Luminescent cadmium phenylenediacetate coordination polymers with bis(pyridylformyl)piperazine tethers: Influence of pendant arm position on topology

Article abstract of DOI:10.1016/j.molstruc.2010.08.047

Hydrothermal synthesis has generated divalent cadmium coordination polymers containing phenylenediacetate (phda) and bis(4-pyridylformyl)piperazine (bpfp) ligands, in which the position of the pendant acetate arms plays a very significant role in structure direction during self-assembly. [Cd(1,2-Hphda)₂(4-bpfp)]_n (1) exhibits 2-D polymeric layers with embedded anti-syn bridged [Cd(OCO)₂]_n ribbons. {[Cd(1,3-phda)(4-bpfp)(H₂O)]₂}_n (2) has crystallographically independent (4,4) grids with different carboxylate binding modes, engaged in parallel interpenetration. {[Cd(1,4-phda)(4-bpfp)(H ₂O)]}_n (3) manifests acentric 1-D chains with an uncommon 4-connected 3³4²5 topology instilled by the mismatch in ligand length. Luminescent properties of all phases are also reported.

Full text of DOI:10.1016/j.molstruc.2010.08.047

Journal of Molecular Structure 983 (2010) 162–168
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Luminescent cadmium phenylenediacetate coordination polymers
with bis(pyridylformyl)piperazine tethers: Influence of pendant
arm position on topology
Curtis Y. Wang a, Robert L. LaDuca b,
⇑
a Diamond Bar High School, Diamond Bar, CA 91765, USA
b Lyman Briggs College and Department of Chemistry, E-30 Holmes Hall, 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:
Received 11 August 2010
Received in revised form 26 August 2010
Accepted 26 August 2010
Available online 17 September 2010
Hydrothermal synthesis has generated divalent cadmium coordination polymers containing phenylene-
diacetate (phda) and bis(4-pyridylformyl)piperazine (bpfp) ligands, in which the position of the pendant
acetate arms plays a very significant role in structure direction during self-assembly. [Cd(1,2-Hphda)2(4-
bpfp)]n (1) exhibits 2-D polymeric layers with embedded anti-syn bridged [Cd(OCO)2]n ribbons. {[Cd(1,3-
phda)(4-bpfp)(H2O)]2}n (2) has crystallographically independent (4,4) grids with different carboxylate
binding modes, engaged in parallel interpenetration. {[Cd(1,4-phda)(4-bpfp)(H2O)]}n (3) manifests acen-
tric 1-D chains with an uncommon 4-connected 33425 topology instilled by the mismatch in ligand
length. Luminescent properties of all phases are also reported.
Keywords:
Cadmium
Coordination polymer
Dicarboxylate
Luminescence
Hydrogen bonding
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
ligands (Scheme 1) have been employed in order to construct coor-
dination polymers whose topologies vary from those obtained with
The design and characterization of crystalline coordination
polymer solids remains a popular basic research interest because
of these materials’ growing industrially important applications
[1] such as gas storage [2], selective adsorption and separation
[3], ion exchange [4], heterogeneous catalysis [5], luminescence
[6], and second harmonic generation [7]. Among most common li-
gands used in the design of these solids are aromatic dicarboxyl-
ates such as terephthalate [8] or isophthalate (ip) [9], which
instill both the structural components and charge balance crucial
for the self-assembly of crystalline frameworks. Variations both
in metal coordination environment and carboxylate group binding
mode promote a wide scope of accessible structural topologies in
aromatic dicarboxylate coordination polymers [10]. The lack of
crystal field stabilization in d10 configuration divalent cadmium
ions allows the specific coordination environment to respond to
the geometric and steric requirements of the carboxylate ligands
during self-assembly [11]. Additionally the absence of d–d transi-
tions with this ion provides the necessary spectral window for
visible light fluorescence [6a].
more rigid carboxylate groups [12–14]. A series of divalent cobalt
coordination polymers with phda and bis(4-pyridylmethyl)pipera-
zine (4-bpmp) ligands reveals the critical dependence of carboxyl-
ate pendant arm position on the final structural topology [15].
{[Co(1,4-phda)(4-bpmp)(H2O)2]Á2H2O}n presents a layered struc-
ture with standard (4,4) grid topology, while [Co(1,3-phda)(4-
bpmp)]n has [Co(1,3-phda)]n layers with embedded {Co2(CO2)2}
dinuclear units pillared by 4-bpmp ligands into a 3-D primitive
cubic topology. The ortho-substituted 1,2-phda derivative {[Co(1,
2-phda)(4-bpmp)1.5(H2O)](H24-bpmp)0.5(ClO4)Á12H2O}n manifests
a unique 5-connected network with an Archimedean topology con-
sisting of triangular and rectangular circuits.
Similarly, divalent zinc phda coordination polymer phases with
neutral 4,4-dipyridylamine (dpa) tethers exhibit divergent topolo-
gies depending on the geometric disposition of the acetate groups.
Although {[Zn(1,4-phda)(dpa)]ÁH2O}n shows a simple (4,4) corru-
gated layer grid structure, {[Zn(1,2-phda)(dpa)]Á2H2O}n and
[Zn(1,3-phda)(dpa)]n possess fourfold interpenetrated 42638 SrAl2
and 66 diamondoid 3-D networks respectively [16].
