Syntheses, Characterization, and Magneto-Structural Analyses in μ1,3-Acetato-Bridged Tetracopper(II) and μ1,3- and μ1,1,3-Acetato-Bridged Pentanickel(II) Clusters

Article abstract of DOI:10.1002/ejic.201301581

Two pentanuclear Ni^II complexes, [Ni₅(L¹)₂(CH₃COO)₆(OH)₂(MeOH)₂] (1) and [Ni₅(L²)₂(CH₃COO)₆(OH)₂(H₂O)₂] (2), and one tetranuclear Cu^II complex, [Cu₄(L³)₂(CH₃COO)₄(O)] (3), have been synthesized from phenol-based end-off compartmental ligands HL¹ to HL³ {HL¹ = 2,6-bis[ethyl(2-thienyl)iminomethyl]-4-tert-butylphenol; HL² = 2,6-bis[ethyl(2-thienyl)iminomethyl]-4-chlorophenol and HL³ = 2,6-bis[ethyl(2-thienyl)iminomethyl]-4-methylphenol, respectively}. The complexes have been structurally characterized and their magnetic properties have been investigated within the temperature range 2.2-300 K. Complexes 1 and 2 comprise two dinuclear [Ni₂L²] units linked to a central Ni ion by bridging μ₃-hydroxo groups. The cluster is stabilized by syn-syn-μ_1,3-bridging and μ_1,1,3-bridging acetate anions. The structural analysis of 3 revealed two crystallographically independent complexes that consisted of a tetrahedron of Cu^II ions connected to a central μ₄-oxo species and further bridged by four acetate groups along four of the six edges of the Cu₄ core. The other two edges are occupied by μ-phenoxo bridges from the deprotonated L³ ligand. Magnetic investigations revealed both ferromagnetic and antiferromagnetic interactions in 1 and 2 with single-ion zero-field splitting of magnitude comparable to exchange interactions, and strong antiferromagnetic interactions in 3.

Full text of DOI:10.1002/ejic.201301581

FULL PAPER
DOI:10.1002/ejic.201301581
Syntheses, Characterization, and Magneto–Structural
Analyses in μ1,3-Acetato-Bridged Tetracopper(II) and μ1,3-
and μ1,1,3-Acetato-Bridged Pentanickel(II) Clusters
Sudhanshu Das,[a] Lorenzo Sorace,*[b] Averi Guha,[a] Ria Sanyal,[a]
Hulya Kara,[c] Andrea Caneschi,[b] Ennio Zangrando,*[d] and
Debasis Das*[a]
Dedicated to Professor Marius Andruh on the occasion of his 60th birthday
Keywords: Nickel / Copper / Magnetic properties / Bridging ligands / Cluster compounds
Two pentanuclear NiII complexes, [Ni5(L1)2(CH3COO)6(OH)2-
(MeOH)2] (1) and [Ni5(L2)2(CH3COO)6(OH)2(H2O)2] (2), and
one tetranuclear CuII complex, [Cu4(L3)2(CH3COO)4(O)] (3),
have been synthesized from phenol-based “end-off” com-
bridging μ3-hydroxo groups. The cluster is stabilized by syn-
syn-μ1,3-bridging and μ1,1,3-bridging acetate anions. The
structural analysis of 3 revealed two crystallographically in-
dependent complexes that consisted of a tetrahedron of CuII
ions connected to a central μ4-oxo species and further
bridged by four acetate groups along four of the six edges of
the Cu4 core. The other two edges are occupied by μ-phen-
oxo bridges from the deprotonated L3 ligand. Magnetic in-
vestigations revealed both ferromagnetic and antiferromag-
netic interactions in 1 and 2 with single-ion zero-field split-
ting of magnitude comparable to exchange interactions, and
strong antiferromagnetic interactions in 3.
partmental ligands HL1 to HL3 {HL1
thienyl)iminomethyl]-4-tert-butylphenol; HL2
=
2,6-bis[ethyl(2-
2,6-bis-
=
[ethyl(2-thienyl)iminomethyl]-4-chlorophenol and HL3 = 2,6-
bis[ethyl(2-thienyl)iminomethyl]-4-methylphenol, respect-
ively}. The complexes have been structurally characterized
and their magnetic properties have been investigated within
the temperature range 2.2–300 K. Complexes 1 and 2 com-
prise two dinuclear [Ni2L2] units linked to a central Ni ion by
the magnetization (QTM), and they are actively investigated
in materials science owing to their potential applications in
high-density data storage, molecular spintronics, and quan-
tum computing.[13–16] Among the features required to ob-
tain new SMMs, the most relevant ones are a high-spin
ground state and easy axis-type anisotropy,[17] both of
which require appropriate design in terms of suitable bridg-
ing linkers that mediate magnetic exchange coupling and
the coordination environment around metal ions to pro-
mote the correct anisotropy.[18] For these reasons, the search
for appropriate ligands with a specific geometry to obtain
polynuclear complexes of desired nuclearity and with pre-
dictable exchange coupling among paramagnetic centers
still remains a challenging task for chemists. Incidentally,
phenol-based multidentate compartmental ligands turned
out to be suitable for synthesizing polynuclear complexes
that exhibit interesting magnetic properties.[19–27] It is im-
portant to note that compartmental ligands with two adja-
cent {N2O} donor sets with the phenoxido oxygen atoms
available for bridging are often used to prepare a range of
homodinuclear complexes.[28–32] However, such ligands can
be used also as efficient building blocks to synthesize com-
plexes of higher nuclearity. This can be achieved either (1)
Introduction
The design and construction of polynuclear transition-
metal complexes has been drawing special attention by
researchers during the last few decades because of their sev-
eral intriguing features as well as for their potential applica-
tions in the field of magnetism, catalysis, biology, clathra-
tion, molecular sieving, and so on.[1–11] In particular, the
field of molecular magnetism has seen a large number of
these molecules synthesized and characterized in the past
decades in the quest for new systems that behave like a sin-
gle-molecule magnet (SMM).[12] These complexes exhibit
interesting phenomena, such as slow magnetization relax-
ation, magnetization hysteresis, and quantum tunneling of
[a] Department of Chemistry, University of Calcutta,
92 A. P. C. Road, Kolkata 700009, India
E-mail: dasdebasis2001@yahoo.com
[b] Dipartimento di Chimica “U. Schiff” and UdR INSTM,
Università di Firenze, 50019 Sesto Fiorentino (FI), Italy
[c] Department of Physics, Faculty of Science and Art,
Balikesir University, 10145 Balikesir, Turkey
[d] Dipartimento di Scienze Chimiche e Farmaceutiche,
University of Trieste, Via L. Giorgieri 1, 34127 Trieste, Italy
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201301581.
