnetic systems with interesting magnetic be-
havior have been generated by optimized synthetic condi-
tions.[3–16] The rich and varied coordination characteristics,[4]
the asymmetric tridentate bridging mode[7,8] as well as the
well-suited distance by cyclic triazolyl group have been
strongly recognized as the main factors for efficient antiferro-
magnetic superexchange between the nearest spin carriers.
Furthermore, the exocyclic substitutes of the triazolate deriva-
* Dr. E.-C. Yang
E-Mail: encui_yang@yahoo.com.cn
* Prof. Dr. X.-J. Zhao
Fax: +86-22-23766556
E-Mail: xiaojun_zhao15@yahoo.com.cn
[a] College of Chemistry
Tianjin Key Laboratory of Structure and Performance for Func-
tional Molecules
Key Laboratory of Inorganic-Organic Hybrid Functional Material
Chemistry, Ministry of Education
Tianjin Normal University
Herein, to continue our interest in the magnetostructural cor-
relations of the mixed triazole-carboxylate-based magnetic
systems,[7,8,16] three carboxylate-modified coligands, o-
phthalic acid (H2pa), 5-hydroxylisophthalic acid (H2hip), and
Tianjin 300387, P. R. China
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201300033 or from the au-
thor.
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Z. Anorg. Allg. Chem. 2013, 639, (6), 974–981

3-Amino-1,2,4-Triazole-Based Magnetic with Carboxylate-Containing Coligands
p-nitrobenzoic acid (Hnb), were selected as secondary media- ing the presence of an amino group of the atz ligand. An obvi-
tors to react with paramagnetic MnII ions and atz molecules, ously broad band centered at 3422 cm–1 for 2 indicates the
respectively. The special interest for introducing these co- presence of water molecule, which probably masks the weak
ligands is that they have different functionality and molecular absorption for the N–H of the amino group. A weak band at
topology, and can hopefully direct the structure and magnetism 3462 cm–1 and a strong one at 3366 cm–1 in 3 should be as-
of the targeted complexes. As a result, three magnetic samples, cribed to the stretching vibrations of N–H and O–H, respec-
a honeycomb-like 3D framework 1, a pillared-layer coordina- tively, revealing the coexistence of the amino group of atz and
tion network 2, as well as a centrosymmetric mononuclear mo- water molecule.
lecule 3, were successfully generated through slow evaporation
As compared with the free organic acids, the disappearance
method at room temperature. The three complexes were struc- of a characteristic band at 1686 cm–1 for 1, at 1712 cm–1 for
turally and magnetically characterized. Structural determi- 2, and at 1703 cm–1 for 3 is an indicative of the full deproton-
nations reveal that the variable structural motifs and dimen- ation of H2pa, H2hip, and Hnb, respectively. The strong ab-
sionality of 1–3 are essentially governed by the flexible bind- sorptions appearing at 1635, 1559, and 1406 cm–1 in 1 are as-
ing fashions of the mixed ligands with the octahedral MnII cribed to the asymmetric (νas) and symmetry stretching vi-
ion. Weak antiferromagnetic interactions are transmitted in the brations (νs) of carboxylate groups. For the latter two com-
nearest neighbors of the spin carriers mainly by the coopera- plexes, they are located at 1650, 1557, 1508, and 1383 cm–1
tive carboxylate and triazolyl heterobridges or through non- for 2 and at 1613 and 1578 cm–1 as well as 1382 and
covalent weak interactions.
1343 cm–1 for 3. The different separations (Δν = νas– νs)
suggest the coexistence of the terminally monodentate and
bridging bidentate modes of the carboxylate groups in 1–3.[21]
Thus, the IR results are in agreement with the single-crystal
X-ray structural analyses.
Results and Discussion
Syntheses and FT-IR Spectroscopy
Complexes 1–3 can be readily obtained by conventional
evaporation method at room temperature, which is apparently
due to the suitable solubility of the reactant mixture in mixed
Structural Description of [Mn(atz)(pa)]n (1)
¯
Complex 1 crystallizes in the rhombohedral R3 space group
methanol/water medium. Notably, two factors, the inorganic (Table 1), exhibiting a microporous honeycomb-like 3D frame-
anions of the metal salts (NO3– for both 1 and 2 and ClO4– for work constructed from the interconnection of helical MnII-atz
3) and the mixed medium with pH = 6, were found to be more and bent MnII-pa2– chains. The asymmetric unit of 1 contains
essential for the growth of the targeted crystalline samples. In one unique MnII atom, one neutral atz ligand, and one doubly
the IR spectra, a weak absorption located at 3446 cm–1 for 1 deprotonated pa2– anion. As illustrated in Figure 1a, the sole
can be assigned to the stretching vibration of N–H,[21] suggest- MnII ion in 1 is hexacoordinate in a distorted octahedral coor-
Table 1. Crystal data and structure refinement parameters for 1–3.