More recently, aromatic dicarboxylates with conformationally
flexible pendant arms such as isomeric phenylenediacetate (phda)
In this contribution we investigate the effect of acetate arm dis-
position on the topology of cadmium phda coordination polymers
incorporating the bis(4-pyridylformyl)piperazine (4-bpfp) neutral
tethering ligand (Scheme 1). This dipodal dipyridyl ligand has sel-
dom been used in coordination chemistry [17], especially with
⇑
Corresponding author. Tel.: +1 517 432 2268.
E-mail address: laduca@msu.edu (R.L. LaDuca).
0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2010.08.047

C.Y. Wang, R.L. LaDuca / Journal of Molecular Structure 983 (2010) 162–168
163
Scheme 1. Ligands used in this study.
dicarboxylate anionic components [18]. Mixed-ligand extended
solid phases with all three phda isomers have been obtained via
hydrothermal synthesis and structurally characterized. {[Cd(1,2-
Hphda)2(4-bpfp)]Á2H2O}n (1), {[Cd(1,3-phda)(4-bpfp)(H2O)]2}n (2)
and {[Cd(1,4-phda)(4-bpfp)(H2O)]}n (3) possesses different 1-D
and 2-D topologies. Luminescent properties of these new materials
are also reported herein.
1 mL of 1.0 M NaOH and 5 mL deionized water were placed into a
15 mL screw-cap vial. The vial was sealed and heated in an oil bath
at 90 °C for 48 h, and then cooled slowly to 25 °C. Colorless blocks
of 2 (20 mg, 0.032 mmol, 32% yield based on Cd) were isolated
after washing with distilled water, ethanol, and acetone and drying
in air. Anal. Calc. for C52H52Cd2N8O14 2: C, 50.46; H, 4.23; N, 9.05%
Found: C, 50.17; H, 4.09; N, 8.96%. IR (cmÀ1): 3400 (w, br) 2995
(w), 2870 (w), 2323 (w), 1633 (s), 1606 (s), 1556 (m), 1499 (w),
1470 (m), 1438 (m), 1416 (m), 1363 (s), 1330 (w), 1286 (s), 1261
(s), 1219 (w), 1162 (w), 1054 (w), 1006 (s), 968 (w), 933 (w), 905
(w), 872 (w), 837 (s), 785 (w), 759 (w), 716 (w), 678 (w).
2. Experimental section
2.1. General considerations
Cadmium salts and dicarboxylic acids were obtained commer-
cially from Aldrich. Bis(4-pyridylformyl)piperazine (4-bpfp) was
prepared via modification of a published procedure [17]. Pyridine
was refluxed with CaH2 under flowing N2 and distilled immedi-
2.4. Preparation of [Cd(1,4-phda)(4-bpfp)(H2O)]n (3)
Cd(NO3)2Á4H2O (29.9 mg, 0.0972 mmol), 4-bpfp (28.7 mg,
0.0972 mmol), 1,3-phenylenediacetic acid (18.9 mg, 0.0972 mmol),
1 mL of 1.0 M NaOH and 5 mL deionized water were placed into a
15 mL screw-cap vial. The vial was sealed and heated in an oil bath
at 90 °C for 48 h, and then cooled slowly to 25 °C. Colorless blocks
of 3 (27 mg, 0.043 mmol, 45% yield based on Cd) were isolated
after washing with distilled water, ethanol, and acetone and drying
in air. Anal. Calc. for C26H26CdN4O7 3: C, 50.46; H, 4.23; N, 9.05%
Found: C, 50.03; H, 4.47; N, 8.89%. IR (cmÀ1): 3110 (w, br), 1708
(w), 1638 (s), 1607 (m), 1577 (s), 1497 (w), 1463 (m), 1436 (m),
1402 (m), 1362 (m), 1325 (w), 1288 (s), 1262 (s), 1211 (w), 1262
(s), 1211 (w), 1162 (w), 1101 (w), 1006 (s), 948 (w), 903 (w), 841
(m), 762 (m), 746 (w), 705 (w), 665 (w).
ately prior to use. Water was deionized above 3 M
X cm in-house.
Elemental analysis was performed by Micro-Analysis, Inc., Wil-
mington, Delaware, USA. IR spectra Infrared spectra were recorded
on powdered samples on a Perkin Elmer Spectrum One instrument.
The luminescence spectra were obtained with a Hitachi F-4500
Fluorescence Spectrometer on solid crystalline samples anchored
to quartz microscope slides with Rexon Corporation RX-22P ultra-
violet-transparent epoxy adhesive.
2.2. Preparation of {[Cd(1,2-Hphda)2(4-bpfp)]Á2H2O}n (1)
Cd(NO3)2Á4H2O (29.9 mg, 0.0972 mmol), 4-bpfp (28.7 mg,
0.0972 mmol), 1,2-phenylenediacetic acid (18.9 mg, 0.0972 mmol),
and 7 mL deionized water were placed into a 23 mL Teflon-lined
acid digestion bomb. The bomb was sealed and heated in an oven
at 120 °C for 48 h, and then cooled slowly to 25 °C. Colorless blocks
of 1 (8 mg, 0.01 mmol, 21% yield based on the limiting reactant 1,2-
phenylenediacetic acid) were isolated after washing with distilled
water, ethanol, and acetone and drying in air. Anal. Calc. for
3. X-ray crystallography
Single-crystal diffraction data for 1–3 were collected using a
Bruker-AXS Apex2 CCD instrument. Diffraction data was acquired
using graphite–monochromated Mo K
a radiation (k = 0.71073 Å).