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Scheme 1. Different bridging modes of carboxylates.
by properly tuning the reaction condition or (2) by using and X-ray single-crystal analysis. The variable-temperature
–
bridging anions such as carboxylate (RCOO–), azide (N3 ), magnetic study has shown that both ferromagnetic and
and so on. A plethora of polynuclear complexes built with antiferromagnetic interactions exist in 1 and 2 and strong
compartmental ligands are available in the litera- antiferromagnetic interactions exist in 3.
ture,[26,33–36] but most of those reports are for copper-based
molecules. In contrast, polynuclear nickel complexes of high
nuclearity (Ͼ3) using similar ligand systems are rather rare,
and only three structurally characterized species have been
Results and Discussion
reported in the literature by Fenton and co-workers, who
described pentanuclear nickel(II) clusters using tetra- and
Synthetic Considerations
2,6-Diformyl-4-methylphenol and 4-tert-butyl-2,6-di-
formylphenol were prepared according to literature meth-
ods.[59] The Schiff base ligands HL1 to HL3 were prepared
by following a reported procedure[60] and their reactions
with NiII–acetate and CuII have been systematically investi-
gated, as summarized in Scheme 3. When Ni(CH3COO)2·
4H2O was treated with HL1 and HL2 in acetonitrile under
reflux conditions, complexes 1 and 2, respectively, were ob-
tained. It is worth mentioning that the use of several Ni/
HL1 or Ni/HL2 stoichiometric ratios (from 1:1 to 1:4) led
only to the pentanuclear complexes for both cases in very
high yield. The reaction to prepare 1 is summarized by
Equations (1) and (2), whereas the formation of 2 is sum-
marized by Equation (3), which accounts for the formation
of hydroxido bridges from water molecules. It is important
to note that both reactions are solely controlled by the acet-
ate anion. Use of anions other than acetate do not produce
the same result. Detailed studies on the nuclearity depen-
dence on the variation of anions continue in our laboratory.
The molar conductivity values (see Table S1 in the Support-
ing Information) in acetonitrile solvent are consistent with
a neutral species, and the elemental analyses are in accord
with the formula [Ni5(L1)2(CH3COO)6(OH)2(MeOH)2]·
2MeOH and [Ni5(L2)2(CH3COO)6(OH)2(H2O)2]·(H2O) for
complexes 1 and 2, respectively, as obtained from the X-
ray diffraction analyses. However, no sign of formation of
phenoxido-bridged dinuclear species was observed, and in-
variably a pair of [Ni2L3] units sandwiching a central NiO6
core was obtained, likely on account of greater stability of
these species.
pentadentate
asymmetric
dicompartmental
ligands
with{N3O} or {N3OS} donor sets in the presence of acetate
anion.[37,38] Owing to diversity in the coordination mode
(see Scheme 1) of the carboxylate anion, it can adopt nu-
merous bridging conformations such as syn-syn, syn-anti,
anti-anti, and μ1,1,3 modes,[37–42] and depending on the two
binding positions (basal or apical) around the metal ions,
these bridging modes can mediate a wide range of exchange
interactions. These observations, and by considering the
properties shown by carboxylate-containing polynuclear
complexes as gas storage,[43–45] molecular recognition,[46,47]
molecular magnet,[48–50] catalyst,[51–55] and nonlinear op-
tical materials,[56–58] inspired us to use carboxylate anions
in the design of polymetallic species.
In this report we have explored the influence of the carb-
oxylate anion on the structural and magnetic properties of
two pentanuclear nickel(II) clusters, namely, [Ni5(L1)2-
(CH3COO)6(OH)2(MeOH)2] (1) and [Ni5(L2)2(CH3COO)6-
(OH)2(H2O)2] (2), and a tetranuclear copper(II) cluster,
[Cu4(L3)2(CH3COO)4(O)] (3), synthesized from phenol-
based “end-off” symmetric di-imine compartmental li-
gands, HL1 to HL3 (see Scheme 2). These complexes have
been characterized by routine physicochemical techniques
However, the reaction of Cu(CH3COO)2·H2O with HL3
in acetonitrile at room temperature resulted in the forma-
tion of complex 3 (Scheme 3). Even in this case, several Cu/
HL3 stoichiometric ratios (from 1:1 to 1:3) were explored,
but we failed to prepare a compound of different nuclearity,
as the product formation was driven by its higher thermo-
dynamic stability. The formation of 3 is very much con-
trolled by the acetate anion, as is observed in 1 and 2. It is
Scheme 2. Phenol-based symmetrical “end-off” compartmental li-
gands.
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Scheme 3. Reaction scheme.
2HL1 + 5Ni(CH3COO)2·4H2O + 2H2OǞ
The coordination bond lengths and angles in both com-
plexes reported in Tables 1 and 2 are comparable in length,
and the central Ni ion has coordination bond values com-
parable to those observed for the metal ions bridged by the
phenolato ligands. The detailed structural description is re-
ported below starting with complex 1, which presents a C2
symmetry.
[Ni5(L1)2(CH3COO)6(OH)2(H2O)2] + 4CH3COOH + 18H2O (1)
[Ni5(L1)2(CH3COO)6(OH)2(H2O)2] + 4MeOHǞ
[Ni5(L1)2(CH3COO)6(OH)2(MeOH)2]·2MeOH (2)
2HL2 + 5Ni(CH3COO)2·4H2O + 2H2OǞ
[Ni5(L2)2(CH3COO)6(OH)2(H2O)2]·H2O + 4CH3COOH + 17H2O (3)
Table 1. Coordination bond lengths [Å] and intermetallic distances
[Å] for complex 1.[a]
worth noting that upon dissolution nickel(II) acetate gener-
ates a weak acid, acetic acid, and a relatively strong base,
nickel(II) hydroxide.[29] As a result, the whole solution be-
comes weakly basic, a consequence that is supposed to be
responsible for generating hydroxy and oxide anions, which
in turn act as ligands to make 1, 2, and 3, respectively (see
below). The elemental analysis and molar conductivity data
are in good agreement with the formula [Cu4(L3)2-
(CH3COO)4(O)], which was confirmed by the X-ray diffrac-
tion analysis [Equation (4)].
Ni1–N1
Ni1–O1
Ni1–O2
Ni1–O3
Ni1–O5
Ni1–O9
Ni3–O2
Ni3–O6
Ni3–O9
2.023(6)
2.018(5)
2.007(4)
2.121(5)
2.034(5)
2.269(5)
2.009(4)
2.063(5)
2.088(5)
95.0(2)
Ni2–N2
Ni2–O1
2.049(6)
2.022(5)
Ni2–O2
Ni2–O4
2.025(4)
2.073(5)
Ni2–O7
2.124(5)
2.063(5)
2.9776(15)
3.1168(13)
3.6222(17)
101.81(19)
127.8(2)
Ni2–O10#1
Ni1–Ni2
Ni1–Ni3
Ni2–Ni3
Ni1–O2–Ni3
Ni2–O2–Ni3
Ni1–O1–Ni2
Ni1–O2–Ni2
95.20(19)
2HL3 + 4Cu(CH3COO)2·H2O + H2OǞ
[a] Symmetry code: #1 –x + 1, y, –z + 3/2.
