Simple layered or complex self-penetrated networks in cadmium homophthalate coordination polymers containing 1,3-bis(4-pyridyl)propane

Article abstract of DOI:10.1016/j.ica.2011.07.029

Hydrothermal reaction of cadmium salts with homophthalic acid (H ₂hmph) and 1,3-bis(4-pyridyl)propane (dpp) afforded coordination polymers whose topologies are determined by the absence or presence of any unligated counteranions. [Cd(hmph)(dpp)]_n (1) has a zig-zag (4,4) layer topology with simple AAA stacking. {[Cd₆(hmph) ₄(dpp)₁₁(H₂O)₄] (ClO ₄)₄·4H₂O}_n (2) has a complicated, unprecedented tetranodal self-penetrated cationic three-dimensional net built from the linkage of 5-fold interpenetrated 3-connected 4.14 ² cds-a topology [Cd₆(H₂O)₄(dpp) ₁₁]_n¹²ⁿ⁺ subnets by bridging and exotridentate hmph ligands. Luminescent properties of these materials are also discussed.

Full text of DOI:10.1016/j.ica.2011.07.029

Inorganica Chimica Acta 376 (2011) 590–597
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Simple layered or complex self-penetrated networks in cadmium
homophthalate coordination polymers containing 1,3-bis(4-pyridyl)propane
⇑
Gregory A. Farnum, Chaun M. Gandolfo, 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:
Received 5 May 2011
Received in revised form 12 July 2011
Accepted 20 July 2011
Available online 28 July 2011
Hydrothermal reaction of cadmium salts with homophthalic acid (H2hmph) and 1,3-bis(4-pyridyl)pro-
pane (dpp) afforded coordination polymers whose topologies are determined by the absence or presence
of any unligated counteranions. [Cd(hmph)(dpp)]n (1) has a zig-zag (4,4) layer topology with simple AAA
stacking. {[Cd6(hmph)4(dpp)11(H2O)4] (ClO4)4ꢀ4H2O}n (2) has a complicated, unprecedented tetranodal
self-penetrated cationic three-dimensional net built from the linkage of 5-fold interpenetrated 3-con-
nected 4.142 cds-a topology [Cd6(H2O)4(dpp)11
]
subnets by bridging and exotridentate hmph
12n+
n
Keywords:
Cadmium
Coordination polymer
Layer
ligands. Luminescent properties of these materials are also discussed.
Ó 2011 Elsevier B.V. All rights reserved.
Self-penetration
Luminescence
1. Introduction
etrate through the shortest circuits between metal atom or multi-
exodentate ligand nodes, are far more rarely observed in these
systems [14–20]. Recent research has uncovered a few approaches
that can generate self-penetrated networks, although their deliber-
ate design remains an elusive goal. High nodal connectivity can
provide multiple points of connection that can establish both sim-
ple and complicated self-penetrated networks, for example in the
6-connected 48668 rob network in {[Cu2(glutarate)2(4,40-bipyri-
dine)]ꢀ3H2O}n [14] and the cluster-based 8-connected 4245.63 ilc
Investigations into crystalline metal–organic aromatic dicar-
boxylate solids remain intensely active because of their significant
potential as gas storage substrates [1], selective small-molecule
absorbents [2], ion-exchange substrates [3], heterogeneous cata-
lysts [4], and in optical devices [5]. The architectural appeal of
the underlying molecular topologies also drives basic research in
this area [6]. Divalent transition metal cations have a variety of
coordination geometry preferences, which in turn can influence
the binding and bridging modes of the aromatic carboxylate func-
tional groups [7]. Even with an identical ligand set, judicious alter-
ation of precursor [8] or synthesis temperature [9] or pH [10] can
instill significant structural diversity, because of changing supra-
molecular conditions during self-assembly. Sensitivity to supramo-
lecular environment is especially prevalent in coordination
polymers based on closed-shell d10 ions such as divalent zinc or
cadmium [11], which lack any crystal field driven geometric pref-
erences. The presence of occluded counteranions can alter the
overall structural framework of crystalline coordination polymers
with similar ligand sets, through the imposition of a different
supramolecular environment [12].
network seen in [Zn5(l3-OH)2(terephthalate)4(1,10-phenanthro-
line)2]n [15]. Self-penetrated coordination polymer networks can
also be built up through the direct pillaring of a system of interpen-
etrated 3-D subnets. For instance, {[Cd(pht)(4,40-dipyridylamine)
(H2O)]ꢀ4H2O}n has a unique 4-connected 3-D self-penetrated 7482
yyz net formed from the phthalate linkage of 3-fold interpene-
trated 123 twt networks [16]. Conformationally flexible tethering
ligands have proven useful in the construction of intriguing self-
penetrated networks, including that in the layered coordination
polymer {[Cu(N,N0-bis(4-pyridyl)suberamide)2 (H2O)2](SO4)ꢀH2Oꢀ
2EtOH}n, whose very long tethering dipyridyl ligands intertwine
with each other within the grid apertures [17].
