Hydrothermal synthesis and structure of new lanthanide coordination polymers with dicarboxylic acid and 1,10-phenanthroline

Article abstract of DOI:10.1016/j.molstruc.2004.01.028

[Ln(oba)(Hoba)(phen)]_n (Ln=Er (1), Yb (2)) and [Er ₂(bpndc)₃(phen)]_n (3) were obtained by hydrothermal reaction of LnCl₃ with 4,4′-oxybis(benzoic acid) (H₂oba), benzophenone-4, 4′-dicarboxylic acid (H ₂bpndc) and 1,10-phenanthroline (phen), respectively, and characterized by single-crystal X-ray diffraction. The crystal structure reveals that 1 and 2 are isomorphous. In the asymmetric unit of 1 and 2, each Ln(III) center is eight-coordinated. 1D chains with two types of rings are formed by Ln(III)-O coordination bond, while 2D network and 3D supramolecular structures are built up by hydrogen bonds and π-π stacking, respectively. Complex 3 is a 3D structure composed of two crystallographically independent Er(III) atoms through bridging bpndc ligands.

Full text of DOI:10.1016/j.molstruc.2004.01.028

Journal of Molecular Structure 692 (2004) 177–186
www.elsevier.com/locate/molstruc
Hydrothermal synthesis and structure of new lanthanide coordination
polymers with dicarboxylic acid and 1,10-phenanthroline
a,
Yibo Wang , Zheming Wang , Chunhua Yan , Linpei Jin
b
b
a,
*
*
aDepartment of Chemistry, Beijing Normal University, Xinwai Street 19, Beijing 100875, China
bState Key Laboratory of Rare Earth Materials Chemistry and Application, Peking University, Beijing 100875, China
Received 26 November 2003; revised 26 November 2003; accepted 21 January 2004
Abstract
[Ln(oba)(Hoba)(phen)]n (Ln ¼ Er (1), Yb (2)) and [Er2(bpndc)3(phen)]n (3) were obtained by hydrothermal reaction of LnCl3 with 4,40-
oxybis(benzoic acid) (H2oba), benzophenone-4, 40-dicarboxylic acid (H2bpndc) and 1,10-phenanthroline (phen), respectively, and
characterized by single-crystal X-ray diffraction. The crystal structure reveals that 1 and 2 are isomorphous. In the asymmetric unit of 1 and 2,
each Ln(III) center is eight-coordinated. 1D chains with two types of rings are formed by Ln(III)–O coordination bond, while 2D network
and 3D supramolecular structures are built up by hydrogen bonds and p–p stacking, respectively. Complex 3 is a 3D structure composed of
two crystallographically independent Er(III) atoms through bridging bpndc ligands.
q 2004 Elsevier B.V. All rights reserved.
Keywords: Hydrothermal reaction; Lanthanides; Coordination polymer; X-ray diffraction
1. Introduction
Multicarboxylate ligands are widely used as tectons in
the construction of coordination polymers to bridge metal
ions. They act as multifunctional organic ligands not only
due to their various coordination modes to metal ions
resulting from completely or partially deprotonated sites to
allow for the large diversity in the topologies, but also to the
ability to act as hydrogen bonds acceptors and donors to
assemble supramolecular structures. Our efforts focus on the
utilization of hydrothermal reactions to construct lanthanide
coordination polymers with novel structural characteristics
and their properties [15–19].
4,40-oxybis (benzoic acid) (H2oba) has been used as
ligand and shows versatility as manifested by the 2D and 3D
polymeric structures [20]. The structural studies in these
metal complexes indicate that the ligand has the ability to
utilize its features to construct supramolecular architecture.
Benzophenone-4,40-dicarboxylic acid (H2bpndc) is also
suitable to construct coordination polymers from the aspect
of its structure and composition. As symmetrical and
divergent ligand bearing oxygen atoms from the two
carboxylate groups at two ends, H2bpndc can connect
multiple metal ions by bridging and/or chelating coordi-
nation modes. As far as we know, the metal coordination
polymers with H2bpndc have not been reported yet. So in
the present work, we select H2oba and H2bpndc as organic
The construction of 1D–3D coordination polymers
consisting of metal ions as nodes and exo-bidentate
ligands as linkers has been well established in recent
years [1–4]. A great deal of attention has been paid to
the design and synthesis of these complexes since their
interesting properties and promising potential in various
applications, such as magnetism [5–7], ion exchange
[8,9], catalysis [10], luminescence [11,12], and adsorption
[13,14]. Therefore, rational design and construction of
coordination polymers with the intriguing diversity of the
architectures have become a particularly important
subject. The key factor to fabricate a desired framework
by assembling metal ions and multifunctional ligands is
the selection of the bridging organic ligand for formation
of coordination bonds and thus coordination compounds.
