Synthesis, crystal structures and magnetic properties of M IICuII chains (M=Mn and Co) with sterically hindered alkyl-substituted phenyloxamate bridging ligands

Article abstract of DOI:10.1002/chem.201002110

A series of neutral oxamato-bridged heterobimetallic chains of general formula [MCu(L^x)₂(S)₂]·p S·q H₂O [p=0-1, q=0-2.5; L¹=N-2,6-dimethylphenyloxamate, S=DMF with M=Mn (1 a) and Co (1 b); L²

Full text of DOI:10.1002/chem.201002110

DOI: 10.1002/chem.201002110
II
II
Synthesis, Crystal Structures and Magnetic Properties of M Cu Chains
M=Mn and Co) with Sterically Hindered Alkyl-Substituted Phenyloxamate
Bridging Ligands**
(
[
a]
[a]
[a, b]
[a, b]
Jesffls Ferrando-Soria, Emilio Pardo,* Rafael Ruiz-García,
Joan Cano,
[d]
[
a]
[a]
[c]
Francisco Lloret,* Miguel Julve, Yves Journaux,* Jorge Pasµn, and
[
d]
Catalina Ruiz-PØrez
ꢀ
1
Abstract: A series of neutral oxamato-
zigzag, oxamato-bridged mangane-
se(II)–copper(II) chains. The intrachain
Cu···Mn distances across the oxamato
bridge are 5.3761(7) and 5.4002(17) ꢀ
for 2a and 3a, respectively, whereas
the shortest interchain Mn···Mn distan-
ces are 9.4475(16) and 8.1649(14) ꢀ for
2a and 3a, respectively. All of these
[ꢀJ=31.4–35.2 and 33.4–44.8 cm , re-
bridged heterobimetallic chains of gen-
spectively; H=ꢀ ꢀJS (S +S
)].
Cu,iꢀ1
i
M,i
Cu,i
x
II
II
eral formula [MCu(L ) (S) ]·pS·qH O
[
Only the Co Cu chains show slow
magnetic relaxation effects characteris-
tic of single-chain magnets (SCMs).
Analysis of the magnetic relaxation dy-
namics of 3d shows a thermally activat-
ed mechanism (Arrhenius law depen-
ACHTUNGTRENUNNGd ence) with values of the pre-exponen-
tial factor (t =2.6ꢁ10 s) and activa-
tion energy (E =7.7 cm ) that are typ-
ical of SCMs. In contrast, two
2
2
2
1
p=0–1, q=0–2.5; L =N-2,6-dimethyl-
phenyloxamate, S=DMF with M=Mn
2
(
1a) and Co (1b); L =N-2,6-diethyl-
phenyloxamate, S=DMF with M=Mn
2a) and Co (2b) or S=DMSO with
(
3
II
II
M=Mn (2c) and Co (2d); L =N-2,6-
diisopropylphenyloxamate, S=DMF
M Cu chains (M=Mn and Co) exhib-
it 1D ferrimagnetic behaviour with
moderately strong intrachain antiferro-
magnetic coupling between the square-
ꢀ
9
0
ꢀ
1
with M=Mn (3a) and Co (3b) or S=
DMSO with M=Mn (3c) and Co (3d)]
were prepared by treating the corre-
sponding anionic oxamatocopper(II)
a
II
planar Cu and octahedral high-spin
relaxation regimes are observed for 2d
in different temperature regions (t =
3.2ꢁ10 s and E =24.7 cm for T<
4.5 K and t =3.2ꢁ10 s and E =
II
M
ions across the oxamato bridge
0
x
2ꢀ
ꢀ10
ꢀ1
complexes [Cu(L ) ]
M
(x=1–3) with
2
a
2
+
ꢀ14
cations (M=Mn and Co) in DMF
0
a
Keywords: chain structures · cobalt ·
copper magnetic properties
manganese
ꢀ
1
or DMSO as the solvent. The single-
crystal X-ray structures of 2a and 3a
reveal the occurrence of well-isolated,
37.5 cm for T>4.5 K).
·
·
[
a] J. Ferrando-Soria, Dr. E. Pardo, Dr. R. Ruiz-Garcꢂa, Dr. J. Cano,
Prof. Dr. F. Lloret, Prof. Dr. M. Julve
Departament de Quꢂmica Inorgꢃnica/Instituto de Ciencia Molecular
[d] Dr. J. Pasꢇn, Prof. Dr. C. Ruiz-Pꢆrez
Laboratorio de Rayos X y Materiales Moleculares
Departamento de Fꢂsica Fundamental II
Facultad de Fꢂsica, Universidad de la Laguna
La Laguna, Tenerife, 38201 (Spain)
(
ICMol)
Universitat de Valꢄncia, Paterna, Valencia, 46980 (Spain)
Fax : (+34)963544322
E-mail: emilio.pardo@uv.es
[
**] Ligand Design for Heterobimetallic Single-Chain Magnets, Part 2; for
Part 1, see: E. Pardo, R. Ruiz-Garcꢂa, F. Lloret, J. Faus, M. Julve, Y.
Journaux, M. A. Novak, F. S. Delgado, C. Ruiz-Pꢆrez, Chem. Eur. J.
2007, 13, 2054.
francisco.lloret@uv.es
[
b] Dr. R. Ruiz-Garcꢂa, Dr. J. Cano
Fundaciꢅ General de la Universitat de Valꢄncia (FGUV)
Universitat de Valꢄncia, Valencia, 46002 (Spain)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem201002110.
[
c] Dr. Y. Journaux
Institut Parisien de Chimie Molꢆculaire, UMR CNRS 7071
UPMC-Univ. Paris 06, Paris, 75005 (France)
Fax : (+33)144273841
E-mail: yves.journaux@upmc.fr
2176
ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 2176 – 2188

FULL PAPER
Introduction
The observation of slow magnetic relaxation effects below a
blocking temperature (T ) in molecule-based chain com-
B
[1]
pounds a decade ago, providing experimental confirmation
[2]
of Glaubersꢉ prediction, opened exciting perspectives for
storing information in low-dimensional molecular magnetic
[3]
materials. This novel class of magnetic chain compounds
has been referred to as single-chain magnets (SCMs) by
analogy to the so-called single-molecule magnets (SMMs).
SMMs have a high-spin (S) ground state with an important
Ising-type magnetic anisotropy (D) that results in a large ac-
tivation energy (E ) for magnetisation reversal, given by
Scheme 1. Ligand design strategy toward oxamato-bridged heterobime-
a
2
[4]
II
II
E =jDjS . In the case of SCMs, the activation energy also
tallic SCMs of general formula [Cu
R’ Ph with R’=Me, Et and iPr and n=1–3; M=Mn and Co; S=DMF,
DMSO and H O).
2 3 2 2 1
ACHTUNGERTNNGNU( m-C O NR) M (S) ] (R=2,4,6-
a
depends upon the intrachain magnetic coupling (J) accord-
n
2
[5]
2
ing to the expression E =(4jJj+jDj)S . In recent years,
a
many groups have focused their efforts on the search for
SCMs because of the possibility of increasing the value of
TB by modifying the intrachain interactions and thus open-
ing the way to future applications in nanoscience and nano-
technology.
laxation effects nor 3D long-range ferromagnetic ordering,
as expected from the magnetically isotropic character of the
II
6
octahedral high-spin Mn ion with a A single-ion ground
1
state (Dꢁ0) and the very good isolation of the chains
II
II
Since the discovery of the first SCM, a cobalt(II) nitronyl
A
H
U
G
R
N
N
(jꢁ0). In contrast, some of the Co Cu chains show slow
nitroxide radical chain with the formula [Co
A
H
U
G
R
N
U
G
magnetic relaxation effects at low temperatures typical of
SCMs because of the magnetically anisotropic character of
the octahedral high-spin Co ion with an orbitally degener-
2
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(NITPhOMe)] (hfac=hexafluoroacetylacetonate,
NIT-
II
PhOMe=4’-methoxyphenyl-4,4,5,5-tetramethylimidazoline-
[
1]
4
1
-oxyl-3-oxide), by Gatteschi et al., some other examples
ate T single-ion ground state. Moreover, when the number
1
[6–11]
[5a,b]
II
II
have been reported.
Recent reviews by Clꢆrac et al.
of methyl substituents along the series of Co Cu chains is
increased from one to three, the TB values increase in ac-
cordance with the steric hindrance of the aryl-substituted
oxamate ligand. This observation is likely related to the
greater separation between chains, and hence to the de-
crease in interchain interactions. In addition, the nature of
the solvent is another factor that significantly influences the
[5c]
and Gao et al. classified SCMs by taking into account the
synthetic strategies and preparative routes towards the chain
compound, the role of the bridging ligand and the nature of
the magnetic coupling, either ferro- or antiferromagnetic,
between neighbouring ions along the chain. Some funda-
mental questions related to the understanding of the relaxa-
tion mechanism in these 1D systems remain open and,
therefore, further experimental work is required to obtain
new examples of SCMs. The conditions to be fulfilled for
the observation of this magnetic behaviour could be sum-
marised as the existence of an easy axis of magnetization
SCM behaviour. Thus, higher T values are observed for the
B
II
II
Co Cu chains with DMSO compared to those with aqua li-
gands and/or water of crystallisation, probably due to better
isolation of the chains because of the larger size of the
former. Although the influence of the interchain interac-
and a high ratio of intra- to interchain magnetic coupling
tions on the slow relaxation dynamics of SCMs has been
4
[12]
(
jJ/jj>10 ). Accordingly, synthetic strategies to build new
predicted theoretically,
scarce compared to the related SMMs.
experimental studies are still
[13]
[14–16]
SCMs have focussed on the search for the perfect system
combining highly anisotropic transition-metal (Co , Fe and
Mn ) and/or lanthanide ions (Dy , Tb and Ho ) with
bridging ligands to give strong ferro- or antiferromagnetic
interactions between the metal centres while maintaining
good isolation between the chains.
II
II
As an extension of this work, herein we report the synthe-
sis and structural and magnetic characterisation of a new
series of heterobimetallic chains of general formula
III
III
III
III
II
II
x
[M Cu (L ) (S) ]·pS·qH O (M=Mn or Co; S=DMF or
2
2
2
DMSO; x=1–3), prepared from the corresponding mononu-
II
x
2ꢀ
1
Previously, we presented a rational strategy to obtain
SCMs based on the use of sterically hindered, dianionic oxa-
matocopper(II) complexes as bis-bidentate ligands (metallo-
ligands) toward solvated divalent transition-metal cations
like manganese(II) or cobalt(II) in either dimethyl sulfoxide
clear copper(II) complexes, [Cu (L ) ] (L =N-2,6-dime-
2
2
thylphenyloxamate, L =N-2,6-diethylphenyloxamate, and
3
L =N-2,6-di
A
H
U
G
R
N
U
G
parison of the static and dynamic magnetic properties in this
II
II
family of oxamato-bridged M Cu chains with sterically hin-
dered, 2,6-dialkyl-substituted, phenyloxamate bridging li-
gands is presented. The influence of the intra- and inter-
chain magnetic interactions and the local magnetic anisotro-
py on the SCM behaviour was analysed by varying the size
of the alkyl substituents of the aromatic ring in the copper-
(II) precursor (R’=Me, Et, iPr) and the nature of the coor-
[
11b]
or water as solvent (Scheme 1).
The resulting family of
II
II
M Cu chains (M=Mn and Co) with 2-, 2,6- and 2,4,6-poly-
methyl-substituted phenyloxamate bridging ligands behave
as ferrimagnetic chains with a moderately large intrachain
antiferromagnetic coupling between Cu and M ions. The
Mn Cu chains show evidence of neither slow magnetic re-
II
II
II
II
Chem. Eur. J. 2011, 17, 2176 – 2188
ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2177