[Cu4(L3)2(CH3COO)4(O)] + 4CH3COOH + 4H2O (4)
Figure 1 shows the molecular structure of complex 1.
The central metal Ni3 (which sits on a crystallographic two-
fold axis) has an O6 donor set, and both Ni1 and Ni2 have
Structural Description of Complexes 1, 2, and 3
The structures of both pentanuclear Ni complexes com- a {NO5} donor compartment that, for the former, is pro-
prise two dinuclear [Ni2L] units that are linked to a central vided by the imino-N atom, the bridging phenolato-O
Ni ion by bridging μ3-hydroxo groups. This bridging is aug- atom, the μ3-OH, and three acetato-O atoms, whereas for
mented by syn-syn μ2-bridging and μ3-bridging acetate Ni2 one acetate O is replaced by a methanol molecule (O7).
anions so that the central nickel atom is six-coordinate in a The metal triangles defined by μ3-OH are rather distorted,
distorted-octahedral Oh geometry. All the other nickel which reflects the nature and connectivity of the bridges:
atoms have a distorted-octahedral {NO5} chromophore. the Ni1···Ni2 distance, fixed by the tridentate phenolato li-
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Table 2. Coordination bond lengths [Å] and intermetallic distances methanol O7 with weaker interactions. The other methanol
[Å] for complex 2.
is appended to O3.
Ni1–N1
Ni1–O1
Ni1–O2
Ni1–O3
Ni1–O5
Ni1–O9
Ni2–N2
Ni2–O1
Ni2–O2
Ni2–O4
Ni2–O7
Ni2–O1w
Ni5–O2
Ni5–O6
Ni5–O8
Ni5–O9
Ni5–O12
Ni5–O14
2.038(7)
2.035(5)
2.027(5)
2.106(5)
2.025(6)
2.167(5)
2.025(6)
2.036(5)
2.005(5)
2.094(5)
2.090(5)
2.102(6)
1.993(5)
2.055(6)
2.141(5)
2.108(5)
1.988(5)
2.068(6)
Ni3–N3
Ni3–O8
2.034(7)
2.126(5)
2.052(5)
2.026(5)
2.071(5)
2.096(6)
2.021(7)
2.064(5)
2.027(5)
2.019(5)
2.112(6)
2.111(7)
2.9723(14)
3.1185(14)
3.5431(14)
3.0612(14)
3.1075(13)
3.5003(14)
Ni3–O11
Ni3–O12
Ni3–O13
Ni3–O3w
Ni4–N4
Ni4–O10
Ni4–O11
Ni4–O12
Ni4–O15
Ni4–O2w
Ni1–Ni2
Ni1–Ni5
Ni2–Ni5
Ni3–Ni4
Ni3–Ni5
Ni4–Ni5
Figure 2. Side view of complex 1 [–(CH2)2–thienyl chains removed
for the sake of clarity]. In this complex, the phenolato ligands
[forming a dihedral angle of 75.7(1)°] draw a rigid basket-shaped
structure also delineated by the two μ3-acetate moieties.
Ni1–O1–Ni2 95.05(16)
Ni1–O2–Ni2 95.29(15)
Ni1–O2–Ni5 102.66(15)
Ni2–O2–Ni5 125.85(19)
Ni3–O11–Ni4 94.01(15)
Ni3–O12–Ni4 94.59(15)
Ni3–O12–Ni5 101.57(16)
Ni4–O12–Ni5 128.01(18)
Complex 2 presents a pseudo-twofold axis if ethylthienyl
chain fragments are excluded, and relative to 1, the differ-
ence in the metal coordination sphere is represented by the
substitution of the coordinated methanol molecules by
aqua ligands for two of the metals. Figure 3 represents the
molecular structure of 2. The coordination bond lengths
reported in Table 2 indicate that values that pertain to the
central metal ion (Ni5) are comparable to those observed
for the peripheral nickel ions bridged by the phenolato li-
gands. Again the metal triangles defined by μ3-OH are sca-
lene. In fact, as noted above for 1, this reflects the bridging
nature and connectivity: the Ni1···Ni2 and Ni3···Ni4 dis-
tances bridged by the phenolato are 2.9709(10) and
2.9643(10) Å, whereas Ni1–Ni5 and Ni3–Ni5 are 3.1224(9)
and 3.103(1) Å; and finally, Ni2–Ni5 and Ni4–Ni5 are
3.563(1) and 3.606(1) Å, respectively. Figure 4 reports a side
gand and a bridging acetate anion, is 2.9723(14) Å;
Ni1···Ni3, which is triply bridged by a syn-syn bidentate
acetate and a single O from a monodentate acetate beside
the capping OH, is 3.1168(13) Å; and the Ni2···Ni3 distance
is 3.6222(17) Å, connected by a single bridging acetate only.
Figure 2 provides a side view of complex 2 in which the
phenolato ligands [which form a dihedral angle of 75.7(1)°]
draw a rigid basket-shaped structure that is delineated also
by the two μ3-acetate moieties. Of the lattice methanol mo-
lecules, one behaves like a hydrogen donor towards acetate
atom O6 [O···O 2.656(9) Å] and like a hydrogen acceptor
with respect to the hydroxo O2–H and the coordinated
Figure 1. Molecular structure of 1 viewed down the twofold axis
with atom labels of crystallographically independent donor atoms.
Figure 3. A perspective view of complex 2.
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view of complex 2 that shows the pocket formed by the a highly distorted square-planar pyramidal coordination
phenolato ligands, the mean planes of which form a dihe- with basal bond lengths that fall in a range from 1.910(4)
dral angle of 80.85(6) to indicate a rigid structure.
to 1.999(5) Å. In all cases a carboxylate oxygen occupies
the apical position at longer distance [2.252(6)–2.359(6) Å].
In the two Cu2L3 phenolato moieties, which are oriented
almost perpendicular to each other (dihedral angle of ca.
87°), the metals are separated by approximately 3.0 Å,
whereas the other Cu–Cu distances are slightly longer
[3.140(1)–3.258(1) Å].
Figure 4. Side view of complex 2 (–CH2–thienyl fragments are re-
moved for sake of clarity).
The coordinated water O1w and O2w and the lattice mo-
lecule O3w form a 1D polymer through a hydrogen-bond-
ing scheme (Figure 5). In particular, the latter has a tetrahe-
dral arrangement that acts as a donor towards acetate oxy-
gen atoms O6 and O13 and as an acceptor with respect to
μ3-hydroxo O12 and water O2w (O···O distance range:
2.74–2.90 Å).