Apart from this, the hydrogen bonds and p–p inter-
actions are both organizing forces in building up
multidimensional arrays and networks, and present lots
of ideal synthetic paradigms for the assembly of
supramolecular structure.
*
Corresponding author. Tel.: þ861062205522; fax: þ 8601062200567.
E-mail address: lpjin@bnu.edu.cn (Y. Wang).
0022-2860/$ - see front matter q 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2004.01.028

178
Y. Wang et al. / Journal of Molecular Structure 692 (2004) 177–186
ligands to fabricate lanthanide coordination polymers, and
expect to investigate the difference of crystal structures
formed by H2oba and H2bpndc. Herein, we report the
synthesis and structural characterization of three complexes
with formulas [Ln(Hoba)(oba)(phen)]n (Ln ¼ Er (1) and Yb
(2)) and [Er2(bpndc)3(phen)]n (3).
air-dried in 60.4% yield (0.104 g). (Found: C, 55.63; H,
2.66; N, 3.11. C40ErH25N2O10 requires C, 55.80; H, 2.93; N,
3.25). IR data (KBr pellet, n/cm21): 3420 (m), 3059(m),
1716(s), 1595(s), 1531(s), 1420(s), 1241(s), 1164(s),
879(m), 785(m), 728(m), 640(m).
[Yb(oba)(Hoba)(phen)]n (2). The synthesis of 2 is similar
to 1. The colorless crystals were collected by filtration,
washed with ethanol, and then air-dried in 53.8% yield
(0.093 g). (Found: C, 55.42; H, 2.68; N, 3.16.
C40H25N2O10Yb requires C, 55.43; H, 2.91; N, 3.20). IR
data (KBr pellet, n/cm21): 3422 (m), 3066(m), 1716(s),
1594(s), 1534(s), 1421(s), 1241(s), 1164(s), 879(m),
784(m), 725(m), 640(m).
2. Experimental
2.1. Materials
ErCl3·6H2O and YbCl3·6H2O were prepared by dissol-
ving their oxides in hydrochloric acid, respectively, and then
dried. 4,40-oxybis (benzoic acid) and benzophenone-4,40-
dicarboxylic acid were purchased from Aldrich and used
without further purification. While all the other reagents
were commercially available and used as received.
[Er2(bpndc)3(phen)]n (3). The mixture of ErCl3·6H2O
(0.057 g, 0.15 mmol), benzophenone-4,40-dicarboxylic acid
(0.061 g, 0.225 mmol), phen·H2O (0.040 g, 0.2 mmol), H2O
(5 ml), C2H5OH (5 ml), and aqueous solution of NaOH
(0.5 ml, 0.325 mmol) was heated in a 23 ml capacity
stainless-steel reactor with Teflon liner at 180 8C for 5
days and then slowly cooled to room temperature by air-
cooling. The light pink crystals were collected by filtration,
washed with ethanol, and then air-dried in 53.8% yield
(0.093 g). (Found: C, 51.49; H, 2.47; N, 2.69.
C57H32N2O15Er2 requires C, 51.84; H, 2.12; N, 2.44). IR
data (KBr pellet, n/cm21): 3444(m), 1636(s), 1585(m),
1530(m), 1415(m), 1276(s), 731(s), 496(m).
2.2. Instrumentation
Elemental analyses were performed on an Elementar
Vario EL analyzer. The IR spectra were recorded with a
Nicolet Avatar 360 FT-IR spectrometer using the KBr pellet
technique.