E. Pardo, F. Lloret, Y. Journaux et al.
1
dinated solvent molecules and solvent molecules of crystalli-
sation (S=DMF and DMSO; Scheme 1b).
ised as reported earlier for [MnCu(L )
2A
T
N
T
N
U
G
2
1
[11b]
[CoCu(L )
A
H
U
G
E
N
N
(DMSO) ]·DMSO (1d).
They were obtained
2
2
as polycrystalline solids from the reaction of the correspond-
x
ing sodium salt of the mononuclear copper(II)–L (x=1–3)
II
II
Results and Discussion
precursor and the nitrate salt of the Mn or Co ions in hot
DMF or DMSO in good yields (ca. 65–80 and 65–75%, re-
spectively) (Scheme 2c). Single crystals of the mangane-
se(II)–copper(II) chain compounds 2a and 3a were grown
Synthesis and general physical characterization: The neutral
II
II
oxamato-bridged M Cu chains (M=Mn and Co) were syn-
thesised in three successive steps (Scheme 2). First, 2,6-di-
by slow diffusion in H-shaped tubes of DMF solutions con-
x
taining Mn
A
H
U
G
R
N
U
G
3
2
2
2
2
2
(
(
x=2 and 3, respectively) in the other at room temperature
Scheme 2d).
The chemical identity of the ligands, the mononuclear
copper(II) complexes and the heterobimetallic chain com-
pounds was determined by elemental analysis (C, H, N, S),
1
and H NMR and IR spectroscopy (see the Experimental
Section). The structures of 2a and 3a were further con-
firmed by single-crystal X-ray diffraction with synchrotron
radiation. Crystallographic data for 2a and 3a are summar-
ised in Table 1.
Table 1. Crystallographic data for 2a and 3a.
2
a
3a
formula
C
703.14
monoclinic
C2/c
13.2213(14)
13.4991(14)
19.0033(16)
99.122(6)
3348.6(4)
4
30
H
40CuMnN
4
O
8
37 5 10
C H57CuMnN O
ꢀ
1
M
r
[gmol
]
850.34
monoclinic
C2/c
20.189(4)
19.672(4)
13.110(3)
113.56(3)
4772.9(16)
4
crystal system
space group
a [ꢀ]
b [ꢀ]
c [ꢀ]
b [8]
V [ꢀ ]
3
Z
ꢀ
3
1
calcd [gcm
]
1.395
1.181
Scheme 2. Synthetic pathway to the oxamato-bridged heterobimetallic
F
A
H
U
G
R
N
U
G
1464
1.064
100(2)
17797
1784
0.761
100(2)
37190
chain compounds: a) C
RT; c) M(NO (M=Co, Mn), DMF or DMSO, 808C; d) Mn
DMF, RT.
2
O
2
ClOEt, THF, 708C; b) NaOH/Cu
A
H
U
G
E
N
N
3
)
2
, H
2
O,
) ,
3 2
ꢀ1
m [mm
T [K]
reflns collected
]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
3
)
2
A
H
U
G
R
N
N
independent reflns (Rint
obsd reflns [I>2s(I)]
)
2723
2459
2723/0/202
0.1021 (0.1074)
0.3000 (0.3055)
1.046
4699
4491
4699/5/235
0.1248 (0.1263)
0.4237 (0.4289)
2.265
x
ethyl- and 2,6-diisopropyl-N-phenyloxamate ligands H L
(
2
data/restraints/parameters
x=2 and 3, respectively) were prepared by direct conden-
sation of ethyl chlorooxoacetate with the corresponding ani-
line derivative in THF (Scheme 2a), as reported earlier for
[
a]
R
1
[I>2s(I)] (all)
[I>2s(I)] (all)
[b]
2
wR
[
c]
S
1
[11b]
2
,6-dimethyl-N-phenyloxamate ligand H L .
They were
2
o
2
c
2
2 2 1/2
o
2
[a] R =ꢀ(jF jꢀjF j)/ꢀjF j. [b] wR =[ꢀw(F ꢀ F ) /ꢀw(F ) ]
. [c] S=
1
o
c
o
2
x
2
1/2
isolated as ethyl ester derivatives HEtL (x=1–3) in excel-
lent yields (ca. 90–95%). In the second step cationic mono-
nuclear copper(II) complexes of L (x=2 and 3) were syn-
[ꢀw(jF jꢀjF j) /(N ꢀN )]
.
o
c
o
p
x
thesised as their sodium salts with general formula
Description of the structures
x
Na [Cu(L ) ]·qH O (q=2 and 4), as reported earlier for
2
2
2
1
[11b]
2
Na [Cu(L ) ]·4H O.
They were obtained in very good
A
H
U
G
R
N
U
G
A
T
N
T
E
N
N
(DMF) ] (2a): Compound 2a consists of neutral
2
2
2
2
2
yields (ca. 80–85%) by deprotonation and hydrolysis of the
oxamato-bridged manganese(II)–copper(II) zigzag chains
(Figure 1). Within each chain, the bis(oxamato)copper(II)
entity acts as a bis-bidentate ligand through the cis carbon-
yl-oxygen atoms toward cis-bis(dimethylformamide)mangan-
x
corresponding pro
subsequent addition of a stoichiometric amount of Cu-
(NO ) ·3H O (Scheme 2b). In a third step, the correspond-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
li
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
gand HEtL with NaOH in water, and
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
3
2
2
ing heterobimetallic chain compounds of general formula
ACHTUNGTRENNUNGe se(II) units (Figure 1a). This situation is similar to that re-
x
1
[MCu(L )
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(DMF) ]·pDMF·qH O [p=0–1, q=0–2.5; M=
ported earlier for [CoCu(L ) ACHTNUGTNERNUG( H O) ], but contrasts with
2 2 2
2
2
2
x
4
4
Mn (1a–3a) and Co (1b–3b) with x=1–3] and [MCu(L ) -
that of [CoCu(L ) ACHTUNGTRNNEG(U H O) ]·2H O (L =N-2,4,6-trimethylphe-
2 2 2 2
2
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(DMSO) ]·pDMSO·qH O [p=0–1, q=0–2.5; M=Mn (2c
nyloxamate), in which cis and trans coordination of the two
2
2
and 3c) and Co (2d and 3d) with x=2 and 3] were synthes-
water molecules to the cobalt atoms leads to zigzag and
2178
www.chemeurj.org
ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 2176 – 2188

Ligand Design for Heterobimetallic Single-Chain Magnets
FULL PAPER
mers (D or L), like that observed for [CoCu
(DMF) ]·DMF [binaba=(M)-1,1’-binaphthalene-2,2’-bis-
Selected bond lengths and angles for 2a are
ACHTUNTGRENUNG( binaba)-
AHCTUNGTRENNUNG
2
[11c]
AHCTUNGTRENNUNG( oxamate)].
summarised in Table 2.
[
a,b]
Table 2. Selected bond lengths [ꢀ] and angles [8] for 2a.
Cu(1)ꢀN(1)
1.984(5)
2.187(5)
2.137(7)
85.9(2)
Cu(1)ꢀO(1)
Mn(1)ꢀO(3)
1.909(5)
2.163(5)
Mn(1)ꢀO(2)
Mn(1)ꢀO(4)
N(1)-Cu(1)-O(1)
N(1)-Cu(1)-O(1’)
O(2)-Mn(1)-O(3)
O(2)-Mn(1)-O(2’’)
O(2)-Mn(1)-O(4’’)
O(3)-Mn(1)-O(3’’)
O(4)-Mn(1)-O(4’’)
N(1)-Cu(1)-N(1’)
O(1)-Cu(1)-O(1’)
O(2)-Mn(1)-O(4)
O(2)-Mn(1)-O(3’’)
O(3)-Mn(1)-O(4)
O(3)-Mn(1)-O(4’’)
180.0
180.0
97.6(2)
92.03(18)
89.3(2)
168.8(2)
94.1(2)
76.50(17)
162.5(3)
95.4(2)
98.6(3)
84.1(4)
[
a] Estimated standard deviations are given in parentheses. [b] Symmetry
codes: (’)=1ꢀx, ꢀy, 1ꢀz; (’’)=1ꢀx, y, 3/2ꢀz.
The twofold-symmetry-related Cu(1) and Cu ACHUTNGRENNUG( 1’’) atoms in
2
a have a four-coordinate square-planar [CuN O ] environ-
2 2
ment formed by two amidate-nitrogen and two carboxylate-
2
oxygen atoms from the two L ligands in a trans arrange-
ment [Cu(1)ꢀN(1)=1.984(5) and Cu(1)ꢀO(1)=1.909(5) ꢀ].
The tetrahedral twist angle (t) at the copper atom is strictly
0
.08 for symmetry reasons. The oxamato groups are almost
coplanar with the metal basal plane [dihedral angle=
2
2
.8(4)8], whereas the phenyl ring of each L ligand is ap-
proximately perpendicular to the oxamato group [dihedral
angle=72.7(3)8] to prevent steric repulsions between the
ethyl substituents and the carbonyl-oxygen atoms. More
2
likely, the alternative cis arrangement of the L ligands is
precluded because of steric hindrance between the 2,6-dieth-
yl-substituted phenyl groups.
The centrosymmetrically related Mn(1) and Mn(1’) atoms
have a six-coordinate octahedral [MnO ] environment. The
6
equatorial plane is defined by two carbonyl-oxygen atoms
from the two cis-dimethylformamide molecules [Mn(1)ꢀ
O(4)=2.137(7) ꢀ] and two carbonyl-oxygen atoms from the
2
amidate groups of the two L ligands [Mn(1)ꢀO(3)=
2
.163(5) ꢀ], whereas two carbonyl oxygen-atoms from the
2
carboxylate groups of the two L ligands [Mn(1)ꢀO(2)=
2
.187(5) ꢀ] occupy the axial positions. The trigonal twist
angle (q) at the manganese atom is 55.0(4)8, a value which
reflects a slight distortion of the octahedral metal environ-
ment (q=608) toward trigonal prismatic (q=08) (a so-called
Bailar twist). This situation is likely explained by the steric
hindrance between the two cis-coordinated dimethylforma-
mide molecules.
Figure 1. a) View of a fragment of the chain of 2a with the atom number-
ing for the metal coordination environments. b), c) Crystal packing of the
chains of 2a along the [001] and [100] directions, respectively. Hydrogen
atoms are omitted for clarity [symmetry codes: (’)=1ꢀx, ꢀy, 1ꢀz; (’’)=
1
ꢀx, y, 3/2ꢀz; (’’’)=ꢀ1/2+x, 1/2+y, z].
In the crystal lattice, the zigzag chains of 2a running par-
allel to the c axis are well separated from each other be-
cause of the effective shielding of the 2,6-diethyl-substituted
phenyl groups and the cis-coordinated dimethylformamide
molecules in the ab plane (Figure 1b). The adjacent chains
related by a simple translation along the [110] direction ex-
hibit a zipper-type close packing (Figure 1c). The intrachain
Mn(1)···Cu(1) distance across the oxamato bridge is
[
11a,b]
linear chain structures, respectively.
Because of the cis
conformation of the octahedral Mn atoms in 2a, two differ-
ent propeller enantiomers (D and L) exist, and thus their
regular alternation along the chain leads to a global achiral
zigzag chain structure. Instead, a chiral helical chain struc-
ture would result from a regular alternation of identical iso-
Chem. Eur. J. 2011, 17, 2176 – 2188
ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2179

