Structure and properties of cobalt ortho-phenylenediacetate coordination polymers with rigid dipyridyl ligands

Article abstract of DOI:10.1016/j.ica.2011.04.029

Divalent cobalt coordination polymers containing both ortho- phenylenediacetate (ophda) and rigid dipyridyl ligands 4,4′-bipyridine (bpy) or 1,2-bis(4-pyridyl)ethylene (dpee) display different topologies depending on carboxylate binding mode, tether length, and inclusion of charged species. [Co(ophda)(H₂O)(dpee)]_n (1) displays a common (4,4) grid layer motif. Use of the shorter bpy tether afforded {[Co ₂(ophda)₂(bpy)₃(H₂O) ₂][Co(bpy)₂(H₂O)₄](NO ₃)₂·2bpy·7H₂O}_n (2) or [Co(ophda)(bpy)]_n (3) depending on cobalt precursor. Compound 2 manifests 5-connected [Co₂(ophda)₂(bpy)₃(H ₂O)₂]_n pillared bilayer slabs with rare 4 ⁸6² SnS topology and entrained [Co(bpy)₂(H ₂O)₄]²⁺ complex cations. The 3-D coordination polymer 3 has an uncommon 4,6-connected binodal (4⁴6 ²)(4⁴6¹⁰8) fsc topology, and shows ferromagnetic coupling (J = +1.5(2) cm^-1) along 1-D spiro-fused [Co(OCO)₂]_n chain submotifs.

Full text of DOI:10.1016/j.ica.2011.04.029

Inorganica Chimica Acta 373 (2011) 201–210
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Inorganica Chimica Acta
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Structure and properties of cobalt ortho-phenylenediacetate coordination polymers
with rigid dipyridyl ligands
⇑
Karyn M. Blake, Arash Banisafar, Robert L. LaDuca
Lyman Briggs College and Department of Chemistry, Michigan State University, East Lansing, MI 48825, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Divalent cobalt coordination polymers containing both ortho-phenylenediacetate (ophda) and rigid
dipyridyl ligands 4,40-bipyridine (bpy) or 1,2-bis(4-pyridyl)ethylene (dpee) display different topologies
depending on carboxylate binding mode, tether length, and inclusion of charged species. [Co(ophda)-
(H2O)(dpee)]n (1) displays a common (4,4) grid layer motif. Use of the shorter bpy tether afforded
{[Co2(ophda)2(bpy)3(H2O)2][Co(bpy)2(H2O)4](NO3)2ꢀ2bpyꢀ7H2O}n (2) or [Co(ophda)(bpy)]n (3) depending
on cobalt precursor. Compound 2 manifests 5-connected [Co2(ophda)2(bpy)3(H2O)2]n pillared bilayer
slabs with rare 4862 SnS topology and entrained [Co(bpy)2(H2O)4]2+ complex cations. The 3-D coordina-
tion polymer 3 has an uncommon 4,6-connected binodal (4462)(446108) fsc topology, and shows
ferromagnetic coupling (J = +1.5(2) cmꢁ1) along 1-D spiro-fused [Co(OCO)2]n chain submotifs.
Ó 2011 Elsevier B.V. All rights reserved.
Received 25 January 2011
Accepted 15 April 2011
Available online 23 April 2011
Keywords:
Cobalt
Coordination polymer
Thermal analysis
Anion dependence
Topology
Ferromagnetism
1. Introduction
bpy tethers [13], while [Co(pht)(dpe)(H2O)]n exhibits a standard
(4,4) grid layer topology with anti-syn bridged dinuclear {Co2(O-
Divalent metal coordination polymers constructed from aro-
matic dicarboxylate ligands show potential industrial applications
[1], including gas storage [2], selective separation [3], ion exchange
[4], catalysis [5], luminescence [6], and non-linear optical second
harmonic generation [7]. Different coordination geometries and a
multitude of possible carboxylate binding modes can promote a
wide range of structural topologies [8]. Cobalt dicarboxylate coordi-
nation polymers often manifest magnetic properties [9] such as
spin canting [10], metamagnetism [11], and single-chain magne-
tism [12]. Structural elaboration and topological variance in these
materials can be enhanced by the incorporation of neutral ligands
such as 4,40-bipyridine (bpy), 1,2-bis(4-pyridyl)ethane (dpe), or
1,2-bis(4-pyridyl)ethylene (dpee) via adjustment of the carboxylate
bridging mode [13–15].