2.3. X-ray crystallographic study
The X-ray single crystal data collections for complexes
1–3 were performed on a Bruker Smart 1000 CCD
diffractometer, using graphite-monochromated Mo Ka
3. Results and discussion
The crystal data of 1–3 are listed in Table 1, which show
that 1 and 2 are isomorphous. The selected bond lengths
˚
radiation (l ¼ 0:71073 A). Semiempirical absorption cor-
rections were applied using the SADABS program. The
structures were solved by direct methods and refined by full-
matrix least square on lFl2 using the SHELXTL-97 program
[21]. All non-hydrogen atoms were refined anisotropically.
The hydrogen atoms were generated geometrically and
treated by a mixture of independent and constrained
refinement. CCDC Nos. 225061–225063 contain the
supplementary crystallographic data for this paper. These
data can be obtained free of charge at www.ccdc.cam.ac.uk/
conts/retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge CB2 1EZ,
UK; fax: (internet) þ44-1223/336-033; e-mail: depos-
it@ccdc.cam.ac.uk).
Table 1
Crystal data of 1–3
Complexes
1
2
3
Empirical formula C40ErH25N2O10 C40H25N2O10Yb C57H32N2O15Er2
FW
860.88
866.66
Monoclinic
C2=c
1319.46
Hexagonal
P6122
15.433(7)
15.433(7)
38.91(2) A
90
Crystal system
Space group
˚
a (A)
˚
b (A)
˚
c (A)
Monoclinic
C2=c
13.8970(2)
17.5455(3)
28.6986(6)
90
13.870(5)
17.564(6)
28.633(10)
90
a (8)
b (8)
g (8)
Z
91.0013(7)
90
91.093(5)
90
90
120
2.4. Syntheses
8
8
6
3
˚
V (A )
6996.5(2)
1.635
6974(4)
1.651
8026(7)
1.638
r
calcd; g cm23
[Er(oba)(Hoba)(phen)]n (1). The mixture of ErCl3·6H2O
(0.115 g, 0.3 mmol), 4,40-oxybis (benzoic acid) (0.077 g,
0.3 mmol), phen·H2O (0.059 g, 0.3 mmol), H2O (10 ml),
and aqueous solution of NaOH (0.5 ml, 0.325 mmol) was
heated in a 23 ml capacity stainless-steel reactor with Teflon
liner at 170 8C for 3 days and then slowly cooled to room
temperature by air-cooling. The pale-pink crystals
were collected by filtration, washed with ethanol, and then
Temp (K)
293(2)
293(2)
2.746
293(2)
3.178
m (mm21
Reflections
collected
)
2.463
45709, 7973
17655, 6143
33168, 4580
Total, independent, 0.1284
0.0551
0.2681
Rint
˚
l (Mo Ka) (A)
0.71073
0.71073
0.71073
R1; wR2½I . 2sðIÞꢀ 0.0424, 0.0612 0.0436, 0.0620 0.0714, 0.0702

Y. Wang et al. / Journal of Molecular Structure 692 (2004) 177–186
179
Table 2
Selected bond lengths (A) and bond angles (8) for 1
Table 4
Selected bond lengths (A) and bond angles (8) for 3
˚
˚
Er(1)–O(1)
2.222(3) Er(1)–O(6)
2.228(3) Er(1)–O(7)
