One- and two-dimensional copper benzenedicarboxylate coordination polymers incorporating the flexible tethering diimine N,N′-bis(3-pyridylmethyl)piperazine: Synthesis, structure, and thermal properties

Article abstract of DOI:10.1016/j.ica.2008.02.040

A family of three copper benzenedicarboxylate coordination polymers has been constructed using the conformationally flexible and hydrogen-bonding capable tethering ligand N,N′-bis(3-pyridylmethyl)piperazine (3-bpmp). These three coordination polymers have been characterized via single crystal X-ray diffraction, infrared spectroscopy and elemental and thermogravimetric analysis. {[Cu(ph)(Hph)(H3-bpmp)(H₂O)] · 3H₂O} (1, ph = phthalate) manifests a 1-D chain motif held into a pseudo 3-D supramolecular structure through hydrogen bonding. While both {[Cu(ip)(3-bpmp)(H₂O)] · 2H₂O} (2, ip = isophthalate) and [Cu(tp)(3-bpmp)] (3, tp = terephthalate) exhibit 2-D (4,4) rhomboid grid-like layers, they possess different layer stacking patterns and supramolecular interactions due to coordination geometry variances.

Full text of DOI:10.1016/j.ica.2008.02.040

Inorganica Chimica Acta 361 (2008) 2887–2894
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
One- and two-dimensional copper benzenedicarboxylate coordination polymers
incorporating the flexible tethering diimine N,N0-bis(3-pyridylmethyl)piperazine:
Synthesis, structure, and thermal properties
Lindsey L. Johnston a, David P. Martin 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:
A family of three copper benzenedicarboxylate coordination polymers has been constructed using the
conformationally flexible and hydrogen-bonding capable tethering ligand N,N0-bis(3-pyridyl-
methyl)piperazine (3-bpmp). These three coordination polymers have been characterized via single
crystal X-ray diffraction, infrared spectroscopy and elemental and thermogravimetric analysis.
{[Cu(ph)(Hph)(H3-bpmp)(H2O)] ꢀ 3H2O} (1, ph = phthalate) manifests a 1-D chain motif held into a pseudo
3-D supramolecular structure through hydrogen bonding. While both {[Cu(ip)(3-bpmp)(H2O)] ꢀ 2H2O} (2,
ip = isophthalate) and [Cu(tp)(3-bpmp)] (3, tp = terephthalate) exhibit 2-D (4,4) rhomboid grid-like layers,
they possess different layer stacking patterns and supramolecular interactions due to coordination geom-
etry variances.
Received 20 December 2007
Received in revised form 19 February 2008
Accepted 19 February 2008
Available online 29 February 2008
Keywords:
Copper
Benzenedicarboxylate
Imine
Ó 2008 Elsevier B.V. All rights reserved.
Tethering ligand
Coordination polymer
Thermogravimetric analysis
Crystal structure
1. Introduction
nanotubular cavities and a large incipient void volume that
permits exchange of its aquo ligands with small amines. [Cu(tp)-
The synthesis and characterization of coordination polymers re-
mains a very active research area due to the potential utility of
these phases in gas storage [1], shape-selective separations [2],
ion-exchange [3], catalysis [4], and optical applications [5]. Aro-
matic di- and tricarboxylate ligands have proven extremely advan-
tageous for the construction of a wide variety of structurally novel
coordination polymers due to their ability to adopt divergent car-
boxylate binding modes in response to geometric requirements
imposed by different metal ions or ancillary ligands [6–14]. These
multi-anionic ligands provide both structural rigidity and the req-
uisite charge balance necessary to avoid incorporation of small an-
ions, an important requirement if porous materials are to be
obtained.
(H2O)2]n (tp = terephthalate) forms 1-D polymeric chains and
manifests tp-mediated antiferromagnetic coupling and low tem-
perature spin-canting behavior; the magnetic properties of its
2-D pseudopolymorph differ because of adjustment of both the
coordination geometry at copper and the carboxylate binding
mode [16]. The 2-D phase {[Cu2(ip)2(DMF)] ꢀ H2O ꢀ DMF ꢀ (etha-
nol)0.5} (ip = isophthalate) undergoes facile desolvation to produce
a material with high permanent porosity with hysteretic methanol
and benzene absorption behavior [17].
Structural complexity of copper dicarboxylate coordination
polymers has been enhanced through the incorporation of organo-
diimines such as pyridine (py), 2,20-bipyridine (2,20-bpy) or 4,40-
bipyridine (4,40-bpy) [18–22]. Zaworotko and colleagues [18]
discovered the first-ever coordination polymer Kagome lattice,
contained within the structure of {[Cu2(py)2(ip)2]3}. {[Cu(ip)(2,20-
bpy)] ꢀ 2H2O} displays 1-D [Cu(ip)]n helices locked together by
supramolecular hydrogen bonding into a 2-D racemic layer [19],
while the 2-D bilayer structure of [Cu(ip)(4,40-bpy)] is formed from
1-D [Cu2(ip)2]n double chains conjoined through tethering 4,40-bpy
ligands [20]. Williams and co-workers employed terephthalate to
prepare the rare 3-D mixed valence CuI/CuII coordination polymer
Copper di- and tricarboxylates represent an especially fertile
coordination polymer system, exhibiting a wide variety of unprec-
edented structural motifs and intriguing physicochemical proper-
ties. [Cu3(btc)2(H2O)3]n (btc = 1,3,5-benzenetricarboxylate) [15]
possesses a complex 3-D structure with orthogonal square-shaped
* Corresponding author. Tel.: +1 517 432 2268.