A large number of previously reported divalent cobalt coordina-
tion polymers have been constructed from isomeric benzenedicar-
boxylate ligands such as phthalate (pht) [16], isophthalate (iph)
[17], terephthalate [18], which provide both the charge balance
and structural rigidity necessary for self-assembly. In these phases,
the geometric disposition of the rigid but twistable carboxylate
arms and the nature of the neutral tethering ligand play a predom-
inant role in enforcing the final topology. For example,
[Co(Hpht)2(bpy)]n possesses a 6-connected self-penetrated 3-D net-
work built from a diamondoid [Co(Hpht)2]n subnet with crossing
CO)2} units and exotridentate pht ligands [14]. [Co(iph)(dpee)]n
has a similar dimer-based (4,4) grid underlying topology as
[Co(pht)(dpe)(H2O)]n [15], despite the wider separation of carboxyl-
ate arms within the benzenedicarboxylate component.
In comparison to benzenedicarboxylates, phenylenediacetate
ligands (phda) have seen more infrequent use to date in this chem-
istry [19–24]. The increased conformational flexibility of the pen-
dant acetate arms of the isomeric phda ligands can result in
variable carboxylate binding modes, providing access to various
coordination polymer topologies. Utilizing the long-spanning
bis(4-pyridylmethyl)piperazine (4-bpmp) as a neutral co-ligand,
a series of cobalt phda coordination polymers were recently pre-
pared in our laboratory [24]. {[Co(pphda)(4-bpmp)(H2O)2]ꢀ2H2O}n
(pphda = para-phenylenediacetate) has a standard (4,4) rhomboid
grid topology, while [Co(mphda)(4-bpmp)]n (mphda = meta-phen-
ylenediacetate) possesses dinuclear {Co2(OCO)2} units linked into a
6-connected primitive cubic topology. The ophda (ortho-phenyl-
enediacetate)
congener
{[Co(ophda)(4-bpmp)1.5(H2O)](H24-
bpmp)0.5(ClO4)ꢀ12H2O}n is a very rare example of a 5-connected
layered net, with a unique Archimedean topology consisting of tri-
angular and rectangular circuits.
A search of the Cambridge Structural Database [25] revealed a
great paucity of cobalt phenylenediacetate coordination polymers,
so we attempted to prepare cobalt ophda phases incorporating the
shorter, more rigid dipyridyl linkers bpy and dpee (Scheme 1). Here-
in we report the synthesis, crystal structures, and thermal degrada-
tion properties of three cobalt ophda coordination polymers with
diverse 2-D and 3-D topologies: [Co(ophda)(dpee)(H2O)]n (1),
⇑
Corresponding author. Address: Lyman Briggs College, E-30 Holmes Hall,
Michigan State University, East Lansing, MI 48825, USA. Tel.: +1 517 432 2268.
E-mail addresses: laduca@msu.edu, laduca@chemistry.msu.edu (R.L. LaDuca).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.04.029

202
K.M. Blake et al. / Inorganica Chimica Acta 373 (2011) 201–210
1120 (w), 1065 (m), 1045 (w), 1007 (w), 812 (s), 807 (s), 730 (s),
673 (w).
2.4. Preparation of [Co(ophda)(bpy)]n (3)
Co(CH3COO)2ꢀ4H2O (111 mg, 0.44 mmol), ortho-phenylenedi-
acetic acid (86 mg, 0.44 mmol), and 4,4’-bipyridine (87 mg,
0.56 mmol), were placed into 8 mL distilled H2O in a Teflon-lined
23 mL Parr acid digestion bomb. The bomb was sealed and heated
at 150 °C for 36 h, whereupon it was cooled slowly in air to 25 °C.
Orange crystals of 3 (69 mg, 38% yield based on Co) were isolated
after washing with distilled water and acetone and drying in air.
Anal. Calc. for C20H16CoN2O4: C, 58.98; H, 3.96; N, 6.88. Found: C,
58.54; H, 3.67; N, 6.64%. IR (cmꢁ1): 2950 (w), 1628 (w), 1603
(w), 1566 (s), 1486 (w), 1438 (w), 1413 (w), 1373 (s), 1317 (w),
1219 (w), 1072 (w), 1047 (w), 924 (w), 853 (w), 825 (s), 745 (w),
716 (s), 670 (w).
Scheme 1. Ligands used in this study.
{[Co2(ophda)2(bpy)3(H2O)2][Co(bpy)2(H2O)4](NO3)2ꢀ2bpyꢀ7H2O}n
(2), and [Co(ophda)(bpy)]n (3). The variable temperature magnetic
susceptibility behavior of 3 was also probed, as it contains paramag-
netic d7 ions in proximity, bridged by carboxylate groups.
