Synthesis, characterization and magnetic properties of four new organically templated metal sulfates [C5H14N2][M II(H2O)6](SO4)2, (M II = Mn, Fe, Co, Ni)

Article abstract of DOI:10.1039/c1dt11030f

A series of novel organically templated metal sulfates, [C ₅H₁₄N₂][M^II(H₂O) ₆](SO₄)₂ with (M^II = Mn (1), Fe (2), Co (3) and Ni (4)), have been successfully synthesized by slow evaporation and characterized by single-crystal X-ray diffraction as well as with infrared spectroscopy, thermogravimetric analysis and magnetic measurements. All compounds were prepared using a racemic source of the 2-methylpiperazine and they crystallized in the monoclinic systems, P2₁/n for (1, 3) and P2₁/c for (2,4). Crystal data are as follows: [C₅H ₁₄N₂][Mn(H₂O)₆](SO₄) ₂, a = 6.6385(10) A, b = 11.0448(2) A, c = 12.6418(2) A, β = 101.903(10)°, V = 906.98(3) A³, Z = 2; [C₅H₁₄N₂][Fe(H₂O) ₆](SO₄)₂, a = 10.9273(2) A, b = 7.8620(10) A, c = 11.7845(3) A, β = 116.733(10)°, V = 904.20(3) A³, Z = 2; [C₅H₁₄N ₂][Co(H₂O)₆](SO₄)₂, a = 6.5710(2) A, b = 10.9078(3) A, c = 12.5518(3) A, β = 101.547(2)°, V = 881.44(4) A³, Z = 2; [C₅H ₁₄N₂][Ni(H₂O)₆](SO₄) ₂, a = 10.8328(2) A, b = 7.8443(10) A, c = 11.6790(2) A, β = 116.826(10)°, V = 885.63(2) A³, Z = 2. The three-dimensional structure networks for these compounds consist of isolated [M^II(H₂O)₆]²⁺ and [C ₅H₁₄N₂]²⁺ cations and (SO ₄)^2- anions linked by hydrogen-bonds only. The use of racemic 2-methylpiperazine results in crystallographic disorder of the amines and creation of inversion centers. The magnetic measurements indicate that the Mn complex (1) is paramagnetic, while compounds 2, 3 and 4, (M^II = Fe, Co, Ni respectively) exhibit single ion anisotropy.

Full text of DOI:10.1039/c1dt11030f

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PAPER
Synthesis, characterization and magnetic properties of four new organically
II
II
templated metal sulfates [C H N ][M (H O) ](SO ) , (M = Mn, Fe, Co,
5
14
2
2
6
4 2
Ni)†
a
a
a
b
a
c
Fadhel Hajlaoui, Houcine Na ¨ı li,* Samia Yahyaoui, Mark M. Turnbull, Tahar Mhiri and Thierry Bataille
Received 1st June 2011, Accepted 18th August 2011
DOI: 10.1039/c1dt11030f
II
II
A series of novel organically templated metal sulfates, [C
5
H
14
N
2
][M (H
2
O)
6
](SO
4
)
2
with (M = Mn (1),
Fe (2), Co (3) and Ni (4)), have been successfully synthesized by slow evaporation and characterized by
single-crystal X-ray diffraction as well as with infrared spectroscopy, thermogravimetric analysis and
magnetic measurements. All compounds were prepared using a racemic source of the 2-methylpipera-
zine and they crystallized in the monoclinic systems, P2
1
/n for (1, 3) and P2 /c for (2,4). Crystal data
1
˚
˚
˚
are as follows: [C
5
H
14
N
2
][Mn(H
2
O)
6
](SO
4
)
2
, a = 6.6385(10) A, b = 11.0448(2) A, c = 12.6418(2) A, b =
◦
3
˚
˚
˚
1
01.903(10) , V = 906.98(3) A , Z = 2; [C
5
H
14
N
2
][Fe(H
˚
2
O)
6
](SO ) , a = 10.9273(2) A, b = 7.8620(10) A,
4
2
◦
3
˚
c = 11.7845(3) A, b = 116.733(10) , V = 904.20(3) A , Z = 2; [C
5
◦
H
14
N
2
][Co(H
2
O)
˚
6
](SO
4
)
2
, a =
3
˚
˚
˚
6
.5710(2) A, b = 10.9078(3) A, c = 12.5518(3) A, b = 101.547(2) , V = 881.44(4) A , Z = 2; [C
5
H
14
2
N ]
◦
˚
˚
˚
[
8
Ni(H
2
O)
6
]-(SO
˚
4
)
2
, a = 10.8328(2) A, b = 7.8443(10) A, c = 11.6790(2) A, b = 116.826(10) , V =
3
85.63(2) A , Z = 2. The three-dimensional structure networks for these compounds consist of isolated
II
2+
2+
2-
[M (H
2
O)
6
]
and [C
5
H
14
N
2
]
cations and (SO ) anions linked by hydrogen-bonds only. The use of
4
racemic 2-methylpiperazine results in crystallographic disorder of the amines and creation of inversion
centers. The magnetic measurements indicate that the Mn complex (1) is paramagnetic, while
II
compounds 2, 3 and 4, (M = Fe, Co, Ni respectively) exhibit single ion anisotropy.
