Dinuclear, tetranuclear and chain (MnII, CoII) complexes of multifunctional hydrazone ligands- Structural and magnetic studies

Article abstract of DOI:10.1002/ejic.201100746

The coordination chemistry of a group of hydrazone-based ligands, modified with carboxylate and heterocyclic terminal donor groups, with Mn^II and Co^II has been investigated. The multifunctional nature of the ligands allows coordinative flexibility based on the hydrazone core, which is well established to lead to spin-coupled polymetallic assemblies through μ-O_hydrazone bridging. Examples of dinuclear, tetranuclear and chain complexes are reported with hydrazone, carboxylate and triazole bridging. Spin exchange through the μ-O and μ-N,N bridging connections leads to antiferromagnetic exchange in most cases, except for the central subunit in the Mn^II₄ chain complex, where small (< 90°) bridge angles result in contributing ferromagnetic interactions. Multifunctional polytopic hydrazone ligands form polymetallic complexes with μ-O (hydrazone, carboxylate) and μ-N,N (triazole) bridging, leading to spin-spin interactions between the metal centres with examples of antiferromagnetic and ferromagnetic exchange.

Full text of DOI:10.1002/ejic.201100746

FULL PAPER
DOI: 10.1002/ejic.201100746
Dinuclear, Tetranuclear and Chain (MnII, CoII) Complexes of Multifunctional
Hydrazone Ligands – Structural and Magnetic Studies
Peter J. Bettle,[a] Louise N. Dawe,[a] Muhammad U. Anwar,[a] and Laurence K. Thompson*[a]
Keywords: Hydrozone ligands / Magnetic properties / Cobalt / Manganese
The coordination chemistry of a group of hydrazone-based
ligands, modified with carboxylate and heterocyclic terminal
donor groups, with MnII and CoII has been investigated. The
multifunctional nature of the ligands allows coordinative
flexibility based on the hydrazone core, which is well estab-
lished to lead to spin-coupled polymetallic assemblies
through μ-Ohydrazone bridging. Examples of dinuclear, tetra-
nuclear and chain complexes are reported with hydrazone,
carboxylate and triazole bridging. Spin exchange through
the μ-O and μ-N,N bridging connections leads to antiferro-
magnetic exchange in most cases, except for the central sub-
unit in the MnII chain complex, where small (Ͻ 90°) bridge
4
angles result in contributing ferromagnetic interactions.
addition to hydrazone bridging. Structures of dinuclear, tet-
ranuclear and chain complexes are described in addition to
magnetic data and an analysis of the intramolecular ex-
change interactions.
Introduction
Functionalized hydrazone-based ligands have enjoyed
considerable success as platforms for the synthesis of square
[nϫn] (n = 2–5) grid complexes by self-assembly, as a result
of the contiguous arrangement of coordination pockets
containing hydrazone oxygen and nitrogen donor atoms, in
addition to donors from terminal groups. A selection of
ditopic, tritopic, tetratopic and pentatopic ligands is illus-
trated in Scheme 1, which produce M4, M9, M16, and M25
complexes with MnII, CoII, NiII, CuII and ZnII.[1] Typically,
the end pieces are heterocyclic N-donor groups. The hydraz-
one oxygen atoms bridge adjacent metal ions leading to
spin-exchange interactions. Modifying the hydrazone func-
tionality with, for example, oxime groups leads to the pos-
sibility of additional further assembly processes involving
the formation of triangular groups of metal ions, which is
frequently observed with simple oximes.[2] This has been
observed with the modified hydrazone ligands HL3C and
H2L4, which produce Cu6 and Cu36 assemblies, respectively,
in which the hydrazone groups act in a bridging capacity,
but the oxime ends bind three CuII ions in [Cu3(μ2-NO)3-
(μ-O)] triangular groups connected to hydrazone-bridged
subunits.[3,4]
Results and Discussion
Structural Descriptions
Crystallographic details for 1–4 are listed in Table 5.
[C28H30MnN8O10]n (1)
The structure of 1 is illustrated in Figure 1, and selected
bond lengths and angles are listed in Table 1. The structure
consists of a 1D chain of metallacyclic rings with each ring
comprising two MnII centres and two ligands. The ligands
adopt an unusual open bidentate bonding mode involving
a 4-pyrazine nitrogen atom and a carboxylate oxygen atom
with two pairs of N and O donor atoms from separate li-
gands occupying cis positions around each six-coordinate
MnIIN2O4 ion. The other two trans coordination sites are
occupied by water molecules. The C5–O1 hydrazone bond
length is 1.23 Å, which indicates ketone double bond char-
acter, with a proton residing on the adjacent nitrogen atom
N3. Each ligand therefore behaves as a monoanion, which
leads to overall charge neutrality. The Mn–Mn separation
is 10.22 Å. One feature, which may in part be responsible
for the chain structure, is the proximity of the pyrazine rings
within each metallacyclic ring in addition to the pyrazine
and phenyl rings. Centroid–centroid distances of 4.40 and
3.78 Å suggest that the pyrazine–phenyl contacts represent
the only significant π contacts (Figure 1).
