Effect of pendant arm position and length on the structure and properties of nickel aromatic dicarboxylate coordination polymers incorporating a kinked organodiimine

Article abstract of DOI:10.1016/j.poly.2008.04.038

Hydrothermal synthesis has afforded three nickel coordination polymers incorporating both aromatic dicarboxylates and the kinked and hydrogen bonding capable organodiimine 4,4′-dipyridylamine (dpa). These were characterized by single-crystal X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. [Ni(1,2-phda)(dpa)(H₂O)]_n (1,2-phda = 1,2-phenylenediacetate, 1) displays (4,4) rhomboid grid-like 2D layers that aggregate into 3D through O-H?O hydrogen bonding. Shortening one of the pendant arms of the dicarboxylate ligand resulted in a shift to (6,3) herringbone style 2D coordination layer motifs in {[Ni(hmph)(dpa)] · 1.33H₂O}_n (hmph = homophthalate, 2), which stack in an AA′B pattern. [Ni(1,3-phda)(dpa)(μ-H₂O)_0.5]_n (1,3-phda = 1,3-phenylenediacetate, 3) manifests a canted primitive cubic type coordination polymer lattice constructed from dinuclear {Ni₂(μ-H₂O)} kernels linked into 3D through tethering 1,3-phda and dpa ligands. Analysis of the variable temperature magnetic susceptibility of 3 indicated the presence of antiferromagnetic superexchange within its dinuclear units (g = 2.290(2), J = -4.21(2) cm^-1).

Full text of DOI:10.1016/j.poly.2008.04.038

Polyhedron 27 (2008) 2291–2300
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Effect of pendant arm position and length on the structure and properties
of nickel aromatic dicarboxylate coordination polymers incorporating
a kinked organodiimine
Maxwell A. Braverman a, Richard J. Staples a, Ronald M. Supkowski b, Robert L. LaDuca a,
*
a Lyman Briggs College and Department of Chemistry, E-30 Holmes Hall, Michigan State University, East Lansing, MI 48825, USA
b Department of Chemistry and Physics, King’s College, Wilkes-Barre, PA 18711, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Hydrothermal synthesis has afforded three nickel coordination polymers incorporating both aromatic
dicarboxylates and the kinked and hydrogen bonding capable organodiimine 4,40-dipyridylamine
(dpa). These were characterized by single-crystal X-ray diffraction, infrared spectroscopy, and thermo-
gravimetric analysis. [Ni(1,2-phda)(dpa)(H2O)]n (1,2-phda = 1,2-phenylenediacetate, 1) displays (4,4)
rhomboid grid-like 2D layers that aggregate into 3D through O–Hꢀ ꢀ ꢀO hydrogen bonding. Shortening
one of the pendant arms of the dicarboxylate ligand resulted in a shift to (6,3) herringbone style 2D coor-
dination layer motifs in {[Ni(hmph)(dpa)] ꢀ 1.33H2O}n (hmph = homophthalate, 2), which stack in an AA0B
Received 20 January 2008
Accepted 21 April 2008
Available online 4 June 2008
Keywords:
Coordination polymer
Nickel
Phenylenediacetate
Homophthalate
Dipyridylamine
Crystal structure
Thermogravimetric analysis
Antiferromagnetism
pattern. [Ni(1,3-phda)(dpa)(
l-H2O)0.5] (1,3-phda = 1,3-phenylenediacetate, 3) manifests a canted prim-
n
itive cubic type coordination polymer lattice constructed from dinuclear {Ni2(
l
-H2O)} kernels linked into
3D through tethering 1,3-phda and dpa ligands. Analysis of the variable temperature magnetic suscepti-
bility of 3 indicated the presence of antiferromagnetic superexchange within its dinuclear units
(g = 2.290(2), J = ꢁ4.21(2) cmꢁ1).
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
More recently, several researchers have augmented the struc-
tural complexity and functional utility of dicarboxylate-containing
Coordination polymer solids generated from divalent metal ions
and dicarboxylate tethering ligands have attracted significant
interest not only for their aesthetically appealing structures, but
also for their promise in diverse technological applications such
as gas storage [1], small molecule shape-selectivity [2], ion-ex-
change [3], catalysis [4], and optical devices [5]. A wide range of
structural patterns occurs in these systems, based on the disposi-
tion of the donor groups within the dicarboxylate moieties, coordi-
nation geometry preferences of the specific metal ions used, and an
array of available binding and bridging modes achievable with
these ligands. While the predominant synthetic effort has focused
on aromatic dicarboxylate tethers such as isophthalate and tere-
inorganic/organic hybrid materials by employing neutral organo-
diimine co-ligands such as the rigid-rod 4,40-bipyridine (4,40-
bpy). These dipodal nitrogen bases can link metal cations through
their distal pyridyl nitrogen donor atoms, supplementing the cova-
lent connectivity provided by the metal/dicarboxylate backbone to
produce structurally interesting solids with promising properties
[8–11]. Several members of this dual-ligand class of coordination
polymers with d10 ions exhibit luminescent properties [9]; one
especially intriguing solid, the interpenetrated 3D material
[Zn(terephthalate)(4,40-bpy)0.5], can serve as a stationary phase
for the chromatographic separation of linear and branched alkanes
[11]. The conformational flexibility of
a,x-dicarboxylate ligands
phthalate, aliphatic
a
,
x
-dicarboxylate ligands have also proven
can also facilitate reversible crystal-to-crystal structural reorgani-
zations upon removal/re-addition of guest species within dual-li-
gand coordination polymers [12].
useful in the construction of new coordination polymer topologies
due to their ability to adopt energetically similar but different con-
formations [6]. However, coordination polymers constructed from
dicarboxylate tethers containing both aromatic rigidity and ali-
phatic pendant arm flexibility, for example phenylenediacetate
isomers, are less common [7].
Recently our group has been investigating the synthesis and
characterization of metal/dicarboxylate coordination polymers
containing the organodiimine 4,40-dipyridylamine (dpa) as a neu-
tral co-ligand. Unlike the more commonly employed 4,40-bpy,
dpa has a kinked disposition of its terminal nitrogen donor atoms
in addition to hydrogen bonding donating capability at its central
amine. We have shown that both covalent and supramolecular
interactions provided by the dpa ligand can synergistically act in
* Corresponding author. Tel.: +1 5174322268.
E-mail address: laduca@msu.edu (R.L. LaDuca).