The diffraction data were integrated with SAINT [19]. Lorentz
and polarization effect and empirical absorption corrections were
applied with SADABS [20]. The structures were solved using direct
methods and refined on F2 using SHELXTL [21]. All non-hydrogen
atoms were refined with anisotropic thermal parameters. Hydro-
gen atoms bound to carbon atoms were placed in calculated posi-
tions and refined with isotropic thermal parameters using a riding
model. Hydrogen atoms bound to water molecules were located by
Fourier difference map and restrained at fixed positions. Enantio-
meric purity within the crystal of 3 is confirmed by the Flack
parameter [22] of 0.00(3). Disorder within the piperazinyl rings
of the 4-bpfp ligands in 1 was modeled successfully with partial
C
36H34CdN4O10 1: C, 54.38; H, 4.31; N, 7.05% Found: C, 54.11; H,
4.28; N, 7.00%. IR (cmÀ1): 2921 (w), 1708 (s), 1637 (s), 1615 (w),
1567 (s), 1504 (w), 1464 (w), 1435 (w), 1412 (w), 1357 (s), 1267
(s), 1224 (w), 1191 (s), 1169 (s), 1101 (w), 1064 (w), 1041 (w),
1006 (m), 910 (w), 895 (w), 860 (w), 843 (m), 819 (w), 772 (m),
736 (w), 716 (w), 688 (s), 661 (w).
2.3. Preparation of {[Cd(1,3-phda)(4-bpfp)(H2O)]2}n (2)
Cd(NO3)2Á4H2O (29.9 mg, 0.0972 mmol), 4-bpfp (28.7 mg,
0.0972 mmol), 1,3-phenylenediacetic acid (18.9 mg, 0.0972 mmol),

164
C.Y. Wang, R.L. LaDuca / Journal of Molecular Structure 983 (2010) 162–168
occupancies. Relevant crystallographic data for 1–3 are listed in
Table 1.
idyl nitrogen donor atoms from two 4-bpfp ligands in the axial
positions and single oxygen atom donors from four different 1,2-
Hphda ligands in the equatorial plane (Fig. S1). Bond lengths and
angles around cadmium are listed in Table 2.
4. Results and discussion
One carboxylate terminus of every 1,2-Hphda ligand bridges
two cadmium atoms in an anti-syn bridging mode, constructing
[Cd(1,2-Hphda)2]n ribbons aligned along the [1 0 0] crystal direc-
tion (Fig. 1a). Eight-membered [Cd(OCO)2] rings are joined in a
spiro fashion within the center of the ribbon motifs, with a CdÁ Á ÁCd
contact distance of 5.174 Å. Each pair of cadmium atoms is bridged
by deprotonated acetate groups belonging to two 1,2-Hphda li-
gands, with the protonated acetate arms projecting towards the
exterior of the [Cd(1,2-Hphda)2]n ribbons.
4.1. Synthesis and spectral characterization
Hydrothermal reaction of cadmium nitrate, the requisite dicar-
boxylic acid, and bis(4-pyridylformyl)piperazine generated crystal-
line samples of 1–3. The infrared spectra of 1–3 were consistent with
their single crystal structures. Features between ꢀ1620 and
ꢀ1640 cmÀ1 in all cases reveal the presence of the C@O formyl group
within the 4-bpfp ligands. Sharp, medium intensity bands in the
range of ꢀ1600 cmÀ1 to ꢀ1200 cmÀ1 are attributed to stretching
modes of the pyridyl rings of the 4-bpfp ligands and the aromatic
rings of the dicarboxylate ligands. Features corresponding to pyridyl
ring puckering modes are evident in the region between ꢀ930 and
ꢀ600 cmÀ1. Asymmetric and symmetric C–O stretching modes of
the fully deprotonated dicarboxylate ligands are present as broad-
ened bands at 1567 cmÀ1 and 1357 cmÀ1 (1), 1606 cmÀ1 and
1363 cmÀ1 (2), and 1577 cmÀ1 and 1402 cmÀ1 (3). Broad, weak spec-
tral features at ꢀ3100–3400 cmÀ1 (O–H stretching modes) denote
the presence of the aqua ligands in 2 and 3. The peak at 1708 cmÀ1
in the spectrum of 1 is indicative of C–O stretching within the pro-
tonated carboxylate groups of the 1,2-Hphda ligands.
Adjacent ribbon motifs are pillared into 2-D [Cd(1,2-Hphda)2(4-
bpfp)]n coordination polymer layers (Fig. 1b) by anti-conformation
4-bpfp tethering ligands, which span
a
CdÁ Á ÁCd distance of
16.753 Å. If both carboxylate groups spanning each pair of cad-
mium atoms are considered a single linkage, the layer motif can
be simplified as a 4-connected (4,4) nearly perfect rectangular grid,
with CdÁ Á ÁCdÁ Á ÁCd angles of 89.7° and 90.3°. Individual layers lie
along the (0 1 1) crystal planes and aggregate into 3-D (Fig. S2)
by hydrogen bonding donation from the protonated pendant ace-
tate groups to oxygen atoms of ligated acetate moieties, resulting
in a 6-connected primitive cubic supramolecular topology. Hydro-
gen bonding information is given in Table 3.