1
2
3
Formula
Fw
C30H24Mn3N12O12
909.43
C11H12MnN6O6
379.21
C18H20MnN10O10
591.38
Crystal system
Space group
a /Å
b /Å
c /Å
rhombohedral
R3
28.801(8)
28.801(8)
7.473(2)
90
90
120
5368(2)
6
1.688
1.123
2754
–34 Յ h Յ 33
–28 Յ k Յ 34
–6 Յ l Յ 8
2067/ 0 / 172
0.0586
monoclinic
C2/c
18.062(4)
7.7841(16)
19.994(4)
90
94.236(6)
90
2803.3(11)
8
1.740
0.986
1496
–17 Յ h Յ 21
–9 Յ k Յ 9
–23 Յ l Յ 18
2477 / 12 / 233
0.0510
triclinic
P1
¯
¯
7.3540(11)
7.5884(11)
11.922(3)
91.739(3)
96.303(3)
118.480(2)
578.65(19)
1
1.697
0.650
303
–8 Յ h Յ 8
–8 Յ k Յ 9
–10 Յ l Յ 14
2020 / 0 / 178
0.0167
α /°
β /°
γ /°
V /Å3
Z
Dc /g·cm–3
μ /mm–1
F(000)
Limiting indices
Data / restraints / params
Rint
GoF on F2
1.070
1.055
1.071
b)
R1a), wR2 [I Ͼ 2σ(I)]
0.0386, 0.0953
0.0517, 0.1024
1.201, –0.385
0.0427, 0.0951
0.0632, 0.1018
0.622, –0.484
0.0328, 0.0755
0.0392, 0.0799
0.245, –0.313
R1, wR2 [all data]
Residuals /e·Å–3
a) R1 = Σ||Fo| – |Fc||/Σ|Fo. b) wR2 = [Σw(|Fo | – |Fc |)2/Σw|Fo | ]
.
2
2
2 2 1/2
Z. Anorg. Allg. Chem. 2013, 974–981
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E.-C. Yang, X.-J. Zhao et al.
ARTICLE
Figure 1. (a) Local coordination environments of MnII ion in 1 (hydrogen atoms are omitted for clarity. Symmetry codes: A = 1 – x, 2 – y,
1 – z; B = 1 – x, 2 – y, 2 – z, C = y – x + 1/3, 3/5 –x, z – 1/3); (b) Bent and helical chains of 1 constructed from MnII ions, carboxylate groups
and μ-N2,N4-atz ligands; (c) 3D honeycomb-like framework of 1 formed by the interconnected MnII-pa2– and MnII-atz chains.
dination arrangement completed by four carboxylate oxygen atz chains are arranged in an alternating left- and right-handed
donors from three separate pa2– coligands and two triazolyl helical manner to lead to a racemic nature of 1. The MnII···MnII
nitrogen atoms from two neutral atz molecules. The Mn–O separations bridged by μ-anti, syn-COO– and μ-N2,N4-atz me-
and Mn–N separations are between 2.108(2) and 2.268(3) Å diators are 4.5999(9), 4.9436(1), and 6.5525(13) Å. Obviously,
(Table 2), which are comparable with those MnII-containing the effective magnetic coupling in 1 is essentially dominated
complexes with mixed carboxylate and tri-/tetrazolyl li- in the bent MnII-pa2– chain. These separated MnII-pa2– and
gands.[14,16]
MnII-atz chains are interwoven together by sharing the crystal-
lographically unique MnII ion, generating an overall 3D micro-
porous framework of 1 (Figure 1c). The solvent accessible
void fraction is 9.5% calculated by PLATON.[22]
Table 2. Selected bond lengths /Å and angles /° for 1.