2. Experimental
2.5. X-ray crystallography
2.1. General considerations
Single crystal X-ray diffraction data for 1–3 were collected with
a Bruker-AXS SMART 1k CCD instrument at 173 K. Reflection data
All chemicals were commercially obtained from Aldrich. Water
were acquired using graphite-monochromated Mo K
a radiation
was deionized above 3 M
X cm in-house. Thermogravimetric anal-
(k = 0.71073 Å). The data was integrated via SAINT [27]. Lorentz
and polarization effect and empirical absorption corrections were
applied with SADABS [28]. The structures were solved using direct
methods and refined on F2 using SHELXTL [29]. All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms bound to
carbon atoms were placed in calculated positions and refined
ysis was performed on a TA Instruments TGA 2050 Thermogravi-
metric Analyzer with a heating rate of 10 °C/min up to 900 °C.
Elemental Analysis was carried out using a Perkin–Elmer 2400 Ser-
ies II CHNS/O Analyzer. IR spectra were recorded on powdered
samples using a Perkin–Elmer Spectrum One instrument. Variable
temperature magnetic susceptibility data (2 K to 300 K) for 3 were
collected on a Quantum Design MPMS SQUID magnetometer at an
applied field of 0.1 T. After each temperature change the sample
was kept at the new temperature for 5 min before magnetization
measurement to ensure thermal equilibrium. The susceptibility
data was corrected for diamagnetism using Pascal’s constants [26].
Table 1
Crystal and structure refinement data for 1–3.
Data
1
2
3
Empirical
Formula
C
22H20CoN2O5
C90H88Co3N16O27
C20H16CoN2O4
Formula weight 451.33
2002.55
triclinic
P1
407.28
monoclinic
P2/c
9.0714(11)
11.4336(14)
9.6453(12)
90
116.633(1)
90
894.25(2)
2
1.513
0.988
0.6472/0.8530
2.2. Preparation of [Co(ophda)(dpee)(H2O)]n (1)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c
12.1087(19)
19.386(3)
8.5589(140
90
ꢀ
Co(NO3)2ꢀ6H2O (28 mg, 0.096 mmol), ortho-phenylenediacetic
acid (19 mg, 0.096 mmol) and 1,2-di(4-pyridyl)ethylene (17 mg,
0.096 mmol) were placed into 10 mL distilled H2O in a 23 mL Tef-
lon-lined Parr acid digestion bomb. The bomb was sealed and
heated at 120 °C for 48 h, whereupon it was cooled slowly to
25 °C. Pink blocks of 1 (33 mg, 76% yield based on Co) were isolated
after washing with distilled water and acetone, and drying in air.
Anal. Calc. for C22H20CoN2O5 1: C, 58.55; H, 4.47; N, 6.21. Found:
C, 58.12; H, 4.09; N, 5.94%. IR (cmꢁ1): 3200 (w, br), 3035 (w),
1607 (w), 1556 (s), 1400 (s), 1283 (w), 1215 (w), 1215 (w), 1153
(w), 1016 (m), 972 (w), 938 (w), 830 (s), 723 (s).
9.7248(14)
11.4547(16)
21.894(3)
94.697(2)
92.004(2)
108.930(2)
2294.4(6)
1
a
(°)
b (°)
98.890(5)
90
1985.0(5)
4
1.510
0.902
c
(°)
V (Å3)
Z
Dcalc (g cmꢁ3
)
1.449
0.624
0.8657/0.9448
l
(mmꢁ1
)
Minimum/
0.7882/0.9412
maximum
transmission
hkl Ranges
ꢁ15 ꢂ h ꢂ 15,
ꢁ25 ꢂ k ꢂ 25,
ꢁ11 ꢂ l ꢂ 10
4 498
ꢁ11 ꢂ h ꢂ 11,
ꢁ13 ꢂ k ꢂ 13,
ꢁ26 ꢂ l ꢂ 26
8 439
ꢁ11 ꢂ h ꢂ 11,
ꢁ13 ꢂ k ꢂ 14,
ꢁ12 ꢂ l ꢂ 12
2 020
2.3. Preparation of
{[Co2(ophda)2(bpy)3(H2O)2][Co(bpy)2(H2O)4](NO3)2ꢀ2bpyꢀ7H2O}n (2)
Unique
reflections
R(int)
0.1000
277/3
0.0134
634/12
0.0220
125/0
Co(NO3)2ꢀ6H2O (28 mg, 0.096 mmol), ortho-phenylenediacetic
acid (19 mg, 0.096 mmol) and 4,40-bipyridine (28 mg, 0.18 mmol)
were placed into 10 mL distilled H2O in a 23 mL Teflon-lined Parr
acid digestion bomb. The bomb was sealed and heated at 120 °C
for 48 h, whereupon it was cooled slowly to 25 °C. Pink blocks of
2 (33 mg, 0.016 mmol, 64% yield based on the limiting reactant
bpy) were isolated after washing with distilled water and acetone,
and drying in air. Anal. Calc. for C90H88Co3N16O27 2: C, 53.98; H,
4.43; N, 11.19. Found: C, 53.23; H, 4.13; N, 10.97%. IR (cmꢁ1):
3259 (w, br), 2821 (w), 1586 (s), 1566 (s), 1532 (s), 1486 (m),
1411 (m), 1378 (s), 1322 (m), 1255 (w), 1219 (m), 1159 (w),
Parameters/
restraints
R1 (all data)
R1 (I > 2
wR2 (all data)
0.0719
0.0490
0.0905
0.0842
0.1034
0.0761
0.1867
0.1734
0.0315
0.0287
0.0811
0.0788
r
(I))
wR2 (I > 2
Max/min
r(I))
0.550/–0.654
0.944/–0.578
0.979/0.992
residual
(eꢁ Å3)
Goodness-of-fit 0.942
(GOF)
1.078
1.144

K.M. Blake et al. / Inorganica Chimica Acta 373 (2011) 201–210
203
Fig. 1. (a) Coordination environment in 1. Symmetry codes refer to those in Table 2. (b) A single [Co(ophda)(dpee)(H2O)]n layer in 1.