1
. Introduction
sulfates, combining transition metals with racemic amines con-
taining N-donors such as 2-methylpiperazine. The use of transition
metals in soft syntheses of sulfate-based compounds has provided
Over the past few decades, the chemistry of organically templated
metal sulfates has been a rapidly expanding research field due to
their fascinating structural diversities and potential applications as
functional materials. Particularly, the open-framework sulfates
combining transition metal and organic groups are of great interest
not only for their potential as model compounds of ferroelectric
and ferroelastic domains, but also for their promising application
in the field of molecular magnetism.
been used previously in the preparation hybrid metal sulfates
including aliphatic,
We have focused our attention on the study of a number of double
supramolecular structures, related to that of the well-known
27–29
Tutton’s salts.
To improve the understanding of this type of
1
–14
hybrid material, a series of 3d transition metal sulfates templated
II
by (±)-2-methylpiperazine, [C
5
H
14
N
2
][M (H
2
O)
6
](SO ) , have been
4
2
prepared. The use of the racemic mixture of the chiral amine
in the reaction provides for alternatives in crystallization: a
centrosymmetric structure where the enantiomers are related
by an appropriate crystallographic symmetry operation, or one
where the enantiomers occupy the same crystallographic position,
generating disorder. The latter is the case in the present work,
where we report the synthesis, crystal structure, thermal behaviour
and magnetic properties of these compounds.
1
5–16
A variety of amines have
1
5,17–18
19–21
3,7,22–26
aromatic
and cyclic amines.
a
Laboratoire de l’Etat Solide, D e´ partement de Chimie, Universit e´ de
Sfax, BP 1171, 3000 Sfax, Tunisia. E-mail: houcine_naili@yahoo.com;
Fax: (+216) 74 274 437; Tel: (+216) 98 66 00 26
b
Carlson School of Chemistry and Biochemistry, Clark University, Worcester,
MA, 01610, USA
2. Experimental section
c
Sciences Chimiques de Rennes (UMR CNRS 6226), Groupe Mat e´ riaux
Inorganiques: Chimie Douce et R e´ activit e´ , Universit e´ de Rennes I, Avenue
du G e´ n e´ ral Leclerc, 35042, Rennes CEDEX, France
2.1. Materials
†
Electronic supplementary information (ESI) available. Crystal data and
MnSO
4
·H
2
O (99%, Merck), FeSO
4
·7H
2
O (99%, Merck), CoSO
4
·
structure refinement for compounds 1–4, selected bond distances and
angles for compounds 1–4 and selected bond distances and angles for
7H O (99%, Merck), NiSO ·6H O (99%, Merck), 2-
2
4
2
methylpiperazine (95%, Aldrich) and H
2
SO
4
(96%, Carlo
[
SO
ESI and crystallographic data in CIF or other electronic format see DOI:
0.1039/c1dt11030f
4
] tetrahedron in 1–4. CCDC reference numbers 828000–828003. For
Erba) were used as received. Distilled water was used in all
syntheses.
1
This journal is © The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 11613–11620 | 11613

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3
4
2
.2. Synthesis
SHELXS-97. The oxygen atoms and the organic moieties were
35
found from successive Fourier calculations using SHELXL-97.
Compounds 1–4 were synthesized via slow evaporation from
aqueous solution. The clear solutions were stirred for 15 min and
allowed to stand at room temperature. After a few days, single
crystals having the specified color (see below) were formed. The
resulting mixtures were filtered, and the products washed with a
small amount of cold distilled water and allowed to air dry. The
yield was almost quantitative.
The aqua H atoms were located in a difference map and refined
˚
with O–H distance restraints of 0.85(2) A and H ◊ ◊ ◊ H restraints
˚
of 1.39(2) A so that the H–O–H angle fitted to the ideal value of a
tetrahedral angle. H atoms bonded to C and N atoms were placed
in geometrically idealized positions. Relevant crystallographic
data are listed in Table 1, ESI.† Selected bond distances and angles
are presented in Table 2 and 3, respectively, ESI.†
[C
5
H
14
N
2
][Mn(H
2
O)
6
](SO
4
2
) (1)
2.4. Infrared spectroscopy
Compound 1 was synthesized through the reaction of 0.1690 g
Infrared measurements were obtained using a Perkin–Elmer FT-
IR Spectrometer as KBr pellets in the range 4000–400 cm .
-
3
-3
(
2
4
1.00 ¥ 10 mol) of MnSO
4
·H
2
O, 0.1000 g (1.00 ¥ 10 mol) of
-1
-
3
-methylpiperazine, 0.1962 g (2.00 ¥ 10 mol) of H
2
SO
4
, and
-
1
.9860 g (2.77 ¥ 10 mol) of water. White prismatic crystals were
2.5. Thermogravimetric analysis
-
1
produced. IR data (cm ): N–H 1515, 1591; C–H 3021; S–O 997,
106; O–H 3435.