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.04.038

2292
M.A. Braverman et al. / Polyhedron 27 (2008) 2291–2300
structure-direction during self-assembly, to produce structural
patterns different from those within similar coordination polymers
based on 4,40-bpy [12–15]. For example, [Ni(adipate)(dpa)(H2O)]n
exhibited the first-ever example of 3-fold interpenetration within
the PtS structure type [12], and {[Ni(dpa)2(succinate)0.5]Cl}n mani-
fested an unprecedented 5-connected self-penetrated network
with a ‘‘regular” 610 topology [13]. The combination of zinc salts
with phenylenediacetate isomers and dpa resulted in luminescent
coordination polymers with differing two-dimensional (2D) and
three-dimensional (3D) structural morphologies, depending on
the position of the pendant acetate arms within the dicarboxylate
moieties [14].
ysis was carried out using a Perkin Elmer 2400 Series II CHNS/O
Analyzer. IR spectra were recorded on powdered samples on a Per-
kin Elmer Spectrum One instrument. Powder X-ray diffraction pat-
terns were obtained via h–2h scans performed on a Rigaku Rotaflex
instrument. Variable temperature magnetic susceptibility data (2–
300 K) were collected on a Quantum Design MPMS SQUID magne-
tometer at an applied field of 0.1 T. After each temperature change
the sample was kept at the new temperature for 5 min before mag-
netization measurement to ensure thermal equilibrium. The sus-
ceptibility data were corrected for diamagnetism using Pascal’s
constants.
Herein we report the successful extension of this previous work
into a nickel-based system, with the synthesis and structural char-
acterization of three new coordination polymers with differing
morphologies, constructed from both dpa and aromatic dicarbox-
ylates with one or more flexible pendant arms: [Ni(1,2-phda)
(dpa)(H2O)]n (1; 1,2-phda = 1,2-phenylenediacetate), {[Ni(hmph)
(dpa)] ꢀ 1.33H2O}n (2; hmph = homophthalate), and [Ni(1,3-phda)
2.2. Preparation of [Ni(1,2-phda)(dpa)(H2O)]n (1)
NiCl2 ꢀ 6H2O (0.088 g, 0.37 mmol), dpa (0.127 g, 0.74 mmol) and
1,2-phenylenediacetic acid (0.072 g, 0.37 mmol) were added to
10 mL of distilled H2O in a 23 mL Teflon-lined Parr acid digestion
bomb. The bomb was sealed, heated to 120 °C for 48 h, and then
gradually cooled to ambient temperature. Green blocks of 1
(0.050 g, 31% yield based on Ni) were obtained after filtration,
washing with distilled water and acetone, and drying in air. Crys-
(dpa)(l-H2O)0.5]n (3; 1,3-phda = 1,3-phenylenediacetate). Thermal
properties of these new coordination polymers are also reported
herein, along with a variable temperature magnetic susceptibility
study for 3.
tals of
1 were stable indefinitely in air. Anal. Calc. for
C
20H19N3NiO51: C, 54.59; H, 4.35; N, 9.55. Found: C, 53.99; H,
4.46; N, 9.54%. IR (cmꢁ1): 3285 w br, 1589 s, 1547 w, 1515 s,
1437 w, 1408 m, 1366 s, 1337 m, 1289 w, 1213 m, 1149 w, 1014
m, 939 w, 903 w, 850 w, 831 w, 812 s, 779 w, 716 s, 695 m, 650 m.
2. Experimental
2.1. General considerations
2.3. Preparation of {[Ni(hmph)(dpa)] ꢀ 1.33H2O}n (2)
NiCl2 ꢀ 6H2O (Fisher) and all dicarboxylic acids (Aldrich) were
obtained commercially. The organodiimine 4,40-dipyridylamine
(dpa) was prepared via a published procedure [15]. Water was
NiCl2 ꢀ 2H2O (0.088 g, 0.37 mmol), homophthalic acid (0.067 g,
0.37 mmol), dpa (0.127 g, 0.74 mmol), and 0.25 mL 1.0 M NaOH
solution were placed into 10 g (555 mmol) distilled H2O in a 23
mL Teflon-lined Parr acid digestion bomb (1:1:2: 1500 mol ratio).
The bomb was sealed and heated at 120 °C for 48 h, whereupon
deionized above 3 MX in-house. Thermogravimetric analysis was
performed on a TA Instruments TGA 2050 Thermogravimetric Ana-
lyzer with a heating rate of 10 °C/min up to 900 °C. Elemental Anal-
Table 1
Crystal and structure refinement parameters for 1–3
1
2
3
Empirical formula
Formula weight
Collection T (K)
k (Å)
Color and habit
Crystal size (mm)
Crystal system
Space group
a (Å)
C
40H38N6Ni2O10
C19H19.667N3NiO5.333
434.09
173
C20H18N3NiO4.5
431.08
173
880.18
293
0.71073
green block
0.45 ꢂ 0.40 ꢂ 0.40
monoclinic
P21/n
17.076(3)
10.987(2)
21.522(4)
108.635(2)
3826.1(13)
4
0.71073
0.71073
green block
0.30 ꢂ 0.12 ꢂ 0.10
monoclinic
I2/a
17.416(6)
11.810(3)
21.913(7)
99.654(3)
4443.1(19)
8
green block
0.31 ꢂ 0.28 ꢂ 0.20
monoclinic
P21/c
14.9502(3)
21.5180(4)
18.4272(3)
103.5970(10)
5761.86(18)
12
b (Å)
c (Å)
b (°)
V (Å3)
Z
Dcalc (g cmꢁ3
)
1.528
1.052
1.492
1.048
1.289
0.903
l
(mmꢁ1
)
Minimum/maximum transmission
0.843
0.765
0.897
hkl ranges
ꢁ22 6 h 6 22,
ꢁ14 6 k 6 13,
ꢁ27 6 l 6 26
41023
8714
0.0204
ꢁ19 6 h 6 19,
ꢁ26 6 k 6 28,
ꢁ23 6 l 6 24
141018
13593
0.0687
ꢁ20 6 h 6 20,
ꢁ14 6 k 6 14,
ꢁ26 6 l 6 26
20942
3911
0.0916
Total reflections
Unique reflections
Rint
Parameters/restraints
541/8
0.1013
0.0384
0.1134
796/12
0.1223
0.0488
0.1404
300/7
R1 (all data)a
R1 (I > 2
wR2 (all data)b
wR2 (I > 2
(I))b
r
(I))a
0.0810
0.2720
0.2446
r
0.1070
0.1171
Maximum/minimum residual (eꢁ/Å3)
Goodness-of-fit
0.764/ꢁ0.457
1.298/ꢁ0.705
1.181/ꢁ0.461
1.049
1.022
1.057
P
P
P
P
a R1
=
jjFoj ꢁ jFcjj/ jFoj. b wR2 = { [w(Fo2 ꢁ Fc2)2]/ [wFo2]2}1/2
.