The structural analysis of compound 3 revealed two crys-
tallographically independent complexes that consist of a tet-
rahedron of copper(II) ions connected to a central μ4-oxo
species and further bridged by four acetate groups along
four of the six edges of the Cu4 core. The other two edges
are occupied by μ-phenoxo bridges from the deprotonated
Figure 6. Molecular structure of one of the two crystallographic
complexes of 3.
Magnetic Properties of Complexes 1, 2, and 3
The magnetic properties of complex 1, in the form of
L3 ligand. Figure 6 shows the molecular structure of one of 1/χM and χMT (χM is the susceptibility per cluster mol) ver-
the two crystallographic complexes of 3. The two complexes sus T plots, are shown in Figure 7 in the temperature range
show coordination bond lengths and angles (Tables 3 and 2.2–300 K. The magnetic susceptibility conforms well to
4) of comparable values, the main difference being related Curie–Weiss law over the whole investigated range, which
to the conformational arrangement of the –(CH2)2–thienyl gives a negative Weiss constant θ of –1.59 K and a Curie
fragments of the Schiff base ligands. All the metals present constant of 6.06 emuKmol–1. The θ value suggests the pres-
Figure 5. Hydrogen bonds in 2 forming a 1D polymer through aqua O(1w) and O(2w) and the lattice molecule O(3w) (indicated as an
ellipsoid).
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Table 3. Coordination bond lengths [Å] and intermetallic distances ence of a globally weak antiferromagnetic interaction be-
[Å] for complex 3.
tween nickel(II) ions, whereas the Curie constant is in agree-
ment with what is expected for five high-spin NiII ions, thus
Molecule A
Molecule B
Cu5–N5
indicating a g value of 2.2. The magnetic data were repro-
duced by using an irreducible tensor operator approach[61]
assuming the following spin Hamiltonian [Equation (5)].
Cu1–N1
Cu1–O1
Cu1–O3
Cu1–O11
Cu1–O10
Cu1–Cu2
Cu2–N2
Cu2–O1
Cu2–O6
Cu2–O7
Cu2–O11
Cu3–N3
Cu3–O2
Cu3–O4
Cu3–O5
Cu3–O11
Cu3–Cu4
Cu4–N4
Cu4–O2
Cu4–O8
Cu4–O9
Cu4–O11
Cu1–Cu2
Cu3–Cu4
Cu1–Cu3
Cu1–Cu4
Cu2–Cu3
Cu2–Cu4
1.986(6)
1.999(5)
2.353(6)
1.910(4)
1.932(6)
3.0069(13)
1.976(6)
1.977(5)
1.937(5)
2.354(6)
1.915(5)
1.954(6)
1.969(5)
1.942(5)
2.337(5)
1.920(4)
2.9951(12)
1.980(6)
1.958(5)
1.962(5)
2.252(6)
1.920(5)
3.0069(13)
2.9951(12)
3.2582(12)
3.2113(13)
3.1401(13)
3.1483(13)
1.971(6)
1.988(5)
2.289(6)
1.952(5)
1.919(4)
3.0046(12)
1.962(6)
1.959(5)
1.942(5)
2.359(6)
1.921(5)
1.994(6)
1.970(5)
1.920(5)
2.359(6)
1.922(5)
3.0085(13)
1.987(6)
1.993(5)
1.946(5)
2.297(6)
1.912(4)
3.0046(12)
3.0085(13)
3.1956(13)
3.2174(13)
3.2103(14)
3.1538(13)
Cu5–O21
Cu5–O23
Cu5–O30
Cu5–O31
Cu5–Cu6
Cu6–N6
Cu6–O21
Cu6–O26
Cu6–O27
Cu6–O31
Cu7–N7
Cu7–O22
Cu7–O24
Cu7–O25
Cu7–O31
Cu7–Cu8
Cu8–N8
Cu8–O22
Cu8–O28
Cu8–O29
Cu8–O31
Cu5–Cu6
Cu7–Cu8
Cu5–Cu7
Cu5–Cu8
Cu6–Cu7
Cu6–Cu8
ˆ
H = –J1(S1·S2 + S3·S4) – J2(S1·S5 + S3·S5) –
J3(S2·S5 + S4·S5) + gβS·H (5)
Operators S1–S4 represent the peripheral nickel ions
(Ni1/Ni2 and N1*/N2*) of the cluster, whereas S5
represents the central one (Ni3) (Figure 8). The best-fit
curve was obtained by using the following values:
g
=
(2.189Ϯ0.002), J1
=
–(0.62Ϯ0.05) cm–1, J2
=
=
–(0.52Ϯ0.4) cm–1, and J3 = (–0.52Ϯ0.4) cm–1 (R2
0.0757). However, a very large correlation exists between J2
and J3 owing to the symmetry of the Hamiltonian, which
does not allow one to discriminate among the interactions
between Ni1–Ni3 and Ni2–Ni3 couples despite the struc-
tural and coordination differences. Furthermore, use of
these values does not provide reasonable agreement with
the field-dependent magnetization curve measured at 2.5 K,
which would attain a value of 10 Nβ at the highest field
versus the experimental one of 7.5 Nβ (see Figure 7, b). We
then resorted to a simultaneous fit[62] of both χT versus T
and M versus H curve by using a model Hamiltonian with
only two coupling constants [Equation (6)].
ˆ
H = –J1(S1·S2 + S3·S4) – J2(S1·S5 + S2·S5 + S3·S5 + S4·S5)
(6)
Table 4. Cu-O-Cu bridging angles [°] for 3.
In a first step we neglected the contribution of the single-
ion zero-field splitting (ZFS) of the five NiII ions. However,
Molecule A
Molecule B
the best-fit parameters obtained by this approach [J1
=
Cu1–O1–Cu2
Cu3–O2–Cu4
Cu1–O11–Cu2
Cu1–O11–Cu3
Cu1–O11–Cu4
Cu2–O11–Cu3
Cu2–O11–Cu4
Cu3–O11–Cu4
98.3(2)
99.4(2)
Cu5–O21–Cu6
Cu7–O22–Cu8
Cu5–O31–Cu6
Cu5–O31–Cu7
Cu5–O31–Cu8
Cu6–O31–Cu7
Cu6–O31–Cu8
Cu7–O31–Cu8
99.1(2)
98.8(2)
(0.51Ϯ0.01) cm–1, J2 = (–1.14Ϯ0.02) cm–1, g fixed to
2.189] did not provide satisfactory reproduction of the iso-
thermal magnetization curve. This clearly points to non-
negligible effects of single-ion ZFS of NiII on the magnetic
properties of this system. Consideration of this term would,
however, introduce a large number of additional param-
eters, namely, the magnitude of the ZFS for the three crys-
103.7(2)
116.6(2)
113.9(2)
109.9(2)
110.4(2)
102.5(2)
103.0(2)
112.6(2)
114.2(2)
113.3(2)
110.7(2)
103.4(2)
Figure 7. (a) Temperature dependence of χMT and 1/χM for complex 1 and best-fit curves obtained using the Hamiltonian model (7) and
Curie–Weiss parameters, respectively. Fits obtained using model Hamiltonian (5) and (6) are essentially indistinguishable. (b) Isothermal
(T = 2.5 K) field-dependent magnetization for complex 1, along with best-fit curves obtained by using model Hamiltonian (6) (dotted
line), and model Hamiltonian (7) (continuous line), with parameters reported in the text.