Thermogravimetric (TG) measurements were performed with
1
a
Rigaku Thermoflex instrument under flowing air for
II
II
[
C
5
H
14
N
2
][M (H
2
O)
6
](SO
4
)
2
(M = Mn (1), Fe (2), Co (3) and
[C
5
H
14
N
2
][Fe(H
2
O)
6
](SO
4
2
) (2)
◦
Ni (4)), in the temperature range 20–800 C, with a heating rate
◦
-1
Compound 2 was synthesized through the reaction of 0.2779 g
of 5 C min . The powdered samples (19.3 mg for 1, 37.9 mg for
2, 17.8 mg for 3 and 42.9 mg for 4) were spread evenly in a large
platinum crucible to avoid mass effects.
-
3
-3
(
1.00 ¥ 10 mol) of FeSO
4
·7H
2
O, 0.1000 g (1.00 ¥ 10 mol) of 2-
-
3
methylpiperazine, 0.2128 g (2.17 ¥ 10 mol) of H
g (2.75 ¥ 10 mol) of water. Dark green prismatic crystals were
produced. IR data (cm ): N–H 1463, 1634; C–H 3014; S–O 1094,
195; O–H 3356.
2
SO
4
, and 4.9500
-
1
-
1
2.6. Powder X-ray diffraction
1
Temperature-dependent X-ray diffraction (TDXD), for com-
pounds 1–4, was performed with a D5005 powder diffractometer
[
C
5
H
14
N
2
][Co(H
2
O)
6
](SO
4
) (3)
2
˚
(
Bruker AXS) using Cu-Ka radiation [l(Ka
1
) = 1.5406 A,
˚
Compound 3 was synthesized through the reaction of 0.2811 g
(
methylpiperazine, 0.2168 g (2.21 ¥ 10 mol) of H
g (2.78 ¥ 10 mol) of water. Red prismatic crystals were produced.
l(Ka
2
) = 1.5444 A] selected with a diffracted-beam graphite
-
3
-3
1.00 ¥ 10 mol) of CoSO
4
·7H
2
O, 0.1000 g (1.00 ¥ 10 mol) of 2-
monochromator and equipped with an Anton Paar HTK1200
high-temperature oven camera. Powder X-ray diffraction was used
to verify that materials used for magnetic and thermal analyses
were the same phase as the single crystal structures for 1–4.
The thermal decomposition of compound 4 was carried out in
-
3
2
SO
4
, and 5.0040
-
1
-
1
IR data (cm ): N–H 1508, 1495; C–H 3019; S–O 1090, 1186; O–H
431.
3
◦
-1
◦
air, with a heating rate of 7 C h from ambient to 600 C.
Temperature calibration was carried out with standard materials
in the involved temperature range. Experimental powder X-ray
diffraction patterns at high temperature have been interpreted also
by comparison with other compounds containing similar amine
[
C
5
H
14
N
2
][Ni(H
2
O)
6
](SO
4
2
) (4)
Compound 4 was synthesized through the reaction of 0.2628 g
(
methylpiperazine, 0.2266 g (2.31 ¥ 10 mol) of H
g (2.73 ¥ 10 mol) of water. Clear green prismatic crystals were
produced. IR data (cm ): N–H 1466, 1501; C–H 3012, S–O 1093,
1
-
3
-3
1.00 ¥ 10 mol) of NiSO
4
·6H
2
O, 0.1000 g (1.00 ¥ 10 mol) of 2-
-
3
5,6,7,37–38
2
SO
4
, and 4.9140
groups.
-
1
-
1
2.7. Magnetic studies
201; O–H 3411.
Magnetic studies were performed on a Quantum Designs MPMS-
XL SQUID magnetometer. Samples of each material were finely
ground and packed in #4 gelatine capsules. The magnetic moment
of the samples was then measured using a magnetic field varying
from 0 to 50000 Oe at 1.8 K. Several data points were also collected
as the field was reduced back to 0 to check for hysteresis effects;
none were observed. For all samples, the moment was linear as
a function of field to at least 4 kOe. The molar susceptibility cM,
defined as cM = limB→0(Mmol/B), was collected as a function of
temperature between 1.8 K and 310 K in a 1 kOe field.
2
.3. Single-crystal X-ray diffraction
Small crystals of the four compounds were glued to a glass
fibre mounted on a four-circle Nonius Kappa CCD area-detector
diffractometer. Intensity data sets were collected using Mo-Ka
radiation through the program COLLECT. Corrections for
Lorentz-polarisation effects, peak integration and background
determination were carried out with the program DENZO.