M.A. Braverman et al. / Polyhedron 27 (2008) 2291–2300
2293
Table 2
it was cooled slowly in air to 25 °C. Small green crystals of 2
Selected bond distance (Å) and angle (°) data for 1
(0.146 g, 91% yield based on Ni) were isolated after washing with
distilled water. Anal. Calc. for C19H19.667N3NiO5.333 (2): C, 52.57;
H, 4.57; N, 9.68. Found; C, 52.11; H, 4.43; N, 9.39%. IR (cmꢁ1):
3450 w br, 3012 w, 1637 w, 1598 s, 1548 w, 1522 s, 1491 m,
1444 w, 1421 m, 1401 s, 1359 s, 1292 w, 1208 m, 1090 w, 1057
w, 1022 m, 943 w, 908 w, 872 m, 852 w, 834 w, 812 s, 724 s,
695 m, 677 m, 661 w.
Ni1–O3
Ni1–O9
Ni1–N4#1
Ni1–O5
Ni1–N6
Ni1–O6
Ni2–O8#2
Ni2–O10
Ni2–N3#3
Ni2–N1
Ni2–O1
Ni2–O2
O1–C28
O2–C28
O3–C30
O4–C30
O5–C38
O6–C38
O7–C40
O8–C40
2.0218(17)
2.0471(19)
2.0732(18)
2.1022(17)
2.1053(18)
2.2343(17)
2.008(2)
2.0213(19)
2.1041(19)
2.1310(19)
2.1608(18)
2.1954(17)
1.260(3)
1.263(3)
1.255(3)
1.237(4)
1.262(3)
1.261(3)
1.236(6)
1.229(5)
O3–Ni1–O9
95.70(8)
89.04(7)
93.41(8)
163.10(7)
101.20(8)
89.85(7)
85.44(7)
92.61(8)
172.20(7)
93.84(7)
102.39(7)
161.91(8)
87.00(7)
60.71(6)
88.81(7)
102.59(9)
84.61(8)
92.41(8)
89.83(8)
94.60(8)
171.86(8)
163.20(9)
94.15(7)
93.41(7)
90.20(7)
102.78(8)
154.23(8)
85.54(7)
89.92(7)
60.42(6)
O3–Ni1–N4#1
O9–Ni1–N4#1
O3–Ni1–O5
O9–Ni1–O5
N4#1–Ni1–O5
O3–Ni1–N6
O9–Ni1–N6
N4#1–Ni1–N6
O5–Ni1–N6
2.4. Preparation of [Ni(1,3-phda)(dpa)(l-H2O)0.5]n (3)
O3–Ni1–O6
NiCl2 ꢀ 6H2O (0.088 g, 0.37 mmol), dpa (0.127 g, 0.74 mmol) and
1,2-phenylenediacetic acid (0.072 g, 0.37 mmol) were added to
10 mL of distilled H2O in a 23 mL Teflon-lined Parr acid digestion
bomb. The bomb was sealed, heated to 120 °C for 48 h, and then
gradually cooled to ambient temperature. Green blocks of 3
(0.100 g, 63% yield based on Ni) were obtained after filtration,
washing with distilled water and acetone, and drying in air. Crys-
O9–Ni1–O6
N4#1–Ni1–O6
O5–Ni1–O6
N6–Ni1–O6
O8#2–Ni2–O10
O8#2–Ni2–N3#3
O10–Ni2–N3#3
O8#2–Ni2–N1
O10–Ni2–N1
N3#3–Ni2–N1
O8#2–Ni2–O1
O10–Ni2–O1
N3#3–Ni2–O1
N1–Ni2–O1
tals of
3 were stable indefinitely in air. Anal. Calc. for
C
20H18N3NiO4.5 3: C, 55.73; H, 4.21; N, 9.75. Found: C, 55.48; H,
4.02; N, 9.48%. IR (cmꢁ1): 2910 w br, 1744 w, 1590 s, 1513 m,
1486 m, 1440 w, 1385 s, 1340 m, 1266 w, 1210 m, 1060 w, 1017
s, 905 w, 843 w, 822 s, 712 s, 680 w, 657 m.
O8#2–Ni2–O2
O10–Ni2–O2
N3#3–Ni2–O2
N1–Ni2–O2
3. X-ray crystallography
O1–Ni2–O2
Single crystals of all materials were subjected to single-crystal
X-ray diffraction using a Bruker-AXS SMART 1k (1, 3) or APEX II
CCD (2) instrument. Reflection data were acquired using graph-
Symmetry transformations to generate equivalent atoms: #1 x ꢁ 1/2, ꢁy + 3/2,
z ꢁ 1/2; #2 x + 1, y, z; #3 x + 1/2, ꢁy + 3/2, z + 1/2.
ite-monochromated MoKa radiation (k = 0.71073 Å). The data
were integrated via SAINT [16]. Lorentz and polarization effect and
empirical absorption corrections were applied with SADABS [17].
The structures were solved using direct methods and refined on
F2 using SHELXTL [18]. All non-hydrogen atoms were refined aniso-
tropically. Hydrogen atoms bound to carbon atoms were placed
in calculated positions and refined isotropically with a riding mod-
el. The hydrogen atoms bound to the central nitrogen of the dpa
moieties and all aqua ligands were found via Fourier difference
maps, restrained at fixed positions, and then refined isotropically
with thermal parameters 1.2 times the average Uij values of the
atoms to which they are bound. Hydrogen atoms could not be lo-
cated for the disordered water molecule of crystallization within
the structure of 2. The aromatic rings within the 1,3-phda ligands
in 3 exhibited disorder over three sets of positions, which were
modeled as a 50:25:25 ratio. Relevant crystallographic data for
1–3 are listed in Table 1.
Fig. 1. Coordination environment of 1 with thermal ellipsoids drawn at 50% pro-
bability and partial atom numbering scheme. Hydrogen atoms have been omitted
for clarity. Atoms labelled with an ‘‘A” designation are generated by crystallo-
graphic symmetry.
Fig. 2. Face-on view of the [Ni(1,2-phda)(dpa)(H2O)]n 2D (4,4)-grid layer in 1. In-
tralayer hydrogen bonding is shown as dashed lines.

2294
M.A. Braverman et al. / Polyhedron 27 (2008) 2291–2300
Fig. 3. Stacking of [Ni(1,2-phda)(dpa)(H2O)]n layers in 1 along the b crystal direction in an ABA pattern by interlayer hydrogen bonding (shown as dashed lines).