E. Pardo, F. Lloret, Y. Journaux et al.
III
5
.3761(7) ꢀ, whereas the shortest interchain Mn(1)···Mn
A
H
U
G
R
N
U
G
through the cis carbonyl oxygen-atoms toward cis-bis(dime-
thylformamide)manganese(II) units to give an achiral zigzag
chain structure with alternating propeller chiralities (D and
L) for the octahedral Mn atoms along the chain (Figure 2a).
Selected bond lengths and angles for 3a are summarised in
Table 3.
III
and Cu(1)···Cu ACHTUNGTRENNUNG( 1 ) separations are 9.4475(16) ꢀ.
3
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[MnCu(L )
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(DMF) ]·DMF·H O (3a): Compound 3a is
2
2
2
made up of neutral oxamato-bridged manganese(II)–cop-
per(II) zigzag chains, together with dimethylformamide and
water molecules of crystallisation (Figure 2). As in 2a, the
bis ACHTUNGTRENNUNG( oxamato)copper(II) entity acts as a bis-bidentate ligand
[
a,b]
Table 3. Selected bond lengths [ꢀ] and angles [8] for 3a.
Cu(1)ꢀN(1)
1.934(3)
2.206(3)
2.138(3)
84.76(14)
95.24(13)
76.81(10)
92.31(19)
174.11(13)
166.20(15)
93.2(3)
Cu(1)ꢀO(1)
Mn(1)ꢀO(3)
1.949(4)
2.150(3)
Mn(1)ꢀO(2)
Mn(1)ꢀO(4)
N(1)-Cu(1)-O(1)
N(1)-Cu(1)-O(1’)
O(2)-Mn(1)-O(3)
O(2)-Mn(1)-O(2’’)
O(2)-Mn(1)-O(4’’)
O(3)-Mn(1)-O(3’’)
O(4)-Mn(1)-O(4’’)
N(1)-Cu(1)-N(1’)
O(1)-Cu(1)-O(1’)
O(2)-Mn(1)-O(4)
O(2)-Mn(1)-O(3’’)
O(3)-Mn(1)-O(4)
O(3)-Mn(1)-O(4’’)
180.0
180.0
87.54(18)
93.54(11)
92.16(14)
97.32(13)
[
a] Estimated standard deviations are given in parentheses. [b] Symmetry
codes: (’)=1/2ꢀx, 1/2ꢀy, 1ꢀz; (’’)=ꢀx, y, 1/2ꢀz.
The twofold-symmetry-related Cu(1) and Cu ACHUTNGRENNUG( 1’’) atoms in
3
a have a four-coordinate square-planar [CuN O ] environ-
2 2
ment formed by two amidate-nitrogen and two carboxylate-
3
oxygen atoms from the two L ligands in a trans arrange-
ment [Cu(1)ꢀN(1)=1.934(3) and Cu(1)ꢀO(1)=1.949(4) ꢀ].
As in 2a, the t value at the copper atom is strictly 0.08 for
3
reasons of symmetry, and the oxamato groups from each L
ligand are also coplanar with the metal basal plane [dihedral
angle=2.2(3)8]. The phenyl ring and the oxamato group
3
from each L ligand are however much closer to perpendicu-
larity [dihedral angle=79.8(3)8] than in 2a, and this reflects
the larger steric hindrance of the isopropyl substituents com-
pared to the ethyl ones.
The centrosymmetrically related Mn(1) and Mn(1’) atoms
have
a six-coordinate octahedral [MnO6] environment
formed by four carbonyl-oxygen atoms from the two cis-di-
methylformamide molecules [Mn(1)ꢀO(4)=2.138(3) ꢀ] and
3
the carboxylate groups of the two L ligands [Mn(1)ꢀO(2)=
2
.206(3) ꢀ] defining the equatorial plane and two carbonyl-
3
oxygen atoms from the amidate functions of the two L li-
gands [Mn(1)ꢀO(3)=2.150(3) ꢀ] occupying the axial posi-
tions. The q value at the manganese atom of 54.4(4)8 is simi-
lar to that found in 2a, and thus reflects a slight trigonal dis-
tortion of the octahedral environment.
In the crystal lattice, the zigzag chains of 3a running par-
allel to the [101] direction are well separated from each
other because of the effective shielding of the 2,6-diisoprop-
yl-substituted phenyl groups and the cis-coordinated dime-
thylformamide molecules in the ab plane (Figure 2b). The
packing of adjacent chains related by a glide translation
along the b axis leads to narrow pores along the c axis that
are occupied by dimethylformamide and water molecules of
crystallisation (Figure 2c). The value of 5.4002(17) ꢀ for the
intrachain Mn(1)···Cu(1) distance across the oxamato bridge
is close to that of 2a, and thus reflects the fact that the indi-
vidual chains are very similar. The value of 8.1649(14) ꢀ for
Figure 2. a) View of a fragment of the chain of 3a with the atom number-
ing for the metal coordination environments. b), c) Crystal packing of the
chains of 3a along the [101] and [001] directions, respectively. Atoms of
the uncoordinated dimethylformamide and water molecules of crystallisa-
tion are shown as large spheres with arbitrary radii. Hydrogen atoms are
omitted for clarity [symmetry codes: (’)=1/2ꢀx, 1/2ꢀy, 1ꢀz; (’’)=ꢀx, y,
1
/2ꢀz; (’’’)=1/2+x, 1/2+y, z].
2180
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Chem. Eur. J. 2011, 17, 2176 – 2188

Ligand Design for Heterobimetallic Single-Chain Magnets
FULL PAPER
Figure 4. a) Temperature dependence of c
an applied magnetic field of 1 T (Tꢂ50 K) and 100 G (T<50 K). In-
set: The c
T minima for 2c (&) and 3c (~). The solid lines are the best-
fit curves (see text). b) Field dependence of M for 2c (&) and 3c (~) at
.0 K. The solid lines are guides for the eye.
M
T for2c (&) and 3c (~) under
Figure 3. a) Temperature dependence of c
~) under an applied magnetic field of 1 T (Tꢂ50 K) and 100 G (T
50 K). Inset: The c
T minima for 1a (*), 2a (&) and 3a (~). The solid
lines are the best-fit curves (see text). b) Field dependence of M for 1a
*), 2a (&) and 3a (~) at 2.0 K. The solid lines are guides for the eye.
M
T for 1a (*), 2a (&) and 3a
(
<
M
M
2
(
the shortest interchain Mn(1)···Mn
A
H
U
G
R
N
N
(1’’’) separation is, howev-
under a dc magnetic field of 100 G. The lack of a maximum
in the cM versus T plot (data not shown) allows us to rule
out the occurrence of a 3D long-range antiferromagnetic
order of the magnetically well-isolated Mn Cu chains, as
revealed by the crystal structures of 2a and 3a.
The M versus H plots for 1a–3a at 2.0 K, in which M is
the magnetisation per MnCu pair and H the applied mag-
netic field, are also similar to those of 2c and 3c (Figures 3b
and 4b, respectively). The values of M in the range of 3.93–
er, smaller than that of 2a, despite both the larger size of
the isopropyl substituents compared to the ethyl ones and
the presence of additional dimethylformamide and water
molecules of crystallisation. This fact reflects the striking
differences in the crystal packing of the individual chains in
the two compounds.
II
II
Static magnetic properties
3
.99Nb at 5.0 T are consistent with that calculated for the
Manganese(II)–copper(II) chains: The dc magnetic proper-
ties of 1a–3a in the form of c T versus T plots, in which c
is the magnetic susceptibility per MnCu pair and T is the
temperature, are similar to those of 2c and 3c (Figures 3a
saturation magnetisation of an S=2 state resulting from the
II
antiparallel alignment of the spins of Mn (SMn =5/2) and
M
M
II
Cu
(SCu =1/2)
ions
along
the
chain
[M =
s
(gMnSMnꢀg S )Nb=3.90Nb with g =2.0 and gCu =2.1].
Cu Cu
Mn
and 4a, respectively). The c T values at room temperature
Moreover, the magnetisation isotherms show fast saturation
with about 90% of the maximum M values being reached at
a field of 1.0 T. This reveals a strong short-range correlation
along the chain because of the relatively large antiferromag-
M
3
ꢀ1
vary in the narrow range of 4.20–4.30 cm mol K, and are
lower than expected for the sum of a square-planar Cu ion
II
2
2
Cu
3
ꢀ1
[
SCu =1/2; c T=(Nb g /3k )S
A
H
U
G
R
N
U
G
K
=
M
B
Cu
Cu
II
II
II
with gCu =2.1] and an octahedral high-spin Mn ion [S
netic coupling between the Mn and Cu ions across the ox-
amato bridge.
Mn
2
2
3
ꢀ1
5
/2; c T=(Nb g /3k )S ACHTUNGTRENNG(U S +1)=4.35 cm mol K with
M Mn B Mn Mn
gMn =2.0] magnetically isolated. Upon cooling, c T decreas-
The magnetic susceptibility data of 1a–3a, 2c and 3c
were analysed by using the one-dimensional model devel-
M
es to attain a minimum around 140 K (inset of Figures 3a
II
II
II
II
II
and 4a), which is characteristic of ferrimagnetic Mn Cu
chains with a relatively large intrachain antiferromagnetic
oped by Kahn et al. for Mn Cu chains, in which the Mn
II
and Cu ions are treated as classic (S =5/2) and quantum
Mn
II
II
[17a]
interaction between the Mn and Cu ions through the oxa-
(SCu =1/2) spins, respectively.
In this model, the spin
[
17]
mato bridge. The c T value then increases to reach maxi-
Hamiltonian is expressed by Equation (1), in which i runs
over the MnCu units, J is the magnetic coupling parameter
M
3
ꢀ1
mum values in the range of 20.4–81.0 cm mol K at 2.0 K
Chem. Eur. J. 2011, 17, 2176 – 2188
ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2181