Frame scaling and unit cell parameter refinements were per-
formed with the program SCALEPACK. Analytical absorption
corrections were performed by modelling the crystal faces. The
structure analyses were carried out in the monoclinic space group
30
31
31
32
3
. Results
P2
1
/n or P2
1
/c, according to the automated search for space
All of the hybrid compounds described within this work crystallize
in the centrosymmetric space groups P2 /n and P2 /c. They
consist of transition metal cations octahedrally coordinated by
33
II
groups available in Wingx. Transition metal ions (M ) and
sulfur atoms were located using the direct methods with program
1
1
1
1614 | Dalton Trans., 2011, 40, 11613–11620
This journal is © The Royal Society of Chemistry 2011

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II
2+
)2-
] . The
six water molecules, [M (H
2
O)
6
] , isolated sulfate anions (SO
4
2
+
and disordered 2-methylpiperazinediium cations [C
5
H
14
N
2
cohesion of these structures is ensured by hydrogen bonds between
the cationic groups and the sulfate O atoms. The crystal structures
II
of [C
5
H
14
N
2
][M (H
2
O)
6
](SO
4
2
) show similar coordination polyhe-
dra. However, the arrangement of these polyhedra and the organic
molecules varies slightly between complexes. We were able to dis-
tinguish two different structure types: [C
and [C ][Co(H O) ](SO (hence referred to as
and 3, respectively) and [C ][Fe(H O) ](SO and
][Ni(H O) ](SO , (hence referred to as 2 and 4, respec-
5
H
14
N
2
][Mn(H
2
O)
6
](SO
4
)
2
5
H
14
N
2
2
6
4
)
2
1
5
H
14
N
2
2
6
)
4 2
[C
5
H
14
N
2
2
6
)
4 2
tively). The resulting H-bonding networks can be alternatively
described by three-dimensional supramolecular frameworks be-
longing to two different structure types, forming channels in which
the 2-methylpiperazinediium cations play a templating role. The
packing for complexes 1 and 3 are depicted in Fig. 1a and 2, while
that for complexes 2 and 4 are shown in Fig. 1b and 5.
Fig.
Mn(H
and yellow polyhedra represent [Mn(H
2
Projection of the extended structures of [C
O) ](SO and [C ][Co(H O) ](SO , along the b-axis. Blue
O) ] or [Co(H O) ] and [SO ],
5 14 2
H N ]-
[
2
6
4
)
2
5
H
14
N
2
2
6
4 2
)
2
6
2
6
4
respectively. Gray, blue and red spheres represent carbon, nitrogen and
oxygen, respectively. Hydrogen atoms have been removed for clarity.
˚
.0787(2) to 2.1105(2) A for 3. These values are in agreement with
the values calculated from the bond valence program VALENCE
2
36
˚
˚
(
2.174 A and 2.113 A in compounds 1 and 3, respectively) for a six-
fold oxygen-coordinated transition metal ion. Bond angles fall in
◦
◦
the range 86.48(8)–93.52(8) for O–Mn–O and 86.00(8)–94.00(8)
for O–Co–O, again analogous with other organically templated
3,7,16,37–40
metal sulfates.
The M(O
w
)
6
octahedra are isolated from
˚
one to each other with a shortest distance Mn ◊ ◊ ◊ Mn = 6.639(3) A
for (1) and Co ◊ ◊ ◊ Co = 6.604(2) A for (3), which are shorter
than those found in related Mn and Co analogues.
˚
6,37,41
The 2-
methylpiperazinediium groups are located about crystallographic
inversion centers, with all atoms located in general positions.
2
+
In these two structures, a single disordered [C
5
H
14
N
2
]
cation
and
2
+
was observed with two orientations of both [R–C
5
H
14
N
2
]
2
+
[
S–C
5
H
14
2
N ]
enantiomers. The C and N atoms are distributed
between two positions related by the symmetry center with a
refined site occupancy factor equal to 0.5. For 1, the N–C distances
˚
and the C–N–C angles range from 1.489(9) to 1.518(8) A and
◦
from 113.0(6) to 113.6(6) , while in 3, the N–C distances vary
from 1.479(10) to 1.507(2) A and the C–N–C angles are in the
range 112.2(7)–112.5(6) . These values are in agreement with those
˚
◦
3,5,7,26
found in related amine complexes.
2
+
The [M(H
2
O)
6
]
cations occupy the corners and the center of
the unit cell while the 2-methylpiperazinediium cations are located
on the positions related by translation by 1/2 unit cell along the
b and c axes, relative to the metal ions. Thus, the organic and
inorganic cations alternate along the [010] and [001] directions and
from mixed cationic layers perpendicular to the crystallographic b
and c axes (see Fig. 1a and 2). The asymmetric unit of compounds 1
Fig. 1 Three-dimensional packing in (a) 1 and (b) 2. Selected hydro-
gen-bonding interactions are shown as dashed lines. Blue, green and yellow
polyhedra represent [Mn(H O) ], [Fe(H O) ] and, [SO ], respectively. Gray,
2 6 2 6 4
blue, red and white spheres represent carbon, nitrogen, oxygen, and
hydrogen, respectively.
Compounds 1 (Mn) and 3 (Co) are isostructural. The transition
metal ions are located in special positions on crystallographic
inversion centers and each is coordinated by six water-molecules
oxygen atoms of which three are crystallographically independent.
and 3 each contain only one independent regular SO tetrahedron.