Mn(1)–O(2)#1
Mn(1)–O(4)#2
Mn(1)–O(3)
2.108(2)
2.155(2)
2.182(2)
Mn(1)–N(3)#3
Mn(1)–N(2)
Mn(1)–O(1)
2.199(3)
2.268(3)
2.187(2)
O(2)#1–Mn(1)–O(4)#2 90.54(9)
O(2)#1–Mn(1)–N(2) 177.83(10)
O(4)#2–Mn(1)–N(2) 88.47(9)
Structural Description of {[Mn(atz)1.5(hip)]·H2O}n (2)
O(2)#1–Mn(1)–O(3)
O(4)#2–Mn(1)–O(3)
O(2)#1–Mn(1)–O(1)
O(4)#2–Mn(1)–O(1)
O(3)–Mn(1)–O(1)
94.32(9)
91.67(9)
93.99(9)
173.80(9)
83.78(8)
Complex 2 is a 3D pillared-layer framework constructed
from cationic MnII-atz layers and anionic hip2– pillars, exhibit-
ing a 6-connected α-Po-type topological structure. There is one
crystallographically independent MnII atom, one and a half
neutral atz ligands, one doubly deprotonated hip2– anion, and
one disordered lattice water molecule in the asymmetry unit of
2. As shown in Figure 2a, the unique MnII atom in 2 is in an
O3N3 donor set completed by three individual triazolyl moie-
O(3)–Mn(1)–N(2)
O(1)–Mn(1)–N(2)
87.64(9)
87.13(9)
N(3)#3–Mn(1)–N(2) 84.32(10)
O(3)–Mn(1)–N(3)#3 171.96(9)
O(1)–Mn(1)–N(3)#3 95.83(9)
O(2)#1–Mn(1)–N(3)#3 93.72(10)
O(4)#2–Mn(1)–N(3)#3 88.09(9)
Symmetry codes: #1 1 – x, 2 – y, 1 – z; #2 1 – x, 2 – y, 2 – z; #3
y – x + 1/3, 3/5 –x, z –1/3.
As shown in Figure 1b, pairs of symmetry-related pa2– li- ties from three neutral atz molecules and three carboxylate
gands present the two adjacent carboxylate groups to link the groups from three different hip2– ligands, assuming a distorted
neighboring MnII ions into a bent MnII-pa2– chain running octahedral coordination arrangement with the Mn–O distances
along the crystallographic c axis, in which the both carboxylate slightly shorter than those of Mn–N separations (Table 3).
groups are in a bidentate bridging anti, syn conformation (μ-
One atz ligand with a crystallographic twofold axis sym-
anti, syn-COO–). By contrast, the atz ligand in 1 adopts a metry in 2 adopts a μ-N1,N2-bridging mode to aggregate two
bridging μ-N2,N4-bridging mode to infinitely extend the adja- adjacent MnII ions into a dimeric subunit with the intermetallic
cent MnII ions into a helical chain also running along the crys- distance of 4.0151(9) Å. To the best of our knowledge, such a
tallographic c axis (Figure 1b). Notably, the independent MnII- bidentate binding mode of atz ligand has been infrequently
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3-Amino-1,2,4-Triazole-Based Magnetic with Carboxylate-Containing Coligands
Figure 2. (a) Local coordination environments of MnII ion in 2 (hydrogen atoms are omitted for clarity. Symmetry codes: A = x, y, 1/2 –z; B =
x, y, z – 1; C = – x, 1 – y, 1 – z); (b) 2D layer of 2 with dinuclear subunits extended by μ-N2,N4-atz connectors; (c) 3D pillared-layer framework
and the topological denotation of 2.
Table 3. Selected bond lengths /Å and angles /° for 2.
gested into a 6-connected α-Po-type topological structure (Fig-
ure 2c).