4.2. Structural description of [Ni(1,2-phda)(dpa)(H2O)]n (1)
4. Results and discussion
As revealed by single-crystal X-ray diffraction, the asymmetric
unit (Fig. 1) of compound 1 contains two crystallographically dis-
tinct nickel atoms (Ni1, Ni2), two 1,2-phda dianions (phda-A,
C21–C30/O1–O4; phda-B, C31–C40/O5–O8), two dpa ligands
(dpa-A, C1–C10/N1–N3; dpa-B, C11–C20/N4–N6), and two ligated
water molecules (O9, O10). Both crystallographically distinct Ni
atoms display a distorted octahedral [NiO4N2] coordination geom-
etry, where the two trans-disposed nitrogen donor atoms belong to
dpa-A and dpa-B ligands, respectively. The equatorial plane of each
coordination octahedron is occupied by two oxygen atoms from a
chelating carboxylate terminus of a 1,2-phda ligand, one oxygen
atom from a monodentate carboxylate group of a crystallographi-
cally distinct 1,2-phda ligand, and an aqua ligand. Bond lengths
and angles about the nickel atoms are consistent with the
chelation-imposed distorted octahedral coordination geometry
(Table 2).
4.1. Synthesis and spectral characterization
The coordination polymers 1–3 were prepared cleanly under
hydrothermal conditions via combination of nickel chloride, dpa,
and the requisite dicarboxylic acid. The infrared spectra of 1–3
were consistent with their structures as determined by X-ray dif-
fraction (vide infra). Sharp, medium intensity bands in the range
of ꢃ1600 cmꢁ1 to ꢃ1200 cmꢁ1 were ascribed to stretching modes
of the pyridyl rings of the dpa moieties [19]. Features correspond-
ing to pyridyl ring puckering mechanisms were evident in the
region between 820 cmꢁ1 and 600 cmꢁ1. Asymmetric and symmet-
ric C–O stretching modes of the carboxylate moieties were evi-
denced by very strong, slightly broadened bands at ꢃ1590 cmꢁ1
and ꢃ1370 cmꢁ1. Broad bands in the region of ꢃ3400 cmꢁ1 to
ꢃ3000 cmꢁ1 in all cases represent N–H stretching modes within
the dpa ligands and O–H stretching modes within ligated or unli-
gated water molecules. The broadness of these latter spectral fea-
tures is caused by significant hydrogen bonding pathways within
1–3. Phase purity was verified with powder XRD by comparison
with powder patterns predicted from the single-crystal structures.
Extension of the structure through the exobidentate chelating/
monodentate 1,2-phda ligands results in a one-dimensional (1D)
[Ni(1,2-phda)(H2O)]n chain motif that propagates along the a crys-
tal direction. Within the [Ni(1,2-phda)(H2O)]n chain Ni1 and Ni2
Table 3
Hydrogen bonding distance (Å) and angle (°) data for 1–3
D–Hꢀ ꢀ ꢀA
d(Hꢀ ꢀ ꢀA)
\DHA
d(Dꢀ ꢀ ꢀA)
Symmetry transformation for A
Complex 1
O9–H9Aꢀ ꢀ ꢀO4
O9–H9Bꢀ ꢀ ꢀO1
O10–H10Aꢀ ꢀ ꢀO5
O10–H10Bꢀ ꢀ ꢀO7
O10–H10Bꢀ ꢀ ꢀO7
N2–H2Nꢀ ꢀ ꢀO6
N5–H5Nꢀ ꢀ ꢀO2
1.833(19)
2.247(18)
1.931(17)
2.24(3)
2.18(2)
2.36(2)
160(3)
165(3)
173(3)
129(3)
137(3)
147(3)
161(3)
2.641(3)
3.043(3)
2.771(2)
2.819(4)
2.824(4)
3.133(3)
3.018(3)
ꢁx + 1, ꢁy + 2, ꢁz
ꢁx + 1, ꢁy + 2, ꢁz
ꢁx + 1, ꢁy + 2, ꢁz
x + 1, y, z
ꢁx + 1, ꢁy + 1, ꢁz
2.195(19)
ꢁx + 3/2, y + 1/2, ꢁz + 1/2
Complex 2
O1W–H1WAꢀ ꢀ ꢀO3
O1W–H1WBꢀ ꢀ ꢀO10
O2W–H2WBꢀ ꢀ ꢀO7
O3W–H3WBꢀ ꢀ ꢀO6
N2–H2Nꢀ ꢀ ꢀO11
N5–H5Nꢀ ꢀ ꢀO4
2.13
1.91
179.2
157.4
161(6)
89(4)
172(3)
172(3)
170(3)
2.983(4)
2.723(4)
2.857(5)
3.115(5)
2.857(3)
2.827(3)
2.849(3)
2.00(3)
3.01(6)
1.987(18)
1.949(18)
1.954(18)
x + 1, y, z
ꢁx + 1, ꢁy + 1, z
x, ꢁy + 3/2, z ꢁ 1/2
N8–H8Nꢀ ꢀ ꢀO5
Complex 3
O1–H1Aꢀ ꢀ ꢀO5
1.79(4)
1.97(3)
151(8)
171(8)
2.573(7)
2.848(8)
ꢁx + 1/2, y, ꢁz + 1
x ꢁ 1/2, ꢁy + 1, z
N2–H2Nꢀ ꢀ ꢀO3

M.A. Braverman et al. / Polyhedron 27 (2008) 2291–2300
2295
Fig. 4. Coordination environments of 2 with thermal ellipsoids shown at 50% probability and partial atom numbering scheme (top, Ni1 and Ni2 and attached ligands; bottom,
Ni3 and attached ligands). Hydrogen atoms and water molecules of crystallization have been omitted for clarity. Atoms labelled with an ‘‘A” designation are generated by
crystallographic symmetry.
centers are linked through phda-A and phda-B ligands in an alter-
nating pattern, with Niꢀ ꢀ ꢀNi distances toggling between 8.112 Å
and 8.976 Å, respectively. The varying Niꢀ ꢀ ꢀNi distances are pro-
moted by the conformational flexibility of the pendant arms of
the 1,2-phda ligands, despite the identical carboxylate binding
modes. The carboxylate termini of phda-A are twisted by ꢃ60°
and ꢃ70° relative to the ligand’s aromatic ring plane, while the re-
lated carboxylate torsions for phda-B are ꢃ40° and ꢃ57°, thus
allowing a greater distance span across the ligated pendant arms
of phda-B. Covalent bonding within the [Ni(1,2-phda)(H2O)]n
chains is supplemented by hydrogen bonding donation by the aqua
ligands to unligated oxygen atoms from the monodentate carbox-
ylate groups of the 1,2-phda ligands.