4.3. Structural description of {[Cd(1,3-phda)(4-bpfp)(H2O)]2}n (2)
4.2. Structural description of [Cd(1,2-Hphda)2(4-bpfp)]n (1)
The large asymmetric unit of compound contains two crystallo-
graphically independent sets, each containing a divalent cadmium
atom, a 1,3-phda ligand, a 4-bpfp ligand, and a ligated water mol-
ecule (Fig. S3). Cd1 displays a distorted {CdN2O5} pentagonal bipy-
ramidal geometry, with the axial positions taken up by 4-bpfp
pyridyl nitrogen donors and the equatorial plane filled by an aqua
ligand and chelating carboxylate groups from two 1,3-phda li-
gands. In contrast Cd2 possesses a distorted {CdN2O4} octahedral
geometry. As seen for Cd1, 4-bpfp pyridyl nitrogen atoms are dis-
posed in a trans fashion. The remaining four coordination sites are
occupied by an aqua ligand, a chelating 1,3-phda carboxylate
group, and a single oxygen atom from a monodentate 1,3-phda
The asymmetric unit of compound 1 contains a divalent cad-
mium ion located on a crystallographic inversion center, one singly
protonated 1,2-Hphda ligand, and one-half of a 4-bpfp molecule
whose central piperazinyl ring and formyl oxygen atoms are disor-
dered equally over two positions. A slightly distorted {CdO4N2}
octahedral coordination sphere exists at cadmium, with trans pyr-
Table 1
Crystal and structure refinement data for 1–3.
Compound
1
2
3
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C
36H34CdN4O10
C52H52Cd2N8O14
1237.82
Monoclinic
P21/n
15.9628(9)
18.7238(10)
16.6373(9)
90
93.667(1)
90
4962.4(5)
4
C26H26CdN4O7
618.91
Orthorhombic
Pna21
9.0634(5)
16.9571(10)
16.8283(9)
90
90
90
2586.3(3)
4
1.589
carboxylate terminus.
A
long CdÁ Á ÁO interaction (2.773(4) Å)
795.07
Triclinic
P1
supplements the octahedral coordination environment at Cd2.
Crystallographic independence is thereby enforced by the differing
coordination environments at Cd1 and Cd2 and binding mode of
the 1,3-phda ligands. Bond lengths and angles within the indepen-
dent coordination environments in 2 are listed in Table 4.
ꢀ
5.1741(8)
10.3722(16)
15.508(2)
77.901(1)
81.973(2)
78.507(1)
793.3(2)
1
b (Å)
c (Å)
a
(°)
Cd1 atoms are connected into zig-zag [Cd(1,3-phda)(H2O)]n
chains, oriented along the [1 0 1] crystal direction, by bis(chelating)
1,3-phda ligands. Cd2 atoms are linked into similar [Cd(1,3-phda)-
(H2O)]n chains by 1,3-phda ligands in a monodentate/chelating
binding mode (Fig. 2). The respective CdÁ Á ÁCd through-ligand con-
tact distances within the crystallographically distinct chain patterns
are 12.204 and 12.308 Å. Different binding modes are reflected in
different C–CÁ Á ÁC–C torsion angles between the 1,3-phda acetate
arms (160.9° and 144.4°, respectively). Both types of chains are
b (°)
c
(°)
V (Å3)
Z
Dcalc (g cmÀ3
)
1.664
0.759
1.657
0.935
l
(mmÀ1
)
0.897
Min./max. trans.
hkl ranges
0.8342/0.9071
À6 6 h 6 6,
À12 6 k 6 12,
À18 6 l 6 18
11 324
0.8214/0.8865
À19 6 h 6 16,
À22 6 k 6 22,
À20 6 l 6 20
30 514
0.8229/0.9284
À9 6 h 6 10,
À20 6 k 6 20,
À20 6 l 6 20
15 187
Total reflections
Unique reflections
R (int)
2 895
0.0558
8 973
0.0450
4 608
0.0497
Table 2
Parameters/restraints
251/0
0.0381
0.0379
0.1015
697/6
0.0478
0.0421
0.1255
349/4
0.0384
0.0346
0.0850
Bond length (Å) and angle (°) data for 1.
R1 (all data)a
O3–Cd1–O3#2
N1–Cd1–O4#1
O3–Cd1–O4#1
N1–Cd1–O4#3
O3–Cd1–O4#3
O4#1–Cd1–O4#3
180
R1 (I > 2
wR2 (all data)b
wR2 (I > 2
(I))b
r
(I))a
Cd1–N1
2.307(3)
2.320(2)
2.371(2)
180
93.87(8)
86.13(8)
Cd1–O3
85.14(8)
91.20(8)
94.86(8)
88.80(8)
180
Cd1–O4#1
r
0.1012
0.1192
0.0822
N1–Cd1–N1#2
N1–Cd1–O3
N1–Cd1–O3#2
Max./min. residual
(eÀ/Å3)
G.O.F.
0.798/À0.855
1.348/À1.457
0.794/À0.749
1.119
1.056
1.088
a
R1
wR2 = {
=
R
||Fo| À |Fc||/
R|Fo|.
Symmetry equivalent positions: #1, x À 1, y, z; #2, Àx + 2, Ày, Àz + 2; #3, Àx + 3, Ày,
Àz + 2.
R
[w(F2o À F2c )2]/
R .