In this study we have used the hydrazone group as a
building block and extended it on one end with a carboxyl-
ate group and at the other end with a potentially bridging
heterocyclic donor group, viz. triazole and pyrazine
(Scheme 1; ligands shown in their carboxylic acid form).
Reaction with MnII and CoII salts produced crystalline
complexes, in which examples of triazole bridging, carb-
oxylate bridging and pyrazine bridging were observed in
[a] Department of Chemistry, Memorial University,
St. John’s, NL, A1B3X7, Canada
E-mail: lk.thompson@mun.ca
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MnII and CoII Complexes of Multifunctional Hydrazone Ligands
Table 1. Selected bond lengths [Å] and angles [°] for 1.
Mn1–O3
Mn1–O4
Mn1–N1
O3–Mn1–O3
O3–Mn1–O4
O3–Mn1–O4
O3–Mn1–O4
O3–Mn1–O4
2.128(3)
2.171(3)
2.319(4)
179.999(1)
94.99(12)
85.02(12)
85.01(12)
94.98(12)
O4–Mn1–O4
O4–Mn1–N1
O4–Mn1–N1
O3–Mn1–N1
O3–Mn1–N1
O4–Mn1–N1
N1–Mn1–N1
180.000(1)
85.64(12)
94.36(12)
90.91(14)
89.09(14)
94.36(12)
180.00(1)
[(C13H8N4O3)2Mn2(CH3OH)2][(CH3OH)(H2O)1.072
(CH2OH)0.928] (2)
-
The structure of 2 is shown in Figure 2, and selected
bond lengths and angles are listed in Table 2. The structure
contrasts sharply with that of 1, as it is a dinuclear complex
with two ligands bridging two seven-coordinate MnII ions
in a [μ-Ohydrazone]2 capacity, with further ligand binding in
the pentagonal plane through the carboxylate oxygen,
Ndiazine and pyrazine nitrogen atoms. Axial positions at
each MnII centre are occupied by oxygen atoms from one
coordinated methanol molecule and an unusual partial oc-
cupancy situation involving a combination of water and
methanol at the other position. The excellent data quality
for this sample, and the presence of all protons in differ-
ence-map positions, revealed this unusual occupancy model
expressed in the formula. Figure 2 shows this coordination
site represented by just the methanol component (O5). The
Scheme 1.
Figure 2. Structural representation of 2.
Table 2. Selected bond lengths [Å] and angles [°] for 2.
Mn1–O4
Mn1–O5
Mn1–O2
Mn1–O1
Mn1–O1
Mn1–N4
Mn1–N1
O4–Mn–1O5
O4–Mn1–O2
O5–Mn1–O2
O4–Mn1–O1
O5–Mn1–O1
O2–Mn1–O1
O4–Mn1–O1
O5–Mn1–O1
2.1894(16)
2.2176(16)
2.2358(17)
2.2449(14)
2.2606(15)
2.2659(17)
2.3707(17)
166.99(5)
82.52(5)
84.83(5)
84.71(5)
105.76(5)
154.32(4)
98.72(5)
O2–Mn1–O1
O1–Mn1–O1
O4–Mn1–N4
O5–Mn1–N4
O2–Mn1–N4
O1–Mn1–N4
O1–Mn1–N4
O4–Mn1–N1
O5–Mn1–N1
O2–Mn1–N1
O1–Mn1–N1
O1–Mn1–N1
N4–Mn1–N1
Mn1–O1–Mn1
138.02(5)
66.05(6)
86.19(6)
92.46(6)
70.65(4)
130.58(5)
67.60(5)
94.26(6)
82.70(5)
89.94(5)
68.87(5)
131.40(4)
160.38(5)
113.95(6)
92.69(5)
Figure 1. Structural representation of 1.
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P. J. Bettle, L. N. Dawe, M. U. Anwar, L. K. Thompson
FULL PAPER
Mn–L distances fall in the range 2.18–2.37 Å, typical for Mn2 115.6°). This difference is reflected in the magnetic
MnII, the Mn–Mn distance is 3.78 Å, and the Mn–O–Mn properties (vide infra). The final pair of ligands bind in an
angle is 114.0°.
unusual monodenate manner to Mn1 and Mn1Ј through
the carboxylate groups and appear to dangle from the ends
of the chain. The two bridging ligands bear a –2 charge,
whereas the others have –1 charges, thus producing a
charge-neutral complex.