E. Pardo, F. Lloret, Y. Journaux et al.
II
II
and gMn and gCu are the Landꢆ factors of the Mn and Cu
ions, respectively.
H ¼ S fꢀJS
ꢃ ðSCu,i þ SCu,iꢀ1Þ þ ðgMnSMn,i þ g SCu,iÞbHg
i
Mn,i
Cu
ð1Þ
The theoretical curves obtained by least-squares fit of the
experimental data of 1a–3a, 2c and 3c through this model
in the temperature range 20–300 K reproduce very well the
observed minimum in the c T versus T plots (solid lines in
M
the insets of Figures 3a and 4a). The magnitude of the intra-
II
II
chain antiferromagnetic coupling between the Cu and Mn
ions through the oxamato bridge for 2c and 3c (ꢀJ=33.3
and 32.4 cm , respectively) is close to that reported for 1c
ꢀ
1
ꢀ
1
[11b]
(
3
ꢀJ=28.2 cm ),
and similar to those in 1a–3a (ꢀJ=
ꢀ
1
1.4–35.2 cm ; Table 4). This fact suggests that the two
II
II
series of Mn Cu chains have similar structures despite the
different nature of the coordinated solvent molecules
(DMSO or DMF).
Table 4. Selected dc magnetic data for 1a–3a and 1c–3c.
ꢀ
1
[a]
[b]
[b]
ꢀJ [cm
]
g
Mn
g
Cu
1
2
3
1
2
3
a
a
a
c
c
c
35.2
32.1
31.4
28.2
33.3
32.4
2.00
2.00
2.00
2.00
2.00
2.00
2.09
2.06
2.08
2.07
2.07
2.08
Figure 5. a) Temperature dependence of c
(~) under an applied static field of 1 T (Tꢂ50 K) and 100 G (T<50 K).
Inset: The c
T minima for 1b (*), 2b (&) and 3b (~). The solid lines are
the best-fit curves (see text). b) Field dependence of M for 1b (*), 2b
&) and 3b (~) at 2.0 K. The solid lines are guides for the eye.
M
T for 1b (*), 2b (&) and 3b
[
c]
M
(
[
a] Intrachain magnetic coupling parameter [see Eq. (1)]. [b] Landꢆ
factor [see Eq. (1)]. [c] Data from ref. [11b].
culated value of the saturation magnetisation for a partial
spin cancellation resulting from the antiparallel alignment of
II
II
Cobalt(II)–copper(II) chains: The dc magnetic properties of
the spins of Co (SCo =Seff =1/2) and Cu (SCu =1/2) ions
1
b–3b in the form of c T versus T plot (cM is the magnetic
[M =(g S ꢀg S )Nb=1.10Nb with g =4.3 and gCu
=
M
s
Co Co
Cu Cu
Co
II
susceptibility per CoCu pair) are similar to those of 2d and
d (Figures 5a and 6a, respectively). At room temperature,
2.1]. In fact, the octahedral high-spin Co ions with an orbi-
4
3
tally degenerate T single-ion ground state (S =3/2 and
1
Co
3
ꢀ1
the c T values in the range of 2.07–2.59 cm mol K are
lower than expected for the sum of a square-planar Cu ion
LCo =1) behave as an effective Seff =1/2 spin state because
only the ground Kramerꢉs doublet resulting from the spin–
orbit coupling is populated at 2.0 K. The magnetisation iso-
therms show fast saturation with up to 90% of the maxi-
mum M value being reached at a field of 0.1 T for 2d. This
reveals a strong short-range correlation along the chain due
to the relatively large antiferromagnetic coupling between
M
II
2
2
Cu
3
ꢀ1
(
SCu =1/2) [c T=(Nb g /3k )S
A
H
U
G
R
N
U
G
K
M
B
Cu
Cu
II
with gCu =2.1] and an octahedral high-spin Co ion (S =3/
2
3
isolated. Upon cooling, c T decreases to attain a minimum
in the range of 85.5–135.0 K (insets of Figures 5a and 6a),
which is typical of ferrimagnetic Co Cu chains with a rela-
tively large intrachain antiferromagnetic interaction between
the Co and Cu ions through the oxamato bridge. Final-
Co
2
2
) with an important orbital contribution (c T=(Nb g
/
Co
M
3
ꢀ1
kB)S ACHTUNGTRENNUNG( S +1)=2.9 cm mol K with gCo =2.5) magnetically
Co Co
M
II
II
the Co and Cu ions across the oxamato bridge. Moreover,
II
II
a magnetic hysteresis loop is observed for 2d at 2.0 K with
relatively low values of the coercive field (H =150 G) and
c
II
II
[18]
3
ꢀ1
the remanent magnetization (M =0.45 cm mol G; inset of
r
ly, c T reaches a maximum in the range of 5.5–7.5 K under
Figure 6b). This is indicative of slow relaxation of the mag-
netisation within the individual chains or 3D long-range fer-
romagnetic order between the chains.
The magnetic susceptibility data of 1c–3c, 2d and 3d
were analysed by using the one-dimensional branch chain
M
a dc magnetic field of 100 G due to the magnetic anisotropy
and/or saturation effects. The lack of a cM maximum allows
us to rule out the occurrence of a 3D long-range antiferro-
II
II
magnetic order, and thus suggests that the Co Cu chains
are magnetically well-isolated from each other, too.
II
II
[18a]
model developed by Kahn et al. for Co Cu chains,
in
II
4
The M versus H plots for 1b–3b at 2.0 K (M is the mag-
netisation per CoCu pair) are also similar to those of 2d
and 3d (Figures 5b and 6b, respectively). The M values in
the range of 0.99–1.21Nb at 5.0 T are consistent with the cal-
which the Co ions are orbitally degenerate ( T1 ground
term). This model assumes that only z components of spin
and orbital momenta are coupled and that the applied mag-
netic field is along the quantization axis. The corresponding
2182
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Chem. Eur. J. 2011, 17, 2176 – 2188

Ligand Design for Heterobimetallic Single-Chain Magnets
FULL PAPER
Table 5. Selected dc magnetic data for 1b–3b and 1d–3d.
ꢀ
1
[a]
[b]
[b]
Cu
ꢀl [cmꢀ1
[c]
[d]
ꢀ1 [e]
ꢀ
J [cm
]
g
Co
g
]
k
D [cm ]
1
2
3
1
2
3
b
b
b
d
d
d
41.2
42.7
46.4
40.5
48.0
33.4
2.17
2.25
2.26
2.30
2.19
2.24
2.12
2.08
2.08
2.07
2.03
2.03
129
123
121
107
121
150
0.97
0.90
0.97
0.97
0.90
0.77
280
352
317
719
758
675
[f]
[
a] Intrachain magnetic coupling parameter [see Eq. (2)]. [b] Landꢆ
factor [see Eq. (2)]. [c] Spin–orbit coupling parameter with A=3/2 [see
Eq. (2)]. [d] Orbital reduction parameter [see Eq. (2)]. [e] Axial orbital
splitting parameter [see Eq. (2)]. [f] Data from ref. [11b].
would lead to a poorer overlap of the magnetic orbitals of
II
II
the Cu and Co ions through the s in-plane orbital path-
way of the oxamato bridge, and thus to a smaller intrachain
antiferromagnetic coupling.
The effective spin–orbit coupling (J’) can be related to the
4
spin–orbit coupling parameter (l) of the T ground term of
1
II
the Co ion in octahedral symmetry through the expression
J’=ꢀAkl, in which k is the reduction of the orbital momen-
tum caused by the ligand delocalization of the unpaired
electrons (nephelauxetic effect) and A is a crystal field pa-
rameter (A=3/2 and 1 for the weak and strong crystal-field
[
18c]
limits, respectively).
The calculated values of the orbital
Figure 6. a) Temperature dependence of c
under an applied static field of 1 T (Tꢂ50 K) and 100 G (T<50 K). In-
set: The c
T minima for 2d (&) and 3d (~). The solid lines are the best-
fit curves (see text). b) Field dependence of M for 2d (&) and 3d (~) at
.0 K. Inset: The hysteresis loop of 2d (&). The solid lines are guides for
M
T for 2d (&) and 3d (~)
II
reduction and spin–orbit coupling parameters of the Co ion
in 1b–3b and 1d–3d (k=0.77–0.97 and ꢀl =107–150 cm
with A=3/2; Table 5) thus reflect the degree of the metal–
ꢀ
1
M
2
ꢀ
1
ligand covalency (k=1.0 and l=ꢀ180 cm for the free
the eye.
ion). On the other hand, the larger magnitude of the local
II
axial octahedral distortion parameter (D) of the Co ion in
1d–3d (D=675–758 cm ) compared to those in 1b–3b (D=
280–352 cm ; Table 5) likely reflects a greater anisotropy of
the DMSO derivatives (1d–3d) when compared to the
DMF ones (1b–3b).
ꢀ
1
Hamiltonian is then expressed by Equation (2), in which i
runs over the CoCu units, J and J’ are the isotropic magnetic
exchange and effective spin–orbit coupling parameters re-
spectively, k is the orbital reduction, D is the splitting of the
T orbital term of the Co ion in a singlet and doublet orbi-
ꢀ
1
II
1
tal terms due to an axial symmetry and g and gCu are the
Landꢆ factors of the Co and Cu ions, respectively.
Dynamic magnetic properties
Co
II
II
Manganese(II)–copper(II) chains: The ac magnetic proper-
ties of 1a–3a, 2c and 3c in the form of c ’ and c ’’ versus T
plots (c ’ and c ’’ are the in-phase and out-of-phase mag-
M M
netic susceptibilities per MnCu pair, respectively) at differ-
ent frequencies (n) of a 1 G oscillating field show neither
evidence of slow magnetic relaxation effects within the indi-
vidual chains nor 3D long-range ferromagnetic order be-
0
H ¼S fꢀJS
ꢃ ðSCu,iðzÞ þ SCu,iꢀ1ðzÞÞ þ J L
ꢃ SCo,iðzÞ
þ
M
M
i
Co,iðzÞ
2
Co,iðzÞ
ð2Þ
DL
þ ðgCo
S
Co,iðzÞ
þ g S
þ kLCo,iðzÞÞbHðzÞ
g
Co,iðzÞ
Cu Cu,iðzÞ
The theoretical curves obtained by least-squares fit of the
experimental data of 1c–3c, 2d and 3d through this model
in the temperature range 50–300 K reproduce quite well the
tween the chains. In fact, no c ’’ signals were observed
M
observed minimum in the c T versus T plots (solid lines in
above 2.0 K for these two series of manganese(II)–cop-
M
the insets of Figures 5a and 6a). The magnitude of the intra-
chain antiferromagnetic coupling between Cu and Co ions
ACHTUNGTRENNUNG
II
II
II
6
through the oxamato bridge for 1b–3b (ꢀJ=41.2–
high-spin Mn ion with a A single-ion ground state and the
1
ꢀ
1
II
II
4
6.4 cm ) is within the range of those found for 1d and 2d
very good isolation of the Mn Cu chains, as revealed by
the crystal structures of 2a and 3a.
ꢀ
1
(
ꢀJ=40.5 and 48.0 cm , respectively), but it is somewhat
ꢀ
1
larger than that found in 3d (ꢀJ=33.4 cm ; Table 5). This
II
fact suggests that the Cu ion in 3d is not ideally square
Cobalt(II)–copper(II) chains: The ac magnetic properties of
1b–3b, 2d and 3d in the form of the c ’ and c ’’ versus T
plots (c ’ and c ’’ are the in-phase and out-of-phase mag-
planar but slightly tetrahedrally distorted, as previously re-
ported for the aforementioned chain compound [CoCu-
M
M
M
M
ꢀ
1
[11c]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(binaba)
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(DMF) ]·DMF (ꢀJ=28.9 cm ).
This situation
netic susceptibilities per CoCu pair, respectively) at differ-
2
Chem. Eur. J. 2011, 17, 2176 – 2188
ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2183