4
The sulfate ions are stacked such that they form anionic layers
parallel to the cationic ones. The crystal structures are described
by an alternation of cationic and anionic layers along [010] and
[001]. The sulfate anions play an important role in the stability
of the crystal structure by linking the organic and inorganic
II
2+
These [M (H
2
O) ] octahedra are slightly distorted. The metal–
6
˚
oxygen distances vary from 2.1602(2) to 2.2013(2) A for 1 and from
This journal is © The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 11613–11620 | 11615

View Article Online
cations via N–H ◊ ◊ ◊ O and O
W
–H
W
◊ ◊ ◊ O hydrogen bonds. Indeed,
and the shape of the amino groups involved in these structures.
Bond valences were calculated for compounds 2 and 4, in which
all the O atoms of the sulfate anion participate as acceptors
in hydrogen bonds (two from H-atoms bonded to N atoms
and two from water H-atoms). These hydrogen bonds are fairly
strong, with donor–acceptor distances range between 2.569(6)
2
+
2+
˚
the values of the Fe and Ni centers are equal to 2.131 A
2
+
2+
˚
and 2.043 A, respectively. The Fe /Ni octahedra are linked
together by O –H ◊ ◊ ◊ O hydrogen bonds through the sulfate
tetrahedra. Fig. 4 shows how each [M (H
W
W
II
2+
˚
˚
and 2.904(3) A for 1 and between 2.566(6) and 2.943(3) A for
3
2
O) ] unit is connected
6
II
II
2-
. Each Mn /Co octahedron is surrounded by six sulfate groups
to two SO
4
anions in a tridentate manner, two sulfate groups
H-bonded in a bidentate manner. Fig. 3 shows the neighbouring
in a bidentate manner and two sulfate groups in a monodentate
fashion. In compound 2, the organic cations become partially
disordered with C–C and N–C distances ranging from 1.294(6)
II
sulphate ions in the environment of the [M (H
2
O) ] octahedron in
6
II
II
II
II
[C
5
H
14
N
2
][M (H
2
O)
6
](SO
4
)
2
with M = Mn or Co .
˚
˚
to 1.516(4) A and from 1.469(5) to 1.498(4) A, respectively. The
◦
C–N–C angles are equal to 111.8(2) . Similarly, the C–C and N–C
˚
bonds in 4 range between 1.298(8) and 1.517(5) A, 1.471(6) and
˚
1
.504(5) A, respectively. The C–N–C angles are the same as those in
2
within experimental error. These values, in agreement with those
37–38
found in the Fe and Ni complexes templated by dabco,
somewhat from others found in the literature. This deviation
seems to be a consequence of the disordered methyl groups in the
deviate
42
2
+
organic cations. The disordered [C
5
H
14
N ] cations reside between
2
the inorganic layers, balancing charge and participating in the
extensive hydrogen-bonding network.
II
Fig. 3 Neighbouring sulfates in the environment of [M (H
2
O)
6
] in 1 and
O) ] and
3
. Blue and yellow polyhedra represent [Mn(H
2
O)
6
] or [Co(H
2
6
[
SO ], respectively.
4
II
The crystal structures of [C
5
H
14
N
2
][M (H
2
O)
6
](SO
4
2
) are similar
to those of the manganese and cobalt templated by piperazine
37,41
itself.
The only differences are observed in the direction of the
charged-layers alternation and in the hydrogen bonds established
between metal octahedra and sulfate tetrahedra.
In the crystal structures of 2 (Fe) and 4 (Ni), transition
metal ions and disordered 2-methylpiperazinediium cations are
again located on crystallographic symmetry centers, while the
sulfate tetrahedra lies in general positions. The supramolecular
character of these phases is preserved, with the molecular ar-
II
Fig. 4 Neighbouring sulfates in the environment of [M (H
2
O)] in 2 and
4. Green and yellow polyhedra represent [Fe(H O) ] or [Ni(H O) ] and
2
6
2
6
II
II
rangement of [C
5
H
14
N
2
][M (H
2
O)
6
](SO
4
)
2
(M = Fe, Ni) built
4
[SO ], respectively.
II
2+
2-
2+
from [M (H
2
O)
6
] , (SO
4
) and disordered [C
5
H
14
2
N ] ions linked
together by an extensive three-dimensional H-bonding network.
The Fe /Ni cations are coordinated by six oxygen atoms
forming a slightly distorted octahedra with the Fe–O distances
As seen in Fig. 1b, the structures of 2 and 4 can also be described
as an alternation between organic and inorganic layers along the
a-axis. On the other hand, the organic and inorganic cations also
alternate along the [101] direction so that they form mixed cationic
layers parallel to b-axis (see Fig. 5).
2
+
2+
˚
in the range 2.1036(16)–2.1403(17) A and the O–Fe–O angles in
◦
the range 86.59(7)–93.41(7) , while the Ni–O distances range from
˚
2
.056(2) to 2.065(2) A and O–Ni–O angles are between 85.98(9)
The structures of compounds 2 and 4 are closely related. Each
asymmetric unit contains only one sulfur atom located on a
general position and tetrahedrally coordinated by four oxygen
atoms. These anions link the organic and inorganic cations by two
◦
and 94.02(9) . These irregular octahedra are separated with a
shortest Fe ◊ ◊ ◊ Fe distance equal to 7.083(2) A and a comparable
Ni ◊ ◊ ◊ Ni distance of 7.034(1) A. These intermetallic distances are
longer than that found in some analogous compounds.