Adjacent [Ni(1,2-phda)(H2O)]n chain subunits are subsequently
conjoined into a two-dimensional (2D) [Ni(1,2-phda)(dpa)(H2O)]n
(4,4) rhomboid grid coordination polymer layer (Fig. 2) by exobid-
entate dpa ligands; the layer motif runs parallel to the ac crystal
plane. Ni1 centers are linked by dpa-B ligands, fostering a Ni1ꢀ ꢀ ꢀNi1
contact distance of 11.525 Å; the pyridyl rings within dpa-B are
twisted by 28.1° with respect to each other. Similarly, Ni2 atoms
are strutted by dpa-A ligands with a Ni2ꢀ ꢀ ꢀNi2 contact distance of
11.548 Å. The inter-ring torsion within dpa-A is slightly larger, at
32.7°.
Due to the conformation-imposed varying tether lengths, two
different grid sizes are observed within the [Ni(1,2-phda)(dpa)
(H2O)]n layers. The grid spaces bracketed by the shorter phda-A
tethers measure 11.067 ꢂ 16.595 Å, as determined by through-
space Niꢀ ꢀ ꢀNi distances, with Niꢀ ꢀ ꢀNiꢀ ꢀ ꢀNi angles of 66.0° and
114.2°. The more pinched grid spaces, delineated by the longer
phda-B tethers, measure 10.766 ꢂ 17.646 Å, with Niꢀ ꢀ ꢀNiꢀ ꢀ ꢀNi an-
gles of 61.8° and 118.0°. Neighboring [Ni(1,2-phda)(dpa)(H2O)]n
layers stack in an ABA pattern along the b crystal direction, primar-
ily through interlayer hydrogen bonding between the central
amine units of the dpa ligands and oxygen atoms belonging to che-
lating carboxylate moieties within 1,2-phda ligands (Fig. 3). Hydro-
gen bonding parameters for 1 are given in Table 3. The 2D non-
interpenetrated layered structure of 1 is dramatically different
from its related zinc congener, {[Zn(1,2-phda)(dpa)] ꢀ H2O}n, which

2296
M.A. Braverman et al. / Polyhedron 27 (2008) 2291–2300
Table 4
Selected bond distance (Å) and angle (°) data for 2
Ni1–N4
Ni1–O5
2.039(2)
2.048(2)
2.057(2)
2.093(2)
2.113(2)
2.215(2)
2.034(2)
2.039(2)
2.089(2)
2.103(2)
2.104(2)
2.193(2)
2.039(2)
2.044(2)
2.089(2)
2.098(2)
2.115(2)
2.137(2)
O5–Ni1–O6
N6–Ni1–O6
O1–Ni1–O6
O2–Ni1–O6
N3#2–Ni2–N1
N3#2–Ni2–O4
N1–Ni2–O4
N3#2–Ni2–O7
N1–Ni2–O7
O4–Ni2–O7
N3#2–Ni2–O8
N1–Ni2–O8
O4–Ni2–O8
O7–Ni2–O8
N3#2–Ni2–O3
N1–Ni2–O3
O4–Ni2–O3
O7–Ni2–O3
O8–Ni2–O3
N9#1–Ni3–N7
61.58(8)
156.58(9)
105.72(8)
90.18(8)
96.57(10)
100.50(9)
97.10(9)
95.27(9)
95.73(9)
158.34(8)
157.06(10)
91.29(9)
99.85(8)
62.42(8)
89.76(9)
158.20(9)
61.18(8)
104.46(8)
90.85(8)
95.30(10)
97.84(9)
96.51(9)
98.01(9)
99.24(9)
156.46(8)
91.59(9)
161.13(9)
99.93(8)
62.34(8)
160.09(9)
88.12(9)
62.26(8)
100.79(8)
91.36(8)
Ni1–N6#1
Ni1–O1
Ni1–O2
Ni1–O6
Ni2–N3#2
Ni2–N1
Ni2–O4
Ni2–O7
Ni2–O8
Ni2–O3
Ni3–N9#1
Ni3–N7
Ni3–O11#3
Ni3–O10
Ni3–O9
Ni3–O12#3
N4–Ni1–O5
N4–Ni1–N6#1
O5–Ni1–N6#1
N4–Ni1–O1
O5–Ni1–O1
N6#1–Ni1–O1
N4–Ni1–O2
O5–Ni1–O2
N6–Ni1–O2#1
O1–Ni1–O2
N4–Ni1–O6
98.52(9)
99.51(10)
95.30(9)
95.90(9)
160.34(8)
95.42(9)
157.12(9)
100.85(8)
90.72(9)
62.59(8)
88.42(9)
N9#1–Ni3–O11#3
N7–Ni3–O11#3
N9#1–Ni3–O10
N7–Ni3–O10
O11#3–Ni3–O10
N9#1–Ni3–O9
N7–Ni3–O9
O11#3–Ni3–O9
O10–Ni3–O9
N9#1–Ni3–O12#3
N7–Ni3–O12#3
O11#3–Ni3–O12#3
O10–Ni3–O12#3
O9–Ni3–O12#3
Symmetry transformations to generate equivalent atoms: #1 x, ꢁy + 1/2, z + 1/2; #2
x, ꢁy + 3/2, z + 1/2; #3 ꢁx, ꢁy + 1, ꢁz + 1.
possesses a 4-fold interpenetrated SrAl2(sra) lattice [14]. The octa-
hedral coordination preference of the nickel ions in 1, at the ex-
pense of tetrahedral coordination in the zinc analogue, is a
plausible rationalization for this significant structural change.
Fig. 5. Layers A (top) and B (bottom) in 2, viewed individually slightly offset from
the a crystal direction.
4.3. Structural description of {[Ni(hmph)(dpa)] ꢀ 1.33H2O}n (2)
hmph-A and hmph-B linkages as a single connector between Ni1
and Ni2 atoms allows the visualization of the coordination polymer
layer as a (6,3) herringbone pattern.
The large asymmetric unit of compound 2 (Fig. 4a and b) con-
sists of three crystallographically unique nickel atoms (Ni1–Ni3),
hmph dianions (hmph-A, O1–O4; hmph-B, O5–O8; hmph-C, O9–
O12) and dpa ligands (dpa-A, N1–N3; dpa-B, N4–N6; dpa-C, N7–
N9), along with four water molecules of crystallization. All nickel
atoms adopt a [NiO4N2] distorted octahedral geometry, with cis-
disposed nitrogen donors from two different, yet crystallographi-
cally identical, dpa ligands. The remaining four coordination sites
are taken up by oxygen atoms from chelating carboxylate groups
from crystallographically distinct hmph-A and hmph-B ligands for
Ni1 and Ni2, and from a pair of crystallographically identical
hmph-C ligands for Ni3. Bond lengths and angles about Ni1, Ni2,
and Ni3 are similar, and are stated in Table 4.