[wF2o ]2}1/2
b

C.Y. Wang, R.L. LaDuca / Journal of Molecular Structure 983 (2010) 162–168
165
Fig. 1. (a) [Cd(1,2-Hphda)2]n ribbon in 1, with embedded [Cd(OCO)2]n chain. (b) [Cd(1,2-Hphda)2(4-bpfp)]n layer in 1.
Table 4
Table 3
Hydrogen bonding distance (Å) and angle (°) data for 1–3.
Bond length (Å) and angle (°) data for 2.
Cd1–O13
Cd1–O6
2.266(3)
2.339(3)
2.371(3)
2.380(3)
2.383(3)
2.399(2)
2.598(2)
Cd2–O14
Cd2–O5
2.233(2)
2.355(2)
2.361(3)
2.368(3)
2.384(3)
2.384(2)
D–HÁ Á ÁA
d(HÁ Á ÁA)
\DHA
d(DÁ Á ÁA)
Symmetry transformation
for A
Cd1–O11#1
Cd1–N7#2
Cd1–N1
Cd2–O10#3
Cd2–N8#2
Cd2–N4
1
O1–H1AÁ Á ÁO3
2
O5–H5BÁ Á ÁO10
O5–H5AÁ Á ÁO11
O6–H6AÁ Á ÁO14
O6–H6BÁ Á ÁO13
1.89
161.3
2.703(3)
Àx + 3, Ày À 1, Àz + 2
Cd1–O12#1
Cd1–O9
Cd2–O8#3
1.99(2)
1.89(2)
1.82(2)
1.89(2)
160(3)
165(3)
167(3)
168(3)
2.783(3)
2.713(3)
2.656(3)
2.712(3)
Àx + 3/2, y À 1/2, Àz + 5/2
Àx + 1/2, y À 1/2, Àz + ½
Àx + 1, Ày, Àz + 1
O13–Cd1–O6
84.34(8)
168.78(9)
84.48(7)
90.01(10)
84.42(8)
89.78(10)
89.60(10)
88.13(8)
89.16(10)
172.55(10)
136.40(8)
138.34(7)
54.78(7)
86.91(9)
98.49(8)
53.10(8)
135.15(7)
137.34(8)
106.46(9)
79.15(9)
86.32(8)
O14–Cd2–O5
91.82(9)
171.81(8)
83.89(8)
83.29(9)
89.05(9)
89.64(9)
87.58(9)
83.32(8)
98.82(9)
167.91(10)
130.76(8)
136.16(8)
55.08(7)
O13–Cd1–O11#1
O6–Cd1–O11#1
O13–Cd1–N7#2
O6–Cd1–N7#2
O11#1–Cd1–N7#2
O13–Cd1–N1
O14–Cd2–O10#3
O5–Cd2–O10#3
O14–Cd2–N8#2
O5–Cd2–N8#2
O10#3–Cd2–N8#2
O14–Cd2–N4
Àx, Ày, Àz
3
O7–H7AÁ Á ÁO3
1.87(3)
1.83(2)
158(5)
179(5)
2.677(5)
2.670(5)
Àx + 1/2, y À 1/2, z À 1/2
x À 1/2, Ày + 3/2, z
O7–H7BÁ Á ÁO2
O6–Cd1–N1
O5–Cd2–N4
O11#1–Cd1–N1
N7#2–Cd1–N1
O13–Cd1–O12#1
O6–Cd1–O12#1
O11#1–Cd1–O12#1
N7#2–Cd1–O12#1#1
N1–Cd1–O12
O10#3–Cd2–N4
N8#2–Cd2–N4
O14–Cd2–O8#3
O5–Cd2–O8#3
O10#3–Cd2–O8#3
N8#2–Cd2–O8#3
N4–Cd2–O8#3
connected into [Cd(1,3-phda)(4-bpfp)(H2O)]n coordination polymer
(4,4) layers by tethering 4-bpfp ligands, which provide CdÁ Á ÁCd dis-
tances of 16.637 Å (c lattice parameter). The full span of the 1,3-phda
ligands, compared to the bridging carboxylate groups of the 1,2-
Hphda ligands in 1, provides substantially longer CdÁ Á ÁCd distances
in 2. As a result, the larger grid windows permit parallel 2-fold inter-
penetration of crystallographically independent [Cd(1,3-phda)(4-
bpfp)(H2O)]n layers (Fig. 3). The grid apertures are significant more
pinched than in 1, with CdÁ Á ÁCdÁ Á ÁCd angles of 129.8/50.4°, and
129.4/50.6°, within the two different layer motifs. Aggregation into
the pseudo 3-D crystal structure of 2 (Fig. S4) occurs by hydrogen
bonding donation from theaqua ligands in one interpenetratedlayer
103.90(9)
88.06(9)
O13–Cd1–O9
O6–Cd1–O9
O11#1–Cd1–O9
N7#2–Cd1–O9
N1–Cd1–O9
O12#1–Cd1–O9
Symmetry equivalent positions: #1, x + 1/2, Ày + 1/2, z + 1/2; #2, x, y, z + 1; #3,
x À 1/2, Ày + 1/2, z À 1/2.

166
C.Y. Wang, R.L. LaDuca / Journal of Molecular Structure 983 (2010) 162–168
Fig. 2. Zig-zag [Cd(1,3-phda)(H2O)]n chains in 2. 1,3-phda ligands in the top and bottom chains adopt bis(chelating) and monodentate/chelating binding modes, respectively.
to ligated carboxylate oxygen atoms belonging to the interpene-
Table 5
trated layers above and below.
