Heptanuclear and Decanuclear Manganese Complexes with the Anion of
2-Hydroxymethylpyridine
Nicholas C. Harden,
†
Milissa A. Bolcar,
‡
Wolfgang Wernsdorfer,
#
Khalil A. Abboud,
†
William E. Streib,
‡,§
and George Christou*
,†,‡
Department of Chemistry, UniVersity of Florida, GainesVille, Florida 32611-7200,
Department of Chemistry and Molecular Structure Center, Indiana UniVersity,
Bloomington, Indiana 47405-4001, and Laboratoire Louis Ne ´ el-CNRS, BP166,
25 AVenue des Martyrs, 38042 Grenoble, Cedex 9, France
Received July 28, 2003
The synthesis and magnetic properties are reported of two new clusters [Mn
10
O
4
(OH)
2
(O
2
CMe)
8
(hmp)
8
](ClO
4
)
4
(1)
and [Mn
7
(OH)
3
(hmp)
9
Cl
3
](Cl)(ClO
4
)(2). Complex 1 was prepared by treatment of [Mn
3
O(O
2
CMe)
6
(py)
3
](ClO
4
) with
2-(hydroxymethyl)pyridine (hmpH) in CH
2
Cl
2
, whereas 2 was obtained from the reaction of MnCl
2
‚4H
2
O, hmpH,
and NBu
n
4
MnO
4
in MeCN followed by recrystallization in the presence of NBu
n
4
ClO
4
. Complex 1‚2py‚10CH
2
Cl
2
‚
2H
2
O crystallizes in the triclinic space group P1 h. The cation consists of 10 Mn
III
ions, 8 µ
3
-O
2-
ions, 2 µ
3
-OH
-
ions, 8 bridging acetates, and 8 bridging and chelating hmp
-
ligands. The hmp
-
ligands bridge through their O
atoms in two ways: two with µ
3
-O atoms and six with µ
2
-O atoms. Complex 2‚3CH
2
Cl
2
‚H
2
O crystallizes in the
triclinic space group P1 h. The cation consists of four Mn
II
and three Mn
III
ions, arranged as a Mn
6
hexagon of
alternating Mn
II
and Mn
III
ions surrounding a central Mn
II
ion. The remaining ligation is by three µ
3
-OH
-
ions, three
terminal chloride ions, and nine bridging and chelating hmp
-
ligands. Six hmp
-
ligands contain µ
2
-O atoms and
three contain µ
3
-O atoms. The Cl
-
anion is hydrogen-bonded to the three µ
3
-OH
-
ions. Variable-temperature
direct current (dc) magnetic susceptibility data were collected for complex 1 in the 5.00-300 K range in a 5 kG
applied field. The
M
T value gradually decreases from 17.87 cm
3
mol
-1
K at 300 K to 1.14 cm
3
mol
-1
K at 5.00
K, indicating an S ) 0 ground state. The ground-state spin of complex 2 was established by magnetization
measurements in the 0.5-3.0 T and 1.80-4.00 K ranges. Fitting of the data by matrix diagonalization, incorporating
only axial anisotropy (DS ˆ
z
2
), gave equally good fits with S ) 10, g ) 2.13, D ) -0.14 cm
-1
and S ) 11, g )
1.94, D ) -0.11 cm
-1
. Magnetization versus dc field scans down to 0.04 K reveal no hysteresis attributable to
single-molecule magnetism behavior, only weak intermolecular interactions.
Introduction
A wide variety of polynuclear Mn clusters have been
synthesized to date with the metal in the oxidation state range
of II-IV, including clusters with mixed-valency. These
complexes usually contain carboxylate ligands, and they are
usually molecular but are sometimes polymeric.
1
Molecular
species with metal nuclearities up to 30 have been reported
to date.
2,3
One of our interests in these molecules is the often
large ground-state spin (S) that they possess and the resulting
possibility that such molecules might function as single-
molecule magnets (SMMs).
4
A SMM possesses a significant
* Author to whom correspondence should be addressed. E-mail:
christou@chem.ufl.edu.
²
University of Florida.
‡
Indiana University.
#
Laboratoire Louis Ne ´el.
§
Deceased.
(1) Tasiopoulos, A. J.; Harden, N. C.; Abboud, K. A.; Christou, G.
Polyhedron 2003, 22, 133.
(2) (a) Aromi, G.; Aubin, S. M. J.; Bolcar, M. A.; Christou, G.; Eppley,
H. J.; Folting, K.; Gatteschi, D.; Hendrickson, D. N.; Huffman, J. C.;
Squire, R. C.; Tsai, H.-L.; Wang, S.; Wemple, M. W. Polyhedron
1998, 17, 3005. (b) Chakov, N. E.; Abboud, K. A.; Zakharov, L. N.;
Rheingold, A. L.; Hendrickson, D. N.; Christou, G. Polyhedron 2003,
22, 1759. (c) Brockman, J. T.; Abboud, K. A.; Hendrickson, D. N.;
Christou, G. Polyhedron 2003, 22, 1765. (d) Soler, M.; Wernsdorfer,
W.; Abboud, K. A.; Hendrickson, D. N.; Christou, G. Polyhedron
2003, 22, 1777. (e) Soler, M.; Wernsdorfer, W.; Sun, Z.; Ruiz, D.;
Huffman, J. C.; Hendrickson, D. N.; Christou, G. Polyhedron 2003,
22, 1783.
(3) Soler, M.; Rumberger, E.; Folting, K.; Hendrickson, D. N.; Christou,
G. Polyhedron 2001, 20, 1365.
(4) Christou, G.; Gatteschi, D.; Hendrickson, D. N.; Sessoli, R. MRS Bull.
2000, 25, 66.
Inorg. Chem. 2003, 42, 7067-7076
10.1021/ic0348906 CCC: $25.00 © 2003 American Chemical Society Inorganic Chemistry, Vol. 42, No. 22, 2003 7067
Published on Web 10/04/2003