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Figure 8. (a) Local coordination environments of NiII atoms and (b) diagram of the magnetic exchange coupling pathway for
complex 1.
tallographically different NiII ions and their orientation, to give a negative Weiss constant θ = –2.90 K and a Curie
which cannot be fixed a priori by symmetry arguments. To constant of 6.36 emuKmol–1. The θ value suggests the pres-
reduce over-parametrization, we then considered a model ence of a dominant antiferromagnetic interaction between
in which the same iso-oriented axial ZFS tensors were as- the nickel(II) ions, whereas the value of the Curie constant
sumed for the five NiII centers, and only the exchange cou- is in agreement with what is expected for five high-spin NiII
pling constants were fitted. The Hamiltonian used was then ions, with g ≈ 2.2. However, an inspection of the χMT versus
[Equation (7)].
T plot immediately shows that, despite the structural simi-
larity with complex 1, the magnetic behavior is partially
different; it does not show the monotonous decrease that
characterizes complex 1. Indeed, upon lowering the tem-
ˆ
H = –J1(S1·S2 + S3·S4) – J2(S1·S5 + S2·S5 +
2
ˆ
S3·S5 + S4·S5) + D
Szi (7)
͚
i = 1–5
perature, χMT decreases to reach
a
plateau at
Satisfactory reproduction of both curves was obtained 5.3 emuKmol–1 between 12 and 8 K then abruptly de-
by fixing D equal to 4.5 cm–1, which is within the expected creases down to 3.9 emuKmol–1 at 1.9 K. The field-de-
range for this type of ion, gi to 2.189, and J1
=
pendent magnetization measured at 2 K (Figure 9, b), even
(1.2Ϯ0.1) cm–1, J2 = (–1.3Ϯ0.1) cm–1. Comparison to the if not saturated at 6 T, clearly points to a value somewhat
fit obtained using Hamiltonian (6) makes it evident that higher than 6 Nβ, which suggests an S = 3 ground state
inclusion of ZFS mostly affects the value of J1, which almost exclusively populated at low temperature and high
should then be considered with some caution in view of the fields. In this framework, the decrease in χMT observed at
assumptions made on the D values.
low temperature has to be attributed to zero-field splitting
The magnetic properties of complex 2 are reported in within the ground state, which can be large owing to the
Figure 9 in the forms of 1/χM and χMT versus T plots, in single-ion contribution of NiII ions.[63] To avoid complica-
the range 1.9–300 K, and as an isothermal magnetization tions owing to the inclusion of these additional parameters,
curve at T = 2.5 K. The magnetic susceptibility conforms we first considered data only down to 7 K by using the spin
well to Curie–Weiss law over the whole investigated range Hamiltonian [Equation (6)] to fit the data.
Figure 9. (a) Temperature dependence of χMT and 1/χM for complex 2 and best-fit curves obtained using the Hamiltonian model (7) and
Curie–Weiss parameters, respectively. (b) Isothermal (T = 2.5 K) field-dependent magnetization for complex 2, along with best-fit curve
obtained by using model Hamiltonian (7) with parameters reported in the text.
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The best-fit curve was obtained by using the parameters decreasing temperature, which reaches
a
value of
g = (2.20Ϯ0.002), J1 = (4.04Ϯ0.01) cm–1, and J2
=
0.0161 cm3 mol–1 K at 2 K that is indicative of an S = 0 spin
(–3.72Ϯ0.01) cm–1. These indeed provide an S = 3 ground ground state with residual paramagnetism owing to un-
state with the first S = 2 and S = 1 excited states at 3.72 avoidable impurities. This is confirmed by the field-depend-
and 7.44 cm–1, respectively, thus being in qualitative agree- ent magnetization data, the very low values of which are
ment with the outcome of isothermal magnetization mea- in agreement with a diamagnetic ground state and a small
surements. Field-dependent magnetization data and the full fraction of paramagnetic impurities (Figure 10, b), esti-
temperature dependence of the χT product could, however, mated to be about 2%.
be simultaneously fit only within the same framework of
As reported in the structural characterization of 3, there
complex 1 (i.e., by considering the same axial iso-oriented are two crystallographically (and magnetically) independent
ZFS tensor for the five NiII ions). With this approach, the clusters, A and B, which have the same pattern and similar
best-fit curve was obtained by fixing gi to 2.188 and J1 = structural parameters (Figure 11, Tables 3 and 4). In both
(4.6Ϯ0.1) cm–1, J2 = (–3.8Ϯ0.1) cm–1, and fixing D to of them, two different magnetic exchange pathways can be
7.5 cm–1.
defined in principle: the first one involves the pairs Cu1/
The combined results of the fits for 1 and 2, despite the Cu2 or Cu3/Cu4, which are bridged by the O1/O2 atom of
approximations used, clearly indicate that J1 is ferromag- the phenoxo ligand and by the central μ4-O11 atom. The
netic and J2 is antiferromagnetic; furthermore, for both second path defines the exchange interaction between Cu1/
coupling constants, the magnitude appears to be somewhat Cu3, Cu1/Cu4, Cu2/Cu3, and Cu2/Cu4, which are bridged
larger in 2 than in 1.
by the central μ4-O11 atom and carboxylate group. It has
The magnetic properties of complex 3 are shown in Fig- to be noted that for the latter four couples, the Cu–O–Cu
ure 10a in the forms of 1/χM and χMT versus T plots in the angles at μ4-O11 are in the range of 110–116°, whereas the
range 2–300 K. The Curie–Weiss plot of 1/χM versus T is interaction with the carboxylato ligand involves the axial
not linear, even in the high-temperature regime. The value position on one CuII and a basal position on the other one.
of χMT at room temperature (1.32 cm3 mol–1 K, 3.25 BM) is
Under this approach, the magnetic properties of 3 should
lower than expected for four uncoupled S = 1/2 ions with be analyzed by means of the following spin Hamiltonian
g = 2. (1.5 cm3 mol–1 K, 3.46 BM), thus indicating the exis- [Equation (8)].
tence of medium to strong antiferromagnetic superexchange
interactions between the copper(II) ions. This is confirmed
by the continuous decrease in the χMT product upon H = –J1(S1·S2 + S3·S4) – J2(S1·S3 + S1·S4 + S2·S3 + S2·S4)
ˆ
(8)
Figure 10. (a) Temperature dependence of χMT and 1/χM for 3. (b) Magnetization as a function of the applied magnetic field for 3,
measured at 2 K.