˚
˚
7,37–38
This
types of hydrogen bonds: O
W
–H ◊ ◊ ◊ O and N–H ◊ ◊ ◊ O. Within the
W
difference in the metal–metal distance is likely due to the size
intermolecular bonds, the N ◊ ◊ ◊ O distances vary between 2.767(3)
1
1616 | Dalton Trans., 2011, 40, 11613–11620
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View Article Online
Fig. 5 View of extended structures of 2 and 4 down the crystallographic [101] axis. Green and yellow polyhedra represent [Fe(H
2 6 2 6
O) ] or [Ni(H O) ] and
[
SO ], respectively. Gray, blue and red spheres represent carbon, nitrogen and oxygen, respectively. Hydrogen atoms have been removed for clarity.
4
˚
˚
and 2.866(3) A in 2 and between 2.763(4) and 2.871(4) A in 4. The
four main stages (see Fig. 6c). Five water molecules are lost
◦
˚
O
W
◊ ◊ ◊ O distances range from 2.694(3) to 2.810(2) A and between
.700(3) and 2.805(3) A in 2 and 4, respectively.
over the temperature range 25–168 C (observed weight loss,
◦
˚
2
20.01%, theoretical, 19.50%). The second stage, near 170 C,
coincides with loss of the remaining water molecule to form the
anhydrous compound [C
5
H
14
N
2
]Co(SO
4
) (observed weight loss,
2
4
. Thermal decomposition
4
3
.12%, theoretical, 3.90%). The anhydrous phase is stable to
41 C and then transforms into the b-phase of cobalt sulfate
◦
The thermogravimetric analysis (TG) curves obtained during the
decomposition of compounds 1–4, under flowing air are shown
in Fig. 6. This demonstrates that the decomposition of the
compounds is complex and takes place through several stages.
Compound 1 (Mn). Fig. 6a shows the TG curve obtained
during the decomposition of [C
temperature range 20–800 C. The first weight loss (7.51%),
observed between room temperature and 125 C, is attributed
to the departure of two water molecules (calculated weight loss,
(observed weight loss, 55.82%; theoretical, 56.12%). The last
◦
stage, beginning near 547 , corresponds to the decomposition of
the cobalt sulfate, giving rise to the mixed cobalt oxide Co
15
3
4
O .
Compound 4 (Ni). The data are shown in Fig. 6d. Four suc-
cessive weight losses are observed. Dehydration of the precursor
occurs in two stages. First, a weight loss of 4.32% observed at
5
H
14
N
2
][Mn(H
2
O)
6
](SO
4
) in the
2
◦
◦
◦
180 C corresponds to the departure of a single water molecule
(theoretical weight loss, 3.90%). The second stage of the dehydra-
◦
◦
tion takes place between 190 and 300 C, and correspond to the
departure of the remaining water molecules (observed weight loss,
7
.87%). The second weight loss, observed between 127 and 191 C,
is attributed to departure of the remaining water molecules to
form the anhydrous compound [C ]Mn(SO . The amine
decomposition together with one sulfate group gives rise to the b
2
0.43%; calculated weight loss, 20.31%). Fig. 6e shows the three-
5
H
14
N
2
4 2
)
dimensional representation of the powder diffraction patterns
obtained during the decomposition of [C
under flowing air in the temperature 20–600 C. This plot reveals
that the precursor is stable until 130 C and then transforms into
◦
5
H
14
N
2
][Ni(H
2
O)
6
4 2
](SO )
variety of manganese sulfate at ~457.27 C (observed weight loss,
◦
4
2.52%, theoretical, 43.34%). The last step takes place between 534
◦
◦
and 794 C and corresponds to the decomposition of b-MnSO
into Mn
4
the anhydrous phase, [C
5
H
14
N
2
]Ni(SO
4
)
2
, amorphous (am.) to X-
6
2
3
O .
rays. The anhydrous compound observed on the TG curve, is
Compound 2 (Fe). The TG curve, carried out between 20 and
◦
◦
◦
stable between 225 C and 300 C. The next transformation starts
800 C, is shown in Fig. 6b and exhibits five successive weight
◦
at ~310 C and corresponds to the decomposition of the amine
losses. The first transformation occurs over the temperature range
◦
entity and partial decomposition of the sulfate groups. NiSO is
4
◦
25–160 C and the weight loss of 11.83% is in agreement with
◦
formed at 430 C, and starts to decompose into NiO at 565 C.
Consequently, the given product is a mixture of crystallized NiSO
the departure of three water molecules (calculated weight loss,
4
1
1
1.78%). The second weight loss of 13.97%, observed between
60–209 C, corresponds to the departure of the last three
◦
◦
◦
(PDF N 01-076-0220) and NiO (PDF N 00-044-1159) phases,
◦
as also confirmed by the TDXD plot at 582 C. This result is not
water molecules (calculated weight loss, 13.35%), leading to
the anhydrous phase [C ]Fe(SO . The decomposition of
the anhydrous phase starts near 230 C, includes loss of the
organic moiety, and leads to Fe (SO . This result is evidenced
37
surprising as it has already been observed in the piperazine and
5
H
14
N
2
4 2
)
38
◦
dabco related compounds. The end of the decomposition corre-
◦
sponds to the total decomposition of the NiSO
4
into NiO at 760 C.