2.319(3)
2.426(3)
2.499(4)
2.504(4)
70.95(12)
Er(1)–O(1)
2.297(7) Er(2)–O(2)
2.297(7) Er(2)–O(2)#4
2.501(7) Er(2)–O(4)
2.501(7) Er(2)–O(4)#4
2.381(8) Er(2)–O(7)#2
2.381(8) Er(2)–O(7)#5
2.679(19) Er(2)–N(1)
2.679(19) Er(2)–N(1)#4
2.459(16)
2.220(8)
2.220(8)
2.391(7)
2.391(7)
2.32(2)
Er(1)–O(2)#1
Er(1)–O(1)#3
Er(1)–O(4)#2
2.437(3) Er(1)–N(1)
Er(1)–O(4)
Er(1)–O(5)#2
2.375(3) Er(1)–N(2)
Er(1)–O(4)#3
O(1)–Er(1)–O(2)#1
O(1)–Er(1)–O(4)#2
O(1)–Er(1)–O(5)#2
O(1)–Er(1)–O(6)
O(1)–Er(1)–O(7)
O(1)–Er(1)–N(1)
O(1)–Er(1)–N(2)
88.44(11) O(4)#2–Er(1)–N(2)
Er(1)–O(5)
79.76(11) O(5)#2–Er(1)–O(4)#2 54.13(11)
Er(1)–O(5)#3
2.32(2)
96.74(12) O(5)#2–Er(1)–O(7)
140.07(13) O(5)#2–Er(1)–N(1)
85.16(12) O(5)#2–Er(1)–N(2)
88.51(12) O(6)–Er(1)–O(7)
145.18(13) O(6)–Er(1)–O(4)#2
79.78(11)
123.38(12)
81.29(13)
55.23(11)
127.00(11)
82.18(12)
125.41(13)
74.44(13)
128.63(11)
156.62(12)
127.95(12)
65.03(13)
Er(1)–O(7)#1
2.705(10)
2.705(10)
Er(1)–O(7)#2
Er(1)–O(8)#1
Er(1)–O(8)#2
2.459(16)
O(1)–Er(1)–O(1)#3
O(1)–Er(1)–O(4)
O(1)–Er(1)–O(4)#3
O(1)–Er(1)–O(5)
O(1)–Er(1)–O(5)#3
O(1)–Er(1)–O(7)#1
O(1)–Er(1)–O(7)#2
O(1)–Er(1)–O(8)#1
O(1)–Er(1)–O(8)#2
O(1)#3–Er(1)–O(4)
151.7(4)
O(8)#1–Er(1)–O(8)#2 35.7(6)
O(7)#1–Er(1)–O(8)#1 50.1(3)
O(2)#1–Er(1)–O(4)#2 146.53(12) O(6)–Er(1)–O(5)#2
O(2)#1–Er(1)–O(5)#2 159.26(11) O(6)–Er(1)–N(1)
79.7(2)
116.3(2)
129.7(3)
75.7(3)
74.9(5)
94.4(5)
74.1(4)
78.9(4)
116.3(2)
O(7)#1–Er(1)–O(8)#2 85.8(6)
O(7)#2–Er(2)–O(7)#5 144.1(10)
O(2)#1–Er(1)–O(6)
O(2)#1–Er(1)–O(7)
O(2)#1–Er(1)–N(1)
O(2)#1–Er(1)–N(2)
O(4)#2–Er(1)–N(1)
81.03(12) O(6)–Er(1)–N(2)
80.68(11) O(7)–Er(1)–O(4)#2
76.66(12) O(7)–Er(1)–N(1)
105.67(12) O(7)–Er(1)–N(2)
71.86(12) N(1)–Er(1)–N(2)
O(5)–Er(1)–O(8)#1
O(5)–Er(1)–O(8)#2
154.0(4)
128.6(4)
O(5)#3–Er(1)–O(7)#1 82.3(4)
O(5)#3–Er(1)–O(7)#2 137.2(4)
O(5)#3–Er(1)–O(8)#1 128.6(4)
Symmetry operation: #1, 2x þ 3=2;2y þ 1=2;2z þ 1; #2, 2x þ 2;
y;2z þ 3=2:
O(2)–Er(2)–O(2)#4
O(2)–Er(2)–O(4)
150.5(4)
79.4(3)
77.3(3)
93.5(5)
95.5(5)
77.3(3)
O(1)#3–Er(1)–O(4)#3 79.7(2)
O(1)#3–Er(1)–O(5) 75.7(3)
O(2)–Er(2)–O(4)#4
O(2)–Er(2)–O(7)#2
O(2)–Er(2)–O(7)#5
O(2)#4–Er(2)–O(4)
O(1)#3–Er(1)–O(5)#3 129.7(3)
O(1)#3–Er(1)–O(7)#1 94.4(5)
O(1)#3–Er(1)–O(7)#2 74.9(5)
O(1)#3–Er(1)–O(8)#1 78.9(4)
O(1)#3–Er(1)–O(8)#2 74.1(4)
and bond angles of 1–3 are listed in Tables 2–4,
respectively. First, we will give our description to the
crystal structure of 1. In the asymmetric unit of 1, there is
one crystallographically independent Er(III) ion and each
Er(III) is coordinated to six oxygen atoms comprising of two