isotropically with a riding model. Relevant crystallographic data
between 820 cmꢁ1 and 600 cmꢁ1. Asymmetric and symmetric C–O
for 1–3 is listed in Table 1.
stretching modes of the fully deprotonated phda ligands corre-
spond to the strong, broadened features at 1551 cmꢁ1 and
1400 cmꢁ1 (for 1), 1532 cmꢁ1 and 1378 cmꢁ1 (for 2), and
1566 cmꢁ1 and 1373 cmꢁ1 (for 3). The absence of any bands in
the region of 1700 cmꢁ1 signifies full deprotonation of the acid pre-
cursor. Broadened yet weak bands in the region of ꢃ3200 cmꢁ1 to
ꢃ3400 cmꢁ1 in 1 and 2 represent O–H stretching modes within the
aqua ligands or co-crystallized water molecules. The band at
3035 cmꢁ1 in the spectrum of 1 is indicative of the alkenyl C–H
bonds. The broadness of these higher energy spectral features is
caused by the hydrogen bonding present in all cases (see below).
3. Results and discussion
3.1. Synthesis and spectral characterization
Compounds 1–3 were prepared under hydrothermal conditions
via reaction of a cobalt salt, ortho-phenylenediacetic acid, and the
appropriate dipyridine. The infrared spectra of all compounds cor-
responded with their single crystal structures. Medium intensity
bands in the range of ꢃ1600 cmꢁ1 to ꢃ1200 cmꢁ1 can be ascribed
to stretching modes of the pyridyl rings of the nitrogen base
ligands and the aromatic rings of the ophda ligands [30]. Puckering
modes of the pyridyl and/or phenyl rings are evident in the region
Table 2
Selected bond distance (Å) and angle (°) data for 1.
Co1–O5
2.0465(19)
2.0930(18)
2.144(2)
N1–Co1–N2#2
O5–Co1–O2
O4#1–Co1–O2
N1–Co1–O2
N2#2–Co1–O2
O5–Co1–O1
O4#1–Co1–O1
N1–Co1–O1
N2#2–Co1–O1
O2–Co1–O1
177.49(8)
88.46(8)
147.78(7)
86.20(7)
91.29(8)
147.26(8)
89.20(7)
91.53(7)
87.01(7)
58.99(6)
Co1–O4#1
Co1–N1
Co1–N2#2
2.145(2)
Co1–O2
Co1–O1
2.1884(18)
2.2608(18)
123.53(8)
89.55(8)
90.00(8)
90.58(8)
O5–Co1–O4#1
O5–Co1–N1
O4#1–Co1–N1
O5–Co1–N2#2
O4#1–Co1–N2#2
92.01(8)
Symmetry transformations to generate equivalent atoms: #1 x, y, z + 1; #2 x + 1, y,
z + 1.
Scheme 2. Binding modes of ophda ligands in 1–3.

204
K.M. Blake et al. / Inorganica Chimica Acta 373 (2011) 201–210
Table 3
Hydrogen bonding distance (Å) and angle (°) data for 1 and 2.