2
)
4 3
by the weight loss of 51.34% (calculated weight loss, 51.2%). The
◦
subsequent decomposition of Fe
in agreement with the global formula Fe
corresponds to the decomposition of the iron sulfate into Fe
2
(SO
4
)
3
between 518 and 680 C is
5
. Magnetic properties
2
O
2
(SO ). The final stage
4
37
2
O
3
.
The temperature dependence of the magnetic susceptibility for
compounds 1–4 was determined over the range 1.8–310 K in a
0.1 T field and the results are shown in Fig. 7 and 8. The Mn
Compound
Co(H O) ](SO
3
(Co). Decomposition of [C
5
H
14
N
2
]-
◦
[
2
6
4
)
2
between 20 and 800 C, proceeds through
This journal is © The Royal Society of Chemistry 2011
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View Article Online
Fig. 6 Thermogravimetric analysis for compounds (a) 1, (b) 2, (c) 3 and (d) 4. The TDXD plot for the decomposition of [C
shown in figure (e) 4.
5 14 2 2 6 4 2
H N ][Ni(H O) ](SO ) is
complex, 1, shows typical paramagnetic behavior with a Curie
constant (C) of 4.46(2) and a Curie–Weiss q = 0.07(10), typical
cobalt complex, 3, behaves similarly (Fig. 8b). The c *T product
m
decreases at low temperatures, approaching a value of 1.7 as T
43
48
of an Mn(II) complex with negligible interactions (Fig. 7). The
magnetic susceptibility values of 2 (the Fe(II) complex) follows a
Curie–Weiss law from room temperature to below 50 (Fig. 8a) with
approaches zero, again in agreement with single ion anisotropy.
The data were fit to a single ion anisotropy model which gave a
Curie constant of 3.03(6) and D = -52(4). A fit to the same model
including a Curie–Weiss correction gave identical results for C
and D within error, and a Weiss correction of -0.1(2) supporting
the weakness of the exchange interactions. Finally, fitting of the
data for the Ni(II) complex 4 (Fig. 8c) resulted in a Curie constant
of 1.24(1) and a D value of -3.58(7), in good agreement with
-
1
values for C and q equal to 3.5(1) emu-K mol , typical of Fe(II)
4
3–46
complexes
interactions. Below 50 K, the value of c
significantly, eventually reaching 0.84 at 1.8 K. Fitting of the data
and 0.7(5) K, respectively, suggesting negligible
m
*T begins to decrease
47
to a single ion anisotropy model using MAGMUN gave a value
43,48
of D = -11(1) and g = 2.16(2) with a Curie–Weiss correction of
expected values.
The Curie–Weiss plot gave a q = 0.4(2), again
48
-
0.2, as expected of isolated octahedral Fe(II) complexes. The
in agreement with negligible intermolecular exchange.
1
1618 | Dalton Trans., 2011, 40, 11613–11620
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Fig. 7 Thermal dependence of the c
m
T product (open circles) and 1/c
m
as a function of temperature for compound 1.
6
. Discussion
Compounds 1–4 all crystallize in centrosymmetric space groups.
The use of racemic 2-methylpiperazine in each system tends to
direct crystallization toward centric space groups (although this
is not required). The result that the enantiomeric organic cations
in the structures are crystallographically disordered, rather than
symmetry related, suggests that there was sufficient void volume in
the structure to accommodate the disorder (the volume required
for the disordered cations is somewhat larger than that required
for either enantiomer). The fact that the disorder occurs in spite
of an extensive hydrogen-bonding network is readily explained by
the observation that the methylpiperazinediium cations in both
positions are hydrogen bonded to water molecules, negating any
possible thermodynamic preference for one or the other. The
use of a rigid diamine can deter orientational disorder within
the organic amine, through the combination of low molecular
flexibility andmultiple points ofinteraction betweenthe amine and
inorganic components. Despite this, two disorder mechanisms are
2
+
observed in these complexes for the [C
5
H
14
N
2
] cations. Inversion
symmetry within the cations results in the superimposition of both
2
+
2+
[
R–C
4
H
12
N
2
]
and [S–C
4
H
12
N
2
] (see Fig. 9). Such disorders are
26
founded in the related gallium fluorophosphates.
Counterpoints to the role of template disorder in these com-
pounds can be found in related systems based upon the templated
3
copper sulfate compound. [C
5
H
14
N
2
][Cu(H
2
O)
6
](SO
4
)·H
2
O which
was synthesized using the same amine under slow evaporation
conditions and crystallized in the centrosymmetric space group
2
+
2+
P2
1
/n. Both [R–C
5
H
14
N
2
]
and [S–C
5
H
14
N
2
]
cations were gen-
Fig. 8 Thermal dependence of the c T product (open circles) and 1/c
m
m
2
+
erated via inversion from a single ordered [C
5
H
14
N
2
]
cation in
as a function of temperature for compounds (a) 2, (b) 3, and (c) 4. For 8b
the asymmetric unit.
and 8c, the solid line shows the fit to a single ion anisotropy model.