In this contribution, we outline our investigations into a
cadmium homophthalate (hmph) coordination polymer system
with the very flexible 1,3-bis(4-pyridyl)propane (dpp) dipodal
nitrogen-base ligand. Herein we discuss the synthesis, crystal
structures, and luminescent properties of [Cd(hmph)(dpp)]n (1)
and {[Cd6(hmph)4(dpp)11(H2O)4](ClO4)4ꢀ4H2O}n (2), with the
latter manifesting a complicated multi-nodal self-penetrated net
based on the interlocking of rarely encountered 3-connected
Interpenetration of distinct coordination polymer networks is a
quite commonly encountered phenomenon [13]. In contrast, self-
penetrated networks, which possesses tethering ligands that pen-
⇑
Corresponding author. Address: Lyman Briggs College, E-30 Holmes Hall,
Michigan State University, East Lansing, MI 48825, USA.
E-mail address: laduca@msu.edu (R.L. LaDuca).
0020-1693/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2011.07.029

G.A. Farnum et al. / Inorganica Chimica Acta 376 (2011) 590–597
591
Table 1
Crystal and structure refinement data for 1–2.
Data
1
2
Empirical formula
Formula weight
Crystal system
Space groupa
a (Å)
C
22H20CdN2O4
C179H194Cl4Cd6N22O40
4109.77
monoclinic
C2/c
488.80
monoclinic
P21/c
10.8890(6)
54.473(6)
b (Å)
13.5368(8)
11.9715(13)
c (Å)
14.2736(8)
27.928(3)
b (°)
107.320(1)
2008.6(2)
100.890(1)
17 885(3)
V (Å3)
Z
4
4
Dcalc (g cmꢁ3
)
1.616
1.118
1.524
0.843
l
(mmꢁ1
)
Minimum/maximum transmission
0.7455/0.8538
0.8169/0.9167
hkl ranges
ꢁ13 6 h 6 13, ꢁ16 6 k 6 14, ꢁ17 6 l 6 17
ꢁ65 6 h 6 65, ꢁ14 6 k 6 14, ꢁ33 6 l 6 33
Total reflections
Unique reflections
Rint
12 245
3683
127 108
16 417
0.1176
0.0196
262/0
Parameters/restraints
1191/9
0.1080
0.0513
0.1235
0.0995
a
R1 (all data)
0.0310
0.0279
0.0740
0.0717
1.060/ꢁ0.502
1.058
a
R1 [I > 2
r
(I)]
b
wR2 (all data)
b
wR2 [I > 2
r(I)]
Maximum/minimum residual (e Å3)
0.837/ꢁ0.724
Goodness-of-fit (GOF) on F2
1.027
a
R1
wR2 = {
=
R
||Fo|ꢁ|Fc||/
R|Fo|.
b
2
R
[w(Fo ꢁ Fc2)2]/
R .
[wFo2]2}1/2
Fig. 1. Coordination environment of 1. The numbering scheme is the same as in Table 2.
interpenetrated networks. Oxoanion occlusion, coordination
geometry preferences, and ligand conformational flexibility play
a crucial cooperative structure-directing role in this system.
2.2. Preparation of [Cd(hmph)(dpp)]n (1)
CdSO4ꢀ8H2O (64 mg, 0.18 mmol), dpp (73 mg, 0.37 mmol) and
homophthalic acid (32 mg, 0.18 mmol) were placed into 5 mL dis-
tilled H2O in a 15 mL screw-cap vial. The vial was sealed as tightly
2. Experimental
Table 2
2.1. General considerations
Selected bond distance (Å) and angle (°) data for 1.
Cd1–O4#1
Cd1–N1
2.248(3)
2.294(2)
2.295(2)
2.307(2)
2.412(2)
2.457(2)
N1–Cd1–N2#2
O2–Cd1–N2#2
O4#1–Cd1–O1
N1–Cd1–O1
88.05(8)
88.34(9)
96.50(8)
89.29(8)
54.25(7)
127.11(8)
54.65(7)
93.33(8)
137.47(10)
85.45(8)
147.42(8)
Cadmium salts and homophthalic acid were obtained from Al-
drich. 1,3-bis(4-Pyridyl)propane was purchased from TCI America.
Water was deionized above 3 MX-cm in-house. IR spectra were re-
corded on a Perkin–Elmer Spectrum One DRIFT instrument on
powdered samples. Elemental analysis was carried out using a
Perkin–Elmer 2400 Series II CHNS/O Analyzer. The luminescence
spectra were obtained with a Hitachi F-4500 Fluorescence Spec-
trometer on solid crystalline samples anchored to quartz
microscope slides with Rexon Corporation RX-22P ultraviolet-
transparent epoxy adhesive.