D–H. . .A
d(H. . .A)
\DHA
d(D. . .A)
Symmetry transformation for A
1
O5–H5A. . .O2
O5–H5B. . .O3
1.929(16)
1.787(15)
2.743(2)
2.646(3)
172(3)
177(3)
x, ꢁy + 3/2, z + 1/2
x, ꢁy + 3/2, z + 1/2
2
O1W–H1WB. . .N6
O1W–H1WA. . .O12
O2W–H2WA. . .O11
O2W–H2WB. . .O3W
O6–H6A. . .O2W
O6–H6B. . .O8
2.05(3)
2.23
2.13
2.38(11)
1.79(2)
1.86(2)
1.80(3)
1.86(2)
2.932(9)
3.084(17)
2.977(18)
3.121(18)
2.671(8)
2.739(7)
2.633(6)
2.738(6)
172(6)
179.5
179.0
141(14)
177(6)
170(6)
158(6)
175(6)
x, y ꢁ 1, z
ꢁx ꢁ 1, ꢁy, ꢁz + 1
ꢁx, ꢁy, ꢁz + 1
O5–H5B. . .O2
ꢁx, ꢁy + 1, ꢁz + 1
ꢁx ꢁ 1, ꢁy, ꢁz + 1
O5–H5A. . .N8
Fig. 2. (a) [Co(H2O)4(bpy)2]2+ coordination complex cation in 2. (b) Coordination environment at Co2 in 2. Symmetry codes refer to those in Table 4.
The band at 1219 cmꢁ1 in the spectrum of 2 is assigned to N–O
stretching modes of the unligated nitrate ions.
Table 4
Selected bond distance (Å) and angle (°) data for 2.
Co1–O5
Co1–O6
2.033(4)
2.117(5)
2.194(5)
2.049(3)
2.079(3)
2.120(4)
2.148(4)
2.168(4)
2.195(4)
180
92.06(19)
87.94(19)
180
89.58(17)
90.42(17)
93.4(2)
86.6(2)
180
O10#1–Co2–O1
O10#1–Co2–O3
O1–Co2–O3
179.34(15)
89.30(15)
90.86(15)
88.52(15)
91.34(15)
177.22(17)
88.51(15)
90.85(14)
89.68(17)
91.99(16)
90.31(15)
90.32(14)
93.05(17)
85.24(16)
177.01(16)
3.2. Structural description of [Co(ophda)(dpee)(H2O)]n (1)
Co1–N7
Co2–O10#1
Co2–O1
O10#1–Co2–N3
O1–Co2–N3
The asymmetric unit of compound 1 comprises a divalent cobalt
atom, an ophda ligand, a dpee ligand, and one ligated water mole-
Co2–O3
Co2–N3
Co2–N1
O3–Co2–N3
cule. The coordination environment at cobalt is
a distorted
O10#1–Co2–N1
O1–Co2–N1
{CoN2O4} octahedron with trans dpee pyridyl donor ligands in
the axial positions, with the equatorial plane containing one mono-
dentate ophda carboxylate group, one chelating ophda carboxylate
group, and an aqua ligand (Fig. 1a). Relevant bond lengths and
angles within the coordination environment are listed in Table 2.
[Co(ophda)(H2O)]n chains are oriented parallel to the c crystal
direction in 1, formed by junction of cobalt atoms through ophda
Co2–N2#2
O5–Co1–O5#3
O5–Co1–O6
O5#3–Co1–O6
O6–Co1–O6#3
O5–Co1–N7
O5#3–Co1–N7
O6–Co1–N7
O6#3–Co1–N7
N7#3–Co1–N7
O3–Co2–N1
N3–Co2–N1
O10#1–Co2–N2#2
O1–Co2–N2#2
O3–Co2–N2#2
N3–Co2–N2#2
N1–Co2–N2#2
tethering ligands with a l2-
j3-O,O0:O00 chelating/monodentate
binding mode (Scheme 2). The 129.9° torsion angle between the
pendant acetate arms of the ophda ligands provides a CoꢀꢀꢀCo dis-
tance of 8.559 Å. Parallel [Co(ophda)(H2O)]n chains are pillared into
a standard (4,4) rhomboid grid [Co(ophda)(H2O)(dpee)]n motif
Symmetry transformations to generate equivalent atoms: #1 x ꢁ 1, y, z; #2 x, y ꢁ 1,
z; #3 ꢁx, ꢁy + 1, ꢁz + 1.

K.M. Blake et al. / Inorganica Chimica Acta 373 (2011) 201–210
205
Table 5
da)(H2O)(dpee)]n layers stack in an offset ABAB pattern along the
b crystal direction (Fig. S1), with hydrogen bonding between the
aqua ligands and oxygen atoms within chelating ophda carboxyl-
ate groups or unligated oxygen atoms within the monodentate
ophda termini providing the necessary supramolecular interac-
tions (Table 3).
