Topological Versatility of Oxalate-Based Bimetallic One-Dimensional
(1D) Compounds Associated with Ammonium Cations
Emilio Pardo,
†,§
Cyrille Train,*
,‡,∥
Kamal Boubekeur,
†
Geoffrey Gontard,
†
Joan Cano,
§
Francesc Lloret,
§
Keitaro Nakatani,
⊥
and Michel Verdaguer*
,†
†
Institut Parisien de Chimie Molé culaire, Universite ́ Pierre et Marie Curie-Paris 6, UMR CNRS 7201, 75252 Paris cedex 05, France
‡
Laboratoire National des Champs Magne ́ tiques Intenses, UPR CNRS 3228, Universite ́ Joseph Fourier, B.P. 166, 38042 Grenoble
cedex 9, France
∥
Institut Universitaire de France, 103, bd Saint-Michel 75005 Paris, France
§
Departament de Química Inorga ̀ nica, Instituto de Ciencia Molecular (ICMOL), Universitat de Vale ̀ ncia, 46980 Paterna, Valè ncia,
Spain
⊥
PPSM (UMR CNRS 8531), Institut d’Alembert (IFR 121, FR 3242), Ecole Normale Supe ́ rieure de Cachan, F-94235 Cachan,
France
* S Supporting Information
ABSTRACT: A new family of oxalate-bridged chains of formula (C
1
)[Mn-
(H
2
O)
3
Cr(ox)
3
]·H
2
O(1), (C
2
)
4
[Mn
2
(H
2
O)
3
ClCr
2
(ox)
6
]Cl·H
2
O·2C
2
H
6
O(2a),
(C
2
)
4
[Co
2
(H
2
O)
3
ClCr
2
(ox)
6
]Cl ·2H
2
O· 2C
2
H
6
O (2b), [Mn(C
3
)(H
2
O)
2
Cr-
(ox)
3
]·H
2
O(3), and (C
4
)
4
[Mn(H
2
O){Cr(ox)
3
}
2
]·H
2
O(4) [C
1
+
= tetramethy-
lammonium, C
2
+
= 4-N,N-dimethylaminopyridinium, C
3
+
= 1-hydroxyethyl-4-
N,N-dimethylamino-pyridinium, C
4
+
= 1-hydroxyethyl-4-(4′-dimethylamino-α-
styryl)-pyridinium, ox
2−
= oxalate] have been synthesized by self-assembly of the
(C
n
)
3
[Cr(ox)
3
](n =1−4) mononuclear compound and the chloride salts of the
corresponding metal(II) ions. The crystal structures of the five chain compounds
have been determined by single-crystal X-ray diffraction. Compounds 1 and 2
crystallize in the Pc and P2
1
/c centrosymmetrical space groups, respectively,
whereas 3 and 4 crystallize in the C2cb and P1 noncentrosymmetrical space
groups, respectively. Compounds 1, 2, and 3 adopt a zigzag chain structure while
4 exhibits a comb-like chain structure consisting of the repetition of the
[Mn(H
2
O){Cr(μ-ox)(ox)
2
}{Cr(μ-ox)
2
(ox)}]
4−
entities. Compound 3 displays large second-order optical nonlinearity. The
magnetic properties of 1−4 have been investigated in the temperature range 2−300 K. Monte Carlo simulations on 1, 2a, 2b, and
3 provide a quantitative description of the magnetic properties indicating ferromagnetic interactions through the bis(bidentate)
oxalate bridges [J = +0.55 cm
−1
(1), J = +1.02 cm
−1
(2a), J = +3.83 cm
−1
(2b), and J = +0.75 cm
−1
(3) using Hamiltonian H
̂
=
−J(S
̂
i
·S
̂
j
)]. On the other side, the fit of the magnetic susceptibility data of 4 by full-matrix diagonalization agrees with a
ferromagnetic exchange interaction within the [Mn(H
2
O){Cr(μ-ox)(ox)
2
}{Cr(μ-ox)
2
(ox)}]
4−
trinuclear units (J = +2.07 cm
−1
)
antiferromagnetically coupled along the chain. Compound 2b exhibits a metamagnetic behavior, the value of the critical field
being H
C
= 1000 G, due to the occurrence of weak interchain antiferromagnetic interactions.
■
INTRODUCTION
Since the pioneering work of Werner on the resolution of
tris(oxalato)metalate(III),
1
the oxalato ligand (C
2
O
4
2−
= ox) is
widely used in coordination chemistry, and a large number of
oxalate-based species have been reported with an extended
range of magnetic properties.
2
This interest in oxalate ligand is
due to the large variety of its coordination modes
3
and to its
efficiency to transmit electronic effects between neighboring
magnetic centers.
4
Furthermore, the anionic coordination
networks [M
II
M′
III
(μ-ox)
3
]
−
synthesized from molecular
precursors such as tris(oxalato)chromate(III) and a divalent
transition metal ion present two other advantages: they can
exhibit chirality and welcome a wide variety of functional
cations. Such a versatility is an open door toward new classes of
hybrid materials and multifunctional molecule-based magnets
exhibiting new physical properties.
5
The synthesis and design of
new hybrids displaying both magnetic properties and large
second-order optical nonlinearities (NLO behavior)
6,7
are of
fundamental interest for chemists, physicists, and materials’
scientists because second harmonic generation (SHG) and
electro-optical (EO) devices are important valuable targets.
8
Insertion of hyperpolarizable guests, such as stilbazolium-type
chromophores, in magnetic hosts is obviously a suitable
strategy.
9,10
Received: July 10, 2012
Published: October 22, 2012
Article
pubs.acs.org/IC
© 2012 American Chemical Society 11582 dx.doi.org/10.1021/ic3014915 | Inorg. Chem. 2012, 51, 11582−11593