E. Pardo, F. Lloret, Y. Journaux et al.
ent frequencies (n) of a 1 G oscillating field show evidence
of slow magnetic relaxation effects for 2d and 3d (Figures 7
and 8, respectively, and Figures S1 and S2, respectively, in
given frequency (n), at which it is assumed that the switch-
ing of the oscillating field matches the relaxation rate of the
magnetisation (1/t=2pn), diverges exponentially as in
SCMs. Thus, the calculated t values at Tmax for 2d and 3d
follow the Arrhenius law given by Equation (4), characteris-
tic of a thermally activated mechanism (Figure 9 and inset
M
Figure 7. Temperature dependence of c ’’ for 2d under zero applied
static field at different frequencies of a ꢄ1 G oscillating field in the
range of 0.1–1000 Hz.
Figure 9. Arrhenius plots for 2d for T>4.5 K (left) and T<4.5 K (right).
The solid lines are best-fit curves (see text).
of Figure 8), but they deviate at higher temperatures (Tꢂ
4
.5 K) or higher frequencies for 2d (Figure 9). The values of
ꢀ
10
the preexponential factor (t ) are 3.2ꢁ10 (T<4.5 K) and
0
ꢀ
14
ꢀ9
3
.2ꢁ10 s (T>4.5 K) for 2d and 2.6ꢁ10 s for 3d, where-
as the values of the energy barrier (E ) are 24.7 (T<4.5 K)
a
ꢀ
1
ꢀ1
and 37.5 cm
(T>4.5 K) for 2d and 7.7 cm
for 3d
(
Table 6). The calculated t and E values for 2d in the low-
0
a
Table 6. Selected ac magnetic data for 2d and 3d.
[
a]
[b]
[c]
a[d]
[e]
[f]
Figure 8. Temperature dependence of c
M
’’ for 3d under zero applied
F
t
0
E
a
c
S
c
T
ꢀ
1
3
ꢀ1
3
ꢀ1
static field at different frequencies of a ꢄ1 G oscillating field in the
range of 10–1000 Hz. Inset: The inset shows the Arrhenius plot for 3d.
The solid line is the best-fit curve
[s]
[cm
]
[cm mol
]
[cm mol ]
[g]
ꢀ10
ꢀ14
2
3
d
d
0.11
.11
0.17
3.2ꢁ10
3.2ꢁ10
2.6ꢁ10
24.7
37.5
7.7
0.25
0.45
0.40
0.18
25.0
1.9
9.5
87.2
2.8
0
ꢀ
9
the Supporting Information) but also for 1b–3b (Figur-
[a] Mydosh parameter [see Eq. (3)]. [b] Pre-exponential factor [see
Eq. (4)]. [c] Activation energy [see Eq. (4)]. [d] Cole–Cole parameter
es S3–S5, Supporting Information). Thus, c ’’ becomes non-
M
[
see Eq. (5)]. [e] Adiabatic susceptibility [see Eq. (5)]. [f] Isothermal sus-
zero below 4.0 K for 1b–3b, but no maxima are observed
above 2.0 K (Figures S3b–S5b, Supporting Information). The
cM’’ value also becomes nonzero below 10.0 and 4.0 K for
ceptibility [see Eq. (5)].
2
d and 3d, respectively, and it shows maxima between 5.6
temperature region and those for 3d are close to the report-
(
(
n=1000 Hz) and 3.6 K (n=0.1 Hz) for 2d, and between 2.5
n=1000 Hz) and 2.1 K (n=350 Hz) for 3d (Figures 7 and 8,
ed values for the related oxamato-bridged SCMs of formula
4
ꢀ9
[CoCu(L ) ACHTNUGTRENN(NUG DMSO) ]·DMSO (4d; t =4.0ꢁ10 s and E =
2 2 0 a
ꢀ
1
4
ꢀ11
respectively), as previously observed for 1d, which shows a
unique maximum at 2.1 K for the highest applied frequency
(
38.0 cm ) and [CoCu(L ) ACHTUNGRTNNEG(U H O) ]·2H O (4e; t =2.3ꢁ10
2 2 2 2 0
ꢀ1
4
and E =16.3 cm ), in which L is the N-2,4,6-trimethylphe-
nyloxamate ligand.
a
[11b]
[11b]
n=1000 Hz).
The relative variation of the temperature
However, the calculated E value for
a
of the maximum of c ’’ with respect to the frequency of the
2d in the high-temperature region is larger and the t value
0
M
[19]
oscillating field is expressed by the so-called Mydosh param-
is smaller.
t ¼ t expðE
The c ’’ versus c ’ plots (so-called Cole–Cole plots)
[19]
eter (F), defined by Equation (3). The calculated F values
of 0.11 (2d) and 0.17 (3d) are within the range of 0.1<F<
=k
B
TÞ
ð4Þ
0
a
0.3 expected for SCMs.
[
20a]
at
M
M
F ¼ ðDTmax=TmaxÞ=Dðlg nÞ
ð3Þ
T=3.0–5.0 K for 2d and at T=2.0 K for 3d again show the
presence of two different relaxation processes for 2d
(Figure 10). This behaviour has already been reported for
The relaxation time (t) of the magnetisation for 2d and
[21]
3
d, which can be calculated from the maximum of c ’’ at a
SMMs, but there are no published examples in the case of
M
2184
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ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 2176 – 2188

Ligand Design for Heterobimetallic Single-Chain Magnets
FULL PAPER
generalised Debye model given by Equation (5) reproduces
the observed semicircle in the Cole–Cole plot (solid line in
Figure 11). In 2d, the theoretical curves obtained by consid-
ering each relaxation process separately provide a rough ap-
proach to the two possible semicircles related to each pro-
cess (solid lines in Figure 10). The coexistence of both semi-
circles occurs at T=4 K (Figure 10b), that is, both relaxation
regimes have similar weights at this temperature. However,
at lower (T=3 K) or higher (T=5 K) temperatures, one of
the processes becomes dominant, in agreement with the
change of the slope in the Arrhenius law at about 4.5 K
(
Figure 9).
The calculated values of the Cole–Cole parameters (a),
which determine the width of the t distribution, the adiabat-
ic (c ) and isothermal (c ) susceptibilities for 2d and 3d, are
S
T
given in Table 6. The a value for 3d (a=0.40) is somewhat
greater than expected for a SCM (a=0 for an ideal Debye
model with a single relaxation time). In general, these large
values (0<a<0.5) are commonly attributed to the existence
of interchain magnetic interactions. However, for 2d a value
of a=0.45 is observed for Tꢂ4.5 K, which is greater than
that observed for Tꢅ4.5 K (a=0.25). Clearly, this large
value of a cannot be attributed to interchain magnetic inter-
actions, because these interactions would increase at lower
temperatures, increasing the value of a, in contrast to what
is observed. Very large values of a indicate a broad distribu-
[19]
tion of relaxation times. Thus, this unique dual regime for
the slow dynamics of the magnetisation in 2d is currently
under investigation.
ꢀ
ꢁ
2
1=2
c ꢀc
ðc ꢀc Þ
2
0
0
T
S
0
0
T
S
c ðcÞ ¼
ðc ꢀc Þðc ꢀc Þþ
S
T
2
tan½ð1þaÞp=2ꢆ
4 tan ½ð1ꢀaÞp=2ꢆ
ð5Þ
Figure 10. Cole–Cole plots for 2d at a) 3, b) 4 and c) 5 K. The solid lines
are best-fit curves (see text).
Conclusion
[11b]
The present work and Part 1 of this series
are illustrative
SCMs. So, although the Cole–Cole plot of 3d follows the
shape of a semicircle characteristic of a single relaxation
process (Figure 11), that of 2d exhibits unprecedented pair-
fused semicircles (Figure 10). The theoretical curve obtained
by least-squares fit of the experimental data of 3d through a
examples of the ligand design strategy for the rational syn-
thesis of a new family of heterobimetallic SCMs from the
self-assembly of bis-bidentate square-planar copper(II) com-
plexes with sterically hindered, polyalkyl-substituted phenyl-
oxamate bridging ligands and transition-metal ions, such as
manganese(II) and cobalt(II), with coordinated solvent mol-
ecules and/or solvent molecules of crystallisation, such as di-
methylformamide, dimethyl sulfoxide or water (see
Scheme 1). Thus, systematic variation of the size, number
and position of the alkyl substituents (R’=Me, Et and iPr
II
x
with n=1–3) in the Cu –L (x=1–4) precursor and the
II
changes in the nature of the Co -coordinated solvent mole-
cules or solvent molecules of crystallisation (S=DMF,
DMSO and H O) are clearly reflected in both the static and
2
dynamic magnetic behaviour of the corresponding oxamato-
II
II
bridged Co Cu SCMs, as summarised in Table 7.
Overall, the blocking temperature for the series of
II
II
Co Cu chains with coordinated DMSO (T =2.1–5.6 K for
B
1
d–4d) and H O (T =2.2 K for 4e and T <2.0 K for 1e)
2 B B
Figure 11. Cole–Cole plot for 3d at 2 K. The solid line is the best-fit
curve (see text).
are higher than those with coordinated DMF (T <2.0 K for
B
Chem. Eur. J. 2011, 17, 2176 – 2188
ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2185