Selected bond distance (Å) and angle (°) data for 3.
Co1–O2
2.0302(12)
2.1585(12)
2.166(2)
2.180(2)
174.60(7)
90.70(5)
88.86(5)
170.59(6)
87.30(3)
85.29(3)
92.70(3)
94.71(3)
180.0
Co1–O1#1
Co1–N1
Co1–N2#2
O2#3–Co1–O2
O2–Co1–O1#1
O2–Co1–O1#4
O1#1–Co1–O1#4
O2–Co1–N1
O1#1–Co1–N1
O2–Co1–N2#2
O1#1–Co1–N2#2
N1–Co1–N2#2
3.3. Structural description of
{[Co2(ophda)2(bpy)3(H2O)2][Co(bpy)2(H2O)4](NO3)2ꢀ2bpyꢀ7H2O}n (2)
The large asymmetric unit of compound 2 contains a cobalt
atom (Co1) on a crystallographic inversion center and another co-
balt atom (Co2) on a general position, two and one-half bpy mole-
cules bound to cobalt, three aqua ligands, one unligated bpy
molecule, and one nitrate counterion, along with three and one-
half water molecules of crystallization. The coordination environ-
ment at Co1 is a distorted {CoN2O4} octahedron with four aqua
ligands in the equatorial plane and trans nitrogen donors from
two pendant, monodentate bpy ligands to construct isolated
[Co(H2O)4(bpy)2]2+ coordination complexes (Fig. 2a). The coordina-
tion environment at Co2 is a distorted {CoN3O3} octahedron, with
Symmetry transformation to generate equivalent
atoms: #1 ꢁ x + 2, ꢁy, ꢁz; #2 x, y ꢁ 1, z; #3 ꢁx + 2, y,
ꢁz ꢁ 1/2; #4 x, ꢁy, z + 1/2.
(Fig. 1b) by rigid dpee tethers, which span a CoꢀꢀꢀCo distance of
13.706 Å. The through-space CoꢀꢀꢀCo distances across the pinched
grid apertures measure 12.109 ꢄ 19.380 Å, with CoꢀꢀꢀCoꢀꢀꢀCo angles
around the grid perimeters subtending 60.8 and 119.2°. [Co(oph-
Fig. 3. Structural submotifs in 2. (a) [Co(ophda)(bpy)(H2O)]n layer (b) neutral [Co2(ophda)2(bpy)3(H2O)2]n slab (c) Network representation of the 5-connected 4862 SnS
topology slab.

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K.M. Blake et al. / Inorganica Chimica Acta 373 (2011) 201–210
Fig. 4. Supramolecular structure of 2. In the online version of this article, the neutral [Co2(ophda)2(bpy)3(H2O)2]n slabs appear green, the [Co(H2O)4(bpy)2]2+ coordination
complex cations appear blue, and the unligated water molecules appear orange. Unligated bpy molecules are positioned within apertures in the slab units, while nitrate
counteranions rest in the inter-slab regions. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
9.725 Å. This longer through-ligand distance, when compared to
that in 1, is promoted by the wider torsion angle of 145.4° between
the ophda acetate arms. These [Co(ophda)(H2O)]n chains are linked
into 2-D [Co(ophda)(bpy)(H2O)]n (4,4) grid layer submotifs (Fig. 3a)
by bpy ligands with an inter-ring torsion angle of 5.4°, which pro-
vide CoꢀꢀꢀCo contacts measuring 11.455 Å. Pairs of [Co(oph-
da)(bpy)(H2O)]n layers are connected by crystallographically
distinct bpy tethers with virtually flat conformation (inter-ring tor-
sion = 0.5°) into neutral [Co2(ophda)2(bpy)3(H2O)2]n coordination
polymer slabs (Fig. 3b). These pillaring bpy molecules span a
CoꢀꢀꢀCo contact distance of 11.379 Å. Treating the cobalt atoms
within the slabs as 5-connected nodes produces a very uncommon
bilayer network with 4862 SnS topology (Fig. 3c). Similar slab mo-
tifs with a 2:5 metal:tether ratio have been seen in the coordina-
tion polymers [Cd(isonicotinate)2(dpe)0.5(H2O)]n [31] and
{[Ag(pyz)2][Ag2(pyz)5](PF6)3ꢀ2CH2Cl2}n (pyz = pyrazine) [32]. The
pillared bilayers in 2 can be considered as slices of a standard prim-
itive cubic topology.