Mn(1)–O(1)
2.123(3)
2.199(3)
2.233(3)
94.57(10)
90.03(10)
Mn(1)–O(2)#1
2.172(3)
2.236(3)
2.268(3)
99.57(11)
94.12(11)
85.96(11)
87.56(12)
88.31(11)
Mn(1)–O(4)#2
Mn(1)–N(5)
Mn(1)–N(3)
Mn(1)–N(2)#3
Structural Description of [Mn(H2O)2(atz)2(nb)2] (3)
O(1)–Mn(1)–O(2)#1
O(1)–Mn(1)–O(4)#2
O(1)–Mn(1)–N(5)
O(2)#1–Mn(1)–N(5)
O(4)#2–Mn(1)–N(5)
Complex 3 is a centrosymmetric mononuclear molecule,
which is assembled into a 3D supramolecular network by
abundant N–H···O hydrogen-bonding interactions. The unique
MnII atom in 3 is in an inversion center, surrounded by two
axial carboxylate oxygen atoms from a pair of symmetry-re-
lated nb– anion and four equatorial N2O2 donors from pairs of
triazolyl groups of atz and terminal water molecules, adopting
axially compressed octahedral coordination arrangement with
axial Mn–Ocarboxylate separations 0.08 Å shorter than those of
equatorial Mn–Oaqua and Mn–N bonds (Table 4)
O(2)#1–Mn(1)–O(4)#2 175.32(9)
O(1)–Mn(1)–N(3)
O(2)#1–Mn(1)–N(3)
O(4)#2–Mn(1)–N(3)
N(3)–Mn(1)–N(2)#3
N(5)–Mn(1)–N(2)#3
172.86(11) N(3)–Mn(1)–N(5)
85.37(11)
89.95(11)
84.55(12)
171.01(12)
O(1)–Mn(1)–N(2)#3
O(2)#1–Mn(1)–N(2)#3 89.53(10)
O(4)#2–Mn(1)–N(2)#3 89.72(11)
Symmetry codes: #1 x, y, 1/2 –z; #2 – x, 1 – y, 1 – z; #3 1/2 –x,
y – 1/2, 1/2 –z.
observed in the atz-based metal complexes. Each dimeric
MnII core in 2 is further extended by four μ-N2,N4-atz li-
2
Table 4. Selected bond lengths /Å and angles /° for 3.
gands, leading to a 22-member metallomacrocycle-based layer
made from six MnII ions, two μ-N1,N2- and four μ-N2,N4- Mn(1)–O(1)
2.1735(14) Mn(1)–N(3)
2.2509(15)
2.2460(18)
Mn(1)–O(5)
atz ligands (Figure 2b). The intermetallic separation by the μ-
N2,N4-atz linker is 6.5630(11) Å, considerable longer than that
held by the μ-N1,N2-atz molecule.
O(1)–Mn(1)–N(3)#1 90.45(6)
N(3)–Mn(1)–O(5)#1 88.87(6)
O(1)–Mn(1)–N(3)
89.55(6)
O(1)–Mn(1)–O(5)
N(3)–Mn(1)–O(5)
88.24(5)
91.13(6)
O(1)–Mn(1)–O(5)#1 91.76(5)
Each wave-like layer in 2 is periodically supported by the
coordination of the carboxylate groups of hip2– pillars with the
interlayer metal ions in bidentate bridging and monodentate
Symmetry codes: #1 1 –x, 2 –y, 1 –z.
Rather than serving as μ-N2,N4 and/or μ-N1,N2-bridging
fashions, leading to a 3D pillared-layered framework of 2 with coordination modes in 1 and 2, the neutral atz ligand in 3 only
the interlayer separation of 10.0910(21) Å (Figure 2c). Topo- presents the N4 donor site to coordinate with MnII atom in a
logically, each dinuclear unit of 2 aggregated by μ-N1,N2-atz monodentate fashion. Additionally, the imino group of atz li-
can be considered as a node, and the hip2– and μ-N2,N4-atz gand can act as a typical hydrogen-bond donor to produce two
ligands can be served as two different kinds of ditopic connec- N–H···O hydrogen-bonding interactions with the coordinated
tors. Thus, the 3D coordination polymer of 2 can be predi- water molecule and free nitro group of nb– anion (Table S1,
Z. Anorg. Allg. Chem. 2013, 974–981
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E.-C. Yang, X.-J. Zhao et al.
ARTICLE
Figure 3. (a) Mononuclear structure of 3 (hydrogen atoms are omitted for clarity. Symmetry codes: A = 1 –x, 2 –y, 1 –z.); (b) 2D supramolecular
layer of 3 generated by hydrogen bond interactions; (c) 3D stacking pattern of 3 formed by non-covalent contacts.
Supporting Information), which connects the discrete mononu- patterns of the two bulk samples (Figure S1, Supporting Infor-
clear molecules into a coplanar supramolecular layer (Fig- mation) are in good agreement with each other, indicating the
ure 3b). These non-covalent layers of 3 can be further stacked phase purity of the as-synthesized products.
into a non-covalent 3D network also by inter-layer N–H···O
contacts between the amino moiety of atz ligand and nitro
group of nb– anion (Figure 3c, Table S1).