E. Pardo, F. Lloret, Y. Journaux et al.
Table 7. Summary of dc and ac magnetic data for 1b–3b, 1d–3d and re-
lated oxamato-bridged Co Cu SCMs.
Alternatively, the greater axial orbital splitting of the oc-
II
II
II
tahedral high-spin Co ion with coordinated DMSO [D=
ꢀ
1
[a]
ꢀ1 [b]
[c]
ꢀ1 [d]
ꢀ1
ꢀ1
ꢀJ [cm
]
D [cm
]
T
B
[K]
E
a
[cm
]
6
75–758 cm (1d–4d)] and H O [D=692 (1e) and 610 cm
2
1
2
3
1
2
3
4
1
4
b
b
b
d
d
d
d
41.2
42.7
46.4
40.5
48.0
33.4
44.3
45.8
35.0
280
352
317
719
758
675
710
692
610
<2.0
<2.0
<2.0
2.1
5.6
2.3
3.3
<2.0
2.2
(4e)] compared to those with coordinated DMF [D=280–
ꢀ
1
3
52 cm (1b–3b)] can also explain the observation of SCM
behaviour at higher blocking temperatures, given that the
intrachain antiferromagnetic coupling is comparable for
[
[
e]
e]
[f]
24.7 (37.5)
7.7
38.0
II
II
these series of Co Cu chains [ꢀJ=41.2–46.4 (1b–3b),
ꢀ1
33.4–48.0 (1d–4d), 45.8 (1e) and 35.0 cm (4e)]. In fact,
[
e]
e]
e
e
the larger the intrachain antiferromagnetic coupling and the
local magnetic anisotropy for 2d–4d, the greater the activa-
tion energy to reverse the magnetisation direction (inset of
Figure 12), as expected from the simple model developed by
Glauber to explain the slow dynamics of the magnetisation
for an Ising 1D system.
[
16.3
[
a] Intrachain magnetic coupling parameter [see Eq. (2)]. [b] Axial orbi-
tal splitting parameter [see Eq. (2)]. [c] Blocking temperature defined as
B
the temperature of the maximum of c ’’ at a given frequency (T =Tmax
M
at n=1000 Hz). [d] Activation energy [see Eq. (4)]. [e] Data from
ref. [11b]. [f] The activation energy for the second relaxation process is
given in parentheses.
1
b–3b; Table 7). This is most likely due to the presence of
DMSO and H O molecules of crystallisation for 1d–4d and
Experimental Section
2
4
e, respectively, which leads to better isolation of the chains
compared to their analogues 1b–3b and 1e, for which only
Reagents: Nitrate salts of the metals, sodium hydroxide, ethyl chloro-
AHCTUNGERTNNUNGo xoacetate and 2,6-dialkylaniline derivatives were purchased from com-
coordinated DMF or H O molecules, respectively, are pres-
2
1
mercial sources and used as received. The ligand HEtL and the mononu-
ent. However, the values of the blocking temperature along
1
clear copper(II) complex Na
reported.
2
[Cu(L )
2
]·2H
2
O were prepared as previously
x
the former series of cobalt(II)–copper(II)–L chain com-
[11b]
pounds vary in the order 1d<3d<4d<2d, which is not the
expected trend from the steric hindrance of the polyalkyl-
substituted phenyloxamate bridging ligands according to
2
N-2,6-Diethylphenyloxamic acid ethyl ester (HEtL ) and N-2,6-diisopro-
3
pylphenyloxamic acid ethyl ester (HEtL ): The ethyl esters of the proli-
gands HEtL (x=2, 3) were prepared by following the synthetic proce-
x
1
[11b]
1
2
3
4
dure previously reported for HEtL .
In a typical preparation, the cor-
L <L <L <L sequence. In this regard, compound 2d re-
responding 2,6-dialkylaniline derivative (60 mmol) was treated with ethyl
chlorooxoacetate (7.0 mL, 60 mmol) in THF (150 mL) at 08C under con-
tinuous stirring. The resulting solution was heated to reflux for 1 h and
the solvent was removed in a rotatory evaporator to afford an oil that
solidified when left at RT. The white solid obtained was filtered off,
washed with a small amount of diethyl ether and dried under vacuum.
ported herein has the highest T value among this family of
B
oxamato-bridged SCMs (Figure 12). It thus appears that the
interchain interactions depend on subtle crystal-packing ef-
fects that are difficult to control by the synthetic chemist, as
revealed by the crystal structures of the manganese(II)–cop-
2
1
HEtL : Yield: 95%; H NMR ([D
t, 3H; CH ), 2.48 (q, 4H; 2CH O), 4.31 (q, 2H; CH
H and 5-H of C ), 7.20 (t, 1H; 4-H of C ), 10.83 ppm (s, 1H; NH);
6
]DMSO): d=1.10 (t, 6H; 2CH
3
), 1.32
x
per(II)–L analogues 2a and 3a, which show longer inter-
(
3
2
2
O), 7.12 (d, 2H; 3-
2
3
chain metal–metal separations for L than for L despite the
smaller steric hindrance of the ethyl substituents compared
to the isopropyl ones.
6
H
3
6 4
H
IR (KBr): n˜ =3238 (NꢀH), 3021, 2967 and 2934 (CꢀH), 1733 and
ꢀ
1
1
6
692 cm (C=O); elemental analysis calcd (%) for C14H19NO (249): C
7.47, H 7.63, N 5.62; found: C 67.27, H 7.41, N 5.72.
3
1
HEtL : Yield: 90%; H NMR ([D
CH(CH ), 1.28 (t, 3H; CH ), 3.98 (h, 2H; CH of CH
H; CH O), 7.16 (d, 2H; 3-H and 5-H of C (iPr) ), 7.28 (t, 1H; 4-H
of C (iPr)
), 10.32 ppm (s, 1H; NH); IR (KBr): n˜ =3275 (NꢀH),
6
]DMSO): d=1.10 (d, 12H; CH
3
of
A
H
U
G
R
N
U
G
3
)
2
3
A
H
U
G
R
N
U
G
3 2
)
2
2
6
H
3
N
A
H
N
T
E
N
N
2
6
H
3
N
A
H
U
G
R
N
U
2
ꢀ
1
3
062, 2963 and 2943 (CꢀH), 1739 and 1687 cm (C=O); elemental analy-
sis calcd (%) for C16
H
23NO
3
(277): C 69.31, H 8.30, N, 5.05; found: C
6
9.27, H 8.41, N 5.12.
2
3
Na
2
[Cu(L )
2
]·4H
2
O and Na
2
[Cu(L )
2
]·4H
2
O: The sodium salts of the cop-
x
per(II)–L (x=2, 3) precursors were prepared by following the synthetic
procedure reported previously for Na
periment, HEtL (x=2, 3; 10 mmol) was suspended in water (25 mL) and
1
[11b]
2
[Cu(L )
2
]·2H
2
O.
In a typical ex-
x
allowed to react with aqueous NaOH (1.0 g, 25 mmol; 25 mL). Cu-
AHCTUNGTREUNNNG( NO ) ·3H O (1.21 g, 5 mmol) dissolved in water (25 mL) was added
3 2 2
dropwise to the resulting colourless solution at RT under continuous stir-
ring. The resulting deep-green solution was then filtered on paper
remove the small amount of solid particles. The solvent was reduced to a
quarter of its volume in a rotatory evaporator and a solid separated. The
green polycrystalline solid was filtered off, washed with acetone and di-
Figure 12. Variation in the blocking temperature (T
B
) for the series of ox-
amato-bridged cobalt(II)–copper(II)–L (x=1–4) chain compounds with
) as coordi-
x
dimethylformamide (*), dimethyl sulfoxide (&) and water (~
ethyl ether and dried under vacuum.
nated solvent molecules (data from Table 7). The solid lines are guides
for the eye. Inset: dependence of the activation energy (E ) for the mag-
netisation reversal of the intrachain magnetic coupling (&) and the axial
orbital splitting ( ) for 2d–4d (data from Table 7). The solid lines are
best linear-fit curves (see text).
2
O: Yield: 85%; IR (KBr): n˜ =3391 (OꢀH), 3028, 2965
a
Na
2
[Cu(L )
2
]·4H
2
ꢀ1
and 2932 (CꢀH), 1613 and 1583 cm (C=O); elemental analysis calcd
(%) for C24 Na 10 (620): C 46.45, H 5.48, N 4.52; found: C
46.43, H 5.41, N, 4.39.
&
H
34CuN
2
O
2
2186
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ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 2176 – 2188