oxygen atoms (O1 and O2A) from two carboxylate groups
of two tetradentate oba ligands, two oxygen atoms (O4A
and O5A) from one chelating carboxylate group of another
tetradentate oba ligand, and two others (O6 and O7) from
one chelating carboxylate group of one monoprotonated
Hoba ligand, as well as two nitrogen atoms (N1 and N2)
from one phen molecule to complete an eight-coordinated
geometry, as shown in Fig. 1. Er(III) is located in the center
O(2)#4–Er(2)–O(4)#4 79.4(3)
O(2)#4–Er(2)–O(7)#2 95.5(5)
O(2)#4–Er(2)–O(7)#5 93.5(5)
O(4)–Er(1)–O(4)#3
O(4)–Er(1)–O(5)
114.7(3)
53.9(2)
74.0(2)
148.8(5)
63.2(4)
137.5(4)
106.9(4)
74.0(2)
O(4)–Er(2)–O(4)#4
O(4)–Er(2)–O(7)#2
O(4)–Er(2)–O(7)#5
75.0(3)
70.5(5)
O(4)–Er(1)–O(5)#3
O(4)–Er(1)–O(7)#1
O(4)–Er(1)–O(7)#2
O(4)–Er(1)–O(8)#1
O(4)–Er(1)–O(8)#2
O(4)#3–Er(1)–O(5)
145.4(5)
O(4)#4–Er(2)–O(7)#2 145.4(5)
O(4)#4–Er(2)–O(7)#5 70.5(5)
N(1)–Er(2)–O(2)
N(1)–Er(2)–O(2)#4
N(1)–Er(2)–O(4)
N(1)–Er(2)–O(4)#4
N(1)–Er(2)–O(7)#2
N(1)–Er(2)–O(7)#5
N(1)#4–Er(2)–O(2)
135.2(4)
74.2(4)
134.3(3)
131.8(3)
77.5(6)
71.7(6)
74.2(4)
O(4)#3–Er(1)–O(5)#3 53.9(2)
O(4)#3–Er(1)–O(7)#1 63.2(4)
O(4)#3–Er(1)–O(7)#2 148.8(5)
O(4)#3–Er(1)–O(8)#1 106.9(4)
O(4)#3–Er(1)–O(8)#2 137.5(4)
O(5)–Er(1)–O(5)#3
O(5)–Er(1)–O(7)#1
O(5)–Er(1)–O(7)#2
73.7(4)
137.2(4)
82.3(4)
N(1)#4–Er(2)–O(2)#4 135.2(4)
N(1)#4–Er(2)–O(4) 131.8(3)
Table 3
˚
Selected bond lengths (A) and bond angles (8) for 2
N(1)#4–Er(2)–O(4)#4 134.3(3)
N(1)#4–Er(2)–O(7)#2 71.7(6)
N(1)#4–Er(2)–O(7)#5 77.5(6)
O(5)#3–Er(1)–O(8)#2 154.0(4)
O(7)#1–Er(1)–O(7)#2 135.9(7)
O(7)#2–Er(1)–O(8)#1 85.8(6)
O(7)#2–Er(1)–O(8)#2 50.1(3)
Yb(1)–O(1)
2.204(4) Yb(1)–O(6)
2.215(4) Yb(1)–O(7)
2.420(4) Yb(1)–N(1)
2.357(4) Yb(1)–N(2)
88.41(15) O(4)#2–Yb(1)–N(2)
2.295(4)
2.414(4)
2.482(5)
2.499(5)
71.32(16)
Yb(1)–O(2)#1
N(1)–Er(2)–N(1)#4
61.2(6)
Yb(1)–O(4)#2
Yb(1)–O(5)#2
O(1)–Yb(1)–O(2)#1
O(1)–Yb(1)–O(4)#2
O(1)–Yb(1)–O(5)#2
O(1)–Yb(1)–O(6)
O(1)–Yb(1)–O(7)
O(1)–Yb(1)–N(1)
O(1)–Yb(1)–N(2)
Symmetry operation: #1, x þ 1; y; z; #2, x þ 1; x 2 y þ 1; 2z þ 1=6 #3,
x; x 2 y; 2z þ 1=6; #4, y; x; -z þ 1=3; #5, x 2 y þ 1; x þ 1; z þ 1=6:
79.55(15) O(5)#2–Yb(1)–O(4)#2 54.65(14)
96.43(16) O(5)#2–Yb(1)–O(7)
139.84(16) O(5)#2–Yb(1)–N(1)
84.64(15) O(5)#2–Yb(1)–N(2)
88.22(16) O(6)–Yb(1)–O(7)
145.58(17) O(6)–Yb(1)–O(4)#2
78.87(15)
124.16(15)
81.59(17)
55.51(15)
127.07(15)
81.77(16)
125.96(17)
74.21(17)
128.08(14)
156.59(15)
127.89(16)
65.84(17)
of triangular dodecahedron formed by these eight atoms.