By means of two bisbridging bischelating hmph ligands (hmph-
A and hmph-B), Ni1 and Ni2 are joined into a binuclear kernel with
a Niꢀ ꢀ ꢀNi distance of 5.590 Å. In turn, Ni1 atoms are linked through
tethering dpa-B ligands (with an inter-ring torsion of 23.5°), pro-
viding a Niꢀ ꢀ ꢀNi distance equal to 11.633 Å. Ni2 atoms conjoin to
other Ni2 atoms through dpa-C (inter-ring torsion = 18.1°) with a
slightly shorter Niꢀ ꢀ ꢀNi through-ligand distance of 11.591 Å. There-
fore each Ni1 is connected to two other Ni1 atoms and one Ni2
atom, while Ni2 is connected to two other Ni2 atoms and one Ni
atom, constructing a 3-connected 2D [Ni(hmph)(dpa)]n coordina-
tion polymer layer motif (Layer A, Fig. 5a). Considering the
A very similar 2D [Ni(hmph)(dpa)]n (6,3) herringbone pattern is
formed by linkage of Ni3 atoms to three other Ni3 atoms, through
two dpa-A ligands (inter-ring torsion = 27.2°) and two hmph-C li-
gands (Layer B, Fig. 5b). The through-dpa Ni3ꢀ ꢀ ꢀNi3 distances with-
in the layer are all identical, at 11.578 Å; while the through-space
Ni3ꢀ ꢀ ꢀNi3 distances bracketed by the crystallographically identical
hmph-C tethers are 5.584 Å. Both layer A and layer B motifs are sit-
uated parallel to the bc crystal plane.
It is likely that the subtle conformational variances between the
dpa and hmph ligands result in the presence of two crystallograph-
ically distinct layers within the structure of 2; the layers should be
considered conformers as opposed to true supramolecular isomers.
The different Niꢀ ꢀ ꢀNi through-space distances across the six-mem-
bered circuits within each layer type may also reflect these vari-
ances. Niꢀ ꢀ ꢀNi through-space distances within layer A measure
15.85, 18.31, and 22.14 Å, allowing accommodation of water mol-
ecule dimers (O1Wꢀ ꢀ ꢀO3W) and isolated water molecules of crys-
tallization (O4W). On the other hand, only isolated water
molecules of crystallization (O2W) are present within layer B,
where the Niꢀ ꢀ ꢀNi through-space distances measure 16.57, 18.25,
and 21.61 Å.
The [Ni(hmph)(dpa)]n (6,3) layer motifs stack along the a crystal
direction in a repeating AA0B pattern (Fig. 6), where layers A and A0

M.A. Braverman et al. / Polyhedron 27 (2008) 2291–2300
2297
Fig. 6. AA0B layer stacking pattern within 2. Water molecules of crystallization can be seen as spheres within the layers.
are related by crystallographic inversion. The pattern repeat dis-
tance of 14.950 Å defines the a lattice parameter. Interlayer supra-
molecular connectivity is fostered by the central amine units of the
dpa ligands, which engage in hydrogen bonding to chelating car-
boxylate oxygen atoms at the longer pendant arm of the hmph li-
gands that project into the incipient voids within the (6,3) layers.
Metrical parameters for the hydrogen bonding patterns in 2 are gi-
ven above in Table 3.
donors belong to three different 1,3-phda ligands, while the
remaining coordination site is occupied by an aqua ligand. Each
1,3-phda ligand serves as an exotridentate linker, connecting two
nickel atoms at one carboxylate terminus in a bisbridging binding
mode with a third nickel atom via the other carboxylate locus in a
monodentate binding mode.
The aqua ligand serves to bridge two Ni atoms in a l2-fashion;
both Ni atoms are in turn also bridged by two carboxylate termini
from two different 1,3-phda ligands to a triply bridged binuclear
unit (Fig. 8). These have a Niꢀ ꢀ ꢀNi distance of 3.603 Å, with the
two bridging carboxylate groups situated 88.13° apart. Individual
4.4. Structural description of [Ni(1,3-phda)(dpa)(l-H2O)0.5]n (3)
The asymmetric unit of compound 3 (Fig. 7) contains a single
divalent nickel atom, one 1,3-phda dianion, one entire dpa mole-
cule, and a ligated water molecule located on a crystallographic
2-fold axis. As is the case for 2, the nickel atom possesses a dis-
torted [NiO4N2] octahedral coordination environment with a cis
orientation of its nitrogen donors, which belong to two different
dpa ligands. Bond lengths and angles about the nickel atom are
standard for octahedral coordination (Table 5). Three of the oxygen
binuclear units are connected into a 1D [Ni2(1,3-phda)2(l-H2O)]n
chain motif, coursing along the a crystal direction, by means of
the monodentate carboxylate termini of the 1,3-phda ligands
(Fig. 9). The Niꢀ ꢀ ꢀNi contact distance through the full extent of
the 1,3-phda dianionic tethers is 8.881 Å.
Adjacent [Ni2(1,3-phda)2(l-H2O)]n chains are conjoined in the b
and c crystal directions by dpa ligands to construct the 3D coordi-
nation polymer network of 3. The dpa ligands contain an inter-ring
Fig. 7. Coordination environment of 3 with thermal ellipsoids shown at 50% probability and partial atom numbering scheme. Atoms labelled with an ‘‘A” designation are
generated by crystallographic symmetry.

2298
M.A. Braverman et al. / Polyhedron 27 (2008) 2291–2300
Table 5
v
mT product values in systems with dimeric {Ni2} kernels can be
Selected bond distance (Å) and angle (°) data for 3
ascribed either to antiferromagnetic superexchange through bridg-
ing ligands, or zero field splitting due to anisotropy.