Ligand Design for Heterobimetallic Single-Chain Magnets
FULL PAPER
3
1
Na
2
2
[Cu(L )
2
]·4H
2
O: Yield: 85%; IR (KBr): n˜ =3420 (OꢀH), 3042 and
lowing the synthetic procedure reported previously for [CoCu(L )
2
-
ꢀ
1
[11b]
963 (CꢀH), 1647 and 1619 (C=O) cm ; elemental analysis calcd (%)
for C28 Na 10 (675): C 49.75, H 3.71, N 4.15; found: C 49.13, H
.56, N 4.19.
A
H
U
G
R
N
U
G
]·DMSO (1d).
In a typical experiment, Co
A
H
U
G
R
N
U
G
3 2 2
) ·6H O
2
H
25CuN
2
2
O
x
3
dropwise to a solution of Na [Cu(L ) ]·4H
2 2 2
1
2
3
solved in hot DMSO (10 mL) at 808C. The resulting dark-green solution
was filtered while hot and the filtrate was allowed to stand at RT. After
several days, green polycrystalline solids of 2d and 3d appeared, and
were filtered off and air-dried.
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[MnCu(L )
(DMF) ]·DMF·H
standard synthetic procedure.
(NO ·4H O (0.062 g, 0.25 mmol) was dissolved in hot DMF (10 mL)
and added dropwise to a solution of Na
.25 mmol) dissolved in hot DMF (10 mL) at 808C. The resulting dark-
2
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(DMF)
2 2 2 2
] (1a), [MnCu(L ) ACHTUNTGERUNNNG( DMF) ] (2a) and [MnCu(L ) -
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
2
2
O (3a): Compounds 1a–3a were prepared by following
[
11b]
a
In a typical experiment, Mn-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
3
)
2
2
x
ꢀ
ꢀ
2d: Yield: 65%; IR (KBr): n˜ =3440 (O H), 2960 and 2945 (C H),
2
[Cu(L )
2
]·qH
2
O (x=1–3, q=2–4;
ꢀ
1
0
2 10 3
1600 cm (C=O); elemental analysis calcd (%) for C30H48CoCuN O S
green solution was filtered while hot and the filtrate was allowed to stand
at RT. After several days, green polycrystalline solids of 1a–3a appeared,
and were filtered off and air-dried. Well-formed tiny deep-green prisms
of 2a and 3a suitable for X-ray diffraction were obtained by slow diffu-
(831): C 43.34, H 5.82, N 3.37, S 11.57; found: C 43.17, H 5.78, N 3.29, S
11.54.
3d: Yield: 70%; IR (KBr): n˜ =3432 (OꢀH), 2960 and 2937 (CꢀH), 1603
ꢀ
1
and 1608 cm
(C=O); elemental analysis calcd (%) for
sion in an H-shaped tube of DMF solutions containing stoichiometric
32 46 2 8 2
C H CoCuN O S (773): C 47.70, H 5.99, N 3.62, S 8.30; found: C 47.79,
H 6.02 N 3.61, S 8.33.
x
amounts of Mn
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(NO
3
)
2
·4H
2
O in one arm and Na
2
[Cu(L )
2
]·4H
2
O (x=2,
3
) in the other at RT.
Physical techniques: Elemental analyses (C, H, N and S) were carried
1
a: Yield: 75%; IR (KBr): n˜ =3431 (OꢀH), 2960 and 2921 (CꢀH), 1603
out by the Microanalytical Service of the Universitat de Valꢄncia.
H NMR spectra were recorded at 250 MHz by using a Bruker AC 250
ꢀ
1
1
and 1628 (C=O) cm ; elemental analysis calcd (%) for C26MnCuH32
N
4
O
8
(
647): C 48.26, H 4.98, N 8.66; found: C 47.76, H 4.98, N 8.95.
spectrometer. Chemical shifts are reported in parts per million (ppm)
versus TMS with the residual proton signals of deuterated DMSO as the
internal standard. IR spectra were recorded by using a Perkin–Elmer 882
spectrophotometer as KBr pellets. Variable-temperature dc and ac mag-
netic susceptibility measurements and variable-field magnetization meas-
urements were carried out on powdered samples by using a Quantum
Design SQUID magnetometer. The susceptibility data were corrected for
the diamagnetism of the constituent atoms and the sample holder.
2
a: Yield: 65%; IR (KBr): n˜ =3431 (OꢀH), 2960 and 2921 (CꢀH), 1602
ꢀ1
and 1648 cm
C
N 7.95.
(C=O); elemental analysis calcd (%) for
30MnCuH40
N
4
O
8
(703): C 51.24, H 5.93, N 7.97; found: C 51.25, H 5.71,
3
a: Yield: 70%; IR (KBr): n˜ =3423 (OꢀH), 2962 and 2929 (CꢀH), 1603
ꢀ1
and 1630 cm
C
(C=O); elemental analysis calcd (%) for
37MnCuH55
N
5
O
9
(850): C 52.26, H 6.75, N 8.24; found: C 52.13, H 6.70,
Crystal data collection and refinement: The X-ray diffraction data of 2a
and 3a were collected at 100(2) K on crystals embedded in oil by using
synchrotron radiation [l=0.7293 (2a) and 0.7380 ꢀ (3a)] at the BM16-
CRG beamline in the ESRF (Grenoble, France). The quality of the data
is far from optimal because of the poor diffraction of the crystals and par-
tial loss of crystallinity during data collection. The brilliance of the syn-
chrotron radiation allowed fast experiments to be carried out, and two
N 8.16.
[CoCu(L )
(DMF) ]·2.5H
standard synthetic procedure.
(NO ·6H O (0.073 g, 0.25 mmol) was dissolved in hot DMF (10 mL)
and added dropwise to a solution of Na
.25 mmol) dissolved in hot DMSO (10 mL) at 808C. The resulting dark-
1
2
3
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
2
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(DMF)
2 2 2 2
] (1b), [CoCu(L ) ACHTUNTGERUNNNG( DMF) ] (2b) and [CoCu(L ) -
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
2
2
O (3b): Compounds 1b–3b were prepared by following a
[
11b]
In
a
typical experiment, Co-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
3
)
2
2
x
2
2 2
[Cu(L ) ]·qH O (x=1–3, q=2–4;
0
satisfactory data sets were obtained that were carefully indexed, integrat-
green solution was filtered while hot and the filtrate was allowed to stand
at room temperature. After several days, green polycrystalline solids of
[22]
ed and scaled by using the HKL2000 program.
All calculations for
data reduction, structure solution and refinement were done by standard
1
b–3b appeared, which were filtered off and air-dried.
[23]
procedures (WINGX).
The structures of 2a and 3a were solved by
2
1
b: Yield: 80%; IR (KBr): n˜ =3433 (OꢀH), 2939 and 2921 (CꢀH), 1601
direct methods and refined with full-matrix least-squares technique on F
by using the SHELXS-97 and SHELXL-97 programs. Some disorder
ꢀ
1
[24]
and 1625 cm (C=O); elemental analysis calcd (%) for C26CoCuH32
N
4
O
8
(
651): C 47.97, H 4.95, N 8.60; found: C 47.08, H 4.89, N 8.59.
was found for the uncoordinated dimethylformamide molecule in 3a, the
atoms of which were refined anisotropically by applying some constraints
with a fixed occupation factor of 0.5. The residual electron density was
assigned to a not fully occupied position of the O(1w) atom from a water
molecule of crystallization (the site occupancy factor was refined and
once converged, it was fixed to that value for subsequent refinements).
The hydrogen atoms of the organic ligands and dimethylformamide mol-
ecules were calculated and refined with isotropic thermal parameters,
whereas those of the water molecule were neither found nor calculated.
The final geometrical calculations and the graphical manipulations were
2
b: Yield: 75%; IR (KBr): n˜ =3448 (OꢀH), 2965 and 2934 (CꢀH), 1601
ꢀ1
4 8
and 1646 cm (C=O); elemental analysis calcd (%) for C30CoCuH40N O
(
706): C 50.95, H 5.70, N 7.93; found: C 50.39, H 5.54, N 7.18.
3
1
(
b: Yield: 75%; IR (KBr): n˜ =3423 (OꢀH), 2962 and 2934 (CꢀH),
ꢀ1
4 10.5
601 cm (C=O); elemental analysis calcd (%) for C34CoCuH53N O
807): C 50.52, H 6.61, N 6.93; found: C 49.05, H 6.24, N 5.93.
2
3
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[MnCu(L )
2
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(DMSO)
2
]
(2c)
and
2
[MnCu(L ) -
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(DMSO)
2
]·0.5DMSO·2.5H
2
O (3c): Compounds 2c and 3c were prepared
1
by following the synthetic procedure reported previously for [MnCu(L )
2
-
carried out with PARST97 and CRYSTAL MAKER programs, respec-
[
11b]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(DMSO)
2
] (1c).
In a typical experiment, Mn
A
H
U
G
R
N
U
G
3
)
2
·4H
2
O (0.062 g,
[25]
tively.
Unfortunately, no reliable information was obtained for com-
0
.25 mmol) was dissolved in hot DMSO (10 mL) and added dropwise to
plexes 1a, 1b–3b and 1c–3c from the analysis of the powder diffraction
patterns because of their quasi-amorphous nature.
x
2 2 2
a solution of Na [Cu(L ) ]·4H O (x=2, 3; 0.25 mmol) dissolved in hot
DMSO (10 mL) at 808C. The resulting dark-green solution was filtered
while hot and the filtrate was allowed to stand at RT. After several days,
green polycrystalline solids of 2c and 3c appeared, which were filtered
off and air-dried.
CCDC 784413 (2a) and 784414 (3a) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
2
c: Yield: 75%; IR (KBr): n˜ =3448 (OꢀH), 2965 and 2918 (CꢀH), 1601
ꢀ1
and 1626 (C=O) cm
;
elemental analysis calcd (%) for
C
28MnCuH38
N
2
O
8
S
2
(713): C 47.15, H 5.37, N 3.92, S 8.99; found: C
4
6.61, H 5.24, N 4.08, S 8.70.
Acknowledgements
3
c: Yield: 75%; IR (KBr): n˜ =3448 (OꢀH), 2963 and 2920 (CꢀH), 1602
ꢀ1
and 1637 cm
C
(C=O); elemental analysis calcd (%) for
This work was supported by the MICINN (Spain; projects CTQ2007-
1690, MAT2007-60660, CSD2007-00010 and CSD2006-00015), the Gen-
eralitat Valenciana (Spain; project PROMETEO/2009/108), the Gobier-
no Autꢅnomo de Canarias (Spain; project PI2002/175) and the CNRS
(France). E. P. and J.F.-S. acknowledge the MICINN and the Generalitat
33MnCuH36
N
2
O
12
S2.5 (872): C 45.48, H 6.48, N 3.22, S 9.20; found: C
6
4
5.24, H 6.45, N 3.16, S 9.13.
2
3
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[CoCu(L )
2
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(DMSO)
2
]·DMSO·2H
2
O
(2d)
and
2
[CoCu(L ) -
2
ACHTUNGTRENNUNG( DMSO) ]·0.5DMSO (3d): Compounds 2d and 3d were prepared by fol-
Chem. Eur. J. 2011, 17, 2176 – 2188
ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2187