˚
The Er(1)–O bond lengths range from 2.222 to 2.437 A, and
˚
the mean distance of Er(1)–O is 2.335 A, while O–Er(1)–
O(2)#1–Yb(1)–O(4)#2 146.67(15) O(6)–Yb(1)–O(5)#2
O(2)#1–Yb(1)–O(5)#2 158.54(15) O(6)–Yb(1)–N(1)
O bond angles are in the range of 54.13–159.268(11).
In 1, oba and Hoba ligands exhibit two types of
coordination modes (Scheme 1a and b). Each tetradentate
oba ligand connects three Er3þ ions in chelating and
bridging coordination modes. And in Fig. 2, every two
opposite oba ligands ligate four Er3þ ions. Therefore a 28-
O(2)#1–Yb(1)–O(6)
O(2)#1–Yb(1)–O(7)
O(2)#1–Yb(1)–N(1)
O(2)#1–Yb(1)–N(2)
O(4)#2–Yb(1)–N(1)
81.11(15) O(6)–Yb(1)–N(2)
80.79(15) O(7)–Yb(1)–O(4)#2
76.74(15) O(7)–Yb(1)–N(1)
105.95(16) O(7)–Yb(1)–N(2)
71.96(15) N(1)–Yb(1)–N(2)
Symmetry operation: #1, 2x þ 3=2; 2y þ 1=2; 2z þ 1; #2, 2x þ 2;
y; 2z þ 3=2:
˚
membered ring with ca. 7.311 £ 13.387 A is formed by two

180
Y. Wang et al. / Journal of Molecular Structure 692 (2004) 177–186
Fig. 1. The coordination environment of the Er(III) ion in 1 with thermal ellipsoids at 30% probability. All hydrogen atoms are omitted for clarity.
oba ligands and two Er3þ ions (Fig. 2A) (7.309 £ 13.360 A
for 2) through coordination bonds, and the distance of two
and coordinated carboxylate oxygen atoms of oba ligands
from adjacent chains; (2) hydrogen bonds (C–H· · ·O)
between uncoordinated carbonyl oxygen atoms of Hoba
ligands and C–H of oba ligands from adjacent chains.
Meanwhile, two Hoba ligands from two 1D chains also form
C–H· · ·O hydrogen bonds in the same pattern (Table 5). All
these hydrogen bonds bring the moieties into a 2D network.
When the 2D networks are packed along b-axis, they are
interdigited to each other and phen molecules from two
adjacent 2D networks are parallel to each other correspond-
ingly (Fig. 4). The interplanar distance between them is ca.
˚
Er3þ ions is ca. 13.387 A. At the same time, an eight-
˚
˚
membered ring with ca. 5.381 £ 4.243 A (Fig. 2B)
˚
(5.360 £ 4.214 A for 2) is composed of four oxygen
atoms, two carbon atoms from two coordinated carboxylate
groups of two tetradentate oba ligands (which are also
involved in 28-membered ring) and two Er3þ ions. The
eight-membered ring displays chair configuration, and the
distance of two Er3þ ions is 5.381 A. So a ladder-like 1D
˚
chain is generated by two rings which alternatively connect
to each other through sharing the edges consisting of Er(1)–
O and C–O in form of · · ·A· · ·B· · ·A· · ·B· · ·, as shown in
Fig. 2. In the 1D chains, the Hoba ligands coordinate to Er3þ
ions in a chelating mode by deprotonated carboxylate
groups, while the undeprotonated ends extend from the two
sides of the 1D chains. The Er3þ ions are arranged on two
waving edges of the 1D ladder-like chain and the two
adjacent Er3þ ions in the same side are linked by the
˚
˚
3.453 A (ca. 3.447 A for 2). Therefore a 3D supramolecular
˚
tetradentate oba ligands with the distance of 15.834 A
˚
(15.788 A for 2) (Fig. 2). Similarly, the 1D chain can also be
viewed
as
a
structure
constructed
by
[Er(oba)(Hoba)(phen)]2 building block through coordi-
nation bonds. In each building block, two [Er(oba)(Hoba)(-
phen)] are centrosymmetric and are linked through
coordination bonds. In the tetradentate oba ligands of the
building blocks, the dihedral angle between two aromatic
rings is 71.58, and two phen molecules are parallel to each
other, but locate on opposite sites. With regard to the
bidentate Hoba ligand, the dihedral angle between two
aromatic rings is 89.48, nearly perpendicular to each other,
and each deprotonated end chelates to one Er3þ ion, but the
protonated end is free and is a potential hydrogen bond site.