Cd1–O2
Cd1–N2#2
Cd1–O1
O2–Cd1–O1
Cd1–O3#1
N2#2–Cd1–O1
O4#1–Cd1–O3#1
N1–Cd1–O3#1
O2–Cd1–O3#1
N2#2–Cd1–O3#1
O1–Cd1–O3#1
O4#1–Cd1–N1
O4#1–Cd1–O2
N1–Cd1–O2
120.35(10)
100.79(12)
128.50(10)
129.39(8)
O4#1–Cd1–N2#2
Symmetry equivalent positions: #1 x, ꢁy + 1/2, z + 1/2; #2 ꢁx + 2, y + 1/2, ꢁz + 1/2.

592
G.A. Farnum et al. / Inorganica Chimica Acta 376 (2011) 590–597
as possible by hand and heated at 80 °C in an oil bath for 48 h. It
was then withdrawn from the oil bath and allowed to air cool to
25 °C. Colorless blocks of 1 (49 mg, 56% yield based on Cd) were
isolated after washing with distilled water and acetone, and drying
in air. Anal. Calc. for C22H20CdN2O4 1: C, 54.06; H, 4.12; N, 5.73.
Found: C, 53.87; H, 3.87; N, 5.39%. IR (cmꢁ1): 3253 w, 3058 w,
2924 w, 2871 w, 1699 w, 1611 w, 1563 s, 1503 w, 1467 w, 1449
w, 1426 w, 1396 s, 1273 w, 1224 s, 1170 w, 1149 w, 1084 w,
1067 w, 1016 s, 940 w, 847 w, 818 w, 806 w, 747 w, 712 w, 712
w, 672 w.
and polarization effect and absorption corrections were applied
with SADABS [22]. The structures were solved using direct methods
and refined on F2 using SHELXTL [23]. 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. Where possible, hydrogen atoms belonging to
water molecules were found by Fourier difference map and refined
with isotropic thermal displacement parameters. Disorder within
the perchlorate ions of 2 was modeled successfully using partial
occupancies. Relevant crystallographic data for 1–2 are listed in
Table 1.
2.3. Preparation of {[Cd6(hmph)4(dpp)11(H2O)4](ClO4)4ꢀ4H2O}n (2)
4. Results and discussion
The procedure for the synthesis of 1 was followed, with the
exception of the use of Cd(ClO4)2ꢀ6H2O (75 mg, 0.18 mmol) as the
metal salt. Colorless blocks of 2 (49 mg, 40% yield based on Cd)
were isolated after washing with distilled water and acetone, and
drying in air. Anal. Calc. for C179H194Cl4Cd6N22O40 2: C, 52.49; H,
4.43; N, 7.52. Found: C, 52.76; H, 4.10; N, 7.73%. IR (cmꢁ1): 3220
w br, 3063 w, 2940 w, 2862 w, 1606 m, 1586 w, 1571 m, 1550 s,
1502 w, 1425 m, 1385 s, 1297 w, 1224 m, 1084 vs, 1064 s, 1013
m, 942 w, 930 w, 865 w, 845 w, 815 m, 804 m, 791 w, 767 w,
735 m, 724 m, 683 w, 665 w.
4.1. Synthesis and spectral characterization
Compounds 1–2 were prepared by the hydrothermal reaction of
the appropriate cadmium salt, homophthalic acid, and dpp. The
infrared spectra of all of the compounds were consistent with their
crystal structures. Weak, highly broadened features above
ꢂ3200 cmꢁ1 in the spectrum of 2 indicate the presence of the
bound and/or unligated water molecules. Bands between 2800
and 3100 cmꢁ1 in both spectra represent C–H stretching modes.
Asymmetric and symmetric C–O stretching modes of the hmph li-
gands are present as broadened, strong bands at 1563 and
1396 cmꢁ1 (1), and 1550 and 1385 cmꢁ1 (2). Medium intensity
bands in the range of ꢂ1600 to ꢂ1200 cmꢁ1 are caused by stretch-
ing modes of the pyridyl rings of the dpp ligands and the aromatic
rings of the hmph ligands [24]. Unligated perchlorate ions in 2 are
marked by the very strong band at 1084 cmꢁ1. Spectral features
3. X-ray crystallography
Single crystal reflection data for 1–2 were collected at 173 K
using a Bruker-AXS Apex II CCD instrument. Reflection data was
acquired using graphite-monochromated Mo K
a
radiation
(k = 0.71073 Å). The data was integrated via SAINT [21]. Lorentz
Fig. 2. (a) [Cd(hmph)]n chain motif in 1. (b) [Cd(hmph)(dpp)]n (4,4) grid layer in 1.

G.A. Farnum et al. / Inorganica Chimica Acta 376 (2011) 590–597
593
corresponding to aromatic ring puckering were observed in the re-
gion between 600 and 820 cmꢁ1
tions (Cꢀ ꢀ ꢀO distance = 3.167(4) Å) between dpp trimethylene teth-
ers and hmph carboxylate groups provide the supramolecular
impetus for the layer aggregation. The rectangular grid structure
of 1 differs from that of the few reported cadmium homophthalate
coordination polymers. {[Cd(hmph)(4,40-dipyridylamine)]ꢀH2O}n
possesses interdigitated herringbone (6,3) grid layers with an ABAB
stacking pattern [25], while [Cd(hmph)(1,10-phenanthroline)]n
and [Cd(hmph)(2,20-bipyridine)]n are simple 1-D chain polymers
[26].