[(C13H9N4O3)4(C13H8N4O3)2Mn4(H2O)5](H2O)2-
(CH3OH)2 (3)
The molecular structure of 3 is shown in Figure 3, and
selected bond lengths and angles are listed in Table 3. The
complex consists of a linear chain of four seven-coordinate
Mn centres bound within a group of six ligands. The Mn–
L distances fall in the range 2.14–2.38 Å, typical of MnII.
Two tetradentate ligands play the most important role in
creating the chain of MnII ions and binding through their
terminal pyrazine N, hydrazone N and O and carboxylate
O atoms. The hydrazone oxygen atoms bridge the outer
Mn1 atoms to the inner Mn2 atoms, and the terminal carb-
oxylate groups surprisingly link the central pair of Mn
centres through μ2-O single atom bridging. A third μ-O
bridge between Mn2 and Mn2Ј is provided by a water mole-
cule (O11). The triple oxygen bridging arrangement brings
the metal ions into close proximity [Mn2–Mn2Ј
3.1565(14) Å]. Two other tridentate ligands bind to the
outer Mn centres through the hydazone N and terminal
hydrazone O atoms, but once again a μ-Ocarboxylate atom
(O2) bridges Mn1 and Mn2. The Mn–O–Mn angles within
the central Mn2 subunit are Ͻ 90° (Mn2–O5–MnЈ 89.22°,
Mn2–O11–Mn2Ј 88.00°), whereas angles on the outer Mn2
subunits are much larger (Mn1–O2–Mn2 103.6°, Mn1–O4–
[(C6H5N5O3)Co(H2O)2]2(H2O)4 (4)
The structure of 4 is shown in Figure 4, and selected dis-
tances and angles are listed in Table 4. Two distorted octa-
hedral cobalt ions are bound in an almost planar arrange-
ment of two tetradentate ligands, with two deprotonated
triazole groups bridging the metal centres. The Co–L dis-
tances fall in the range 2.02–2.23 Å, typical of CoII, with
short contacts to the triazole nitrogen atoms. The Co–Co
distance is 3.75 Å. The Co–N–N–Co torsion angles are
Ͻ 4°, which indicates essential planarity of the metal ions
and the triazole rings. Each triazole ring provides two equa-
torial nitrogen donors at each Co ion, with water molecules
occupying the axial positions and pyruvate oxygen and hy-
drazone nitrogen donor atoms completing the equatorial
coordination. Each ligand has a –2 charge, which results in
a charge-neutral species.
Figure 4. Structural representation of 4.
Table 4. Selected bond lengths [Å] and angles [°] for 4.
Co1–O2
Co1–N1
Co1–O7
Co1–N7
Co1–N5
Co1–O8
Co2–O5
Co2–O5
2.0447(16)
2.0424(17)
2.0817(15)
2.0880(18)
2.1723(18)
2.1851(14)
2.0261(16)
2.0261(16)
2.0413(17)
2.0943(15)
2.0981(18)
2.1803(18)
2.2299(16)
163.45(5)
91.40(6)
92.47(7)
109.08(6)
87.01(6)
90.03(6)
85.37(6)
78.36(5)
92.94(7)
N7–C o1–N5
N1–Co1–O8
O2–Co1–O8
O7–Co1–O8
N7–Co1–O8
N5–Co1–O8
O5–Co2–N6
O5–Co2–O9
N6–Co2–O9
O5–Co2–N2
N6–Co2–N2
O9–Co2–N2
O5–Co2–N10
N6–Co2–N10
O9–Co2–N10
N2–Co2–N10
O5–Co2–O10
N6–Co2–O10
O9–Co2–O10
N2–Co2–O10
N10–Co2–O10
165.18(6)
84.91(6)
92.60(6)
173.42(5)
86.04(6)
92.20(6)
161.46(6)
94.33(6)
90.58(6)
87.90(6)
109.49(6)
94.99(6)
78.05(5)
84.56(6)
85.36(6)
165.93(6)
89.95(6)
86.18(6)
174.93(5)
82.45(6)
98.19(6)
Figure 3. Structural representation of 3.
Co2–N6
Co2–O9
Co2–N2
Table 3. Selected bond lengths [Å] and angles [°] for 3.