Bond length (Å) and angle (°) data for 3.
Despite their common layered topology, compound 2 and its 4-
bpmp analog [Cd(1,3-phda)(4-bpmp)]n exhibit stark structural dif-
ferences [23]. The latter material possesses (4,4) grids based on
{Cd2O2} dimeric units and exotridentate 1,3-phda ligands, and
lacks any interpenetration. It is plausible that the inclusion of aqua
ligands in 2 alters the binding mode of the 1,3-phda carboxylate
groups and therefore the overall coordination polymer topology.
Cd1–O7
2.253(3)
2.274(3)
2.362(4)
2.364(4)
2.412(4)
2.467(3)
2.563(4)
132.26(12)
91.40(13)
97.55(12)
88.90(12)
137.15(11)
91.74(13)
135.80(11)
O7–Cd1–N3
O5–Cd1–N3
84.27(14)
86.44(12)
175.45(13)
86.76(14)
140.82(12)
86.87(11)
79.46(12)
53.84(11)
103.02(13)
80.66(11)
53.41(10)
86.79(12)
169.41(11)
93.90(13)
Cd1–O5
Cd1–N4#1
N4#1–Cd1–N3
O3#2–Cd1–N3
O7–Cd1–O4#2
O5–Cd1–O4#2
N4#1–Cd1–O4#2
O3#2–Cd1–O4#2
N3–Cd1–O4#2
O7–Cd1–O2
Cd1–O3#2
Cd1–N3
Cd1–O4#2
Cd1–O2
O7–Cd1–O5
O7–Cd1–N4#1
O5–Cd1–N4#1
O7–Cd1–O3#2
O5–Cd1–O3#2
N4#1–Cd1–O3#2
O4#2–Cd1–O2
4.4. Structural description of [Cd(1,4-phda)(4-bpfp)(H2O)]n (3)
O5–Cd1–O2
N4#1–Cd1–O2
O3#2–Cd1–O2
N3–Cd1–O2
Compound 3 crystallizes in an acentric space group with an
asymmetric unit containing a divalent cadmium atom, a fully
deprotonated 1,4-phda ligand, a 4-bpfp ligand, and an aqua ligand
(Fig. S5). The cadmium atom displays a distorted {CdN2O5} pentag-
onal bipyramidal geometry, with trans 4-bpfp pyridyl nitrogen do-
nors in the axial positions. The equatorial plane is filled by an aqua
ligand and chelating carboxylate groups from two 1,4-phda
ligands. Bond parameters within the coordination environment in
3 are listed in Table 5.
Symmetry equivalent positions: #1, x, y, z À 1; #2, Àx, Ày + 2, z À 1/2.
ing mode to produce [Cd(1,4-phda)(H2O)]n chains aligned along
the [0 0 1] crystal direction (Fig. 4a) and coincident with the crys-
tallographic 21 screw axes. The CdÁ Á ÁCd through-ligand distance is
9.623 Å. Despite the para disposition of the acetate pendant arms
within the 1,4-phda ligands, the ‘‘staple” configuration enforces a
shorter metal–metal contact distance than seen for the meta dicar-
Cadmium ions are connected by ‘‘staple” configuration 1,4-phda
ligands (C–CÁ Á ÁC–C torsion angle = 38.6°) in a bis(chelating) bind-
Fig. 3. Parallel 2-fold interpenetration of [Cd(1,3-phda)(4-bpfp)(H2O)]n layers in 3. (a) Face view. (b) Side view.

C.Y. Wang, R.L. LaDuca / Journal of Molecular Structure 983 (2010) 162–168
167
Fig. 4. (a) [Cd(1,4-phda)(H2O)]n chain in 3. (b) 4-connected [Cd(1,4-phda)(4-bpfp)(H2O)]n 1-D chains in 3. (c) Schematic representation of the 33425 chain topology.
boxylate 1,3-phda ligands in 2. Next nearest neighbor Cd atoms
(CdÁ Á ÁCd distance = 16.835 Å) within these chains are bridged by
4-bpfp ligands (Fig. 4b). Thus the resulting [Cd(1,4-phda)(4-
bpfp)(H2O)]n 1-D chains in 3 stand in direct contrast with the
non-interpenetrated 2-D layers in 1 and 2-fold interpenetrated 2-
D layers in 2. The topology of the 1-D chain motifs in 3 can be
determined by considering each cadmium ion as a 4-connected
node with all ligands as simple linkers. According to TOPOS soft-
ware [24], this treatment produces a 4-connected chain with
33425 topology (Fig. 4c). Adjacent [Cd(1,4-phda)(4-bpfp)(H2O)]n
1-D chains aggregate by hydrogen bonding donation from aqua li-
gands to ligated 1,4-phda carboxylate oxygen atoms (Fig. S6).
The 1-D topology of compound 3 stands in marked contrast
with the 2-D structure of its 4-bpmp analog {[Cd(1,4-phda)(4-
bpmp)]Á1.5H2O}n [23]. The latter material possesses [Cd(1,4-phda)]
double chains containing {Cd2O2} dimeric units and exotridentate
1,4-phda ligands, pillared into 2-D by 4-bpmp tethers. As in the
aforementioned 1,3-phda derivative 2, it is likely that the presence
of bound water molecules in 3 affects the carboxylate binding
mode and overall coordination polymer topology.
or p–n transitions within the phda and 4-bpfp ligands, while the
lower energy band is perhaps best ascribed to ligand-to-metal
charge transfer (LMCT) transitions potentially involving the anti-
syn bridged carboxylate groups. These latter modes are apparently
absent for 2 and 3, which show single intraligand-based emission
maxima at 470 and 440 nm, respectively.