In fact, there are two types of hydrogen bonds are found in 1,
as shown in Fig. 3: (1) hydrogen bonds (O–H· · ·O) between
hydrogen atoms of carboxylate groups of Hoba ligands
Scheme 1. Coordination modes of oba ligand (a) and Hoba ligand (b) in
complexes 1 and 2 and bpndc ligand (c) and (d) in 3.

Y. Wang et al. / Journal of Molecular Structure 692 (2004) 177–186
181
Fig. 2. 1D chain of 1 with two types of rings viewed along the b-axis.
structure is formed through p–p stacking of phen
molecules, as shown in Fig. 5. In the 3D structure, as two
adjacent 2D networks are packed along b-axis via p–p
stacking, phen molecules and Hoba ligands are clamped
between the two adjacent 2D networks. And thus, the 3D
supramolecular architecture can also be described by a
corrugated multiplayer sandwich structure.
A comparison of crystal data between 1 and 2 shows that
˚
the mean distance of Er–O (2.335 A) is longer than that of
˚
Yb–O (2.318 A), and the mean distance of Er–N (2.502 A)
˚
Fig. 3. 2D network of 1 viewed along the b-axis. Hydrogen bonds are shown in dotted line.

182
Y. Wang et al. / Journal of Molecular Structure 692 (2004) 177–186
Table 5
˚
Hydrogen bonding geometry (A) and (8) for 1 and 2
D–H
d(D–H)
d(H· · ·A)
,(DHA)
d(D· · ·A)
A
1
O10E–H10I
C22G–H22G
C36A–H36A
0.820
0.930
0.930
1.897
2.519
2.507
164.6
167.5
134.8
2.696
3.433
3.230
O4 [X,Y,Z]
O9 [2X þ 5/2, 1/2 2 Y, 2Z þ 1]
O9 [2X þ 3, Y, 0.52Z]
2
O10E–H10I
C22G–H22G
C36A–H36A
0.820
0.930
0.930
1.916
2.522
2.525
161.3
166.9
132.8
2.706
3.434
3.230
O4 [X, Y, Z]
O9 [2X þ 5/2, 1/2 2 Y, 2Z þ 1]
O9 [2X þ 3, Y, 0.52Z]
Fig. 4. p–p stacking in 1. All hydrogen atoms are omitted for clarity.
Fig. 5. 3D network of 1 viewed along the a-axis. Hydrogen bonds are shown in dotted line.

Y. Wang et al. / Journal of Molecular Structure 692 (2004) 177–186
183
Fig. 6. The coordination environment of Er(1) (a) and Er(2) (b) in 3.
˚
is also longer than that of Yb–N (2.491 A). Moreover, the
separations of the two adjacent lanthanide ions in 1 are
longer than those of 2 too, whether they lie in the same
chains or not. The distances of p–p stacking of phen
and the dimensions of two types of rings (A and B) all
decrease with the decreasing of atomic radii from Er3þ to
Yb3þ ions. Thus we conclude that lanthanide contraction
plays an important role in crystal structures of 1 and 2.