The magnetic data was fit to Eq. (1), derived for a Heisenberg di-
mer of S = 1 spins [20], and a temperature independent magnetism
term was included (Fig. 11). The variables have their usual magne-
tochemical meanings. Best fit parameters were g = 2.290(2),
Ni1–O2#1
Ni1–O4
Ni1–O3
Ni1–N1
Ni1–O1
2.061(5)
2.067(5)
2.069(5)
2.094(6)
2.094(4)
2.108(6)
O2#1–Ni1–O1
O4–Ni1–O1
O3–Ni1–O1
91.22(19)
90.7(2)
92.29(18)
90.1(2)
89.4(2)
88.8(2)
90.0(2)
87.6(3)
177.6(2)
118.7(3)
177.7(2)
N1–Ni1–O1
O2#1–Ni1–N3#2
O4–Ni1–N3#2
O3–Ni1–N3#2
N1–Ni1–N3#2
O1–Ni1–N3#2
Ni1–O1–Ni1#1
O3–Ni1–N1
Ni1–N3#2
O2#1–Ni1–O4
O2#1–Ni1–O3
O4–Ni1–O3
O2#1–Ni1–N1
O4–Ni1–N1
176.1(2)
J = ꢁ4.21(2) cmꢁ1
,
v
TI = ꢁ 6.2 ꢂ 10ꢁ4 cm3 molꢁ1 with R = 1.48 ꢂ
P
10ꢁ3 = { [(
v
mT)obs ꢁ (
v
mT)calc]2}1/2. The negative value of J corrob-
88.2(2)
88.3(2)
91.6(2)
91.7(2)
orates the presence of antiferromagnetic coupling through the
bridging carboxylate and aqua ligands in 3. However, this value
should be construed as an upper limit due to the likely presence
of cooperative effects due to zero-field splitting (D parameter).
Symmetry transformations to generate equivalent atoms: #1 ꢁx + 1/2, y, ꢁz + 1; #2
ꢁx, y + 1/2, ꢁz + 1/2.
!
ꢀ
ꢁ
Ng2b2
k
ex þ 5e3x
v
mT ¼
þ
v
TIT
ð1Þ
1 þ 3ex þ 5e3x
where x = J/kT.
Given the substantially longer Niꢀ ꢀ ꢀNi distances in 1 and 2, the
magnetic behavior of these materials is expected to be dominated
by zero-field splitting. As such, they were not subjected to variable
temperature magnetic study.
4.6. Thermal analysis of 1–3
Thermogravimetric analysis was performed on samples of com-
pounds 1–3 to investigate their robustness and decomposition
pathways. Compound 1 manifested minimal mass loss until
ꢃ150 °C, whereupon dehydration commenced. This process was
complete by ꢃ240 °C, with the mass loss of 5.1% roughly consistent
with elimination of one equivalent of water per nickel atom (4.1%
calc.). The thermogram then exhibited a plateau until ꢃ300 °C, at
which temperature the organic components of the coordination
polymer were ejected. The final mass remnant of 14.3% at 900 °C
roughly matches with the deposition of Ni metal (13.3% calc.).
Compound 2 underwent dehydration between 25 °C and 330 °C,
with an observed mass loss of 5.2% (5.5% calc. for complete loss
of water molecules of crystallization). At this latter temperature
combustion of the organic ligands occurred. The final mass rem-
nant of 17.6% represents the production of NiO (17.2% predicted).
Compound 3 released its bridging water molecules between
25 °C and ꢃ250 °C (3.0% mass loss, 2.1% predicted). Removal of
the organic components took place between ꢃ275 °C and
ꢃ600 °C, likely depositing NiO (17.2% mass loss observed, 17.7%
calc.). TGA traces for 1–3 are depicted in Figs. S1–S3.
Fig. 8. Triply bridged {Ni2(l-H2O)} binuclear unit in 3, with complete coordination
spheres shown.
torsion of 41.3°, which fosters a Niꢀ ꢀ ꢀNi distance of 11.337 Å. Alter-
natively, the structure of 3 may be visualized as ½Ni2ð -H2OÞ
l
4nþ
ðdpaÞ2ꢄn
cationic layers buttressed via 1,3-phda ligands. Treating
the centroids of the {Ni2(l-H2O)} kernels as the connecting nodes
allows the coordination polymer connectivity of 3 to be considered
as a 6-connected canted primitive cubic (pcu) lattice with 41263
topology (Fig. 10). The 3D covalent connectivity of 3 is supple-
mented by hydrogen bonding patterns mediated by the bridging
water molecules and the central amine groups of the dpa ligands
(see Table 3 for more detail).
4.5. Variable temperature magnetism of 3
To probe possible spin communication across its binuclear sub-
units, a sample of 3 was subjected to variable temperature mag-
netic study. The
v
mT product at 300 K was 1.09 cm3 K molꢁ1 Ni,
slightly higher than expected for an uncoupled Ni2+ S = 1 ion
(1.00 cm3 K molꢁ1), perhaps indicative of some crystal field anisot-
5. Conclusions
ropy. The value of
vmT decreased slowly below 50 K, reaching
1.00 cm3 K molꢁ1; the decrease was significantly more rapid below
this temperature, reaching 0.00796 cm3 K molꢁ1 at 2 K. Decreasing
Variance of pendant arm length and position within aromatic
dicarboxylate ligands has allowed access to a diversity of two-
Fig. 9. [Ni2(1,3-phda)2(
l
-H2O)]n 1D chain motif in 3.

M.A. Braverman et al. / Polyhedron 27 (2008) 2291–2300
2299
Fig. 10. Framework view of the canted primitive cubic 3D structure pattern in 3. The {Ni2(
l-H2O)} binuclear units are represented as spheres, with organic ligands shown as
solid rods. The 1,3-phda ligands connect the binuclear units along the a crystal direction.
Fig. 11.
vmT vs. T plot for 3. The solid line indicates the best fit to Eq. (1) in the text.
and three-dimensional nickel coordination polymer structure
types in a co-ligand system with the kinked and hydrogen bonding
donating organodiimine dpa. The ortho disposition of acetate
groups within 1,2-phda results in a ‘‘standard” rhomboid grid 2D
coordination polymer morphology in 1, albeit with slightly differ-
ent grid apertures imparted by the conformational flexibility of
the dpa ligands and the pendant arms of the dicarboxylate ligands.
Shortening one of the pendant arms by one methylene unit did not
change the overall coordination polymer dimensionality, but did
adjust the layer morphology into a herringbone pattern and also al-
tered the stacking pattern of the layered motifs. Use of the 1,3-
phda ligand, which possesses a meta disposition of acetate pendant
arms and a wider separation between its carboxylate termini, ap-
peared to promote the formation of antiferromagnetically coupled
triply bridged dinuclear units which conjoined into a 3D coordina-
tion polymer with a canted primitive cubic structure type. In all
cases, the supramolecular hydrogen bonding pathways provided
by the dpa ligand serve an important ancillary structure-directing
role. Additional coordination polymers incorporating the dpa li-
gand have been recently prepared in our laboratory; reports con-
cerning their structures and physicochemical properties will
ensue in due course.