E-mail address: laduca@msu.edu (R.L. LaDuca).
0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2008.02.040

2888
L.L. Johnston et al. / Inorganica Chimica Acta 361 (2008) 2887–2894
6 g (333 mmol) distilled H2O (1:1:2 mol ratio) into a borosilicate
glass tube that had been previously flame sealed at one end. The
tube was sealed and heated at 80 °C for 240 h, whereupon it was
cooled slowly in air to 25 °C. Light blue crystals of 2 (125 mg,
40% yield based on Cu) were isolated after washing with distilled
water and acetone and drying in air. Anal. Calc. for C24H30CuN4O7
(2): C, 52.41; H, 5.50; N, 10.19. Found: C, 51.98; H, 5.22; N,
9.89%. IR (cmꢁ1): 3082 w br, 2829 w, 2556w br, 1680 s, 1608 m,
1553 s, 1524 m, 1480 m, 1434 m, 1383 s, 1309 s, 1269 m, 1160
m, 1108 m, 1077 m, 1005 m, 930 m, 857 m, 835 m, 817 m, 799
m, 735 s, 728 s, 682 s, 673 s, 658 s.
Scheme 1.
[Cu4(tp)3(4,40-bpy)2]n [21]; a different solvent mixture promoted
the formation of a 2-D {[Cu(tp)(4,40-bpy)](H2tp)} layered phase
that retained its structural integrity upon elimination of the inter-
lamellar terephthalic acid guest molecules [22].
2.4. Preparation of [Cu(tp)(3-bpmp)] (3)
Cu(NO3)2 ꢀ 6H2O (67 mg, 0.277 mmol), terephthalic acid (46 mg,
0.277 mmol), and 3-bpmp (74 mg, 0.55 mmol) were suspended in
6 g (333 mmol) distilled H2O (1:1:2 mol ratio) into a borosilicate
glass tube that had been previously flame sealed at one end. The
tube was sealed and heated at 80 °C for 216 h, whereupon it was
cooled slowly in air to 25 °C. Purple crystals of 3 (119 mg, 49% yield
based on Cu) were isolated after washing with distilled water and
acetone and drying in air. Anal. Calc. for C24H24CuN4O4 (3): C,
58.11; H, 4.88; N, 11.30. Found: C, 57.88; H, 4.61; N, 10.96%. IR
(cmꢁ1): 3017 w, 2937 w, 2815 w, 1595 s, 1578 s, 1499 m, 1474
m, 1458 m, 1421 m, 1400 s, 1375 m, 1342 s, 1320 s, 1301 s,
1213 m, 1181 m, 1160 m, 1138 m, 1101 m, 1062 m, 1033 w,
1010 m, 965 w, 925 s, 879 w, 840 m, 825 s, 798 s, 741 s, 705 s,
557 m.
Given these prior results, we were encouraged that variance of
the organoimine component in mixed-ligand aromatic dicarboxyl-
ate copper coordination polymers could potentially expand the
scope of this interesting class of materials. We therefore sought
to investigate the under-utilized organodiimine N,N0-bis(3-pyridyl-
methyl)piperazine (3-bpmp, Scheme 1) as a tethering co-ligand for
the construction of coordination polymers, wherein the conforma-
tional flexibility and hydrogen bonding capability of the central
piperazinyl moiety could likely serve an ancillary structure-direct-
ing role during self-assembly. Herein we report the results of our
first synthetic forays with 3-bpmp, with the structural character-
ization and thermogravimetric analysis of the 1-D chain compound
{[Cu(ph)(Hph)(H3-bpmp)(H2O)] ꢀ 3H2O} (1, ph = phthalate) and
the 2-D layered phases {[Cu(ip)(3-bpmp)(H2O)] ꢀ 2H2O} (2) and
[Cu(tp)(3-bpmp)] (3).
3. X-ray crystallography
Single crystals of all materials were subjected to single crystal
X-ray diffraction at 173 K using a Bruker-AXS Apex II CCD instru-
ment. Reflection data was acquired using graphite-monochromat-
ed Mo Ka radiation (k = 0.71073 Å). The data was integrated via
SAINT [24]. Lorentz and polarization effect and absorption correc-
tions were applied with SADABS [25]. The structures were solved
using direct methods and refined on F2 using SHELXTL [26]. All
non-hydrogen atoms were refined anisotropically. Hydrogen
atoms bound to carbon atoms were placed in calculated positions
and refined isotropically with a riding model. Supramolecular con-
tacts (hydrogen bonding, p–p stacking) were probed and calculated
using PLATON [27].