The structural aspects of 1–4 are reminiscent of another group of
compounds with the formula A M(H O) (XO (A = monovalent
2
7–29
2
2
6
4
)
2
rise to the isostructural Tutton’s salts structure.
Further studies
cation, M = divalent cation, X = hexavalent cation), popularly
referred to as Tutton’s salts. It is surprising since there is no
relation between the decrease of ionic radius of the cation from
to understand the templating role of diamines in the presence of
transition metal sulfates are under way. The thermogravimetric
analysis (TGA) curves for compounds 1–4 show that there
are similar changes in the decompositions of precursors with
somewhat smaller differences, which could be associated with the
structural variations. The first noticeable point is related to the
2
+
2+
Mn to Ni and the structural arrangement observed for these
+
supramolecular sulfates. On the contrary, the use of NH
4
instead
2
-methylpiperazinediium with all transition metal sulfates gives
This journal is © The Royal Society of Chemistry 2011
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View Article Online
1
1
1
2 J. N. Behera, K. V. Gopalkrishnan and C. N. R. Rao, Inorg. Chem.,
2
004, 43, 2636.
3 I. Bull, P. S. Wheatley, P. Lightfoot, R. E. Morris, E. Sastre and P. A.
Wright, Chem. Commun., 2002, 1180.
4 P. S. Halasyamani and A. J. Norquist, Cryst. Growth Des., 2005, 5,
1
913.
2
+
15 W. Rekik, H. Na ¨ı li, T. Mhiri and T. Bataille, Mater. Res. Bull., 2008,
5 14 2
Fig. 9 Disorder mechanism present in the [C H N ] cations for the (a)
4
3, 2709.
in (2, 4) and for (b) in (1, 3). Gray and blue spheres represent carbon and
nitrogen, respectively. Hydrogen atoms have been removed for clarity.
1
1
6 J. N. Bahera and C. N. R. Rao, Chem.–Asian J., 2006, 1, 742.
7 E. A. Kaufman, M. Zeller and A. J. Norquist, Cryst. Growth Des., 2010,
1
0, 4656.
difference of the dehydration temperatures that could be explained
by the nature of the metal as well as the hydrogen bonds involved
in the structures.
1
1
2
8 A. J. Norquist, M. B. Doran and D. O’Hare, Inorg. Chem., 2005, 44,
3837.
9 C. Y. Chen, K. H. Lii and A. J. Jacobson, J. Solid State Chem., 2003,
1
72, 252.
0 X. Y. Wang, H. Y. Wei, Z. M. Wang, Z. D. Chen and S. Gao, Inorg.
Chem., 2005, 44, 572.
Concluding remarks
2
2
1 Y. Li, J. L u¨ and R. Cao, Inorg. Chem. Commun., 2009, 12, 181.
2 E. A. Muller, R. J. Cannon, A. N. Sarjeant, K. M. Ok, P. S. Halasyamani
and A. J. Norquist, Cryst. Growth Des., 2005, 5, 1913.
3 H. S. Casalongue, S. J. Choyke, A. N. Sarjeant, J. Schrier and A. J.
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Four new organically templated complexes with the formula
II
[C
5
H
14
N
2
][M (H
2
O)
6
](SO
4
) have been prepared by slow evap-
2
2
II
oration. The structures consist of isolated M ions (M = Mn,
Fe, Co, Ni) octahedrally coordinated by six water molecules,
diprotonated 2-methylpiperazinediium cations and sulfate anions
linked by hydrogen bonds. Two structure types were distinguished
and described. The centrosymmetric crystal structures of the title
compounds were expected from the racemic character of the amine
used in these syntheses. The thermal behaviour of the precursors
is shown to be dependent not only on the structure type but also
on the transition metal atom involved in the structure. Magnetic
measurements revealed the presence of single ion anisotropy for
compounds 2–4. This work contributes to the research on the
sulfate chemistry based organic–inorganic hybrids complex with
novel topologies and interesting magnetic properties.
24 W. Rekik, H. Na ¨ı li, T. Mhiri and T. Bataille, Acta Crystallogr., Sect. E:
Struct. Rep. Online, 2009, E65, 1404.
2
5 A. J. Norquist, P. M. Thomas, M. B. Doran and D. O’Hare, Chem.
Mater., 2002, 14, 5179.
26 S. J. Choyke, S. M. Blau, A. A. Larner, A. N. Sarjeant, J. Yeon, P. S.
Halasyamani and A. J. Norquist, Inorg. Chem., 2009, 48, 11277.
2
2
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Acknowledgements
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5 G. M. Sheldrick, SHELXL-97, Programs for Crystal Structure Refine-
Grateful thanks are expressed to Dr T. Roisnel (Centre de
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3
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1620 | Dalton Trans., 2011, 40, 11613–11620
This journal is © The Royal Society of Chemistry 2011