Incipient 1-D cuboid channels coursing through the bilayer slab
motifs of 2 contain unligated bpy molecules, which occupy 24.7%
of the unit cell volume according to PLATON [33]. These engage in
hydrogen bonding acceptance from unligated water molecules in
Fig. 5. Coordination environment of 3. Symmetry codes refer to those in Table 5.
their vicinity (Table 3). The presence of the unligated bpy mole-
cules appears to prevent the 2D + 2D ? 3D interpenetration of bi-
nitrogen donor atoms from three different bpy ligands in a merid-
ional arrangement, trans oxygen atom donors from two ophda li-
gands, and an aqua ligand (Fig. 2b). Bond lengths and angles
within the respective coordination environments are listed in Ta-
ble 4.
layer motifs seen in the previously reported cadmium isonicotinate
phase [31].
Situated between individual [Co2(ophda)2(bpy)3(H2O)2]n coor-
dination polymer slabs are the isolated [Co(H2O)4(bpy)2]2+ coordi-
nation complex cations, unligated nitrate ions required for charge
balance, and numerous water molecules of crystallization (Fig. 4).
The complex cations are anchored to the [Co2(ophda)2 (bpy)3
(H2O)2]n slabs by hydrogen bonding donation from their aqua
Bis(monodentate) ophda ligands with a l2-
j2-O:O0 binding
mode (Scheme 2) link Co2 atoms into [Co(ophda)(H2O)]n 1-D
chains, which have CoꢀꢀꢀCo through-ligand contact distances of

K.M. Blake et al. / Inorganica Chimica Acta 373 (2011) 201–210
207
Fig. 6. [Co(ophda)]n layer in 3.
ligands to unligated ophda carboxylate oxygen atoms. They also
engage in hydrogen bonding to each other to form supramolecular
ribbons, via their aqua ligands and pendant pyridine rings of their
bpy ligands. Information regarding these hydrogen-bonding inter-
actions is listed in Table 3. Co-crystallized charged coordination
complexes are rarely seen in divalent metal carboxylate coordina-
tion polymers, although a divalent copper phase reported by Shi-
ligands are considered connecting nodes, the [Co(ophda)]n grid
patterns can be construed as simple 4-connected regular (4,4) nets.
Parallel [Co(ophda)]n layers are pillared into a non-interpene-
trated [Co(ophda)(bpy)]n 3-D coordination polymer network by
tethering bpy ligands (Fig. 7a), which span a CoꢀꢀꢀCo contact dis-
tance of 11.434 Å. The inter-ring torsion angle within the bpy li-
gands is 62.0°. Thus, the cobalt atoms in 3 can be construed as 6-
connected nodes, joining to four 4-connected ophda ligand nodes
within a single [Co(ophda)]n layer, and to cobalt atoms in two
adjacent [Co(ophda)]n layers via bpy tethers. Topological analysis
with TOPOS software [35] reveals an underlying non-interpene-
trated 4,6-connected binodal fsc net (Fig. 7b) with a Schläfli
mizu provides some precedent [34]. This material consists of
2n+
[Cu(dpe)(H2O)2]n
grids cationic encapsulating octahedrally
coordinated [Cu(4-pyridinesulfonate)4(H2O)2]2– anions. To the best
of our knowledge, cationic complexes of the generic type
[M(H2O)4L2]2+ have never been entrained within a carboxylate
coordination polymer framework.
symbol of (4462)(446108) and
a
long Vertex Symbol of
[4.4.4.4.62.62][4.4.4.4.65.65.65.65.65.65.65.65.ꢅ.ꢅ.ꢅ]. This net can be
considered a derivative of the commonly encountered 6-connected
primitive cubic pcu net, but with two trans pillars removed
at every other node. This fsc net is seldom encountered in coordi-
nation polymer chemistry, with the cluster-based species
3.4. Structural description of [Co(ophda)(bpy)]n (3)
The asymmetric unit of compound 3 consists of a divalent
cobalt atom on a crystallographic 2-fold rotation axis, half of a
[(CuI)7(DABCO)2.5]n [36] and pillared sheet coordination polymer
bpy ligand whose central C–C
r bond and nitrogen atoms are sit-
[Cd( 4-SO4)(bpy)]n [37] being among the few reported examples.
l
uated along the same axis, and half of an ophda ligand bisected by
another crystallographic 2-fold rotation axis. The coordination
environment at cobalt is an axially compressed {CoN2O4} octahe-
dron (Fig. 5) with trans bpy pyridyl nitrogen donors in equatorial
positions. Oxygen donor atoms from four different ophda ligands
complete the coordination sphere, with two occupying trans equa-
torial positions and two taking up the shortened axial positions.
Bond lengths and angles within the coordination environment
are listed in Table 4.