Figure 11. (a) Local coordination environments of CuII atoms and (b) diagram of the magnetic exchange coupling pathway for complex
3.
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The resulting expression for the magnetic susceptibility agreement with expectations; in particular, the ferromag-
is, however, not suitable for a meaningful fit of the data, netic character of J1 is consistent with the reported mag-
since the two coupling constants turned out to be highly neto–structural correlations in phenoxo-bridged nickel(II)
correlated. Such a problem has already been reported for complexes (with θ angles = 90–95°) that contain syn-syn-
systems of similar magnetic topology and has partially been carboxylate and either alkoxo, hydroxo, or water[65,66] bridg-
solved in the regime of strong antiferromagnetic coupling ing ligands (Figure 12, Table 5). We note here that this be-
by using a Bleaney–Bowers equation[64] to reproduce the havior is due to two different contributions: the ferromag-
magnetic properties that arise essentially from the S = 0 netic one of the small angle Ni–Ophenoxo–Ni path, and the
and the first S = 1 excited state. However, this method does carboxylate bridge, which is almost perfectly orthogonal to
not seem appropriate here, since the strong coupling regime the Ni2O2 plane (89.8°). Some recent theoretical results
is not achieved and other states are possibly populated. As indicate that the syn-syn bridging carboxylate ligand that
a further complication, one has to note that the coupling connects two NiII ions in triply mixed-bridged complexes
constants for the two independent clusters may be, at least shows in some cases an antiferromagnetic contribution to
partially, different, definitely requiring too many param- the exchange coupling[67] and in other cases a ferromagnetic
eters to be fit to a single equation.
contribution.[68] Finally, we note that other structural fac-
tors such as the folding of the bridging fragment and the
shift of the phenolic carbon atom from the Ni2O2 plane
have a significant influence on the magnetic coupling in di-
Magneto–Structural Correlations
We have examined the magneto–structural correlation on phenoxo-bridged NiII complexes. As for J2, the large Ni1/
a few pentanuclear nickel(II) and tetranuclear copper(II) 2–O–Ni3 angle would suggest a relevant value of the anti-
complexes published in recent years, and the results are re- ferromagnetic coupling constant,[65,69] quite in contrast
ported in Tables 5 and 6, respectively. The exchange cou- with the experimental findings. However, even in this case,
pling constants obtained for both 1 and 2 are essentially in the compensating effect of additional exchange coupling
Table 5. J as a function of the Ni–O–Ni angles and Ni–Ni distances inside the [Ni5(μ3-OH)2] core.
Complex[a]
Carboxylate
bridging mode
Ni–O–Ni[b]
angle [°]
Ni–Ni[c]
distance [Å]
J [cm–1]
g
Ref.
[66]
[65]
[37]
[NiII5LN4(μ3-OH)2(μ2-OH2)2(EtOH)2]
[Ni5(OH)2(l-aba)4(OAc)4]·0.4EtOH·0.3H2O
[Ni5(L5)2(OAc)6(OH)2]
–
95.42–103.88
94.0–126.9
93.91–95.12
94.96
3.049–3.181
2.85–3.47
2.986–2.988
2.978
+6.5
J1 = +3.0, J2 = –1.0
–
very weak, AF
very weak, AF
2.32
2.08
–
2.189
2.236
μ2 and μ3
μ2 and μ3
μ2 and μ3
μ2 and μ3
[Ni5(L1)2(Ac)6(OH)2(MeOH)2]·4MeOH (1)
[Ni5(L2)2(Ac)6(OH)2(H2O)2]·(H2O) (2)
this work
this work
93.99–95.04
2.964–2.971
[a] H2LN is methylamino-N,N-bis(2-methylene-4,6-dimethylphenol); l-abaH = l-2-aminobutyric acid; HL5 = 2-{[(2-dimethylaminoethyl)-
ethylamino]methyl}-6-ethyliminomethyl-4-methylphenol. [b] Ni–O–Ni angles only in phenoxide-bridged Ni2O2 core. [c] Adjacent Ni–Ni
distances in phenoxide-bridged Ni2O2 core. ST = ground-state spin, AF = antiferromagnetic.
Table 6. J, Cu–Cu distances [Å], and Cu–O–Cu angles [°] in complexes with [Cu4O] complex core.
Complex[a]
Carboxylate
bridging mode
Cu–O–Cu[b]
angle [°]
Cu–Cu[c]
distance [Å]
J [cm–1]
ST
g
Ref.
[33]
[Cu4(L)2(O)(OH)2(MeOH)2(ClO4)2]
[Cu4(O)(L1)2(CH3COO)4]
[Cu4(O)(L2)2(CH3COO)4]
[Cu4(O)(L3)2(CH3COO)4]
[Cu4(O)(L4)2(CH3COO)4]
[Cu4(μ4-OH)(dmae)4][Ag(NO3)4]
[Cu4(μ4-OH)(dmae)4][Na(NO3)4]
[Cu4(μ4-O)(μ-bip)2(μ-O2CPh)4]·0.5CH2Cl2
[Cu4(μ3-OH)2(μ-bip)2(N3)4]
[Cu4-(μ3-OH)2(μ-bip)2(NCS)4(dmf)2]
[CuII4(μ3-L1)2(μ-OH)2(H2O)2](ClO4)2·H2O
[Cu4(μ4-O)-(μ-cip)2(μ1,3-O2CPh)4]·2CH3OH
[CuII4(bdmmp)2(μ4-O)(O2CCF3)]
[Cu4(L3)2(CH3COO)4(O)] (3)
–
100.01–101.25
99.56–103.62
97.60–101.84
98.44–103.45
97.81–102.39
101.0
2.993
3.017
–720
–210
–219
–227
0
2.19
syn-syn, μ2
syn-syn, μ2
syn-syn, μ2
syn-syn, μ2
–
2.977–2.984
2.998–3.010
2.992–2.987
2.9472–4.152
2.9485–4.149
3.068
2.986–2.996
3.043
3.092–3.095
2.993–3.011
2.930–2.933
2.995–3.008
[34]
0,1
0
–
–271
J = +1.8, JЈ = –29.2
J = +2.9, JЈ = –32.2
2.10
2.10
2.0
2.2
2.2
[72]
[74]
–
100.7
syn-syn, μ2
–
101.88–103.74
97.28–102.83
100.65–104.38
91.98–106.41
99.20–103.39
98.4–99.1
–289
–464
–405
–16.9
–340
0
–
–
[26]
[35]
[36]
0
2.03
syn-syn, μ2
syn-syn, μ2
syn-syn, μ2
1/2 2.03
0
0
–60
strong, AF
2.22
98.29–99.41
2.0 this work
[a] HL = 2,6-bis(pyrrolidinomethyl)-4-methylphenol; HL1 = 4-methyl-2,6-bis(cyclohexylmethyliminomethyl)phenol; HL2 = 4-methyl-2,6-
bis(phenylmethyliminomethyl)phenol; HL3 = 4-methyl-2,6-bis{[(3-trifluoromethyl)phenyl]methyliminomethyl}phenol; HL4 = 4-methyl-
2,6-bis{[(4-trifluoromethyl)phenyl]methyliminomethyl}phenol; Hdmae = dimethylaminoethanol, Hbip = 2,6-bis(benzyliminomethyl)-4-
methylphenol; H2L1 = 2-hydroxobenzylidene-[2-(4-{2-[(2-hydroxobenzylidene)amino]ethyl}-piperazin-1-yl)ethyl]amine; Hcip = 2,6-bis(cy-
clohexyliminomethylene)-4-methylphenol; bdmmpH = 2,6-bis[(dimethylamino)methyl]-4-methylphenol. [b] Cu–O–Cu angles only in phen-
oxide-bridged Cu2O2 core. [c] Adjacent Cu–Cu distances in phenoxide-bridged Cu2O2 core. ST = ground-state spin, AF = antiferromag-
netic.