E. Pardo, F. Lloret, Y. Journaux et al.
Valenciana for a postdoctoral (“Juan de la Cierva”) and a predoctoral
grant, respectively.
Pardo, R. Ruiz-Garcꢂa, F. Lloret, J. Faus, M. Julve, Y. Journaux,
M. A. Novak, F. S. Delgado, C. Ruiz-Pꢆrez, Chem. Eur. J. 2007, 13,
2
054; c) E. Pardo, C. Train, R. Lescouꢊzec, Y. Journaux, J. Pasꢇn, C.
Ruiz-Pꢆrez, F. S. Delgado, R. Ruiz-Garcꢂa, F. Lloret, C. Paulsen,
Chem. Commun. 2010, 46, 2322.
[12] S. Zumer, Phys. Rev. B 1980, 21, 1298.
[
1] A. Caneschi, D. Gatteschi, N. Lalioti, C. Sangregorio, R. Sessoli, G.
Venturi, A. Vindigni, A. Rettori, M. G. Pini, M. Novak, Angew.
Chem. 2001, 113, 1810; Angew. Chem. Int. Ed. 2001, 40, 1760.
2] R. J. Glauber, J. Math. Phys. 1963, 4, 294.
[13] a) H. Miyasaka, M. Yamashita, Dalton Trans. 2007, 399; b) R. Sesso-
li, Angew. Chem. 2008, 120, 5590; Angew. Chem. Int. Ed. 2008, 47,
5508.
[14] a) W. Wernsdorfer, N. Aliaga-Alcalde, D. N. Hendrickson, G. Chris-
tou, Nature 2002, 416, 406; b) W. Wernsdorfer, S. Bhaduri, R. Tiron,
D. N. Hendrickson, G. Christou, Phys. Rev. Lett. 2002, 89, 197201;
c) K. Park, M. R. Pederson, S. L. Richardson, N. Aliaga-Alcalde, G.
Christou, Phys. Rev. B 2003, 68, 020405; d) S. Hill, R. S. Edwards, N.
Aliaga-Alcalde, G. Christou, Science 2003, 302, 1015.
[
[
3] D. Gatteschi, R. Sessoli, J. Villain, Molecular Nanomagnets, Oxford
University Press, 2006.
[
4] a) R. E. P. Winpenny, Adv. Inorg. Chem. 2001, 52, 1; b) D. Gatteschi,
R. Sessoli, Angew. Chem. 2003, 115, 278; Angew. Chem. Int. Ed.
2
003, 42, 268; c) V. Marvaud, J. M. Herrera, T. Barilero, F. Tuyꢄras,
R. Garde, A. Scuiller, C. Decroix, M. Cantuel, C. Desplanches,
Monatsh. Chem. 2003, 134, 149; d) E. K. Brechin, Chem. Commun.
2
2
3
005, 5141; e) G. Aromꢂ, E. K. Brechin, Struct. Bonding (Berlin)
006, 122, 1; f) T. C. Stamatatos, G. Christou, Inorg. Chem. 2009, 48,
308.
[15] a) R. Tiron, W. Wernsdorfer, N. Aliaga-Alcalde, G. Christou, Phys.
Rev. B 2003, 68, 140407(R); b) R. Tiron, W. Wernsdorfer, D. Foguet-
Albiol, N. Aliaga-Alcalde, G. Christou, Phys. Rev. Lett. 2003, 91,
227203; c) C. Boskovic, R. Bircher, P. L. W. Tregenna-Piggott, H. U.
Gꢋdel, C. Paulsen, W. Wernsdorfer, A. L. Barra, E. Khatsko, A.
Neels, H. Stoeckli-Evans, J. Am. Chem. Soc. 2003, 125, 14046.
[16] a) H. Miyasaka, K. Nakata, K. Sugiura, M. Yamashita, R. Clꢆrac,
Angew. Chem. 2004, 116, 725; Angew. Chem. Int. Ed. 2004, 43, 707;
b) J. Yoo, W. Wernsdorfer, E. C. Yang, M. Nakano, A. L. Rheingold,
D. N. Hendrickson, Inorg. Chem. 2005, 44, 3377; c) H. Miyasaka, K.
Nakata, L. Lecren, C. Coulon, Y. Nakazawa, T. Fujisaki, K. Sugiur,
M. Yamashita, R. Clꢆrac, J. Am. Chem. Soc. 2006, 128, 3770.
[17] a) O. Kahn, Y. Pei, M. Verdaguer, J. P. Renard, J. Sletten, J. Am.
Chem. Soc. 1988, 110, 782; b) H. O. Stumpf, Y. Pei, L. Ouahab, F.
Leberre, E. Codjovi, O. Kahn, Inorg. Chem. 1993, 32, 5687; c) H. O.
Stumpf, Y. Pei, O. Kahn, J. Sletten, J. P. Renard, J. Am. Chem. Soc.
1993, 115, 6738.
[18] a) P. J. Van Koningsbruggen, O. Kahn, K. Nakatani, Y. Pei, J. P.
Renard, M. Drillon, P. Legoll, Inorg. Chem. 1990, 29, 3325; b)
C. L. M. Pereira, A. C. Doriguetto, C. Konzen, L. C. B. Meira, N. G.
Fernandes, Y. P. Mascarenhas, J. Ellena, M. Knobel, H. O. Stumpf,
Eur. J. Inorg. Chem. 2005, 5018; c) F. Lloret, M. Julve, J. Cano, R.
Ruiz-Garcꢂa, and E. Pardo, Inorg. Chim. Acta 2008, 361, 3432.
[19] a) M. A. Girtu, C. M. Wynn, W. Fujita, K. Awaga, A. Epstein, J.
Phys. Rev. B 1998, 57, R11058; b) J. A. Mydosh, Spin Glasses: An
Experimental Introduction, Taylor & Francis, London, 1993; c) D.
Chowdhury, Spin Glasses and Other Frustrated Systems, Princeton
University Press, New Jersey, 1986; d) K. Moorjani, J. M. D. Coey,
Magnetic Glasses, Elsevier, New York, 1984; e) K. Binder, A. P.
Young, Rev. Mod. Phys. 1986, 58, 801.
[
[
5] a) C. Coulon, H. Miyasaka, R. Clꢆrac, Struct. Bonding (Berlin) 2006,
22, 163; b) H. Miyasaka, M. Julve, M. Yamashita, R. Clꢆrac, Inorg.
1
Chem. 2009, 48, 3420; c) H. L. Sun, Z. M. Wanga, S. Gao, Coord.
Chem. Rev. 2010, 254, 1081.
6] a) A. Caneschi, D. Gatteschi, N. Lalioti, C. Sangregorio, R. Sessoli,
G. Venturi, A. Vindigni, A. Rettori, M. G. Pini, M. Novak, Euro-
phys. Lett. 2002, 58, 771; b) A. Caneschi, D. Gatteschi, N. Lalioti, R.
Sessoli, L. Sorace, V. Tangoulis, A. Vindigni, Chem. Eur. J. 2002, 8,
2
86; c) L. Bogani, A. Caneschi, M. Fedi, D. Gatteschi, M. Massi,
M. A. Novak, M. G. Pini, A. Rettori, R. Sessoli, A. Vindigni, Phys.
Rev. Lett. 2004, 92, 207204; d) L. Bogani, C. Sangregorio, R. Sessoli,
D. Gatteschi, Angew. Chem. 2005, 117, 5967; Angew. Chem. Int. Ed.
2
005, 44, 5817; e) K. Bernot, L. Bogani, A. Caneschi, D. Gatteschi,
R. Sessoli, J. Am. Chem. Soc. 2006, 128, 7947; f) N. Ishii, Y. Oka-
mura, S. Chiba, T. Nogami, T. Ishida, J. Am. Chem. Soc. 2008, 130,
2
7] a) R. Clꢆrac, H. Miyasaka, M. Yamashita, C. Coulon, J. Am. Chem.
Soc. 2002, 124, 12837; b) H. Miyasaka, R. Clꢆrac, K. Mizushima, K.
Sugiura, M. Yamashita, W. Wernsdorfer, C. Coulon, Inorg. Chem.
4.
[
[
[
2
003, 42, 8203; c) A. Saitoh, H. Miyasaka, M. Yamashita, R. Clꢆrac,
J. Mater. Chem. 2007, 17, 2002; d) H. Miyasaka, A. Saitoh, M. Ya-
mashita, R. Clꢆrac, Dalton Trans. 2008, 2422; e) M. Ferbinteanu, H.
Miyasaka, W. Wernsdorfer, K. Sugiura, K. Nakata, M. Yamashita, C.
Coulon, R. Clꢆrac, J. Am. Chem. Soc. 2005, 127, 3090; f) H. Miyasa-
ka, T. Madanbashi, K. Sugimoto, Y. Nakazawa, W. Wernsdorfer, K.
Sugiura, M. Yamashita, C. Coulon, R. Clꢆrac, Chem. Eur. J. 2006,
1
2, 7028.
8] a) R. Lescouꢊzec, J. Vaissermann, C. Ruiz-Pꢆrez, F. Lloret, R. Car-
rasco, M. Julve, M. Verdaguer, Y. Dromzꢆe, D. Gatteschi, W. Werns-
dorfer, Angew. Chem. 2003, 115, 1521; Angew. Chem. Int. Ed. 2003,
[20] a) K. S. Cole, R. H. Cole, J. Chem. Phys. 1941, 9, 341; b) C. J. F.
Boettcher, Theory of Electric Polarization, Elsevier, Amsterdam,
1952; c) S. M. Aubin, Z. Sun, L. Pardi, J. Krzysteck, K. Folting, L. J.
Brunel, A. L. Rheingold, G. Christou, D. N. Hendrickson, Inorg.
Chem. 1999, 38, 5329.
[21] a) J. D. Rinehart, K. R. Meihaus, J. R. Long, J. Am. Chem. Soc.
2010, 132, 7572; b) Y.-N. Guo, G.-F. Xu, P. Gamez, L. Zhao, S.-Y.
Lin, R. Deng, J. Tang, H.-J. Zang, J. Am. Chem. Soc. 2010, 132,
8538.
4
2, 1483; b) L. M. Toma, R. Lescouꢊzec, F. Lloret, M. Julve, J. Vais-
sermann, M. Verdaguer, Chem. Commun. 2003, 1850; c) L. M.
Toma, F. S. Delgado, C. Ruiz-Pꢆrez, R. Carrasco, J. Cano, F. Lloret,
M. Julve, Dalton Trans. 2004, 2836; d) L. M. Toma, R. Lescouꢊzec, J.
Pasꢇn, C. Ruiz-Pꢆrez, J. Vaissermann, J. Cano, R. Carrasco, W.
Wernsdorfer, F. Lloret, M. Julve, J. Am. Chem. Soc. 2006, 128, 4842;
e) L. M. Toma, R. Lescouꢊzec, S. Uriel, R. Llusar, C. Ruiz-Pꢆrez, J.
Vaissermann, F. Lloret, M. Julve, Dalton Trans. 2007, 3690.
9] a) T. Liu, D. Fu, S. Gao, Y. Zhang, H. Sun, G. Su, Y. Liu, J. Am.
Chem. Soc. 2003, 125, 13976; b) S. Wang, J. L. Zuo, S. Gao, Y. Song,
H. C. Zhou, Y. Z. Zhang, X. Z. You, J. Am. Chem. Soc. 2004, 126,
[22] Z. Otwinowski, W. Minor in Methods in Enzymology, Vol. 276, Mac-
romolecular Crystallography, Part A (Eds.: C. W. Carter, Jr., R. M.
Sweet), 1997, p. 307.
[23] L. J. Farrugia, J. Appl. Crystallogr. 1999, 32, 837.
[24] G. M. Sheldrick, SHELX-97, Programs for Crystal Structure Analy-
sis release 97-2, Institut fꢋr Anorganische Chemie der Universitꢌt
Gçttingen, Gçttingen, 1998.
8
900; c) H. R. Wen, C. F. Wang, Y. Song, J. L. Zuo, X. Z. You, Inorg.
Chem. 2006, 45, 8942.
[
[
10] a) E. Coronado, J. R. Galꢇn-Mascarꢅs, C. Martꢂ-Gastaldo, J. Am.
Chem. Soc. 2008, 130, 14987; b) E. Coronado, J. R. Galꢇn-Mascarꢅs,
C. Martꢂ-Gastaldo, CrystEngComm 2009, 11, 2143.
11] a) E. Pardo, R. Ruiz-Garcꢂa, F. Lloret, J. Faus, M. Julve, Y. Jour-
naux, F. S. Delgado, C. Ruiz-Pꢆrez, Adv. Mater. 2004, 16, 1597; b) E.
[25] a) M. Nardelli, J. Appl. Crystallogr. 1995, 28, 659; b) D. Palmer,
CRYSTAL MAKER Cambridge University Technical Services, Cam-
bridge, 1996.
Received: July 23, 2010
Published online: January 24, 2011
2188
www.chemeurj.org
ꢈ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 2176 – 2188