5. Conclusions
The geometric disposition of the acetate arms of phda ligands
appears to play a critical role in structure direction during
self-assembly of cadmium coordination polymers containing long
4-bpfp tethering ligands. Ortho disposed acetate arms in 1,2-phda
ligands promote 1-D spiro [Cd(OCO)2] ribbons, which are pillared
into a standard (4,4) grid topology by the dipodal neutral tethers.
A longer span between dicarboxylate termini in the 1,3-phda
ligand resulted in larger grid apertures and a twofold parallel inter-
penetrated layered net. In the para substituted 1,4-phda derivative,
the conformational flexibility of the acetate arms instills a helical
twist and overall acentricity of the resulting 4-connected coordina-
tion polymer chains. The structural topologies of compound 2 and
3 differ greatly from those of their analogous bis(4-pyridyl-
methyl)piperazine derivatives, indicating a significant structure-
directing effect via the 4-bpfp formyl groups and concomitant loss
of lone pair electron density at the piperazinyl nitrogen atoms.
Luminescent properties in this series appear to depend on the spe-
cific binding mode of the dicarboxylate ligands and coordination
environment at cadmium. The results herein portend a potentially
rich coordination polymer chemistry for the under-utilized 4-bpfp
neutral tethering ligand.
4.5. Luminescent properties
Polycrystalline samples of 1–3 all underwent visible light fluo-
rescence upon excitation with ultraviolet light (kex values: 1,
315 nm; 2, 390 nm; 3, 330 nm). Emission spectra are shown in
Fig. 5. The emission spectrum of 1 shows two broad maxima, cen-
tered at 400 and 555 nm. According to a review of d10 metal coor-
dination polymer luminescent behavior by Houk et al. [6a], the
higher energy maximum is likely attributable to intraligand
p–
pÃ
Acknowledgements
The authors gratefully acknowledge the donors of the American
Chemical Society Petroleum Research Fund for financial support of
this work. C.Y.W. thanks Dr. Gail Richmond and the MSU High
School Honors Science Program for his participation in the work,
and thanks Dr. Ayasheed Mahpanzah for helpful discussions
regarding the crystallography. We thank Ms. Amy Pochodylo for
assistance with the fluorescence spectroscopy.
Appendix A. Supplementary material
Crystallographic data (excluding structure factors) for 1–3 have
been deposited with the Cambridge Crystallographic Data Centre
with Nos. 784854–784856, respectively. Copies of the data can
be obtained free of charge via the Internet at http://www.ccdc.
cam.ac.uk/conts/retrieving.html. Supplementary data associated
Fig. 5. Emission spectra of 1–3.

168
C.Y. Wang, R.L. LaDuca / Journal of Molecular Structure 983 (2010) 162–168
(f) W. Mori, S. Takamizawa, C.N. Kato, T. Ohmura, T. Sato, Micropor. Mesopor.
Mater. 73 (2004) 31;
(g) N. Guillou, Q. Gao, P.M. Forster, J.S. Chang, M. Noguès, S.-E. Park, G. Férey,
A.K. Cheetham, Angew. Chem. Int. Ed. 40 (2001) 2831.
[6] (a) M.D. Allendorf, C.A. Bauer, R.K. Bhakta, R.J.T. Houk, Chem. Soc. Rev. 38
(2009) 1330, and references therein;
with this article can be found, in the online version, at doi:10.1016/
j.molstruc.2010.08.047.
References
(b) J. He, J. Yu, Y. Zhang, Q. Pan, R. Xu, Inorg. Chem. 44 (2005) 9279;
(c) S. Wang, Y. Hou, E. Wang, Y. Li, L. Xu, J. Peng, S. Liu, C. Hu, New J. Chem. 27
(2003) 1144;
[1] (a) A.U. Czaja, N. Trukhan, U. Mueller, Chem. Soc. Rev. 38 (2009) 1284, and
references therein;
(d) L.G. Beauvais, M.P. Shores, J.R. Long, J. Am. Chem. Soc. 122 (2000) 2763.
[7] (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.
[8] (a) M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J. Wachter, M. O’Keefee, O.M. Yaghi,
Science 295 (2002) 469;
(b) C. Janiak, Dalton Trans. (2003) 2781, and references therein;
(c) U. Mueller, M. Schubert, F. Teich, H. Puetter, K. Schierle-Arndt, J. Pastré, J.
Mater. Chem. 16 (2006) 626.
[2] (a) S.S. Han, J.L. Mendoza-Cortes, W.A. Goddard III, Chem. Soc. Rev. 38 (2009)
1460, and references therein;
(b) X.-N. Cheng, W.-X. Zhang, Y.-Y. Lin, Y.-Z. Zheng, X.-M. Chen, Adv. Mater. 19
(2007) 1494.
(b) L. Pan, D.H. Olson, L.R. Ciemnolonski, R. Heddy, J. Li, Angew. Chem. Int. Ed.
45 (2006) 616;
[9] J. Tao, M.L. Tong, X.M. Chen, J. Chem. Soc. Dalton Trans. (2000) 3669.