Co2–N10
Co2–O10
N1–Co1–O2
N1–Co1–O7
O2–Co1–O7
N1–Co1–N7
O2–Co1–N7
O7–Co1–N7
N1–Co1–N5
O2–Co1–N5
O7–Co1–N5
Mn1–O8
Mn1–O4
Mn1–O10
Mn1–O2
Mn1–O1
Mn1–N4
Mn1–N5
Mn2–O4
Mn2–O12
Mn2–O5
2.141(3)
2.145(2)
2.156(3)
2.282(2)
2.295(2)
2.321(3)
2.372(3)
2.148(2)
2.166(3)
2.195(2)
Mn2–O11
Mn2–O5
Mn2–N8
Mn2–O2
2.272(2)
2.298(2)
2.306(3)
2.341(2)
3.1565(14)
103.57(9)
115.59(10)
89.22(8)
88.00(11)
Mn2–Mn2
Mn1–O2–Mn2
Mn1–O4–Mn2
Mn2–O5–Mn2
Mn2–O11–Mn2
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MnII and CoII Complexes of Multifunctional Hydrazone Ligands
Magnetic Properties
On examining the structure of 3 and the bridging con-
nections within the dinuclear MnII subunits, there is an
2
Variable-temperature magnetic data for 1 indicate a
roughly constant moment of 6.1 μB throughout the 2–300 K
temperature range, which indicates Curie behaviour consis-
tent with the large distance separating the Mn ions. Vari-
able-temperature magnetic data for 2 are shown in Figure 5
as plots of molar susceptibility and moment as a function
of temperature. The overall smooth drop in moment with
decreasing temperature indicates the presence of intramo-
lecular antiferromagnetic exchange, and the shoulder on the
susceptibility plot suggests a small amount of paramagnetic
impurity. The data were fitted to a simple isotropic ex-
change Hamiltonian for two spin-coupled S = 5/2 centres
[Equation (1)], using MAGMUN4.1.[5]
obvious difference between the central and outer subunits
based on the Mn–O–Mn bridging angles. All Mn–O–Mn
angles in the central subunit are Ͻ 90°, whereas the angles
in the outer subunits are 103.6°and 115.6°. The classical
exchange paradigm for O-bridged dinuclear species is asso-
ciated with the magnitude of the M–O–M angle, particu-
larly in the case of copper,[7,8] and on the basis of overlap
arguments involving metal ion orbitals and the oxygen p-
orbitals, angles of around 90° represent a changeover region
from ferromagnetic (Ͻ 90°) to antiferromagnetic (Ͼ 90°)
behaviour. On this basis the magnetic behaviour of 3 was
fitted to Equation (2), which assumes a positive J value for
the central subunit (J2) and negative J values (J1) for the
outer subunits. A good fit was obtained with the software
package MAGMUN4.1,[5] to give g = 2.03(1), J1 = –2.9(1)
cm–1, J2 = 2.5(1) cm–1 and TIP = 0, θ = 0.4 K (102R =
3.1), and the solid line in Figure 6 was calculated with these
parameters. The presence of both ferromagnetic and anti-
ferromagnetic exchange in 3 is unusual but in agreement
with orbital arguments based on M–O–M bridge angles.
Examples of μ-O-bridged MnII dinuclear complexes exhib-
iting ferromagnetic exchange are rare. However, one exam-
ple with two μ-Ocarboxylate bridges and Mn–O–Mn bridge
angles of 101.8° exhibits ferromagnetic exchange (J =
0.462 cm–1), supported by theoretical calculations.[9] The
much smaller Mn–O–Mn angles in 3, would be expected to
lead to enhanced ferromagnetic exchange, as is observed.
Hex = –J1{S1·S2}
(1)
Hex = –J1{S1·S2 + S3·S4} – J2{S2·S3}
(2)
Figure 5. Variable-temperature magnetic data for 2. See text for
fitting parameters.
Variable-temperature magnetic data for 4 are shown in
Figure 7 as plots of molar susceptibility and moment as a
function of temperature. A characteristic maximum in χmol
at 12 K signifies the presence of intramolecular antiferro-
magnetic exchange between the two CoII centres. The mo-
ment drops steadily from 6.7 μB at 300 K to 1.05 μB at 2 K,
which suggests a ground-state singlet. The orbital contri-
butions to the magnetic properties of high-spin CoII species
An excellent fit was obtained for g = 2.00(1), J = –3.9(1)
cm–1, TIP = 0 cm3 mol–1, ρ = 0.031 and 102R = 0.33 (R =
[Σ(χobs – χcalc)2/Σχobs2 1/2). The J value is consistent with the
]
structural arrangement of the two MnII centres connected
by μ-O bridges with an Mn–O–Mn angle of 114.0°.[6]
Variable-temperature magnetic data for 3 are shown in
Figure 6 as plots of molar susceptibility and moment as a
function of temperature. A characteristic maximum in χmol
at 10 K signifies the presence of dominant intramolecular
antiferromagnetic exchange.