3.5. Magnetic properties of 3
A variable temperature magnetic susceptibility study was car-
ried out on a polycrystalline sample of 3 to probe magnetic super-
exchange between the S = 3/2 Co2+ ions within the 1-D {Co(OCO)2}n
chain motifs. For magnetic behavior in divalent cobalt complexes
with tetragonally distorted octahedral coordination environments,
both magnetic superexchange (J) and single ion effects such as
zero-field splitting (D) must be taken into account. A phenomeno-
logical expression by Rueff (Eq. (1)) can estimate the cooperative
effect of these parameters, and has been successfully applied in
the modeling of the magnetic behavior of S = 3/2 chains [38].
Exotetradentate ophda ligands, with a l4-
j4-O:O0:O00:O000 bind-
ing mode (Scheme 2) and a torsion angle of 127.6° between their
acetate arms, link the divalent cobalt atoms into 2-D [Co(ophda)]n
coordination polymer layers (Fig. 6). Bridging of adjacent cobalt
ions in syn-anti fashion by the pendant arm acetate groups of the
ophda ligands produces 1-D [Co(OCO)2]n chain submotifs contain-
ing spiro-fused {Co(OCO)Co(OCO)} 8-membered rings, whose
CoꢀꢀꢀCo through-space contact distances measure 4.871 Å. The clos-
est inter-chain CoꢀꢀꢀCo contact distances, through the full span of
the ophda ligands, is 8.173 Å. If both the cobalt atoms and ophda
vTm ¼ A expðꢁD=kTÞ þ B expðJ=kTÞ
where A + B = C = ð5Ng2b2=4kÞ.
ð1Þ
The
vmT(T) data for 3 were fit to Eq. (1), with the best fit
values A = 0.81(6) cm3 K molꢁ1 and B = 2.42(3) cm3 K molꢁ1 (giving

208
K.M. Blake et al. / Inorganica Chimica Acta 373 (2011) 201–210
Fig. 7. (a) [Co(ophda)(bpy)]n 3-D network (b) schematic perspective of 4,6-binodal (4462)(446108) fsc topology in 3. In the web version of this article, 6-connected cobalt
nodes and 4-connected ophda nodes are shown in blue and gray, respectively, while pillaring bpy ligands are represented as red sticks. (For interpretation of the references to
colour in this figure legend, the reader is referred to the web version of this article.)
g = 2.23), J = +1.5(2) cmꢁ1 and D = 30(1) cmꢁ1, with R = 1.0 ꢄ 10ꢁ3
their thermal stability. Compound 1 lost 4.5% of its mass between
85 °C and 150 °C, consistent with loss of its aqua ligands (4.0%
calc’d). The mass remained stable until 300 °C, at which tempera-
ture the organic components were pyrolyzed. The final mass rem-
nant of 19.3% at 475 °C is consistent with a deposition of CoO
(16.6% calc’d) along with some carbonaceous material. For com-
pound 2, an initial mass loss of 6.3% between 25 and 75 °C matches
exactly with the loss of all unligated water molecules. A subse-
quent 27.8% mass loss between 75 and 230 °C corresponds to the
ejection of the free bpy molecules, ligated water molecules, and ni-
trate ions (27.1% calc’d combined). The final mass remnant of 13.7%
at 475 °C is likely CoO (11.2% calc’d) with some carbon-containing
material. The mass of compound 3 remained stable until ꢃ230 °C,
when ligand ejection commenced. Degradation appeared to occur
in two steps, one between ꢃ230 and 275 °C and the other between
= {R
[(
vmT)obs ꢁ (
v R[(v
mT)calc]2/ mT)obs]2} (Fig. 8). The positive J indi-
cates the presence of ferromagnetic superexchange along the
{Co(OCO)2}n chains in 3, revealed by the large upsurge in mT value
below 20 K. However this ferromagnetism acts cooperatively with
single ion effects, which serves to reduce the mT(T) product value
v
v
as temperature decreases from 300 K to 20 K. It should be noted that
the fit to Eq. (1) is somewhat mediocre, so the best-fit values should
be taken as only estimates. No field-dependent hysteresis was
observed at 2 K.
3.6. Thermogravimetric analysis
Polycrystalline samples of compounds 1–3 were subjected to
thermogravimetric analysis under flowing N2 in order to probe

K.M. Blake et al. / Inorganica Chimica Acta 373 (2011) 201–210
209
Appendix A. Supplementary material
CCDC 806640, 806639, and 806638 contain the supplementary
crystallographic data for complexes 1, 2, and 3, respectively. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2011.04.029.
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the research. We thank Dr. Rui Huang for performing the elemental
analyses, Ms. Amy Pochodylo for acquiring the magnetic data, and
Mr. Chaun Gandolfo for spectral analysis.

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