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paths[63] has to be considered, and indeed, the values ob- the thiophene moiety of the end-off compartmental ligands
served in 1 and 2 are consistent with a recent report on an and the bridging property of acetato ligand are supposed to
amino acid based pentanuclear nickel cluster.
be responsible for generating polynuclear transition-metal
assemblies. Variable-temperature magnetic studies in the
range 2.2–300 K have shown a dominant antiferromagnetic
interaction quite generally for a syn-syn-phenoxido and syn-
syn-carboxylato-bridged tetracopper(II) species. However,
pentanuclear nickel complexes have shown weak ferromag-
netic interactions owing to the small Ni–OPhO–Ni phenoxo
bridging angles close to 90–95° and of syn-syn-μ1,3-carbox-
ylato bridge, which is practically orthogonal to the Ni2O2
plane. This provides an additional and compensating ex-
change coupling path. A comparative study of the magnetic
properties of 1 and 2 revealed a slight increase in the magni-
tude of the exchange coupling constants J1 and J2 in com-
plex 2.
Figure 12. Coordination environment in the [Ni5] core of com-
plexes 1 and 2 showing the different carboxylate bridging modes.
Experimental Section
As for the magnetic behavior of complex 3, the observa-
tion of a relatively strong, albeit not quantitatively deter-
mined, antiferromagnetic-type exchange interaction is in
good agreement with previously reported data for similar
systems.[33,34,70–72] A comparable structural motif is present
in [Cu4(Ln)2(O)(O2CPh)4][70] and [Cu4(O)(Ln)2(Ac)4][34]
(Ln = N2O-donor Schiff base ligand), in which a strong
Reagents and Materials: Copper acetate monohydrate and nickel
acetate tetrahydrate were purchased from Merck (India). [2-(2-
Thiophenyl)ethyl]amine was purchased from Sigma–Aldrich and
used without purification. All other chemicals and solvents were of
reagent grade and were used as received without further purifica-
tion.
antiferromagnetic exchange coupling of –289(4) cm–1 was Synthesis of Ligands HL1 to HL3: See Scheme 4; 4-tert-butyl-2,6-
diformylphenol (0.206 g, 1 mmol) and [2-(2-thiophenyl)ethyl]amine
(0.254 g, 2 mmol) were used at a 1:2 equiv. ratio in acetonitrile
(15 mL) in a round-bottomed flux and heated under reflux condi-
tions for 2 h as previously reported.[60] A yellow solution of HL1
was obtained. The solvent was evaporated and an orangelike sticky
liquid resulted. The other two ligands, HL1 and HL2, were pre-
pared by following the same procedure by using 4-chloro-2,6-difor-
mylphenol (0.189 g, 1 mmol) and 2,6-diformyl-4-methylphenol
(0.164 g, 1 mmol), respectively, instead of 2,6-diformyl-4-tert-but-
measured in the former, and in the range from –210.1 to
–271.3 cm–1 in the second. To understand the antiferromag-
netic behavior in this kind of system, it is necessary to con-
sider that two types of exchange interactions, one through
μ2-phenoxido and the other through the syn-syn-carboxyl-
ato bridge, are active. It is well established that the syn-syn
bridging mode of the carboxylate ligand causes antiferro-
magnetic coupling, whereas the μ2-phenoxido bridge can
transmit either antiferro- or ferromagnetic interaction de-
1
ylphenol. H NMR ([D6]DMSO, 25 °C): For HL1: δ = 8.589 (s, 2
pending on the Cu–O(phenoxido)–Cu bridging angles[71,73] H, Hc), 7.721 (s, 2 H, Hb), 7.305, 7.290 (d, 2 H, Hf), 6.930 to 6.862
(Table 6). Krebs and co-workers previously reported the
temperature-dependent magnetic properties of μ4-oxo-
bridged tetracopper(II) systems, which revealed the antifer-
romagnetic type of interaction between the copper(II)
ions.[33] Ray and co-workers also reported tetracopper(II)
complexes with both μ4-oxo and μ1,3-acetato bridges and
studied their magnetic properties extensively, wherein again
the interactions between copper(II) centers were found to
have an antiferromagnetic nature.[26,35,36,74] In our case, the
observed relatively strong antiferromagnetic interaction in
complex 3 is very much expected considering the higher
Cu–O(phenoxido)–Cu bridging angles (Ͼ95°) and is in
good agreement with the above reports.
Conclusion
The complexation of CuII and NiII acetates with phenol-
based symmetrical Schiff base compartmental ligands
yielded tetranuclear copper and pentanuclear nickel irre-
spective of whether the ratio of metal to salt and ligands are
maintained. The noncoordinating behavior of the S atom of ing.
Scheme 4. Structure of the ligands (HL1–HL3) with hydrogen label-
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(m, 4 H, Hg), 3.852, 3.822, 3.800 (t, 4 H, Hd), 3.193, 3.158, 3.135 oled to room temperature. Crystals suitable for X-ray structural
(t, 4 H, He), 1.259 (s, 9 H, Ha) ppm; for HL2: δ = 8.498 (s, 2 H, determination
formed in the solution, yield 79%.
C50H54Cu4N4O11S4 (1269.42): calcd. C 47.31, H 4.29, N 4.41;
Hc), 7.464 (s, 2 H, Hb), 7.281, 7.277 (d, 2 H, Hf), 6.909 to 6.848
(m, 4 H, Hg), 3.814, 3.792, 3.770 (t, 4 H, Hd), 3.145, 3.123, 3.101 found C 47.01, H 4.17, N 4.32.