4
(S = 3/2) are associated with the T1g ground state and
should be taken into account, unless their effect is effec-
Figure 7. Variable-temperature magnetic data for 4. See text for
fitting parameters by using isotropic spin-only models (inset: fitting
from 2 to 40 K).
Figure 6. Variable-temperature magnetic data for 3. See text for
fitting parameters.
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P. J. Bettle, L. N. Dawe, M. U. Anwar, L. K. Thompson
FULL PAPER
tively quenched due to large distortions from octahedral
symmetry.[10,11] Complex 4 is quite distorted, and so an at-
tempt was made to fit the data to a simple isotropic dinu-
clear exchange expression [Equation (1), S = 3/2], which as-
sumes orbital-moment quenching. Surprisingly, a reason-
ably good fit was obtained over the full temperature range
with MAGMUN4.1,[5] to give g = 2.43(8), J = –5.3(1) cm–1
and θ = –0.2 K (102R = 2.4). The solid line in Figure 7 was
plotted with these parameters.
Conclusions
The incorporation of multiple sites in a polyfunctional
ligand creates donor complexity, and it is difficult to predict
a priori which particular group will dominate on coordina-
tion. The hydrazone group has been shown to produce μ-
O
hydrazone-bridged complexes in simple polytopic ligands
with one type of substituent other than the hydrazone (e.g.
poap, 2poap and related ligands Scheme 1) with grid sys-
tems prevailing.[1] The introduction of carboxylate groups
creates opportunities for new coordination motifs and the
possibility of forming charge-neutral complexes. Ligands
H2L5 and H2L6 also include heterocyclic components,
which can bridge in their own right. With MnII and CoII,
three structural types were observed: 1D chain, dinuclear
and tetranuclear, with short-range bridging through μ2-
The single-ion excited states for octahedral high-spin
CoII are well separated from the ground state, and the Kra-
4
mer’s doublet component of the T1g ground state, which
arises from spin–orbit coupling, is the only one significantly
populated at low temperatures (Ͻ 30–40 K). Consequently,
an isotropic fitting of the magnetic data to Equation (1) (S
= 3/2) is perhaps considered more valid in this temperature
range and should yield a more reasonable estimate of J.
The magnetic data from 2–40 K were therefore fitted to the
isotropic exchange expression [Equation (1), S = 3/2] to give
g = 2.28(2), J = –4.0(1) cm–1, TIP = 150ϫ10–6 cm3 mol–1
and θ = –1 K (102R = 2.07). The fit is shown in the inset
of Figure 7. The reduced value of –J using this treatment is
reasonable, based on an expected overestimation of J when
orbital contributions are ignored at higher tempera-
tures.[10,11] In an attempt to evaluate the single-ion CoII
contributions more thoroughly, Sakiyama’s approach was
adopted by using the software package MagSaki.[12–14] Al-
though an exactly comparable geometric model for the dis-
tortion in 4 was not available, an axial, anisotropic dinu-
clear CoII model was used. A good fit was obtained for J
= –3.9 cm–1, gz = 2.20, gx = 4.95, λ = –158 cm–1, κ = 0.93
and Δ = 793 cm–1 (102R = 2.3) (λ = spin–orbit coupling
constant, κ = orbital reduction factor, Δ = axial splitting
parameter), and the result is shown in Figure 8. This model
cannot be considered rigorous, but the parameters evalu-
ated are reasonable compared with related dinuclear CoII
systems,[10–14] and in particular the J value is entirely consis-
Ohydrazone-, μ2-Ocarboxylate- and μ2-triazole-based groups.
Spin–spin interactions through these bridges resulted in
antiferromagnetic exchange in most cases, except for the
central dimanganese portion of the Mn4 chain cluster,
where rare ferromagnetic coupling was observed as a result
of the acute average Mn–O–Mn angles (Ͻ 90°).
Experimental Section
Experimental Methods: Commercially available solvents and chemi-
cals were used without further purification. Infrared (IR) spectra
were obtained as Nujol mulls between KBr discs with a Mattson
Polaris FT-IR instrument. Mass spectra were recorded with an Ag-
ilent 1100 Series LC/MSD in atmospheric-pressure chemical-ion-
ization positive (APCI+) mode with methanol/acetonitrile mixtures
as solvents. Variable-temperature magnetic data were collected with
a Quantum Design MPMS5S Squid Magnetometer by using field
strengths of 0.1–5 T and in the temperature range of 2–300 K.