.
4.2. Structural description of [Cd(hmph)(dpp)]n (1)
Compound 1 contains a small asymmetric unit containing one
cadmium atom, one hmph ligand, and one dpp ligand (Fig. 1), with
a {CdN2O4} distorted octahedral coordination environment. Chelat-
ing carboxylate groups from two hmph ligands fill axial and equa-
torial coordination sites, while the two remaining cis positions are
occupied by dpp pyridyl donors. Bond lengths and angles within
the coordination sphere are given in Table 2.
4.3. Structural description of
{[Cd6(hmph)4(dpp)11(H2O)4](ClO4)4ꢀ4H2O}n (2)
The hmph ligands connect cadmium atoms into [Cd(hmph)]n
chain motifs (Fig. 2a), with a bis(chelating) l2
-
j4-O,O0:O00,O000 bind-
The very large asymmetric unit of compound 2 contains three
divalent cadmium atoms, two hmph ligands, five full dpp ligands,
another dpp ligand whose central methylene carbon atom is sited
on a crystallographic 2-fold rotation axis, two aqua ligands, two
unligated perchlorate anions, and two water molecules of crystal-
lization (Fig. 3). To aid in the discussion of this complex structure,
crystallographically distinct hmph and dpp ligands are named as
follows: hmph-A, O1–O4; hmph-B, O5–O8; dpp-A, N1–N2; dpp-
B, N3, situated across the 2-fold axis; dpp–C, N5–N6; dpp-D, N7–
N8; dpp-E, N9–N10; dpp-F, N11–N12. The first cadmium atom
(Cd1) has a nearly ideal {CdN4O2} octahedral coordination environ-
ment, with oxygen donor atoms from acetate carboxylates of
hmph-A and hmph-B in trans axial positions. In the equatorial
positions at Cd1 are pyridyl nitrogen donor atoms from dpp-A,
dpp-C, dpp-D, and dpp-E. Both Cd2 and Cd3 have distorted
{CdN3O3} octahedral coordination geometries. Nitrogen donors
from dpp-B and dpp-D are located in the axial positions at Cd2,
ing mode. Along the chains, the Cdꢀ ꢀ ꢀCd internuclear through-li-
gand distance is 7.141 Å. Individual [Cd(hmph)]n chains are
strutted by anti–anti conformation dpp tethers (torsion an-
gles = 175.6° and 178.2°) into [Cd(hmph)(dpp)]n coordination poly-
mer 4-connected (4,4) grid layers (Fig. 2b). The through-ligand
Cdꢀ ꢀ ꢀCd distance across the splayed open dpp tethers is 13.663 Å.
Because of the cis orientation of the pyridyl donors at each cad-
mium atom, a sawtooth grid morphology is adopted. The peak-
to-peak ‘‘wavelength’’ of the grid pattern is 13.537 Å. Two subtly
different types of grid window are evident in the layers in 1, brack-
eted by ‘‘concave’’ and ‘‘convex’’ pairs of dpp ligands, with Cdꢀ ꢀ ꢀCd
through-space distances of 14.72 ꢃ 16.08 or 14.50 ꢃ 16.28 Å.
Adjacent [Cd(hmph)(dpp)]n coordination polymer layers stack
along the a crystal direction, with hmph phenyl rings interdigitat-
ing from above and below into apertures within a single grid
(Fig. S1). Crystal packing forces and non-classical C–Hꢀ ꢀ ꢀO interac-
Fig. 3. Coordination environments of 2. The numbering scheme is the same as in Table 3.

594
G.A. Farnum et al. / Inorganica Chimica Acta 376 (2011) 590–597
Table 3
by nitrogen donors from dpp-A and dpp-F, while an oxygen atom
from a hmph-A acetate group, two aqua ligands, and a pyridyl do-
nor from another dpp-F ligand are located in the equatorial posi-
Selected bond distance (Å) and angle (°) data for 2.
Cd1–O7
2.281(4)
2.312(4)
2.339(5)
2.348(5)
2.386(5)
2.391(4)
2.239(4)
2.318(4)
2.381(5)
2.402(5)
2.408(5)
2.429(4)
2.262(4)
2.280(4)
2.344(5)
2.346(5)
2.365(5)
2.371(4)
N9–Cd1–N6#3
N2–Cd1–N6#3
O1–Cd2–O6#4
O1–Cd2–N3
170.14(17)
86.46(16)
171.56(16)
87.62(16)
87.74(16)
100.28(17)
83.88(17)
171.00(18)
87.49(17)
85.08(16)
84.88(17)
91.11(17)
132.05(17)
55.22(15)
92.26(16)
85.67(15)
140.29(16)
89.93(15)
96.63(16)
91.31(19)
89.56(15)
174.90(18)
93.79(17)
94.64(16)
92.22(19)
168.20(17)
82.77(18)
174.21(15)
84.28(15)
83.65(16)
96.19(15)
85.50(16)
Cd1–O3
tions. At both Cd2 and Cd3, the nitrogen donors lie in
a
Cd1–N8#1
Cd1–N9
meridional orientation. Bond lengths and angles within the various
coordination environments in 2 are listed in Table 3.
With the exception of dpp-E, which binds to Cd1 as a pendant
monodentate ligand with a curled gauche–anti conformation
Cd1–N2#2
Cd1–N6#3
Cd2–O1
O6#4–Cd2–N3
O1–Cd2–N7
O6#4–Cd2–N7
N3–Cd2–N7
Cd2–O6#4
Cd2–N3
(torsion angles = 59.5°/168.4°), all other dpp ligands in 2 serve as
O1–Cd2–N5
dipodal tethers, linking cadmium atoms into complicated
Cd2–N7
O6#4–Cd2–N5
N3–Cd2–N5
12n+
[Cd6(H2O)4(dpp)11 n
]
subnets, which are 5-fold interpenetrated
Cd2–N5
Cd2–O5#4
Cd3–O4
N7–Cd2–N5
(Fig. S2). The anti–anti conformation dpp-A ligands (torsion an-
gles = 172.5°/174.3°) join Cd1 and Cd3 with a metal–metal inter-
nuclear distance of 12.839 Å, while anti–anti conformation dpp-D
ligands (torsion angles = 177.3°/174.7°) connect Cd1 and Cd2
atoms at an inter-nuclear distance of 13.174 Å. Cd1 and Cd2 atoms
are also connected by twisted gauche–anti conformation dpp-C
ligands (torsion angles = 72.0°/178.2°), at a slightly shorter inter-
nuclear distance of 12.742 Å. Neighboring Cd3 atoms are linked
by pairs of gauche–anti conformation dpp-F ligands (torsion
O1–Cd2–O5#4
O6#4–Cd2–O5#4
N3–Cd2–O5#4
N7–Cd2–O5#4
N5–Cd2–O5#4
O4–Cd3–O9
Cd3–O9
Cd3–N1
Cd3–N11
Cd3–N12#5
Cd3–O10
O4–Cd3–N1
O9–Cd3–N1
O7–Cd1–O3
172.95(14)
90.36(16)
96.68(16)
88.07(15)
91.43(15)
96.65(18)
84.03(15)
88.93(15)
174.14(17)
84.89(16)
95.72(15)
83.69(15)
92.43(17)
O7–Cd1–N8#1
O3–Cd1–N8#1
O7–Cd1–N9
O4–Cd3–N11
O9–Cd3–N11
N1–Cd3–N11
O4–Cd3–N12#5
O9–Cd3–N12#5
N1–Cd3–N12#5
N11–Cd3–N12#5
O4–Cd3–O10
O9–Cd3–O10
N1–Cd3–O10
N11–Cd3–O10
N12#5–Cd3–O10
angles = 40.9°/175.3°), which provide
a
Cdꢀ ꢀ ꢀCd distance of
O3–Cd1–N9
12.646 Å. Pairs of Cd2 atoms are further conjoined by gauche–
gauche dpp-B ligands, whose torsion angles are restricted by
crystallographic symmetry to be identical (47.7°). Among all the
dpp-bridged contacts in 2, these latter interactions are the shortest
N8#1–Cd1–N9
O7–Cd1–N2#2
O3–Cd1–N2#2
N8#1–Cd1–N2#2
N9–Cd1–N2#2
O7–Cd1–N6#3
O3–Cd1–N6#3
N8#1–Cd1–N6#3
(9.117 Å) due to the very curled dpp-B conformation. The resulting
12n+
[Cd6(H2O)4(dpp)11 n
]
subnet has prodigious incipient voids,
measuring ꢂ51 Å ꢃ 57 Å from closest Cdꢀ ꢀ ꢀCd contacts, which
allow the mutual 5-fold interpenetration of identical subnets.
In order to understand the underlying topology of these cat-
ionic nets, the Cd1 atoms are considered 3-connected nodes,
linked by dpp ligands to one Cd3 atom and two Cd2 atoms,
and the Cd2 atoms are also treated as 3-connected nodes, linked
by dpp ligands to two Cd1 atoms and another Cd2 atom. Each
Cd3 atom is only 2-connected, joined by a single tether (dpp-A)
Symmetry equivalent positions: #1 x, ꢁy + 2, z + 1/2 ; #2 x, ꢁy + 1, z ꢁ 1/2 ; #3 ꢁx,
y + 1, ꢁz + 1/2; #4 x, y ꢁ 1, z; #5 ꢁx + 1/2, ꢁy + 3/2, ꢁz + 1.
with the equatorial plane filled by a donor from dpp-C, an oxygen
atom from a monodentate carboxylate group from hmph-A, and a
chelating carboxylate from hmph-B. At Cd3, axial sites are taken up
Fig. 4. Schematic representation of the 5-fold interpenetrated 4.142 cds-a [Cd6(H2O)4(dpp)11 12n+ 3-D cationic subnets within 2. Cd1 and Cd2 atoms are rendered as spheres.
]
n

G.A. Farnum et al. / Inorganica Chimica Acta 376 (2011) 590–597
595
to Cd1 atom, and by a pair of dpp-F ligands to one other Cd3
3-connected phase {[Ag6Cl(3-amino-1,2,4-triazolate)4]OHꢀ6H2O}n
atom. Therefore the Cd3 atoms should just be considered linkers,
[28], which is based on face-sharing Ag8( 8-Cl) cluster nodes,
l
12n+
instead of connecting nodes, within the [Cd6(H2O)4(dpp)11 n
]
but its dia-f net is uninodal and has a Vertex symbol of
subnet. From this perspective, the resulting 3-connected binodal
net has a 4.142 cds-a topology (Fig. 4), with a Vertex symbol of
[4.144.144][4.148.148] as calculated by TOPOS [27]. The same
4.142 point symbol can be invoked for the 5-fold interpenetrated
[4.1412.1412]. To date, there are only two known examples of
the 3-connected cds-a net in chemical systems, [Cu2Co(1,3,5-
tris(pyrazol-l-ylmethyl)benzene)2Cl6(H2O)3]n [29] and [Mn(ethy-
lenediamine)2Ga2S4]n [30]. Neither of these cases exhibit any
Fig. 5. [Cd3(hmph)2(H2O)2]n chain motif in 2.
Fig. 6. {[Cd6(hmph)4(dpp)11(H2O)4](ClO4)4ꢀ4H2O}n 3-D network in 2. Perchlorate ions and water molecules occupy the extra-framework space.
Fig. 7. Schematic perspective of the 3,3,5,5-connected tetranodal self-penetrated net in 2. The blue, purple, and magenta spheres represent Cd1, Cd2, and Cd3 atom nodes,
respectively. The black spheres represent the hmph-A 3-connected ligand nodes. (For interpretation of the references to color in this figure legend, the reader is referred to the
web version of this paper.)

596
G.A. Farnum et al. / Inorganica Chimica Acta 376 (2011) 590–597
Table 4
Hydrogen bonding distance (Å) and angle (°) data for 2.
D–Hꢀ ꢀ ꢀA
d(Hꢀ ꢀ ꢀA)
2.09(2)
2.11
1.94(3)
1.97(4)
1.89(2)
1.89(2)
\DHA
d(Dꢀ ꢀ ꢀA)
Symmetry transformation for A
ꢁx + 1/2, ꢁy + 1/2, ꢁz + 1
O1W–H1WAꢀ ꢀ ꢀO12
O1W–H1WBꢀ ꢀ ꢀO11
O9–H9Aꢀ ꢀ ꢀO2
174(3)
179.7
162(6)
147(6)
167(5)
163(5)
2.931(9)
2.955(10)
2.767(6)
2.720(6)
2.731(6)
2.716(6)
O9–H9Bꢀ ꢀ ꢀO8
x, y ꢁ 1, z
x, y ꢁ 1, z
O10–H10Gꢀ ꢀ ꢀO1W
O10–H10Hꢀ ꢀ ꢀO8
interpenetration, so the 5-fold interpenetration of cds-a subnets
in 2 is unprecedented.
12n+
The 5-fold interpenetrated [Cd6(H2O)4(dpp)11 n
then conjoined into a [Cd6(hmph)4(H2O)4(dpp)11 n
tridentate hmph-A ligands with a l3
j3-O:O0:O00 binding mode and
by hmph-B ligands with a chelating/monodentate l2
j3-O,O0:O00
]
subnets are
]
4n+ lattice by exo-
-
-
binding mode. The hmph-A ligands connect Cd1, Cd2, and Cd3
atoms, with their acetate arms bridging Cd1 and Cd3 atoms, and
their short carboxylate arms binding to Cd2 atoms in a monodentate
fashion. Meanwhile the hmph-B ligands chelate via their acetate
carboxylate groups to Cd2 atoms, while their short carboxylate arms
act as monodentate donors to Cd1 atoms. The hmph ligands and cad-
mium atoms within the net of 2 form [Cd3(hmph)2(H2O)2]n chain
motifs (Fig. 5). A self-penetrated network is therefore formed the
covalent linkage of separate interpenetrated [Cd6(H2O)4
(dpp)11 n
Topological analysis of this complicated [Cd6(hmph)4
]
12n+ subnets through the hmph ligands (Fig. 6).
Fig. 8. Emission spectra of 1 and 2.
4n+
(H2O)4(dpp)11 n
]
net was undertaken by treating the exotriden-
tate hmph-A ligands as 3-connected nodes and the exobidentate
hmph-B as simple linkers. In turn, the Cd1 atoms and Cd2 atoms
now become 5-connected nodes because of a new connection to
an hmph-A node and linkage through hmph-B. Instead of acting
as linkers, Cd3 atoms now serve as 3-connected nodes because of
the additional connection to an hmph-A ligand node. A schematic
view of the resulting 3,3,5,5-connected tetranodal net is shown in
Fig. 7 with dpp connections in blue and hmph connections in red.
The Schläfli symbol for this self-penetrated network is
(729)(7.102)(3.4.5.73.82.9.10)(32425.6.738), with the individual
symbols referring to the hmph-A, Cd3, Cd1, and Cd2 nodes, respec-
tively. All dpp ligands with the exception of dpp-E and the
monodentate dpp-B engage in self-penetration through shortest
8-membered, 9-membered, and 10-membered circuits within the
network of 2. In one of the self-penetration mechanisms, the
dpp-C ligands linking Cd1 and Cd2 atoms from two different
8-membered circuits penetrate through a third 8-membered cir-
cuit, while all three circuits are joined through hmph-B linkers. A
close-up view of the mutual self-penetration of the 8-membered
circuits is shown in Fig. S3. Full details of the topological analysis
can be found in the Supplementary information.
by comparison with other d10 metal coordination polymers with
aromatic ligands [32], the emissive behavior of 1 and 2 plausibly
arises from ligand-centered
tronic transitions within the pyridyl rings of the dpp ligands and/
or the phenyl rings of the hmph ligands. The similarity in the emis-
sion profiles is likely caused by the presence of the same aromatic
ligands, despite some differences in carboxylate binding mode.
p– p–n molecular orbital elec-
p⁄ or
5. Conclusions
Oxoanion occlusion in luminescent cadmium homophthalate
coordination polymers with flexible dipyridylpropane coligands
results in a switch from a layered grid network to a complicated
self-penetrated framework. The conformational flexibility of the
dpp trimethylene tethers allows self-assembly of cationic subnets
with very large apertures in 2, generating a simple 3-connected
5-fold interpenetrated cds-a network. Self-penetration is then
achieved in 2 via bridging and exotridentate dicarboxylate ligands.
The self-penetrated network of 2 shows pillaring of interpene-
trated subnets and conformationally flexible ligands, two features
in common with other reported self-penetrated networks.
Although some approaches towards self-penetrated networks have
been identified, their deliberate design is as yet an unrealized goal.
Unligated perchlorate counteranions and water molecules oc-
cupy the tight solvent-accessible extra-framework space within
the self-penetrated net, which comprises 13.2% of the unit cell vol-
ume according to PLATON [31]. Supramolecular aggregations of
perchlorate ion pairs through water molecule dimers, or pairs of
isolated water molecules, are formed via hydrogen bonding
(Table 4).
Acknowledgments
The authors gratefully acknowledge the donors of the American
Chemical Society Petroleum Research fund for financial support of
this work. We thank Ms. Amy Pochodylo for experimental
assistance.
4.4. Luminescent properties
Irradiation of crystalline samples of complexes 1 and 2 with
ultraviolet light (kex = 375 nm) caused moderately intense blue-
violet visible light emission with kmax values of 449 and 443 nm,
respectively (Fig. 8). These emission maxima correspond closely
to those produced by the free homophthalic acid (445 nm) or
dpp ligands (460 nm) under the same excitation wavelength. Thus,
Appendix A. Supplementary material
CCDC 811778 and 811777 contain the supplementary crystallo-
graphic data for 1 and 2. These data can be obtained free of

G.A. Farnum et al. / Inorganica Chimica Acta 376 (2011) 590–597
597
(b) L. Yi, B. Ding, B. Zhao, P. Cheng, D. Liao, S. Yan, Z. Jiang, Inorg. Chem. 43
(2004) 33;
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.ica.2011.07.029.
(c) G.A. Farnum, R.L. LaDuca, Cryst. Growth. Des. 10 (2010) 1897.
[13] V.A. Blatov, L. Carlucci, G. Ciani, D.M. Proserpio, CrystEngComm 6 (2004) 377.
[14] B. Rather, M.J. Zaworotko, Chem. Commun. (2003) 830.
[15] X.L. Wang, C. Qin, E.B. Wang, Z.M. Su, L. Xu, S.R. Batten, Chem. Commun. (2005)
4789.
[16] E. Shyu, R.M. Supkowski, R.L. LaDuca, Inorg. Chem. 48 (2009) 2723.
[17] L. Rajput, K. Biradha, Cryst. Growth. Des. 9 (2009) 3848.
[18] X.L. Wang, C. Qin, E.B. Wang, Z.M. Su, Chem. Eur. J. 12 (2006) 2680.
[19] M. Bi, G. Li, Y. Zou, Z. Shi, S. Feng, Inorg. Chem. 46 (2007) 604.
[20] V. Niel, A.L. Thompson, A.E. Goeta, C. Enachescu, A. Hauser, A. Galet, M.C.
Munoz, J.A. Real, Chem. Eur. J. 11 (2005) 2047.