TGA and PXRD of 1–3
Thermogravimetric analyses (TGA) of 1–3 were carried out
to evaluate their compositional stability (Figure 4). As a result,
complex 1 can be thermally robust up to 320 °C, and is fol-
lowed by a continuous weight-loss process between 320 and
503 °C for the decomposition of the mixed ligands. The re-
maining residue of the complex is MnO (exp. 22.7%, calcd.
23.4%). In contrast, 2 exhibits a continuous two-step weight-
loss stage from 50 °C to 192 °C for the release of disordered
lattice molecule and between 258 and 517 °C for the collapse
of the pillared-layer framework. The final product of 2 above
517 °C is calculated to be MnO (exp. 18.3%, calcd. 18.7%).
Complex 3 also displays a two-step weight-loss process be-
yond 120 °C. The first stage between 120 °C and 137 °C is
due to the loss of two coordinated water molecules (exp. 6.4%,
calcd. 6.1%). The second obvious weight-loss process that be-
gins 224 °C and ends at 828 °C is ascribed to the removal of
Figure 4. TG curves for 1–3.
Magnetic Properties
Variable-temperature (2–300 K) magnetic susceptibilities of
the mixed ligands. The remaining residue of the mononuclear 1–3 were measured under an applied field of 2.0 kOe. As
molecule is MnO (exp. 11.9%, calcd. 12.0%). PXRD experi- shown in Figure 5a, the observed χMT value for per MnII unit
ments were carried out for 1–3 to confirm their crystalline of 1 (4.38 cm3·K·mol–1) is consistent with the spin-only value
phase-purity. The experimental and computer-simulated PXRD (4.37 cm3·K·mol–1) expected for one magnetically uncoupled
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3-Amino-1,2,4-Triazole-Based Magnetic with Carboxylate-Containing Coligands
–1
Figure 5. (a) Plots of χMT and χM vs. T for 1–3. The solid lines correspond to the best least-square fit indicated in the text. (b) Isothermal
magnetizations for 1–3 at 2.0 K.
–1
MnII ion with S = 5/2 and g = 2.0. The χMT product continu- 1.11 cm3·K·mol–1 at 2.0 K. The plot of χM vs. T above 10 K
ously decreases with the decreased temperature, suggesting follows the Curie-Weiss law with C = 8.91 cm3·K·mol–1 and
that an antiferromagnetic coupling occurs in the nearest neigh- θ = –7.60 K. The negative Weiss constant θ suggest antiferro-
bors of 1. The plot of χM–1 vs. T above 10 K follows the Curie- magnetic couplings between the nearest spin carriers in 2 that
Weiss law with C = 4.68 cm3·K·mol–1 and θ = –20.8 K. The is transmitted by the mixed μ-N1,N2-atz and syn, anti-COO–
negative θ value further confirms the antiferromagnetic inter- heterobridges. Analogous to 1, the magnetization of 2 in-
actions dominated between the neighboring MnII ions of 1, creases linearly with the increasing field at 2.0 K, and the
which can be further evidenced by the field-dependent magne- value (5.4 Nβ) at 50 kOe is far from the saturation value for
tization of 1. As shown in Figure 5b, the isothermal magnetiza- two MnII ions (10.0 Nβ, Figure 5b).