Background corrections for the sample holder assembly and dia-
magnetic components of the complexes were applied.
Synthesis of Ligands
H2L5: SOCl2 (5 drops) was added to 2-pyrazinecarboxylic acid
tent with simpler models based on isotropic exchange (vide (Aldrich) (10.00 g, 0.08000 mol), dissolved in methanol (80 mL),
and the mixture was heated to reflux for 3 d to give a clear brown
solution. The solution was concentrated under reduced pressure to
yield the corresponding methyl ester as a pink solid in quantitative
supra). It is clear from all fitting attempts that the antiferro-
magnetic exchange is based on the dinuclear structure and
is propagated through the almost planar arrangement of
the two N2 triazole bridges, as expected.
yield. MS: m/z = 139.0, 107.0. IR: ν = 1720 [ν(CO) ester], 954
˜
[ν(pyrazine)] cm–1. The crude product was dissolved in methanol
(200 mL), hydrazine monohydrate (4.97 g, 0.0993 mol) in methanol
(10 mL) was added, and the mixture was heated to reflux for 24 h.
2-Pyrazinoic acid hydrazide was obtained as an off-white precipi-
tate (yield 8.97 g, 81.2%), which was collected by filtration and
washed with methanol (2ϫ10 mL). MS: m/z = 139.0, 121.0, 193.0.
IR: ν = 3305 [ν(NH)], 3226 [ν(NH)], 1647 [ν(CO amide)], 961
˜
[ν(pyrazine)] cm–1. 2-Pyrazinoic acid hydrazide (1.98 g, 0.0143 mol)
was dissolved in methanol (100 mL) in a round-bottomed flask.
Phenylglyoxylic acid (1.91 g, 0.0174 mol) was added with methanol
(40 mL) to produce a clear light yellow solution. The solution was
heated to reflux for approximately 24 h to yield H2L5 as a white
precipitate, which was collected by suction filtration and washed
with methanol (yield 2.32 g, 60% based on 2-pyrazinoic acid hydra-
zide). MS: m/z = 271.1 [M + H]+, 227.1, 225.1, 228.1. M.p. 220–
225 °C. IR: ν = 3214 [ν(NH)], 1707 [ν(CO)], 1643, 1510 [ν(CO),
˜
Figure 8. Variable-temperature magnetic data for 4. See text for
fitting parameters by using anisotropic model with orbital contri-
butions.
ν(CN)], 933 [ν(pyrazine)] cm–1. C13H10N4O3 (270.25): calcd. C
57.80, H 3.70, N 20.74; found C 58.36, H 3.61, N 20.93.
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MnII and CoII Complexes of Multifunctional Hydrazone Ligands
HL6Na: Methyl-1H-1,2,4-triazole-3-carboxylate (Aldrich) (2.03 g,
0.0160 mol) was added to methanol (80 mL) in a round-bottomed
flask to give a colourless solution. A solution of hydrazine hydrate
(0.98 g, 0.020 mol) in methanol was added to the flask. The mixture
was heated to reflux for 24 h to yield a white precipitate. The solid
was isolated by suction filtration and washed with methanol to
yield 1H-1,2,4-triazole-3-carbohydrazide (yield 1.86 g, 91% based
on triazole carboxylate). MS: m/z = 128.1 [M + H]+, 73.1, 110.1,
analysis indicates some water of solvation of the sample in com-
parison with the crystal chosen for X-ray analysis.
[(C13H9N4O3)4(C13H8N4O3)2Mn4(H2O)5](H2O)2(CH3OH)2
(3):
MnCl2·4H2O (0.090 g, 0.46 mmol) was dissolved in methanol
(10 mL) in a round-bottomed flask. H2L5 (0.10 g, 0.34 mmol) was
added to the flask with a methanol/water (5:1) mixture (12 mL).
The ligand did not dissolve initially, so triethylamine (4 drops) was
added, which produced a dark yellow solution. The solution was
gravity-filtered to give a dark yellow clear filtrate. The filtrate was
left to slowly concentrate at room temperature. Orange, rod-shaped
crystals suitable for X-ray diffraction formed after 1 week (yield
70.1, 96.0. IR: ν = 3299 [ν(NH)], 3220 [ν(NH)], 1671 [ν(CO amide)]
˜
cm–1. 1H-1,2,4-Triazole-3-carbohydrazide (1.86 g, 0.0146 mol) was
dissolved in methanol (100 mL) in a round-bottomed flask to give
a colourless solution. Sodium pyruvate (1.93 g, 0.0175 mol) and
methanol (30 mL) were added, and the mixture was heated to re-
flux for 24 h to give a white precipitate. The white fluffy solid
(HL6Na) was collected by suction filtration and washed with meth-
anol (yield 3.12 g, 98% based on triazole hydrazide). M.p.