[10] D.J. Tranchemontagne, J.L. Mendoza-Cortés, M. O’Keeffe, O.M. Yaghi, Chem.
Soc. Rev. 38 (2009) 1257, and references therein.
[11] (a) Y. Dai, E. Ma, E. Tang, J. Zhang, Z. Li, X. Huang, Y. Yao, Cryst. Growth Des. 5
(2005) 1313;
(c) M. Dinca, A.F. Yu, J.R. Long, J. Am. Chem. Soc. 128 (2006) 8904;
(d) J.L.C. Roswell, O.M. Yaghi, Angew. Chem. Int. Ed. 44 (2005) 4670;
(e) R. Matsuda, R. Kitaura, S. Kitagawa, Y. Kubota, R.V. Belosludov, T.C.
Kobayashi, H. Sakamoto, T. Chiba, M. Takata, Y. Kawazoe, Y. Mita, Nature 436
(2005) 238;
(b) N.L. Rosi, J. Eckert, M. Eddaoudi, D.T. Vodak, J. Kim, M. O’Keeffe, O.M. Yaghi,
Science 300 (2003) 1127;
(f) A.C. Sudik, A.R. Millward, N.W. Ockwig, A.P. Côté, J. Kim, O.M. Yaghi, J. Am.
Chem. Soc. 127 (2005) 7110;
(c) S. Zhu, H. Zhang, Y. Zhao, M. Shao, Z. Wang, M. Li, J. Mol. Struct. 892 (2008)
420.
(g) X. Zhao, B. Xiao, A.J. Fletcher, K.M. Thomas, D. Bradshaw, M.J. Rosseinsky,
Science 306 (2004) 1012;
[12] X.-F. Xie, S.-P. Chen, Z.-Q. Xia, S.-L. Gao, Polyhedron 28 (2009) 679.
[13] F. Yang, Y. Ren, D. Li, F. Fu, G. Qi, Y. Wang, J. Mol. Struct. 892 (2008) 283.
[14] Z. Su, S.S. Chen, J. Fan, M.S. Chen, Y. Zhao, W.Y. Sun, Cryst. Growth Des. 10
(2010) 3675.
(h) G. Férey, M. Latroche, C. Serre, F. Millange, T. Loiseau, A. Percheron-Guegan,
Chem. Commun. (2003) 2976.
[3] (a) J.-R. Li, R.J. Kuppler, H.-C. Zhou, Chem. Soc. Rev. 38 (2009) 1477, and
references therein;
[15] K.M. Blake, L.L. Johnston, J.H. Nettleman, R.M. Supkowski, R.L. LaDuca, Cryst.
Eng. Commun. 12 (2010) 1927.
[16] M.A. Braverman, R.L. LaDuca, Cryst. Growth Des. 7 (2007) 2343.
[17] H. Hou, Y. Song, H. Xu, Y. Wei, Y. Fan, Y. Zhu, L. Li, C. Du, Macromolecules 36
(2003) 999.
(b) S. Galli, N. Masciocchi, G. Tagliabue, A. Sironi, J.A.R. Navarro, J.M. Salas, L.
Mendez-Liñan, M. Domingo, M. Perez-Mendoza, E. Barea, Chem. Eur. J. 14
(2008) 9890;
(c) J.S. Seo, D. Whang, H. Lee, S.I. Jun, J. Oh, Y.J. Jeon, K. Kim, Nature 404 (2000)
982.
[18] Z.M. Wilseck, C.M. Gandolfo, R.L. LaDuca, Inorg. Chim. Acta, in press. doi:
10.1016/j.ica.2010.07.045.
[19] SAINT, Software for Data Extraction and Reduction, Version 6.02 Bruker AXS,
Inc.: Madison, WI, 2002.
[20] SADABS, Software for Empirical Absorption Correction. Version 2.03 Bruker
AXS, Inc.: Madison, WI, 2002.
[21] G.M. Sheldrick, SHELXTL, Program for Crystal Structure Refinement, University
of Göttingen: Göttingen, Germany, 1997.
[4] (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. 160
(2001) 118;
(c) O.M. Yaghi, H. Li, T.L. Groy, Inorg. Chem. 36 (1997) 4292.
[5] (a) J.Y. Lee, O.K. Farha, J. Roberts, K.A. Scheidt, S.T. Nguyen, J.T. Hupp, Chem.
Soc. Rev. 38 (2009) 1450, and references therein;
(b) L. Ma, C. Abney, W. Lin, Chem. Soc. Rev. 38 (2009) 1248, and references
therein;
[22] H.D. Flack, Acta Crystallogr. A29 (1983) 876.
[23] K.M. Blake, G.A. Farnum, L.L. Johnston, R.L. LaDuca, Inorg. Chim. Acta 363
(2010) 88.
[24] V.A. Blatov, A.P. Shevchenko, V.N. Serezhkin, J. Appl. Crystallogr. 33 (2000)
1193.
(c) S.G. Baca, M.T. Reetz, R. Goddard, I.G. Filippova, Y.A. Simonov, M. Gdaniec,
N. Gerbeleu, Polyhedron 25 (2006) 1215;
(d) H. Han, S. Zhang, H. Hou, Y. Fan, Y. Zhu, Eur. J. Inorg. Chem. 8 (2006)
1594;
(e) C.-D. Wu, A. Hu, L. Zhang, W. Lin, J. Am. Chem. Soc. 127 (2005) 8940;