2. Experimental
2.1. General considerations
Copper nitrate hexahydrate and benzenedicarboxylic acids
were obtained from Aldrich. N,N0-Bis(3-pyridylmethyl)piperazine
(3-bpmp) was prepared via a published procedure [23]. Water
was deionized above 3 MX in-house. Thermogravimetric analysis
was performed on a TA Instruments TGA 2050 Thermogravimetric
Analyzer with a heating rate of 10 °C/min up to 900 °C. Elemental
analyses were carried out using a Perkin Elmer 2400 Series II
CHNS/O Analyzer. IR spectra were recorded on a Perkin Elmer
Spectrum One instrument on ground powdered samples.
Compound 1 crystallized only in the habit of thin small plates.
Multiple crystals were poorly diffracting, especially at high 2H an-
gles; nevertheless refinement gave a reasonable set of R1 and wR2
values. Relevant crystallographic data for 1–3 are listed in Table 1.
2.2. Preparation of {[Cu(ph)(Hph)(H3-bpmp)(H2O)] ꢀ 3H2O} (1)
Cu(NO3)2 ꢀ 6H2O (67 mg, 0.277 mmol), phthalic acid (46 mg,
0.277 mmol), and 3-bpmp (74 mg, 0.55 mmol) were suspended in
6 g (333 mmol) distilled H2O (1:1:2 mol ratio) in a borosilicate
glass tube that had been previously flame sealed at one end. The
tube was sealed and heated at 80 °C for 216 h, whereupon it was
cooled slowly in air to 25 °C. Dark blue crystals of 1 (69 mg, 65%
yield based on Cu) were isolated after washing with distilled water
and acetone and drying in air. Anal. Calc. for C32H38CuN4O12 (1): C,
52.35; H, 5.22; N, 7.63. Found: C, 52.33; H, 5.08; N, 7.59%. IR
(cmꢁ1): 3335 w br, 2458 w br, 1702 w br, 1606 m, 1590 m, 1551
m, 1463 w, 1442 m, 1377 s, 1302 m, 1280 m, 1228 m, 1203 m,
1160 m, 1104 m, 1071 m, 1056 m, 966 s, 865 m, 824 m, 790 s,
759 s, 780 s, 680 s, 657 s.
4. Results and discussion
4.1. Synthesis and spectral characterization
Hydrothermal treatment of copper nitrate, 3-bpmp, and the
requisite benzenedicarboxylic acid permitted production of single
crystals of 1–3 as monophasic products. Once formed, the crystal-
line solids remained insoluble in water and common organic sol-
vents. The infrared spectra of all materials were consistent with
their crystal structures. Features corresponding to pyridyl ring flex-
ing and puckering modes were observed in the region between
600 cmꢁ1 and 820 cmꢁ1. Medium intensity bands in the range of
ꢂ1600 cmꢁ1 to ꢂ1200 cmꢁ1 arise from stretching modes of the
aromatic rings of the dicarboxylate ligands and pyridyl rings with-
in the 3-bpmp ligands [28]. Bands between 3050 cmꢁ1 and
3150 cmꢁ1 represent C–H stretching modes. Asymmetric and sym-
metric C–O stretching modes of the benzenedicarboxylate moieties
2.3. Preparation of {[Cu(ip)(3-bpmp)(H2O)] ꢀ 2H2O} (2)
Cu(NO3)2 ꢀ 6H2O (67 mg, 0.277 mmol), isophthalic acid (46 mg,
0.277 mmol), and 3-bpmp (74 mg, 0.55 mmol) were suspended in

L.L. Johnston et al. / Inorganica Chimica Acta 361 (2008) 2887–2894
2889
features in the region of ꢂ3400 cmꢁ1 for 1 and 2 cases represent O–
H stretching modes within bound and/or co-crystallized water
molecules, and the N–H stretching mode for the protonated piper-
azinyl moiety in 1.
Table 1
Crystal and structure refinement data
Data
1
2
3
Empirical formula
Formula weight
C
32H38CuN4O12
C24H30CuN4O7
550.06
C24H24CuN4O4
496.01
734.21
Crystal morphology blue plate
blue block
purple plate
4.2. Structural description of {[Cu(ph)(Hph)(Hbpmp)(H2O)] ꢀ 3H2O}
Crystal size (mm)
0.46 ꢃ 0.10 ꢃ 0.04 0.35 ꢃ 0.20 ꢃ 0.16 0.43 ꢃ 0.33 ꢃ 0.03
(1)
T (K)
173
173
173
k (Å)
0.71073
triclinic
P1
0.71073
triclinic
P1
0.71073
triclinic
P1
According to single-crystal X-ray diffraction, compound 1 pos-
sesses an asymmetric unit consisting of two crystallographically
distinct copper atoms on inversion centers, one bpmp molecule
that is protonated at one of its piperazinyl nitrogen atoms, one
aqua ligand, one phthalate (ph) dianion, and one hydrogen phthal-
ate (Hph) monoanion (Fig. 1). Three water molecules of crystalliza-
tion are also present in the asymmetric unit; one of these is
disordered over two positions in a 70/30 ratio. The coordination
environment about Cu1 is a Jahn–Teller distorted [CuO4N2] octahe-
dron with longer bond lengths to the trans aqua ligands. The nitro-
gen donors, belonging to two different Hbpmp ligands, are also
arranged in a trans fashion. The coordination sphere is rounded
out by oxygen donor atoms from two different doubly deproto-
nated ph dianions. In contrast to Cu1, Cu2 manifests a [CuO2N2]
square planar coordination geometry, where the oxygen and nitro-
gen donors belong to two symmetry related Hph monoanions and
H3-bpmp ligands, respectively. Long ‘‘4 + 2” interactions (2.940 Å)
exist between Cu2 and unligated carboxylate oxygen atoms (O2).
Bond lengths and angles about Cu1 and Cu2 are given in Table 2.
Extension of the structure along the c crystal direction gener-
ates a 1-D sinusoidal [Cu(ph)(Hph)(H3-bpmp)(H2O)]n coordination
polymer chain, wherein [Cu(ph)2(H2O)2]2ꢁ and [Cu(Hph)2] units
Crystal system
Space group
a (Å)
b (Å)
c (Å)
a (°)
b (°)
ꢀ
ꢀ
ꢀ
8.9937(3)
9.7284(4)
20.1745(7)
92.766(2)
95.740(2)
113.040(2)
1598.09(10)
2
9.058(3)
10.253(3)
14.243(4)
106.268(5)
101.111(5)
97.901(5)
1220.1(6)
2
5.9516(1)
9.0485(2)
10.9071(3)
91.163(1)
104.855(2)
108.914(1)
533.65(2)
1
c (°)
V (Å3)
Z
Dcalc. (g cmꢁ3
)
1.522
0.756
0.842
1.497
0.948
0.870
1.543
1.064
0.854
l (mmꢁ1
Minimun/
maximum
transmission
hkl ranges
)
ꢁ9 6 h 6 9,
ꢁ10 6 k 6 10,
ꢁ21 6 l 6 21,
15179
3891
0.1246
ꢁ11 6 h 6 11,
ꢁ13 6 k 6 13,
ꢁ18 6 l 6 18,
13711
5451
0.0283
ꢁ8 6 h 6 8,
ꢁ12 6 k 6 11,
ꢁ14 6 l 6 15
8508
2935
0.0300
Total reflections
Unique reflections
R(int)
Parameters/
restraints
R1 (all data)
R1 (I > 2r(I))
wR2 (all data)
wR2 (I > 2r(I))
Maximum/
468/10
343/9
151/0
0.0834
0.0539
0.1428
0.1274
0.0437
0.0348
0.0893
0.0850
0.0549
0.0404
0.1161
0.0995
0.463/ꢁ0.666
0.498/ꢁ0.387
0.498/ꢁ0.455
minimum
residual (eꢁ/Å3)
Goodness-of-fit
Table 2
1.040
1.044
1.124
Selected bond distance (Å) and angle (°) data for 1
Cu1–O5
Cu1–N1
Cu1–O9
Cu2–O1
Cu2–N4
1.965(3)
1.999(4)
2.427(4)
1.945(4)
1.996(5)
O5#1–Cu1–O9
N1–Cu1–O9
91.38(12)
87.42(14)
92.58(14)
179.999(1)
180.0
88.9(2)
91.1(2)
88.9(2)
180.0
N1–Cu1–O9#1
O9–Cu1–O9#1
O1–Cu2–O1#2
O1–Cu2–N4#2
O1–Cu2–N4
were evꢁid1enced by very strong, slightly broadened bands at
1590 cm and 1377 cmꢁ1 (1), 1553 cmꢁ1 and 1383 cmꢁ1 (2), or
1595 cmꢁ1 and 1342 cmꢁ1 (3). The Dm values of ꢂ230 to
250 cmꢁ1 are consistent with monodentate coordination of the
carboxylate units [29]; the slight redshifting of the asymmetric
carboxylate stretching band for 2 could be ascribed to the presence
of its chelating terminus. A band for the protonated uncoordinated
carboxylate group in 1 was observed at 1716 cmꢁ1. Broad spectral
O5–Cu1–O5#1
O5–Cu1–N1
180.0
87.34(14)
92.66(14)
180.0
O1#2–Cu2–N4
N4#2–Cu2–N4
O5–Cu1–O9
O5#1–Cu1–N1
N1–Cu1–N1#1
88.62(12)
Symmetry equivalent atoms: #1: ꢁx, ꢁy, ꢁz + 1; #2: ꢁx, ꢁy, ꢁz.
Fig. 1. Asymmetric unit of 1 with thermal ellipsoids shown at 50% probability. Most hydrogen atoms have been omitted for clarity, with the exception of that belonging to the
protonated H3-bpmp ligand.

2890
L.L. Johnston et al. / Inorganica Chimica Acta 361 (2008) 2887–2894
Fig. 2. A single [Cu(ph)(Hph)(H3-bpmp)(H2O)]ncoordination polymer chain in 1.
are linked together through the exobidentate H3-bpmp+ tethers
with a Cuꢀ ꢀ ꢀCu distance of 10.087 Å (Fig. 2). The H3-bpmp+ ligand
adopts a ‘‘U”-shaped conformation within the chain motif, with an
angle (defined as j) between its two nitrogen termini of 110.3° as
measured from the centroid of its piperazine ring. Neighboring
chains interact along the a crystal direction through hydrogen
bonding between the aqua ligands in one chain and unligated car-
boxylate oxygen atoms (O7) belonging to the fully deprotonated
ph ligand bound to Cu1, forming a pseudo 2-D layer substructure
coincident with the ac crystal plane. In turn, these aggregate into
the full pseudo 3-D crystal structure of 1 through a hydrogen bond-
ing pattern from the protonated piperazinyl nitrogen atoms within
the H3-bpmp ligands in one chain to unligated water molecule di-
mers situated between chains, and on to the unligated oxygen
atoms (O2) of the ligated carboxylate groups of the ph ligands in
neighboring chains in different pseudo 2-D layers (Fig. 3). Geomet-
ric details for the hydrogen bonding interactions in 1 are given in
Table 3.
and two water molecules of crystallization (Fig. 4). The coordina-
tion environment about copper is a distorted [CuO4N2] octahedron
with two nitrogen donors from two different 3-bpmp ligands ar-
ranged in a trans manner. Two cis oxygen donors are part of a che-
lating carboxylate endgroup of an ip ligand; the remaining
coordination sites are occupied by the aqua ligand and an ip oxy-
gen donor atom from a monodentate carboxylate group. The bond
lengths and angles about the Cu atom in 2 are consistent with the
Jahn–Teller active d9 electronic configuration (Table 4); the long
trans bond lengths exist between Cu and the aquo ligand (O5)
and one of the oxygen donors of the chelating ip carboxylate group
(O1).
Copper atoms are conjoined by exobidentate chelating/mono-
dentate ip ligands to form [Cu(ip)]n chains that run along the b
crystal direction; the through-ligand Cu–Cu contact distance of
10.253(3) Å marks the b lattice parameter. These in turn establish
a 2-D [Cu(ip)(3-bpmp)(H2O)]n (4,4) rhomboid grid layered coordi-
nation polymer morphology by linkage through exobidentate
bpmp tethers (Fig. 5). Unlike in 1, the methylpyridyl arms of the
3-bpmp ligands are almost completely splayed open, with a j angle
of 174.7°. As a result, the Cuꢀ ꢀ ꢀCu distance through the 3-bpmp
tethers is significantly longer than in 1, at 12.714 Å. The Cuꢀ ꢀ ꢀCu
through-space distances across the pinched rhomboid grid voids
4.3. Structural Description of {[Cu(ip)(3-bpmp)(H2O)] ꢀ 2H2O} (2)
The asymmetric unit of compound 2 consists of one divalent
copper atom, one ip dianion, one 3-bpmp moiety, one aqua ligand,
Fig. 3. View down c of the pseudo 3-D structure of 1.

L.L. Johnston et al. / Inorganica Chimica Acta 361 (2008) 2887–2894
2891
Table 3
Hydrogen bonding distance (Å) and angle (°) data for 1 and 2
Table 4
Selected bond distance (Å) and angle (°) data for 2
D–H. . .
A
d(H. . .A)
\DHA
d(D. . .A)
Symmetry transformation
for A
Cu1–O3#1
Cu1–N4#2
Cu1–N1
Cu1–O2
Cu1–O5
Cu1–O1
1.9794(15)
2.0019(18)
2.0059(18)
2.0544(14)
2.3436(18)
2.4601(16)
N4#2–Cu1–O2
N1–Cu1–O2
O3#1–Cu1–O5
N4#2–Cu1–O5
N1–Cu1–O5
O2–Cu1–O5
O3#1–Cu1–O1
N4#2–Cu1–O1
N1–Cu1–O1
O2–Cu1–O1
O5–Cu1–O1
90.15(6)
86.23(6)
93.66(6)
93.59(7)
87.88(7)
105.97(6)
102.60(6)
89.11(7)
88.54(7)
57.58(5)
163.38(5)
Compound 1
N2–H2N. . .O1W
O9–H9A. . .O6
1.80(2)
1.94(3)
2.05(2)
1.95(3)
1.83(2)
2.10(3)
1.93(3)
168(4) 2.719(5)
156(4) 2.777(5)
O9–H9B. . .O7
177(5) 2.918(5) x ꢁ 1, y, z
152(4) 2.761(5) x, y ꢁ 1, z
172(4) 2.719(6) ꢁx, ꢁy ꢁ 1, ꢁz
155(6) 2.918(8) x, y ꢁ 1, z
163(7) 2.794(9)
O1W–H1A. . .O6
O1W–H1B. . .O2W
O2W–H2A. . .O3
O2W–H2B. . .O2
O3#1–Cu1–N4#2
O3#1–Cu1–N1
N4#2–Cu1–N1
O3#1–Cu1–O2
92.69(6)
90.54(6)
176.35(6)
159.95(6)
Compound 2
O1W–H1WA. . .N2
O1W–
Symmetry equivalent atoms: #1: x, y ꢁ 1, z; #2: x ꢁ 1, y ꢁ 1, z.
2.036(17) 173(3) 2.867(2) ꢁx + 2, ꢁ y + 2, ꢁz + 2
2.033(17) 174(3) 2.874(3) ꢁx + 1, ꢁ y + 2, ꢁz + 2
H1WB. . .O2W
O2W–
2.108(15) 165(4) 3.034(4) ꢁx + 1, ꢁ y + 2, ꢁz + 2
H2WA. . .O1W
O2W–H2WB. . .O2
O5–H5A. . .O1W
O5–H5B. . .O4
ion, and one half of a 3-bpmp moiety. The coordination environ-
ment at copper is a [CuO2N2] square planar arrangement with
trans oxygen and nitrogen donors from two different tp and 3-
bpmp ligands, respectively (Fig. 7). Bond lengths and angles (Table
5) are standard for divalent square planar coordinated copper ions.
Long-range ‘‘4 + 2” interactions, common for the Jahn–Teller active
Cu2+ ion, are present between the unligated tp oxygen atoms and
copper (Cuꢀ ꢀ ꢀO distance = 2.749(2) Å).
2.05(2)
161(5) 2.864(3) ꢁx + 2, ꢁ y + 2, ꢁz + 2
1.947(17) 171(3) 2.785(3)
2.036(18) 171(3) 2.776(2) x, y ꢁ 1, z
measure 9.058 Å and 21.248 Å, with Cuꢀ ꢀ ꢀCuꢀ ꢀ ꢀCu angles of 44.9°
and 135.1°.
Two individual [Cu(ip)(3-bpmp)(H2O)]n layers, related by crys-
tallographic inversion, aggregate into a double layer motif through
hydrogen bonding mediated by water molecule dimers situated in
the interlamellar region (Fig. 6). Water molecules of crystallization
(O1W) bridge unligated carboxylate oxygen atoms (O4) and piper-
azinyl nitrogen atoms (N2) in one layer with the aquo ligands (O5)
in the other layer. The other water molecule of crystallization,
O2W, engages in hydrogen bonding with O1W and the ligated car-
boxylate oxygen atom O2. The interlamellar regions filled by the
water molecules of crystallization occupy 7.3% of the unit cell vol-
ume, according to a calculation performed with PLATON. Hydrogen
bonding information is given in Table 3. Double layer units stack
along the c crystal direction in an ABAB pattern, primarily through
p–p interactions between the phenyl rings of the ip ligands (cen-
troid-to-centroid distance = 3.798(2) Å).
Adjacent copper atoms are connected along the c crystal
direction by bridging bismonodentate tp dianions to form
[Cu(tp)]n chains with a Cuꢀ ꢀ ꢀCu distance of 10.907 Å. In turn
these chains are conjoined into a 2-D [Cu(tp)(3-bpmp)]n (4,4)
rhomboid grid coordination polymer layer via tethering 3-bpmp
ligands (Fig. 8), with a Cuꢀ ꢀ ꢀCu distance of 12.809 Å through
the organodiimine. The j angle across the 3-bpmp ligand is
180°, restricted by the crystallographic symmetry, enforcing the
longest Cuꢀ ꢀ ꢀCu distance in the series 1–3. The Cuꢀ ꢀ ꢀCu
through-space distances across the rhomboid grids measure
9.077 and 21.992 Å, with Cuꢀ ꢀ ꢀCuꢀ ꢀ ꢀCu angles of 44.1° and
135.9°. Due to the flexibility of the 3-bpmp ligands, these param-
eters are not dissimilar from those seen in 2, despite the lack of
ligated or unligated water molecules in 3. Neighboring [Cu(tp)(3-
bpmp)]n layers stack in a simple AAA pattern, with the interlayer
Cuꢀ ꢀ ꢀCu distance of 5.952 Å defining the a lattice parameter
(Fig. S1). As no classical hydrogen bonding or p–p stacking is
present within the structure of 3, the layers aggregate solely
via weaker crystal packing forces.
4.4. Structural description of [Cu(tp)(3-bpmp)] (3)
The asymmetric unit of compound 3 contains a copper atom on
a crystallographic inversion center, one half of a terephthalate an-
Fig. 4. Coordination environment of 2 with thermal ellipsoids shown at 50% probability. Hydrogen atoms and unligated water molecules have been omitted.

2892
L.L. Johnston et al. / Inorganica Chimica Acta 361 (2008) 2887–2894
Fig. 5. A single [Cu(ip)(3-bpmp)(H2O)]n layer in 2, viewed down the c crystal axis.
Fig. 6. Stacking of [Cu(ip)(3-bpmp)(H2O)]n layers in 2 in an ABAB pattern, viewed down the c crystal axis. Some of the specific hydrogen bonding interactions are shown as
dashed lines.
4.5. Thermogravimetric analysis
9.6% mass loss consistent with the expulsion of 4 equiv. of water
(9.9% calc.). At ꢂ160 °C removal of the organic ligands com-
menced, with a series of mass losses complete by ꢂ550 °C. The fi-
nal 10.5% mass remnant at ꢂ850 °C is consistent with CuO (10.8%
calc.).
Thermogravimetric analysis was performed in order to probe
the thermal stability of coordination polymers 1–3. Compound 1
underwent dehydration between ꢂ30 °C and ꢂ110 °C, with a

L.L. Johnston et al. / Inorganica Chimica Acta 361 (2008) 2887–2894
2893
Fig. 7. Coordination environment of 3 with thermal ellipsoids shown at 50% probability. Hydrogen atoms have been omitted.
Table 5
5. Conclusion
Selected bond distance (Å) and angle (°) data for 3
Three divalent copper coordination polymers incorporating
benzenedicarboxylate isomers and the rarely used tethering
organodiimine bis(3-pyridylmethyl)piperazine have been pre-
pared through a low temperature solution phase route. The donor
disposition and binding mode within the specific benzenedicar-
boxylate isomer used, along with the conformational flexibility
of the organodiimine, allowed the self-assembly of one- and
two-dimensional coordination polymer matrices. Although the
flexibility of the tethering bpmp ligand permitted the construction
of two-dimensional layer motifs in both the isophthalate and tere-
phthalate cases 2 and 3, a different layer stacking pattern is ob-
served due to differences in coordination geometry and the
supramolecular environment. As expected, 2 and 3 exhibit greater
thermal robustness than 1 due to their higher dimensionality. The
three different structures uncovered in this study hint at a rich
coordination polymer chemistry accessible with the bis(3-pyridyl-
methyl)piperazine ligand. Studies in this direction are underway
in our laboratory.
Cu1–O1 (ꢃ2)
Cu1–N1 (ꢃ2)
O1–Cu1–O1#1
O1–Cu1–N1
1.9205(14)
2.0443(18)
180.00(9)
89.52(7)
90.48(7)
179.998(1)
O1#1–Cu1–N1
N1– Cu1–N1#1
Symmetry equivalent atoms: #1: ꢁx + 2, ꢁy ꢁ 1, ꢁz ꢁ 1.
Compound 2 underwent stepwise dehydration between ꢂ40 °C
and ꢂ210 °C, totalling 9.7% of the original mass (9.8% calc. for
3 equiv. of water). Decomposition of the coordination polymer lay-
ers likely occurred above ꢂ210 °C, as revealed by a significant and
rapid mass loss. The mass remnant of 15.0% at ꢂ900 °C corre-
sponds roughly with a deposition of CuO (14.4% calc.). Compound
3 remained intact to ꢂ250 °C whereupon its organic components
were rapidly ejected. The final mass remnant of 15.4% at ꢂ850 °C
corresponds to CuO (16.0% calc.). TGA traces for 1–3 are given in
Figs. S2–S4, respectively.
Fig. 8. A single [Cu(tp)(3-bpmp)]n layer in 3, viewed down the a crystal axis.

2894
L.L. Johnston et al. / Inorganica Chimica Acta 361 (2008) 2887–2894
(c) S. Wang, Y. Hou, E. Wang, Y. Li, L. Xu, J. Peng, S. Liu, C. Hu, New J. Chem. 27
Acknowledgements
(2003) 1144;
(d) Y.F. Zhou, D.Q. Yuan, B.L. Wu, R.H. Wang, M.C. Hong, New J. Chem. 28
(2004) 1590;
(e) G.W. Zhou, Y.Z. Lan, F.K. Zheng, X. Zhang, M.H. Lin, G.C. Guo, J.S. Huang,
Chem. Phys. Lett. 426 (2006) 341;
(f) L. Han, M. Hong, R. Wang, J. Luo, Z. Lin, D. Yuan, Chem. Commun. (2003)
2580.
The authors gratefully acknowledge Michigan State University
for financial support of this work. We thank Dr. Rui Huang (MSU)
for elemental analysis and Mr. Paul Szymanski for acquisition of
the infrared spectra, SDG.