24.1 mg, 10.5% based on metal salt). IR: ν = 3219 [ν(NH)], 1691
˜
[ν(CO)], 1673, 1521 [ν(CO, ν(CN)]. 933 [ν(pyrazine)] cm–1.
(C13H9N4O3)4(C13H8N4O3)2Mn4(H2O)5(H2O)3(CH3OH)2 (2040.28):
calcd. C 47.05, H 3.72, N 16.47; found C 46.80, H 3.34, N 16.51.
[(C6H5N5O3)Co(H2O)2]2(H2O)4 (4): Co(NO3)2·4H2O (0.16 g,
0.55 mmol) was dissolved in H2O (5 mL) in a round-bottomed
flask. H2L6 (0.10 g, 0.46 mmol) was dissolved in H2O (5 mL). The
two solutions were combined and stirred at room temperature for
20 min to give a cloudy light pink solution. The solution was grav-
ity-filtered to give a pink precipitate and a light pink, clear filtrate.
The filtrate was left to slowly concentrate at room temperature. Red
crystals suitable for X-ray diffraction formed after 2 weeks (yield
Ͼ260 °C. IR: ν = 3351, 3116 [ν(NH)], 1691 [ν(CO)], 1531 [ν(CN)]
˜
cm–1. C6H6N5NaO3 (219.13): calcd. C 32.73, H 3.18, N 31.82;
found C 32.90, H 2.72, N 31.87.
Synthesis of Complexes
[C28H30MnN8O10]n (1) and (C13H8N4O3)2Mn2(CH3OH)(H2O)3 (2):
Mn(CH3COO)2·4H2O (0.10 g, 0.41 mmol) was dissolved in meth-
anol (10 mL) in a round-bottomed flask. H2L5 (0.10 g, 0.34 mmol)
was added to methanol (10 mL), and the solution was warmed.
The two mixtures were combined to give a cloudy orange solution.
H2O was added dropwise, but the precipitate still did not dissolve.
The reaction mixture was then stirred and heated gently for 24 h.
A cloudy orange solution resulted, which was gravity-filtered to
give a clear light yellow filtrate, and an orange precipitate. Attempts
to redissolve the precipitate were unsuccessful. The yellow filtrate
was left to slowly concentrate at room temperature. Colourless
crystals of 1 suitable for X-ray diffraction formed after 2 weeks
15.5 mg, 10.5% based on metal salt). IR: ν = 3415, 3351, 3116
˜
[ν(NH), ν(OH)], 1676 [ν(CO)] cm–1. (C6H5N5O3)2Co(H2O)2-
(H2O)4 (652.03): calcd. C 22.09, H 3.98, N 21.47; found C 22.19,
H 3.68, N 21.75.
X-ray Crystallography: Crystals of 1–4 were mounted on low-tem-
perature diffraction loops and measured with a Rigaku Saturn 70
CCD area detector with graphite-monochromated Mo-Kα radia-
tion (Table 5). The structures were solved by direct methods[15] and
expanded by using Fourier techniques.[16] Neutral atom scattering
(yield 45 mg, 16% based on metal salt). IR: ν = 3214 [ν(NH)], 1686 factors were taken from Cromer and Waber.[17] Anomalous disper-
˜
[ν(CO amide)], 937 [ν(pyrazine)] cm–1. C28H30MnN8O6 (629.53): sion effects were included in Fcalcd.
,
and the values for ΔfЈ and
[18]
calcd. C 48.48, H 4.32, N 16.16; found C 47.83, H 4.08, N 16.42.
On further standing, a small quantity of orange crystals (ca. 15 mg)
of 2 was obtained from the mother liquor, which were also suitable
ΔfЈЈ were those of Creagh and McAuley.[19] The values for the mass
attenuation coefficients are those of Creagh and Hubbell.[20] All
calculations were performed by using the CrystalStructure[21,22]
for X-ray diffraction. C27H26Mn2N8O10 (732.43): calcd. C 43.94, H crystallographic software package except for refinement, which was
3.03, N 15.74; found C 44.25, H 3.57, N 15.30. The elemental
performed by using SHELXL-97.[15] All non-hydrogen atoms were
Table 5. Crystallographic details for 1–4.