(t, 4 H, He), 2.204 (s, 3 H, Ha) ppm; for HL3: δ = 8.690 (s, 2 H,
Physical Measurements: Elemental analyses (C, H, and N) were
Hc), 7.536 (s, 2 H, Hb), 7.416, 7.411 (d, 2 H, Hf), 6.998 to 6.958
(m, 4 H, Hg), 3.163, 3.148, 3.137 (t, 4 H, He), 3.132 (s, 4 H, Hd),
2.226 (s, 3 H, Ha) ppm.
performed using a Perkin–Elmer 240C elemental analyzer. FTIR
spectra were recorded with a Shimadzu FTIR 8400S instrument
with KBr pellets in the 4000–400 cm–1 range. The molar conductiv-
ity of the synthesized complexes was measured with a Systronics
Conductivity Meter 306. Electronic spectra (800–200 nm) in solu-
tion were recorded with a Shimadzu UV-3101PC UV/Vis/near-IR
spectrophotometer at 28 °C using acetonitrile as medium, whereas
those in the solid state were recorded with a Hitachi U-3501 spec-
trophotometer. DC magnetic measurements were performed with
a Cryogenics Squid S600 magnetometer with an applied field of
0.1 T. To avoid possible orientation effects, microcrystalline pow-
ders were pressed in pellets. The data were corrected for sample
holder contribution, measured in the same field and temperature
range (2.2–300 K), and the intrinsic diamagnetism of the sample
was measured by using Pascal constants.
[Ni5(L1)2(CH3COO)6(OH)2(MeOH)2]·2MeOH (1): Nickel(II) acet-
ate tetrahydrate (0.620 g, 2.5 mmol) dissolved in water/acetonitrile
(10 mL, 1:4 ratio v/v) was added to the yellow solution of HL1 in
acetonitrile (15 mL). Upon stirring the brown solution that had
formed initially changed to green within 5–10 min. The green mix-
ture was then heated under reflux conditions for another 1 h to
obtain a clear intense green solution. The solution was kept in a
dark place. A few days later a powdered solid was obtained.
Needle-shaped, green single crystals suitable for X-ray analyses
were separated out after recrystallization from methanol, yield
89%. C66H98N4Ni5O22S4 (1721.30): calcd. C 46.01, H 5.69, N 3.25;
found C 45.88, H 5.56, N 3.17.
[Ni5(L2)2(CH3COO)6(OH)2(H2O)2]·(H2O) (2): Complex 2 was syn-
thesized by adopting a procedure similar to that for complex 1.
Nickel(II) acetate tetrahydrate (0.620 g, 2.5 mmol) dissolved in
water/acetonitrile (10 mL, 1:4 ratio v/v) was added to the yellow
solution of HL2 in acetonitrile (15 mL). Upon stirring, the brown
solution that had formed initially changed to green in about
10 min. The green mixture was then heated under reflux conditions
for 45 min to obtain a very deep green solution. Block-shaped, in-
tense-green single crystals suitable for X-ray analyses were obtained
after 2–3 d, yield 82%. C52H62Cl2N4Ni5O19S4 (1539.77): calcd. C
40.56, H 4.06, N 3.64; found C 40.18, H 3.96, N 3.55.
Crystallographic Refinement and Structure Solution: Data collec-
tions for crystal structure analysis for all complexes were carried
out at room temperature with a Bruker Smart Apex diffractometer
equipped with charge-coupled device (CCD) and Mo-Kα radiation
(λ = 0.71073 Å). Cell refinement, indexing, and scaling of the data
sets were carried out with Bruker Smart Apex and Bruker Saint
packages.[75] Structures were solved by direct methods and subse-
quent Fourier analyses[76] and refined by the full-matrix least-
squares method based on F2 with all observed reflections.[77] Owing
to their conformational freedom some of the thiophene rings were
found disordered: only one of the rings in 2 was successfully refined
[Cu4(L3)2(CH3COO)4(O)] (3): Solid copper(II) acetate monohy- over two positions at half occupancy (S2/S2a). In other cases, resid-
drate (0.399 g, 2 mmol) was added dropwise to a yellow solution
of HL3 (0.382 g, 1 mmol) in acetonitrile (25 mL). The resulting
solution was heated under reflux conditions for 30–40 min and co-
uals around these groups (difficult to model) indicate a disorder
over two coplanar orientations of the thienyl rings, which were re-
fined with restraints on thermal U factors (the ISOR instruction in
Table 7. Crystallographic data and details of refinement for complexes 1, 2, and 3.
1·2MeOH
2·H2O
3
Empirical formula
Mr
Crystal system
Space group
C66H98N4Ni5O22S4
1721.27
monoclinic
C2/c
C52H62Cl2N4Ni5O19S4
1539.75
C50H54Cu4N4O11S4
1269.37
triclinic
triclinic
¯
¯
P1
P1
a [Å]
b [Å]
c [Å]
α [°]
29.618(10)
15.614(4)
18.653(8)
–
114.174(9)
–
7870(5)
4
1.453
14.7008(5)
16.0701(10)
16.4301(6)
99.3040(10)
114.3660(10)
100.3590(10)
3355.5(3)
2
17.988(2)
18.467(2)
18.826(2)
80.742(2)
62.9590(10)
87.158(2)
5495.7(11)
4
β [°]
γ [°]
V [Å3]
Z
Dcalcd [gcm–3]
μ(Mo-Kα) [mm–1]
F(000)
1.524
1.649
1584
1.534
1.739
2600
1.352
3608
θ range [°]
1.51–24.17
14167
5370
1.34–25.52
39354
12260
1.12–24.57
37857
18210
Reflections collected
Independent reflections
Rint
0.1118
0.0343
0.0583
Number of reflections [IϾ2σ(I)]
Refined parameters
GoF (F2)
3423
459
1.054
0.0609, 0.1570
0.789, –0.521
9636
796
1.024
0.0597, 0.1757
1.012, –1.338
9294
1297
1.027
0.0700, 0.1838
1.200, –1.011
R1, wR2 [IϾ2σ(I)][a]
Residuals [eÅ3]
[a] R1 = Σ||Fo| – |Fc||/Σ|Fo|, wR2 = [Σw(F2o – Fc2)2/Σw(F2o)2]½.
Eur. J. Inorg. Chem. 2014, 2753–2765
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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FULL PAPER
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Crystal data and details of refinements for all the complexes are
given in Table 7.
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CCDC-933620 (for 1), -937379 (for 2), and -937380 (for 3) contain
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Acknowledgments
The authors wish to thank the Council of Scientific and Industrial
Research (CSIR), New Delhi [project number 01(2464)/11/EMR-II
dated 16-05-2011, to D. D. and project number 09/028(0766)/2010-
EMR-I dated 22/02/2010, to S. D.] for financial support. The au-
thors also thank the Department of Science and Technology
(DST), New Delhi for use of the single-crystal diffractometer facil-
ity at the Department of Chemistry, University of Calcutta,
through the DST-FIST program.
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Received: December 17, 2013
Published Online: May 8, 2014
Eur. J. Inorg. Chem. 2014, 2753–2765
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim