Triply interpenetrating coordination polymers based on paddle-wheel type secondary-building units

Article abstract of DOI:10.1016/S0020-1693(03)00246-9

Triply interpenetrating 3-dimensional nickel and cobalt coordination polymers, [M₃(2,6-NDC)₃(bipy)_1.5], were prepared from metal nitrate {M(NO₃)₂·6H ₂O}, 2,6-naphthalenedicarboxylic acid (2,6-NDCH₂), and 4,4′-bipyridine (bipy) under hydrothermal (M=Ni) or water-benzene hydro(solvo)thermal (M=Co) conditions. Both polymers have the same secondary building units (SBUs) of paddle-wheels of the type [M₂(CO ₂R)₄], which are composed of two metals and four di(monodentate) bridging carboxylates. On the other hand, the hydrothermal reaction of Co(NO₃)₂·6H₂O with 1,3-benzenedicarboxylic acid (1,3-BDCH₂) and trans-1,2-bis(4-pyridyl)ethylene (bipyen) gave a 2-dimensional polymer [Co(1,3-BDC)(bipyen)]. The structures of all products were determined by X-ray diffraction.

Full text of DOI:10.1016/S0020-1693(03)00246-9

Inorganica Chimica Acta 353 (2003) 151ꢁ158
/
www.elsevier.com/locate/ica
Triply interpenetrating coordination polymers based on paddle-wheel
type secondary-building units of M2(CO2R)4:
[Ni3(2,6-NDC)3(bipy)1.5], [Co3(2,6-NDC)3(bipy)1.5], and
[Co(1,3-BDC)(bipyen)] (2,6-NDCꢀ
1,3-BDCꢀ1,3-benzenedicarboxylate; bipyꢀ
bipyenꢀtrans-1,2-bis(4-pyridyl)ethylene)
/
2,6-naphthalenedicarboxylate;
/
/
4,4?-bipyridine;
/
Soon W. Lee *, Hye Jin Kim, Yeon Kyoung Lee, Kyungsoo Park, Jung-Ho Son,
Young-Uk Kwon
Department of Chemistry (BK21), Institute of Basic Science, Sungkyunkwan University, Natural Science Campus, Suwon 440-746, Republic of Korea
Received 20 November 2002; accepted 28 February 2003
Abstract
Triply interpenetrating 3-dimensional nickel and cobalt coordination polymers, [M3(2,6-NDC)3(bipy)1.5], were prepared from
metal nitrate {M(NO3)2×
(MꢀNi) or waterꢁbenzene hydro(solvo)thermal (Mꢀ
(SBUs) of paddle-wheels of the type [M2(CO2R)4], which are composed of two metals and four di(monodentate) bridging
carboxylates. On the other hand, the hydrothermal reaction of Co(NO3)2×6H2O with 1,3-benzenedicarboxylic acid (1,3-BDCH2)
/
6H2O}, 2,6-naphthalenedicarboxylic acid (2,6-NDCH2), and 4,4?-bipyridine (bipy) under hydrothermal
/
/
/
Co) conditions. Both polymers have the same secondary building units
/
and trans-1,2-bis(4-pyridyl)ethylene (bipyen) gave a 2-dimensional polymer [Co(1,3-BDC)(bipyen)]. The structures of all products
were determined by X-ray diffraction.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Triply interpenetrating; Coordination polymers; Paddle wheels; SBU
1. Introduction
become a fundamental tool in the rational design of
crystalline architectures (crystal engineering) [6].
Coordination polymers with a variety of cavities or
channels are currently under intensive studies because of
their useful properties such as chemical separations,
sorption, and catalysis, as well as potential applications
Linear spacers such as carboxylates [7,8] and pyridyls
[9] frequently provide rigid grid-type frameworks with
large voids although the carboxylates tend to form
relatively more rigid frameworks due to the potential
bidentate coordination of their carboxylate groups. In
preparing the frameworks based on those linear spacers,
the phenomenon of interpenetration often hinders the
formation of useful coordination polymers at least in
terms of porosity [10]. Although interpenetration in
some cases has been proposed as a means of increasing
the dimensionality and structural rigidity of coordina-
tion polymers [3,4], it has been a plague to constructing
a desired high-dimensional network with large voids.
in functional materials [1ꢁ5]. In designing 1-, 2-, and 3-
/
D extended porous coordination polymers, the selection
of appropriate ligands is crucial to determining the
structural outcome of target polymers. In this context,
the concept of ‘node-spacer’, in which the node corre-
sponds to a metal center and the spacer to a ligand, has
* Corresponding author. Tel.: ꢂ
7075.
E-mail address: swlee@chem.skku.ac.kr (S.W. Lee).
/
82-31-290 7066; fax: ꢂ82-31-290
/
Recently, from the study on M-carboxylate (Mꢀ
/Co,
Ni, Cu, Zn; carboxylateꢀ1,4-benzenedicarboxylate,
/
0020-1693/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00246-9

152
S.W. Lee et al. / Inorganica Chimica Acta 353 (2003) 151ꢁ158
/
1,4-azidobenzoate, 1,3,5-benzenetricarboxylate, 1,3,5,7-
adamantanetetracarboxylate) coordination polymers,
Yaghi and co-workers found that the rodlike carbox-
ylate has a great tendency to form interpenetrating
frameworks when either large guests or hydrogen-
bonded guest aggregates are absent [11]. In addition,
longer ligands compared with shorter ones will generally
favor the formation of interpenetrating over non-inter-
penetrating polymers [10,12].
2. Experimental
Co(NO3)2×6H2O, Ni(NO3)2×
BDCH2, bipy, and bipyen were purchased. IR spectra
were recorded with a Nicolet 320 FTIR spectrophot-
ometer. Elemental analyses were performed with
EA1110 (CE instrument, Italy) by the Korea Basic
Science Institute. TGA analysis was conducted on a
TA4000/SDT 2960 instrument.
/
/6H2O, 2,6-NDCH2, 1,3-
Secondary building units (SBUs) are molecular com-
plexes and clusters, in which ligand coordination modes
and metal coordination environments are utilized to
transform these fragments into extended networks using
multidentate ligands [8]. The SBUs have long been
fundamental concepts in zeolite chemistry [13,14], and
now draw considerable attention as a firm basis of
synthetic strategies for constructing high-dimensional
coordination polymers. For example, Yaghi and co-
workers used the paddle-wheel cluster of the type
2.1. Preparation of [Ni3(2,6-NDC)3(bipy)1.5] (1)
A mixture of Ni(NO3)2×
/
6H2O (0.135 g, 0.403 mmol),
2,6-NDCH2 (0.100 g, 0.403 mmol), bipy (0.072 g, 0.403
mmol), and H2O (6.0 ml, 0.333 mol) in the mole ratio of
1:1:1: 600 was heated in a 23-ml capacity Teflon-lined
reaction vessel at 180 8C for 2 days, and then cooled to
room temperature. The green crystalline product was
collected by filtration, washed with H2O (2ꢃ
/5 ml),
EtOH (3ꢃ5 ml), and acetone (2ꢃ5 ml), and then air-
/
/
[M2(OCOR)4] (MꢀCu or Zn) as a square-planar SBU
/
dried to give 0.081 g (0.077 mmol, 57%) of [Ni3(2,6-
BDC)3(bipy)1.5]. Anal. Calc. for C51H30N3Ni3O12: C,
58.18; H, 2.87; N, 3.99. Found: C, 57.99; H, 2.84; N,
to prepare porous polymers with large voids and
channels [8]. In addition, there are currently two general
synthetic strategies to prepare non-interpenetrating
square-grid (or rectangular-grid) coordination polymers
and to control the size of their channels: (1) the use of
bipyridine-type ligands of different lengths [15,16]; and
(2) the modification of the ligand to affect the shape of
the grid [17].
4.05%. IR (KBr): 1688 (m, Cꢀ
(m, CꢀO), 1490 (m, CꢀO), 1421 (s, Cꢀ
(s), 784 (s), 645 (s), 564 (s), 501 (s) cmꢄ1
/
O), 1618 (s, Cꢀ
/
O), 1537
/
/
/
O), 921 (s), 821
.
2.2. Preparation of [Co3(2,6-NDC)3(bipy)1.5] (2)
This polymer was prepared similar to 1, except that a
We recently prepared several coordination polymers
based on carboxylates or bipyridyls by hydrothermal
benzeneꢁ
Co(NO3)2×
/
water mixture was used as
a solvent.
6H2O (0.100 g, 0.344 mmol), 2,6-NDCH2
reactions [18ꢁ21]. We now become interested in prepar-
/
/
ing coordination polymers based on a mixed-ligand
system possessing dicarboxylates {2,6-naphthalenedicar-
boxylate (2,6-NDC) and 1,3-benzenedicaboxylates (1,3-
BDC)} and linear dipyridyls {trans-1,2-bis(4-pyridy-
l)ethylene (bipyen) and 4,4?-bipyridine (bipy)}. We
report here two triply-interpenetrating coordination
polymers formed by the bipyridyl linking of square-
grid nets based on paddle-wheel type SBUs of
(0.025 g, 0.115 mmol), bipy (0.054 g, 0.344 mmol),
benzene (1.53 ml, 17.18 mmol), and H2O (6 ml, 0.333
mol) in the mole ratio of 3:1:3:150:2900 was heated at
180 8C for 3 days. The black crystalline product of
[Co3(2,6-NDC)3(bipy)1.5] along with orange powdery
impurity of unknown nature was collected by filtration
and air-drying. The desired product was mechanically
separated from the impurity. The yield was 52% based
on cobalt. Anal. Calc. for C51H30Co3N3O12: C, 59.41;
H, 2.26; N, 3.92; Found: C, 58.45; H, 2.83; N, 3.94%. IR
[M2(CO2R)4],
[Ni3(2,6-NDC)3(bipy)1.5
]
(1)
and
H2O (2), which were prepared
[Co3(2,6-NDC)3(bipy)1.5]×
/
from metal nitrate, NDCH2, and bipy by hydrothermal
or hydro(solvo)thermal reactions. As expected, the
variation in the coordination angle of the dicarboxylate
led to a fundamental change in the structural outcome
of the resulting polymer. When we treated a bent
(Nujol): 1619 (s, Cꢀ
/
O), 1409 (vs, Cꢀ
/
O), 921 (m), 818
.
(m), 782 (vs), 642 (w), 567 (w), 493 (vs) cmꢄ1
2.3. Preparation of [Co(1,3-BDC)(bipyen)] (3)
A mixture of Co(NO3)2×6H2O (0.10 g, 0.344 mmol),
1,3-BDCH2 (0.10 g, 0.602 mmol), bipyen (0.050 g, 0.274
mmol), and H2O (6.0 ml, 333 mmol) in the mole ratio of
1:1.75:0.80:968 was heated at 180 8C for 2 days to give
0.074 g (0.183 mmol, 67%) of [Co(1,3-BDC)(bipyen)].
Anal. Calc. for C20H14CoN2O4: C, 59.27; H, 3.48; N,
6.91. Found: C, 59.52; H, 3.27; N, 6.89%. IR (KBr):
dicarboxylate (1,3-BDCH2; coordination angle :
instead of a linear counterpart (2,6-NDCH2; coordina-
tion angle :1808) with Co(NO3)2×6H2O and bipyen, a
/
1208)
/
/
/
2-dimensional polymer [Co(1,3-BDC)(bipyen)] (3) was
formed. In this paper, we would like to show: (i) square-
grid networks based on the paddle-wheel type SBUs
linked to triply interpenetrating polymers; and (ii) a
coordination-angle dependence of the structural out-
come of the resulting polymer.
3433 (br), 2924 (s), 1611 (s, Cꢀ
/
O), 1397 (s, Cꢀ
/O), 1074
(s), 832 (s), 718 (s), 554 (s), 459 (s) cmꢄ1
.

S.W. Lee et al. / Inorganica Chimica Acta 353 (2003) 151ꢁ
/158
153
2.4. X-ray structure determination
Table 1
X-ray data collection and structure refinements
X-ray data were collected with the use of either a
Bruker CCD SMART diffractometer (polymer 1) or a
Siemens P4 diffractometer (polymers 2 and 3) equipped
with a Mo X-ray tube. Intensity data were empirically
corrected for absorption with c-scan data, except for
polymer 1 for which absorption corrections were made
with SADABS. All calculations were carried out with use
of the SHELXTL programs [22]. All structures were
solved by direct methods. All non-hydrogen atoms
were refined anisotropically. All hydrogen atoms were
generated in ideal positions and refined in a riding
mode.
Polymer 1
C51H30N3O12Ni3 C51H30Co3N3O12 C20H14CoN2O4
Polymer 2
polymer 3
Empirical for-
mula
Formula
weight
1052.91
153(2)
1053.57
296(2)
405.26
296(2)
triclinic
Temperature
(K)
Crystal system monoclinic
monoclinic
C2
¯
P1
Space group
˚
C2
/
A (A)
˚
17.159(4)
19.747(5)
13.709(4)
90.000(0)
95.935(4)
90.000(0)
4620(2)
4
17.209(4)
19.865(5)
13.880(11)
90.000(0)
95.81(4)
90.000(0)
4721(4)
4
9.729(2)
10.067(1)
10.341(1)
80.13(1)
85.98(2)
68.59(1)
929.0(3)
2
B (A)
˚
C (A)
a (8)
b (8)
A green crystal of 1, shaped as a cube of approximate
0.30ꢃ
0.28 mm3, was used. The unit-
g (8)
3
V (A )
˚
dimensions 0.32ꢃ
/
/
Z
cell parameters suggested a monoclinic unit cell with
three possible space groups: C2, C2/m and Cm. A
statistical analysis of reflection intensities suggested a
non-centrosymmetric space group, and the structure
analysis converged only in C2. A black crystal of 2,
Dcalc (g cmꢄ3
)
1.319
1.278
1.449
1.109
1.482
0.951
m (mmꢄ1
F(000)
Tmin
)
2148
0.2608
0.3013
2136
0.2192
0.3293
414
0.7231
0.9250
Tmax
2u Range (8)
Scan type
3.5ꢁ/50
3.5ꢁ/50
3.5ꢁ50
/
shaped as a block of approximate dimensions 0.41ꢃ
/
v
v
v
0.24ꢃ
/
0.21 mm3, was placed in a sealed glass capillary.
Scan speed
Reflections
measured
variable
9795
variable
4403
variable
3474
The structure analysis of 2 was also successful only in
C2. A pink crystal of 3, shaped as a block of
0.18ꢃ
0.12 mm3, was
used. This crystal belongs to the triclinic system and was
/
Reflections un- 5971
ique
4254
3189
622
3262
2471
245
approximate dimensions 0.38ꢃ
/
Reflections
with I ꢀ2s(I)
Parameters re- 556
4066
¯
solved in the centrosymmetric space group P1:
Details on crystal data and refinement details are
given in Table 1. Selected bond lengths and bond angles
are given in Tables 2 and 3.
/
/
fined
Max., in Dr (e 0.728
0.900
0.277
ꢄ3
˚
A
)
Min., in Dr (e
ꢄ
/
0.432
ꢄ
/
0.564
ꢄ0.545
/
ꢄ3
˚
A
Goodness-of- 0.978
fit on F2
)
1.073
1.023
3. Results and discussion
R
0.0389
0.0903
0.0532
0.1307
0.0487
0.1046
a
3.1. Formation of interpenetrating polymers
wR2
a
wR2ꢀ
/
a[w(Fo2ꢄ
/
Fc2)2]/a[w(Fo2)2]1/2
.
Triply interpenetrating Ni and Co coordination poly-
mers, [M3(2,6-NDC)3(bipy)1.5] (Mꢀ
were prepared from metal nitrate {M(NO3)2×
2,6-NDCH2, and bipy under hydrothermal or hy-
dro(solvo)thermal conditions (Eq. (1)). The crystalline
products have been characterized by elemental analysis,
IR spectroscopy, thermal gravimetric analysis (TGA),
and X-ray crystallography.
/
Ni (1) or Co (2)),
to be pure from the looks. We speculated that the poor
solubility of bipy in water among many other possible
causes was mainly responsible for the poor crystalline
state of polymer 2. Therefore, we decided to add
benzene to the reaction mixture in order to facilitate
the dissolution of bipy. Later on, we have found that
reactions starting with a mixture of a benzene solution
/6H2O},
M(NO3)2 ×6H2Oꢂ2; 6-NDCH2 ꢂbipy
of bipy and an aqueous solution of Co(NO3)2×
/H2O and
0 [M3(2; 6-NDC)3(bipy)1:5
(MꢀNi (1) or Co (2))
]
(1)
2,6-NDCH2 give the highest yields of 2. This observa-
tion strongly supports our assumption that the low
solubility of bipy hinders the formation of high-quality
crystals. However, it still remains unclear why the
similar reaction for 1 without added benzene produced
single crystals. At any rate, because of the immiscibility
of benzene and water, the formation of 2 presumably
occurs at the interfaces between the two solvents. A
The preparation of polymer 2 deserves some con-
siderations. Contrary to the successful synthesis of
polymer 1 by the hydrothermal reaction, the attempted
synthesis of 2, a cobalt analog of 1, under the same
conditions did not produce single crystals suitable for
structure determination although the product appeared

154
S.W. Lee et al. / Inorganica Chimica Acta 353 (2003) 151ꢁ158
/
Table 2
Table 3
˚
˚
Selected bond lengths (A) and bond angles (8) in 1 and 2
Selected bond lengths (A) and bond angles (8) in 3
Bond lengths
Bond lengths
Ni1ꢁ
Ni2ꢁ
Ni3ꢁ
Ni1ꢁ
Ni2ꢁ
Ni3ꢁ
Ni1ꢁ
Ni2ꢁ
Ni3ꢁ
/
O5
1.990(9)
2.006(8)
2.008(9)
2.012(8)
2.014(8)
2.015(8)
2.654(2)
2.028(9)
2.645(3)
Co1ꢁ
Co1ꢁ
Co1ꢁ
Co1ꢁ
Co1ꢁ
Co1ꢁ
/
O2#1
N2#3
O1
2.014(3)
2.169(3)
2.039(2)
2.169(3)
2.141(2)
2.234(3)
/O2
/
/N3
/
/O1
/N1
/O6
/O4#2
/O9
/O3#2
/Ni2
Bond angles
O2#1ꢁCo1ꢁ
O2#1ꢁCo1ꢁ
N2#3ꢁ
O1ꢁCo1ꢁ
O1ꢁCo1ꢁ
O1ꢁCo1ꢁ
O1ꢁCo1ꢁ
O4#2ꢁ
N1ꢁCo1ꢁ
/N1
/
/
O1
110.8(1)
87.0(1)
176.9(1)
153.0(1)
88.3(1)
93.0(1)
94.0(1)
89.1(1)
88.4(1)
/Ni3#7
/
/N1
Bond angles
/
Co1ꢁ
/
N1
O4#2
N1
O5ꢁ
O6ꢁ
N1ꢁ
O2ꢁ
O2ꢁ
N3ꢁ
O2ꢁ
O6ꢁ
/
Ni1ꢁ
Ni2ꢁ
Ni2ꢁ
Ni2ꢁ
Ni2ꢁ
Ni3ꢁ
Ni2ꢁ
Ni2ꢁ
/
O1
89.0(3)
94.6(4)
175.3(3)
90.8(3)
81.7(3)
94.4(4)
94.1(4)
83.5(3)
/
/
/
/N1
/
/
/
/
Ni1
/
/O3#2
/
/O6
/
/N2#3
/
/Ni1
/
Co1ꢁ
/O3#2
/N1
/
/
O9
N1
Ni1
/
/
/
Symmetry transformations used to generate equivalent atoms: #1ꢀ
/
/
/
ꢄ
/
xꢂ1, ꢄyꢂ1, ꢄzꢂ2; #2ꢀx, yꢄ1, z; #3ꢀxꢄ1, y, zꢂ1.
/
/
/
/
/
/
/
/
/
/
Bond lengths
Co1ꢁ
Co2ꢁ
Co3ꢁ
Co1ꢁ
Co2ꢁ
Co3ꢁ
Co1ꢁ
Co2ꢁ
Co3ꢁ
/
O5
2.048(11)
2.054(11)
2.055(10)
2.025(10)
2.029(11)
2.030(10)
2.736(3)
According to the TGA, polymer 1 exhibits no weight
/O2
loss up to 430 8C, which indicates its thermal stability up
to that temperature. An abrupt weight loss (57.7%)
occurs between 430 and 480 8C, and above 480 8C the
second process occurs to give an ultimate solid residue.
Polymer 2 shows practically the same thermal behavior
with a single weight loss step between 473 and 517 8C by
72.7% to result in Co(CO3)2 (calculated: 76.7%), which
gradually decomposes into CoO at higher temperatures.
Polymers 1 and 2 are isostructural. We will discuss
only polymer 1 in detail. The local coordination
environments of the Ni metals (Ni1, Ni2, and Ni3) in
polymer 1 with the atom-numbering schemes are shown
in Figs. 1 and 2. Fig. 1 illustrates a SUB of a paddle-
wheel of the type [M2(OOCR)4], which comprises two
nickel metals and four di(monodentate) bridging car-
/N3
/O1
/O6
/O9
/Co2
/N1
2.068(10)
2.725(4)
/Co3#8
Bond angles
O5ꢁ
O6ꢁ
N1ꢁ
O2ꢁ
O2ꢁ
N3ꢁ
O2ꢁ
O6ꢁ
/
Co1ꢁ
Co2ꢁ
Co2ꢁ
Co2ꢁ
Co2ꢁ
Co3ꢁ
Co2ꢁ
Co2ꢁ
/
O1
N1
89.5(4)
96.9(5)
175.1(3)
91.0(3)
81.9(4)
96.0(5)
93.7(5)
81.1(3)
/
/
/
/
Co1
/
/
O6
/
/
Co1
/
/
O9
/
/
N1
/
/
Co1
Symmetry transformations used to generate equivalent atoms: #7ꢀ
/
boxylates. The Niꢁ
range of 1.990(9)ꢁ
respectively. In addition, the distances of Ni1ꢁ
/
O and Niꢁ
/
N bond lengths lie in the
ꢄ
/
x, y, ꢄz; #8ꢀ xꢄ1/2, yꢄ1/2, ꢄz.
/
/
ꢄ/
/
/
/
˚
/
2.015(8) and 2.005(9)ꢁ
/
2.028(9) A,
Ni2 and
Ni3 are 2.654(2) and 2.645(3) A, respectively,
indicating a NiꢁNi single bond. In crystal structure of
2, the corresponding bond lengths are 1.996(11)ꢁ
/
˚
Ni3ꢁ
/
similar approach was previously employed in the synth-
esis of Cu3(C6H8O4)3(H2O)2(C6H11OH), where a cyclo-
haxanol solution of adipic acid was layered on an
/
/
˚
˚
2.062(12) A for Coꢁ
/
O, 2.055(10)ꢁ
N, 2.736(3) A for Co1ꢁCo2, and 2.725(4) A for Co3ꢁ
Co3 (Table 2).
/
2.073(11) A for Coꢁ
/
aqueous solution of Cu(OAc)2×
/
H2O and heated at
˚
˚
/
/
120 8C. In this case, however, the solvent cyclohexanol
is incorporated into the product as a ligand, different
from the present system in which the benzene functions
only as an aid to grow single crystals [23]. In addition, it
is worth noting that Williams and co-workers recently
carried out the hydro(solvo)thermal reaction of
Each nickel metal has a pseudo-octahedral geometry,
whose equatorial plane consists of four oxygen atoms
from four 2,6-NDC carboxylates. In addition, the axial
positions are occupied by one nickel atom and one
nitrogen atom from the bipy ligand. Two nickel metals
(Ni1 and Ni2) and four NDC ligands form the paddle-
wheel SBUs, which are linked by 2,6-NDC ligands to
give two square-grid nets in the [110] direction that
subsequently interpenetrate. The remaining nickel metal
(Ni3) and one 2,6-NDC form a half of another paddle-
wheel whose partner is generated by the crystallographic
Cu(NO3)2×
ratio in 50% aqueous ethanol at 180 8C for 1 day. Their
reaction produced an interpenetrating, 3-D Cu(I)ꢁ
Cu(II) coordination polymer [Cu4(BDC)3(bipy)2], which
has little porosity and consequently contains no guest
molecules [24].
/
H2O, BDCH2, and bipy in the 1:1:1 mole
/

S.W. Lee et al. / Inorganica Chimica Acta 353 (2003) 151ꢁ
/158
155
Fig. 1. ORTEP drawing of the local coordination environments of Ni1 and Ni2 in polymer 1, showing the atom-labeling scheme and 50% probability
thermal ellipsoids.
inversion operation. The packing diagram resulting
from a combination of the three units is illustrated in
Fig. 3, where a light gray unit is a doubly interpenetrat-
ing unit and a dark gray unit is a single non-interpene-
trating unit. In overall, polymer 1 (and 2) is a triply
interpenetrating 3-D polymer based on three square-grid
networks in the [110] direction, which are linked by bipy
ligands in the [001] direction. Although the constituent
square grid, based on the paddle-wheel units and the
2,6-NDC ligands, has a relatively large dimension of
˚
17.2ꢃ
/
19.7 A (a ꢃ
/
b) along the c-axis, the triple
˚
interpenetration has extremely reduced it to 4.3ꢃ4.3 A.
/
Representing the points of extension of a SBU (that
is, the carboxylate carbon atoms in a paddle-wheel
Fig. 2. Local coordination environment of Ni3 in polymer 1.

156
S.W. Lee et al. / Inorganica Chimica Acta 353 (2003) 151ꢁ158
/
the polymer [Zn2(2,6-NDC)3]{(HNEt3)(DEF)}(ClBz)}2,
the bipy ligands link the SBUs in polymers 1 and 2.
These observations suggest that large guests or hydro-
gen-bonded guest aggregates play an important role in
the formation of non-interpenetrating porous polymers,
as suggested by Yaghi and co-workers [11] and that the
pyridine-type ligands can act as linear spacers in a mixed
ligand system of carboxylates and pyridyls.
3.2. Forming a 2-dimensional polymer by employing 1,3-
BDCH2
We have decided to employ 1,3-BDCH2 instead of
2,6-NDCH2 to prevent the interpenetration that occurs
in the formation of polymers 1 and 2. Because 1,3-
BDCH2 has a coordination angle of 1208, we expected a
different topology of the polymer to be formed. As is
consistent with our expectation, the different coordina-
tion angle of 1,3-BDCH2 led to a totally different
structure of the resulting coordination polymer. The
Fig. 3. A perspective view along the c-axis for a combination of the
two polymers.
SBU) by simple points is frequently useful to describe
and predict the topology of coordination polymers
constructed by SBUs and organic spacers [25]. The
paddleꢁpaddle SBU in polymers 1 and 2 can be
/
represented by a square as shown in Chart 1. The
SBUs are linked to form porous 2-dimensional layers in
the [110] direction, which are linked by organic spacers
(bipyridines) in the [001] direction to give a 3-dimen-
sional basic unit. A related zinc coordination polymer,
hydrothermal reaction of Co(NO3)2×
/
6H2O with 1,3-
BDCH2 and bipyen gave a 2-dimensional coordination
polymer with an empirical formula of [Co(1,3-BDC)(bi-
pyen)] (Eq. (2)). Polymer 3 is also thermally stable up to
410 8C, and a drastic weight loss occurs at 410ꢁ450 8C,
/
followed by a gradual decomposition at higher tempera-
tures.
[Zn2(2,6-NDC)3]{(HNEt3)(DEF)}(ClBz)}2
(DEFꢀ
/
N,N?-diethylformamide; ClBzꢀchlorobenzene), was
/
very recently reported, in which the paddle-wheel
SBUs ([Zn2(CO2R)4]) are linked to form 2-dimensional
layers that are spaced by the 2,6-NDC ligands [26].
Although the polymer [Zn2(2,6-NDC)3]{(HNEt3)-
(DEF)}(ClBz)}2 has the same SBU type as that in our
polymers, this polymer does not form an interpenetrat-
ing polymer due to the presence of hydrogen-bonded
guests that have probably prevented the interpenetra-
tion. Whereas 2,6-NDC ligands participate both in the
formation of the SBU and in the linking of the SBUs in
Co(NO3)2 ×6H2Oꢂ1; 3-BDCH2 ꢂbipyen
0 [Co(1; 3-BDC)(bipyen)] (3)
(2)
Polymer 3 has an infinite 2-dimensional structure
based on a double layer in which constituent layers are
related by inversion. The monomer unit of 3 is shown in
Fig. 4. The coordination sphere of cobalt can be
described as a pseudo-octahedron, whose equatorial
plane consists of two nitrogens from two bipyen ligands
and two oxygens from two 1,3-BDC ligands. The axial
sites are occupied by two carboxylate oxygens. The Coꢁ
/
˚
N bond length is 2.169(3) A and Coꢁ
/
O bond lengths are
˚
2.014(3)ꢁ2.234(3) A (Table 3).
/
Two carboxylate groups of 1,3-BDC ligand are
distinct, one of which acts as a bidentate end. The other
carboxylate group acts as a bis(monodentatate) bridge
that links Co metals in the adjacent layers in the double
layer unit. This phenomenon contrasts with that in
polymers 1 and 2, in which all four 1,3-BDC ligands act
as a bis(monodentatate) ligand linking metals to form a
paddle-wheel SBU. The 1,3-BDC ligands link the double
layers in the [010] direction and the bipyen ligands in the
[100] direction to complete an infinite 2-dimensional
network (Fig. 5). Polymer 3 appears to have a rectan-
gular channel of an approximate dimension of 9.7ꢃ
/
˚
10.1 A (a ꢃ
In summary, two triply interpenetrating coordination
polymers of the type [M3(2,6-NDC)3(bipy)1.5] (MꢀNi;
/
b) along the c-axis.
Chart 1.
/

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/158
157
Fig. 4. Local coordination environment of Co in polymer 3. Unlabeled atoms are related to the labeled atoms by the crystallographic inversion
center.
Co) have been synthesized under hydrothermal or
hydro(solvo)thermal conditions. Benzene was required
to form high-quality crystals of polymer 2. On the other
on the structural outcome of the resulting coordination
polymer. Studies on the prevention of interpenetration
are currently under study.
hand, the hydrothermal reaction of Co(NO3)2×
/6H2O
with 1,3-BDCH2 and bipyen gave a 2-dimensional
coordination polymer with an empirical formula of
[Co(1,3-BDC)(bipyen)]. These results indicate that a
solvent composition and a coordination angle of a
molecular building block can exert a great influence
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data
Fig. 5. A perspective view of polymer 3 along the c-axis.

158
S.W. Lee et al. / Inorganica Chimica Acta 353 (2003) 151ꢁ158
/
[10] S.R. Batten, R. Robson, Angew. Chem., Int. Ed. Engl. 37 (1998)
1460.
Center, CCDC Nos. 197029ꢁ31 for polymers 1, 2 and 3.
Copies of this information may be obtained free of
charge from The Director, CCDC, 12 Union Road,
/
[11] O.M. Yaghi, H. Li, C. Davis, D. Richardson, T.L. Groy, Acc.
Chem. Res. 31 (1998) 474.
Cambridge, CB2 1EZ, UK (fax: ꢂ44-1223-336-033;
email: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
/
[12] T.M. Reineke, M. Eddaoudi, D.B. Moler, M. O’Keeffe, O.M.
Yaghi, J. Am. Chem. Soc. 122 (2000) 4843.
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Acknowledgements
This work was supported by the Ministry of Educa-
tion through the Brain Korea 21 Project and CNNC of
SKKU.
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