References
[1] L.J. Murray, M. Dinca, J.R. Long, Chem. Soc. Rev. 38 (2009) 1294 (and references
therein).
[2] J.R. Li, R.J. Kuppler, H.C. Zhou, Chem. Soc. Rev. 38 (2009) 1477 (and references
therein).
[3] (a) M. Plabst, L.B. McCusker, T. Bein, J. Am. Chem. Soc. 131 (2009) 18112;
(b) Y. Liu, V.C. Kravtsov, M. Eddaoudi, Angew. Chem., Int. Ed. 47 (2008) 8446;
(c) F. Nouar, J. Eckert, J.F. Eubank, P. Forster, M. Eddaoudi, J. Am. Chem. Soc. 131
(2009) 2864.
[21] SAINT, Software for Data Extraction and Reduction, Version 6.02, Bruker AXS,
Inc., Madison, WI, 2002.
[22] SADABS, Software for Empirical Absorption Correction, Version 2.03, Bruker AXS,
Inc., Madison, WI, 2002.
[4] (a) J. Lee, O.K. Farha, J. Roberts, K.A. Scheidt, S.T. Nguyen, J.T. Hupp, Chem. Soc.
Rev. 38 (2009) 1450 (and references therein);
[23] G.M. Sheldrick, SHELXTL, Program for Crystal Structure Refinement, University of
Gottingen, Gottingen, Germany, 1997.
(b) L. Ma, C. Abney, W. Lin, Chem. Soc. Rev. 38 (2009) 1248 (and references
therein).
[24] M. Kurmoo, C. Estournes, Y. Oka, H. Kumagai, K. Inoue, Inorg. Chem. 44 (2005)
217.
[5] M.D. Allendorf, C.A. Bauer, R.K. Bhakta, R.T. Houk, Chem. Soc. Rev. 38 (2009)
1330 (and references therein).
[25] E. Shyu, M.A. Braverman, R.M. Supkowski, R.L. LaDuca, Inorg. Chim. Acta 362
(2009) 2283.
[6] S.R. Batten, R. Robson, Angew. Chem., Int. Ed. 37 (1998) 1460.
[7] (a) S.A. Bourne, A. Mondal, M.J. Zaworotko, Cryst. Eng. 4 (2001) 25;
(b) B. Moulton, J. Lu, R. Hajndl, S. Hariharan, M.J. Zaworotko, Angew. Chem., Int.
Ed. 41 (2002) 2821;
(c) S.Y. Yang, L.S. Long, R.B. Huang, L.S. Zheng, Chem. Commun. (2002) 472;
(d) R.H. Groeneman, L.R. MacGillivray, J.L. Atwood, Inorg. Chem. 38 (1999) 208;
(e) J. Tao, M.L. Tong, X.M. Chen, Dalton Trans. (2000) 3669;
(f) K. Davies, S.A. Bourne, L. Öhström, C.L. Oliver, Dalton Trans. 39 (2010) 2869.
[8] J. Zhang, X. Huang, X. Chen, Chem. Soc. Rev. 38 (2009) 2385 (and references
therein).
[9] U. Garcia-Couceiro, O. Castillo, J. Cepeda, M. Lanchas, A. Luque, S. Perez-Yañez,
P. Roman, D. Vallejo-Sanchez, Inorg. Chem. 49 (2010) 11346.
[10] P.K. Chen, Y.X. Che, Y.M. Li, J.M. Zheng, J. Solid State Chem. 179 (2006) 2656.
[11] M. Eddaoudi, H. Li, O.M. Yaghi, J. Am. Chem. Soc. 122 (2000) 1391.
[12] (a) S. Noro, R. Kitaura, M. Kondo, S. Kitagawa, T. Ishii, H. Matsuzaka, M.
Yamashita, J. Am. Chem. Soc. 124 (2002) 2568;
[26] J. He, Y. Wang, W. Bi, Y. Wang, R. Cao, Polyhedron 25 (2006) 1239.
[27] V.A. Blatov, A.P. Shevchenko, V.N. Serezhkin, J. Appl. Crystallogr. 33 (2000)
1193.
[28] J. Zhang, Y. Lin, W. Zhang, X. Chen, J. Am. Chem. Soc. 127 (2005) 14162.
[29] W.K. Chang, S.C. Sheu, G.S. Lee, Y. Wang, T. Ho, Y. Lin, J. Chem. Soc., Dalton
Trans. (1993) 687.
[30] P. Vaquiero, Inorg. Chem. 45 (2006) 4150.
[31] A.L. Spek, PLATON, A Multipurpose Crystallographic Tool, Utrecht University,
Utrecht, The Netherlands, 1998.
[32] (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;
(c) S. Wang, Y. Hou, E. Wang, Y. Li, L. Xu, J. Peng, S. Liu, C. Hu, New J. Chem. 27
(2003) 1144;
(d) L.G. Beauvais, M.P. Shores, J.R. Long, J. Am. Chem. Soc. 122 (2000) 2763.