tion of 1 measured at 2.0 K increases linearly with the increas-
From the viewpoint of magnetostructural correlations, the
ing fields, and gets to a maximum value (1.2 Nβ) at 50 kOe, magnetic interactions of 2 are significantly interacted with the
which is far from the saturation value of one MnII ion (5.0 Nβ). 2D layer with [Mn2(μ-N1,N2-atz)(syn, anti-COO–)2] subunit
Magnetically, the MnII-pa2– chain extended two carboxylate periodically extended by μ-N2,N4-atz ligand. Therefore, the
groups should be essentially dominated the superexchange in- magnetic data of 2 can be treated by a dinuclear model with a
teraction of 1 due to the relatively short intermetallic distance. molecular field approximation to evaluate the inter-dinuclear
The magnetic model of an infinite uniform chain can thus be interactions.[23]
used to fit the superexchange couplings, in which the molecu-
lar field approximation is introduced to evaluate the interchain
magnetic interaction mediated by the μ-N2,N4-atz ligand.[23]
The molar magnetic susceptibility of 1 can be fitted by the
following expressions Equation (1) and Equation (2):
(3)
(4)
χchain = [N g2β2 S (S+1)/(3kT)][(1+u)/(1–u)]
(1)
The best least-square fit of the theoretical Equation (3) and
Equation (4) to the experimental magnetic data of 2 gave rise
to g = 2.02, J = –0.51 cm–1, zJЈ = –0.15 cm–1, and R =
with u = coth[JS(S+1)/kT]–kT/[JS(S+1)]
χM = χchain/(1–(2zJЈ/Nβ2g2)χchain
)
(2)
The best least-squares fit of the theoretical equations 2.2ϫ10–4. The comparable values for J and zJЈ reveal that
to the experimental data led to g = 2.01, J = –0.53 cm–1, the consistently antiferromagnetic interactions mediated by the
zJЈ = –0.11 cm–1, and R = 5.7ϫ10–4, where R = ∑[(χMT)obsd
–
triple heterobridges. It should be noted that the 2D {Mn(atz)}
(χMT)calcd]2/[(χMT)obsd]2. Obviously, the negative value for J layer of 2 is structurally analogous to the {Cu2(trz)2} sheet of
confirms the antiferromagnetic interaction mediated by the two spin-canted [CuII2CuI(trz)3(Hbtc)]n (trz = 1,2,4-triazolate,
carboxylate bridges is compared with those previous reported H3btc = 1,3,5-benzenetricarboxylic acid).[8] However, no spon-
MnII-containing complexes with double syn-, anti-COO– medi- taneous magnetization was found in 2 at low temperature. This
ators, [Mn2(Hphth)2(phen)4](Hphth)2·2H2O (phth = phthalate is due to that the net magnetic generated by the dinuclear sub-
and phen = 1,10-phenanthroline) with J = –0.34 cm–1[24] and unit is completely canceled out in the isotropic 2D magnetic
[Mn(μ-ClCH2COO)2(phen)]n with J = –0.89 cm–1.[25] The rel- layer of 2.
atively weak zJЈ component supports the weak interchain anti-
ferromagnetic contact through μ-N2,N4-atz ligand.
The χMT value of 3 is 4.49 cm3·K·mol–1 at room tempera-
ture, which is close to the excepted value for one magnetically
The χMT product for each MnII2 unit of 2 is 8.61 cm3·K·mol–1 uncoupled MnII ion. Upon cooling, the χMT product of 3 stead-
at 300 K (Figure 5a), close to the theoretical value ily decreases between 300 and 20 K and then abruptly down
–1
(8.74 cm3·K·mol–1) for two isolated MnII ions with S = 5/2 and to 3.97 cm3·K·mol–1 at 2.0 K. A plot of χM vs. T shows that
g = 2.0. The χMT value of 2 is continuously decreases as the 3 follows the Curie-Weiss law with C = 4.50 cm3·K·mol–1 and
temperature decreases and reaches a minimum value of θ = –0.40 K. These features are indicative of weak antiferro-
Z. Anorg. Allg. Chem. 2013, 974–981
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
979

E.-C. Yang, X.-J. Zhao et al.
ARTICLE
magnetic coupling between the discrete MnII units. The experi-
mentally magnetic data of 3 can be analyzed by a mononuclear
model with a molecular field approximation to evaluate the
intermolecular interactions:[23]
Synthesis of [Mn(atz)(pa)]n (1): To an aqueous solution (4.0 mL) of
Mn(NO3)2 (35.8 mg, 0.2 mmol) was slowly added a methanol solution
(4.0 mL) containing H2pa (16.6 mg, 0.1 mmol) and atz (25.2 mg,
0.3 mmol) with constant stirring. The pH value of the mixture was
adjusted to 6 by triethylamine, and the resulting mixture was further
stirred for 0.5 h and filtered. Upon slow evaporation of the solvent at
room temperature, colorless block-shaped crystals of 1 were obtained
within one month. Yield: 50.0% (based on H2pa). C30H24Mn3N12O12:
calcd. C 39.62; H 2.66; N 18.48%; found C 39.63; H 2.63; N 18.49%.
IR (KBr): ν˜ = 3446 (w), 3063 (w), 1654 (s), 1635 (s), 1559 (s), 1543
(s), 1505 (s), 1473 (m), 1406 (s), 1248 (w), 1081 (w), 770 (w), 694
(w), 665 (m), 647 (w), 615 (w), 549 (w) cm–1.