1
2
3
4
Empirical formula
M
T [K]
C28H30MnN8O10
693.53
153(2)
C30H34.14Mn2N8O11.07
793.78
153(2)
C80H74Mn4N24O27
2023.36
153(2)
C12H26Co2N10O14
652.26
153(2)
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
monoclinic
P21/c (#14)
9.357(8)
16.212(14)
12.732(11)
90
127.562(14)
90
1531(2)
2
1.504
5.02
11994
2733
triclinic
P1 (#2)
monoclinic
C2/c (#15)
28.616(9)
18.375(5)
21.610(7)
90
125.292(3)
90
9275(5)
4
1.449
6.21
58060
9131
triclinic
P1 (#2)
¯
¯
7.390(4)
10.504(6)
12.691(7)
110.803(7)
91.396(2)
108.263(7)
864.2(8)
1
1.525
8.01
8014
3802
8.730(5)
11.850(7)
12.771(8)
114.910(6)
100.277(5)
90.136(7)
1174.6(12)
2
1.844
15.03
9527
4602
γ [°]
V [Å3]
Z
Dcalcd. [g/cm3]
μ(Mo-Kα) [cm–1]
Reflections total
Reflections unique [IϾ2.00σ(I)]
Rint
0.0650
0.0846
0.2736
0.0248
0.0317
0.0930
0.0956
0.0679
0.2043
0.0223
0.0253
0.0757
R1 [IϾ2.00σ(I)]
wR2 (all reflections)
Eur. J. Inorg. Chem. 2011, 5036–5042
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5041

P. J. Bettle, L. N. Dawe, M. U. Anwar, L. K. Thompson
FULL PAPER
[5] MAGMUN4.1/OW01.exe is available as a combined package
free of charge from the authors (http://www.ucs.mun.ca/
~lthomp/magmun). MAGMUN has been developed by Dr.
Zhiqiang Xu (Memorial University) and OW01.exe by Dr. O.
Waldmann. We do not distribute the source codes.
[6] H. Sakiyama, A. Sugawara, M. Sakamoto, K. Unoura, K. In-
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[9] M. Wang, B. Wang, Z. Chen, THEOCHEM 2007, 816, 103
and references cited therein.
refined anisotropically. All O–H and N–H hydrogen atoms were
located in difference-map positions. They were refined positionally
with distance restraints and with fixed displacement ellipsoids
(1.2 Ueq for N–H, and 1.5 Ueq for O–H). All other hydrogen atoms
were introduced in calculated positions and refined on a riding
model. Solution and refinement proceeded normally for 1, 3 and
4. For 2, a complicated solvent model was required, however; excel-
lent data quality revealed all protons in difference-map positions,
and therefore allowed the refinement of several partial occupancy
molecules. Of particular interest is the identity of O5, which was a
member of two SHELXL parts; the first, at 0.464(4) occupancy,
revealed that Mn1 was coordinated to a methanol molecule con-
sisting of C15, H15(a,b,c), O5 and H5, with no uncoordinated lat-
tice methanol present; the second, at 0.536(4) occupancy, revealed
that Mn1 was coordinated to a water molecule consisting of O5,
H5 and H5a. An additional lattice solvent methanol molecule was
present, consisting of C16, H16(a,b,c), O6 and H6. CCDC-835343
(for 1), -835344 (for 2), -835345 (for 3) and -835346 (for 4) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from the Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[10] G. deMunno, M. Julve, F. Lloret, J. Faus, A. Caneschi, J.
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[14] H. Sakiyama, Inorg. Chim. Acta 2007, 360, 715.
[15] SHELX97: G. M. Sheldrick, Acta Crystallogr., Sect. A 2008,
64, 112–122.
[16] DIRDIF99: P. T. Beurskens, G. Admiraal, G. Beurskens, W. P.
Bosman, R. de Gelder, R. Israel, J. M. M. Smits, The DIRDIF-
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[17] D. T. Cromer, J. T. Waber, International Tables for X-ray Crys-
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[18] J. A. Ibers, W. C. Hamilton, Acta Crystallogr. 1964, 17, 781.
[19] D. C. Creagh, W. J. McAuley, International Tables for Crystal-
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[20] D. C. Creagh, J. H. Hubbell, International Tables for Crystal-
lography, vol. C, (Ed.: A. J. C. Wilson), Kluwer Academic Pub-
lishers, Boston, 1992, 200–206, Table 4.2.4.3.
Acknowledgments
We thank the Natural Sciences and Engineering Research Council
of Canada (NSERC) for financial support for this study.
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Received: July 18, 2011
Published Online: October 7, 2011
5042
www.eurjic.org
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2011, 5036–5042