[6] W.G. Lu, C.Y. Su, T.B. Lu, L. Jiang, J.M. Chen, J. Am. Chem. Soc. 128 (2006)
34.
[7] S. Horike, R. Matsuda, S. Kitagawa, Stud. Surf. Sci. Catal. 156 (2005) 725.
[8] C. Qin, X.L. Wang, Y.G. Li, E.B. Wang, Z.M. Su, L. Xu, R. Clerac, Dalton Trans.
(2005) 2609.
[9] Y.Q. Zheng, E.R. Ying, Polyhedron 24 (2005) 397.
[10] S.K. Ghosh, J. Ribas, P.K. Bharadwaj, Cryst. Growth Des. 5 (2005) 623.
[11] X.Z. Sun, Y.F. Sun, B.H. Ye, X.M. Chen, Inorg. Chem. Commun. 6 (2003) 1412.
[12] L. Xu, G.C. Guo, B. Liu, M.S. Wang, J.S. Huang, Inorg. Chem. Commun. 7 (2004)
1145.
[13] H.P. Jia, W. Li, Z.F. Ju, J. Zhang, Eur. J. Inorg. Chem. (2006) 4264.
[14] 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.
Appendix A. Supplementary material
CCDC 661423, 661422, and 661424 contain the supplementary
crystallographic data for 1–3. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. A stacking diagram for 3
and TGA traces for 1–3. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.ica.2008.02.040.
[15] S.Y. Chui, M.F. Lo, J.P.H. Charmant, A.G. Orpen, I.D. Williams, Science 283
(1999) 1128.
References
[16] L. Deakin, A.M. Arif, J.S. Miller, Inorg. Chem. 38 (1999) 5072.
[17] D.X. Xue, Y.Y. Lin, X.N. Cheng, X.M. Chen, Cryst. Growth Des. 7 (2007) 1332.
[18] (a) B. Moulton, J. Lu, R. Hajndl, S. Hariharan, M.J. Zaworotko, Angew. Chem., Int.
Ed. 41 (2002) 2821;
[1] For example: (a) J.L.C. Roswell, O.M. Yaghi, Angew. Chem., Int. Ed. 44 (2005)
4670;
(b) J.L. Atwood, Nature Mater. 1 (2002) 91.
(b) M. Kondo, T. Okubo, A. Asami, S.I. Noro, T. Yoshitomi, S. Kitagawa, T. Ishii, H.
Matsuzaka, Angew. Chem., Int. Ed. 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;
[19] X.M. Chen, G.F. Liu, Chem.-Eur. J. 8 (2002) 4811.
[20] Y.H. Wen, J.K. Cheng, Y.L. Feng, J. Zhang, Z.J. Li, Y.G. Yao, Inorg. Chim. Acta 358
(2005) 3347.
[21] M.F. Lo, S.Y. Chui, L.Y. Shek, Z. Lin, X.X. Zhang, G.H. Wen, I.D. Williams, J. Am.
Chem. Soc. 112 (2000) 6293.
[22] J.Y. Baeg, S.W. Lee, Inorg. Chem. Commun. 8 (2003) 313.
[23] D. Pocic, J.M. Planeix, N. Kyritsakas, A. Jouaiti, H. Abdelaziz, M. Wais,
CrystEngComm 7 (2005) 624.
[24] SAINT, Software for Data Extraction and Reduction, Version 6.02; Bruker AXS,
Inc., Madison, WI, 2002.
[25] SADABS, Software for Empirical Absorption Correction, Version 2.03; Bruker AXS,
Inc., Madison, WI, 2002.
[26] Sheldrick, G.M. SHELXTL, Program for Crystal Structure Refinement, University of
Gottingen: Gottingen, Germany, 1997.
[27] A.L. Spek, PLATON, A Multipurpose Crystallographic Tool, Utrecht University:
Utrecht, The Netherlands, 1998.
[28] M. Kurmoo, C. Estournes, Y. Oka, H. Kumagai, K. Inoue, Inorg. Chem. 44 (2005)
217.
(d) A.K. Cheetham, C.N.R. Rao, R.K. Feller, Chem. Commun. (2006) 4780.
[2] For example: (a) 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] For example: (a) Q.R. Fang, G.S. Zhu, M. Xue, J.Y. Sun, S.L. Qiu, Dalton Trans.
(2006) 2399;
(b) X.M. Zhang, M.L. Tong, H.K. Lee, X.M. Chen, J. Solid State Chem. 180 (2001)
118;
(c) O.M. Yaghi, H. Li, T.L. Groy, Inorg. Chem. 36 (1997) 4292.
[4] For example: (a) 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. (2006) 1594;
(c) W. Mori, S. Takamizawa, C.N. Kato, T. Ohmura, T. Sato, Micropor. Mesopor.
Mater. 73 (2004) 15.
[29] K. Nakamoto, Infrared Spectra and Raman Spectra of Inorganic and
Coordination Compounds, John Wiley & Sons, New York, 1986.
[5] For example: (a) 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;