N β2 g2 S (S+1)
χ =
(5)
3kT
χ
χM
=
(6)
1 – (2zJЈ/Ng2 β2)
The least-squares fitting of magnetic susceptibilities data
over the whole temperature range by Equation (5) and Equa-
tion (6) gives rise to g = 2.02, zJЈ = –0.03 cm–1 and R =
1.3ϫ10–4. The small negative coupling constant zJЈ confirms
the existence of rather weak antiferromagnetic exchange be-
tween the spin carriers through abundant hydrogen-bonding in-
teractions. The magnetization of 3 increases quickly at low
external magnetic elds below 30 kOe and slowly up to 5.03 Nβ
at 50 kOe (Figure 5b), corresponding to the saturation value
(5.00 Nβ) for one MnII with paramagnetic S = 5/2 state.
Synthesis of {[Mn(atz)1.5(hip)]·H2O}n (2): To a methanol solution
(4.0 mL) containing atz (16.8 mg, 0.2 mmol) and H2hip (18.2 mg,
0.1 mmol) was slowly added an aqueous solution (6.0 mL) of
Mn(NO3)2 (26.8 mg, 0.15 mmol) with constant stirring. The resulting
mixture was filtered after further stirring for 0.5 h. Colorless block-
shaped crystals of 2 suitable for X-ray diffraction were generated by
slow evaporation of the filtrate within two weeks. Yield: 66.7% (based
on H2hip). C11H12MnN6O6: calcd. C 34.84; H 3.19; N 22.16%; found
C 34.85; H 3.21; N 22.18%. IR (KBr): ν˜ = 3422 (br), 1650 (s), 1557
(s), 1539 (s), 1508 (s), 1383 (s), 1272 (w), 961 (w), 792 (w), 671 (m),
547 (w), 453 (w) cm–1.
Conclusions
Three 3-amino-1,2,4-triazole based magnetic samples con-
sisting of two extended 3D frameworks and one discrete mo-
nonuclear molecule were obtained by incorporating with dif-
ferently carboxylate-containing aromatic coligands. The com-
binatorial binding fashions of bi- and/or monodentate atz and
carboxylate groups significantly determine the fundamental
motifs and the dimensionality of the resulting complexes. Anti-
ferromagnetic interactions with comparable coupling constants
can be transmitted in the nearest spin carriers in the local
MnII-COO– chain of 1, in the MnII-atz-COO– sublayer of 2,
and by the hydrogen bonding of 3.
Synthesis of [Mn(H2O)2(atz)2(nb)2] (3): To an aqueous solution
(6.0 mL) of Mn(ClO4)2·6H2O (72.4 mg, 0.2 mmol) was slowly added
a methanol solution (4.0 mL) containing Hnb (16.7 mg, 0.1 mmol) and
atz (25.2 mg, 0.3 mmol) with constant stirring. The pH value of the
mixture was adjusted to 6 by triethylamine, and the resulting mixture
was filtered by further stirring for 0.5 h. Upon slow evaporation of the
solvent at room temperature, colorless block-shaped crystals of 3 were
obtained within one month. Yield: 25.0% (based on Hnb).
C18H20MnN10O10: calcd. C 36.56; H 3.41; N 23.69%; found C 36.55;
H 3.43; N 23.66%. IR (KBr): ν˜ = 3462 (w), 3366 (s), 3069 (w), 1613
(s), 1578 (s), 1556 (s), 1515 (s), 1382 (s), 1343 (s), 1318 (m), 1261
(m), 1065 (m), 798 (m), 723 (s), 704 (w), 523 (m) cm–1.