Acknowledgements
The authors gratefully acknowledge Michigan State University
for financial support of this work. M.A.B. acknowledges the MSU
Quality Fund Undergraduate Research Program for financial sup-
port. We thank Dr. Rui Huang for elemental analysis and Mr. Hayed
D. Salaame for experimental assistance. SDG.
Appendix A. Supplementary data
CCDC 674722, 674723 and 674724 contain the supplementary
crystallographic data for 1, 2 and 3. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:

2300
M.A. Braverman et al. / Polyhedron 27 (2008) 2291–2300
[7] (a) L. Pan, K.M. Adams, H.E. Hernandez, X. Wang, C. Zheng, Y. Hattari, K.
Kaneko, J. Am. Chem. Soc. 125 (2003) 3062;
deposit@ccdc.cam.ac.uk. TGA traces for 1, 2 and 3 are also available
via the Web edition of this journal. Supplementary data associated
with this article can be found, in the online version, at doi:10.1016/
j.poly.2008.04.038.
(b) Y.-F. Zhou, R.-H. Wang, B.-L. Wu, R. Cao, M.-L. Hong, J. Mol. Struct. 697
(2004) 73;
(c) J. Zhou, C. Sun, J. Linpei, J. Mol. Struct. 832 (2007) 55;
(d) Y. Yang, M.-H. Zheng, S.H. Zhang, H. Liang, Acta Crystallogr., Sect. E 63
(2007) m2392.
References
[8] (a) W.-G. Lu, C.-Y. Su, T.-B. Lu, L. Jiang, J.-M. Chen, J. Am. Chem. Soc. 128 (2006)
34;
(b) S. Horike, R. Matsuda, S. Kitagawa, Stud. Surface Sci. Cat. 156 (2005) 725;
(c) C. Qin, X.-L. Wang, Y.-G. Li, E.-B. Wang, Z.-M. Su, L. Xu, R. Clerac, Dalton
Trans. (2005) 2609;
(d) Y.-Q. Zheng, E.-R. Ying, Polyhedron 24 (2005) 397;
(e) S.K. Ghosh, J. Ribas, P.K. Bharadwaj, Cryst. Growth Des. 5 (2005) 623;
(f) X.-Z. Sun, Y.-F. Sun, B.-H. Ye, X.-M. Chen, Inorg. Chem. Commun. 6 (2003)
1412.
[1] (a) For example: J.L.C. Roswell, O.M. Yaghi, Angew. Chem., Int. Ed. Engl. 44
(2005) 4670;
(b) M. Kondo, T. Okubo, A. Asami, S.-I. Noro, T. Yoshitomi, S. Kitagawa, T. Ishii,
H. Matsuzaka, Angew. Chem., Int. Ed. Engl. 38 (1999) 140;
(c) A.C. Sudik, A.R. Millward, N.W. Ockwig, A.P. Cote, J. Kim, O.M. Yaghi, J. Am.
Chem. Soc. 127 (2005) 7110.
[2] (a) For example: J.S. Seo, D. Whang, H. Lee, S.I. Jun, J. Oh, Y.J. Jeon, K. Kim,
Nature 404 (2000) 982;
(b) A. Cingolani, S. Galli, N. Masciocchi, L. Pandolfo, C. Pettinari, A. Sironi, J. Am.
Chem. Soc. 127 (2005) 6144.
[3] (a) For example: Q.-R. Fang, G.-S. Zhu, M. Xue, J.-Y. Sun, S.-L. Qiu, Dalton Trans.
(2006) 2399;
[9] L. Xu, G.-C. Guo, B. Liu, M.-S. Wang, J.-S. Huang, Inorg. Chem. Commun. 7
(2004) 1145.
[10] H.-P. Jia, W. Li, Z.-F. Ju, J. Zhang, Eur. J. Inorg. Chem. (2006) 4264.
[11] B. Chen, C. Liang, J. Yang, D.S. Contreras, Y.L. Clancy, E.B. Lobkovsky, O.M. Yaghi,
S. Dai, Angew. Chem., Int. Ed. 45 (2006) 1390.
[12] M.R. Montney, S. Mallika Krishnan, R.M. Supkowski, R.L. LaDuca, Inorg. Chem.
46 (2007) 7362.
[13] M.R. Montney, S. Mallika Krishnan, N.M. Patel, R.M. Supkowski, R.L. LaDuca,
Cryst. Growth Des. 7 (2007) 1145.
[14] M.A. Braverman, R.L. LaDuca, Cryst. Growth Des. 7 (2007) 2343.
[15] P.J. Zapf, R.L. LaDuca, R.S. Rarig, K.M. Johnson, J. Zubieta, Inorg. Chem. 37 (1998)
3411.
[16] SAINT, Software for Data Extraction and Reduction, Version 6.02, Bruker AXS,
Inc., Madison, WI, 2002.
[17] SADABS, Software for Empirical Absorption Correction, Version 2.03, Bruker AXS,
Inc., Madison, WI, 2002.
[18] G.M. Sheldrick, SHELXTL, Program for Crystal Structure Refinement, University of
Gottingen, Gottingen, Germany, 1997.
(b) X.-M. Zhang, M.-L. Tong, H.K. Lee, X.-M. Chen, J. Solid State Chem. (2001)
118;
(c) O.M. Yaghi, H. Li, T.L. Groy, Inorg. Chem. 36 (1997) 4292.
[4] (a) For example: S.G. Baca, M.T. Reetz, R. Goddard, I.G. Filippova, Y.A. Simonov,
M. Gdaniec, N. Gerbeleu, Polyhedron 25 (2006) 1215;
(b) H. Han, S. Zhang, H. Hou, Y. Fan, Y. Zhu, Eur. J. Inorg. Chem. 8 (2006) 1594;
(c) W. Mori, S. Takamizawa, C.N. Kato, T. Ohmura, T. Sato, Micropor. Mesopor.
Mater. 73 (2004) 15.
[5] (a) For example: S. Zang, Y. Su, Y. Li, Z. Ni, Q. Meng, Inorg. Chem. 45 (2006)
174;
(b) L. Wang, M. Yang, G. Li, Z. Shi, S. Feng, Inorg. Chem. 45 (2006) 2474;
(c) S. Wang, Y. Hou, E. Wang, Y. Li, L. Xu, J. Peng, S. Liu, C. Hu, New J. Chem. 27
(2003) 1144.
[19] M. Kurmoo, C. Estournes, Y. Oka, H. Kumagai, K. Inoue, Inorg. Chem. 44 (2005)
217.
[20] O. Khan, Molecular Magnetism, VCH Publishers, New York, 1993.
[6] (a) For example: D. Ghoshal, A.K. Ghosh, G. Mostafa, J. Ribas, N.R. Chaudhuri,
Inorg. Chim. Acta 360 (2007) 1771;
(b) C. Livage, C. Egger, M. Nogues, G. Ferey, Compt. Rend. Acad. Sci. Ser. Chem.
4 (2001) 221.