X-ray Data Collection and Structure Determinations: Diffraction
intensities for 1–3 were collected with a Bruker APEX-II QUAZAR
Experimental Section
Materials and General Methods: All chemicals were commercially diffractometer equipped with graphite-monochromated Mo-Kα radia-
purchased (3-amino-1,2,4-triazole, o-phthalic acid, 5-hydroxylisoph- tion with a radiation wavelength of 0.71073 Å by using the φ-ω scan
thalic acid, and p-nitrobenzoic acid were from Acros; other analytical- technique at 173(2) K. Semiempirical multi-scan absorption correc-
grade reagents were from Tianjin chemical reagent factory) and used
as received without further purification. Elemental analyses for C, H,
tions were applied by SADABS, and the program SAINT was used
for integration of the diffraction profiles.[26] The structures were solved
and N were carried out with a CE-440 (Leeman-Labs) analyzer. Fou- by direct methods and refined with the full-matrix least-squares tech-
rier transform (FT) IR spectra (KBr pellets) were taken with an Avatar-
370 (Nicolet) spectrometer in the range 4000–400 cm–1. Thermogravi-
nique using the SHELXS-97 and SHELXL-97 programs.[27] Non-hy-
drogen atoms were located by difference Fourier maps and subjected
metric analysis (TGA) experiments were performed with a Shimadzu to anisotropic refinement. The hydrogen atom was added according to
simultaneous DTG-60A compositional analysis instrument from room
temperature to 800 °C in a nitrogen atmosphere at a heating rate of
theoretical models. The oxygen atom of the lattice water molecule
(O6) in 2 was varied between two positions with the site occupancies
5 K·min–1. Powder X-ray diffraction (PXRD) patterns were obtained of 0.78 for O6 and 0.22 for O6’. No hydrogen atoms were located
with a Bruker D8 ADVANCE diffractometer at 40 kV and 40 mA for for the disordered water molecule. Detailed crystallographic data are
Cu-Kα radiation (λ = 1.5406 Å), with a scan speed of 0.1 sec per step summarized in Table 1. Selected bond lengths and angles are given in
and a step size of 0.01° in 2θ. The simulated PXRD patterns were
Table 2, Table 3, and Table 4, respectively.
calculated using single-crystal X-ray diffraction data and processed by
the free Mercury v1.4 program provided by the Cambridge Crystallo- Crystallographic data (excluding structure factors) for the structures in
graphic Data Center. Magnetic susceptibilities were acquired with a this paper have been deposited with the Cambridge Crystallographic
Quantum Design SQUID MPMS-XL-7 magnetometer with polycrys-
talline samples, in which the phase purity of the samples was deter-
mined by PXRD experiments. The magnetic susceptibility was cor-
rected for the contribution of the gel capsule and for the core diamag-
netism (using Pascal’s constants).
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK.
Copies of the data can be obtained free of charge on quoting
the depository numbers CCDC-910490, CCDC-910491, and CCDC-
910492 (for complexes 1–3) (Fax: +44-1223-336-033; E-Mail:
deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
980
www.zaac.wiley-vch.de
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2013, 974–981

3-Amino-1,2,4-Triazole-Based Magnetic with Carboxylate-Containing Coligands
[10] S. Ferrer, P. J. van Korringsbruggen, J. G. Haasnoot, J. Reedijk,
Supporting Information (see footnote on the first page of this article):
Hydrogen-bonding parameters for 3 and PXRD patterns for 1–3.
H. Kooijman, A. L. Spek, L. Lezama, A. M. Arif, J. S. Miller, J.
Chem. Soc. Dalton Trans. 1999, 4269.
[11] D. Sarma, V. Srivastava, S. Natarajan, Dalton Trans. 2012, 41,
4135.
Acknowledgements
[12] S.-P. Chen, S. Shu, S.-L. Gao, Inorg. Chim. Acta 2009, 362, 3043.
[13] a) Z.-G. Gu, Y.-F. Xu, X.-H. Zhou, J.-L. Zuo, X.-Z. You, Cryst.
Growth Des. 2008, 8, 1306; b) J.-C. Liu, G.-C. Guo, J.-S. Huang,
X.-Z. You, Inorg. Chem. 2003, 42, 235; c) J.-H. Zhou, R.-M.
Cheng, Y. Song, Y.-Z. Li, Z. Yu, X.-T. Chen, Z.-L. Xue, X.-Z.
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This present work was financially supported by the National Natural
Science Foundation of China (Grants 21171129 and 21173157) and
Tianjin Municipal Education Commission (2012ZD02), which are
gratefully acknowledged.
[14] B. Liu, Y.-H. Chen, X.-C. Zhang, Inorg. Chem. Commun. 2008,
11, 965.
[15] B. Ding, Y.-Q. Huang, Y.-Y. Liu, W. Shi, P. Cheng, Inorg. Chem.
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[17] E.-C. Yang, Z.-Y. Liu, C.-H. Zhang, Y.-L. Yang, X.-J. Zhao, Dal-
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Received: January 21, 2013
Published Online: March 28, 2013
Z. Anorg. Allg. Chem. 2013, 974–981
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
981