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Y. Wang et al. / Journal of Molecular Structure 692 (2004) 177–186
Different from 1 and 2, there are two types of
From the difference of coordination number of two
crystallographically independent Er3þ ions, it can be seen
that the steric hindrance around Er(2) is greater than that
around Er(1) due to the coordinated phen molecule. The
˚
average bond length of Er–O is 2.387 A in 3, which is
longer than that of 1. And the average Er–N bond length is
coordination environment of Er atoms in 3, and the
asymmetric unit of 3 contains two crystallographically
independent Er3þ ions. Er(1) is coordinated to eight oxygen
atoms (O7B, O8B, O7C, O8C, O4, O5, O4A, O5A) from
four hexadentate bpndc ligands and two oxygen atoms (O1,
O1A) from two carboxylate groups of two tetradentate
bpndc ligands (Fig. 6a). The Er(1)–O bond length is in the
˚
˚
2.705 A in 3, which is also longer than that of 1 (2.501 A).
The bpndc ligands exhibit two types of coordination
modes (Scheme 1c and d) in 3. Each carboxylate group of a
hexadentate bpndc ligand links two Er3þ ions through a
chelating–bridging coordination mode and each carbox-
ylate group of a tetradentate bpndc ligand connects two Er3þ
ions through a bridging coordination mode. Obviously, the
carbonyl oxygen atom between two phenyl rings is not
coordinated to Er (III) ions.
˚
range of 2.297A–2.459 A and the mean distance of Er(1)–O
˚
˚
is 2.463 A. The Er(2) is coordinated by six oxygen atoms
(O2, O2B, O4, O4D, O7C, O7E) from four hexadentate
bpndc ligands and two tetradentate bpndc ligands, as well as
two nitrogen atoms from one phen molecule (Fig. 6b). The
˚
˚
bond length of Er(2)–O ranges from 2.220 A to 2.320 A,
˚
and the mean distance of Er(2)–O is 2.310 A. While the
˚
bond lengths of Er(2)–N are both 2.705 A. Er(1) and Er(2)
In 3, Er(1) atoms are linked by bpndc ligands into a 3D
architecture, which can be regarded as a structure fused by
two similar (4,4) nets (Fig. 7). In each (4,4) net, 1D channels
along the a-axis are formed by bridging bpndc ligands and
Er(1) atoms. But when the two (4,4) nets are interpenetrated
to each other, each Er(1) in one (4,4) net occupies the voids
are linked by two carboxylate groups of two hexadentate
bpndc ligands through chelating–bridging coordination
mode and one carboxylate group of one tetradentate
bpndc ligand by bridging coordination mode and the
˚
separation between Er(1) and Er(2) is 3.914 A.
Fig. 7. The (4,4) net formed by Er(1) atoms and bpndc ligands viewed along the a-axis in 3.

Y. Wang et al. / Journal of Molecular Structure 692 (2004) 177–186
185
Fig. 8. The 3D structure formed by bpndc ligands and Er(1) (a) and Er(2) (b) viewed along the a-axis in 3.

186
Y. Wang et al. / Journal of Molecular Structure 692 (2004) 177–186
of the other (4,4) net. Therefore, a 3D architecture is built up
by all Er(1) atoms and bpndc ligands (Fig. 8a).
Similarly, Er(2) atoms are also bridged by bpndc ligands
into a 3D structure (Fig. 8b). But the phen molecules
coordinated to Er(2) atoms occupy the 1D channels and
phen molecules are all parallel to each other along the c-
axis. Thus the 3D structure of 3 is constructed by these two
3D structures built up of bpndc ligands and Er(1) and Er(2)
atoms, respectively.
Acknowledgements
This work is supported by National Natural Science
Foundation of China (20331010).
References
¨
[1] D.-L. Long, A.J. Blake, N.R. Champness, C. Wilson, M. Schroder,
J. Am. Chem. Soc. 123 (2001) 3401.
[2] T.J. Prior, M.J. Rosseinsky, Chem. Commun. (2001) 495.
[3] J. Li, H. Zeng, J. Chen, Q. Wang, X. Wu, Chem. Commun. (1997)
1213.
From Scheme 1, it can be seen that the H2oba and
H2bpndc ligands display completely different coordination
modes in 1 and 3. In view of this, the differences in
crystal structures of 1 and 3 are mainly result from the
different coordination modes of ligands. Because one of
carboxylate groups of bidentate Hoba ligand is not
deprotonated and the carboxylate oxygen is liable to
form H-bonds, 1 and 2 are built up into 3D super-
molecular structure by 1D chains through hydrogen bonds
and p–p stacking, while 3 is a 3D structure formed only
by Er–O coordination bonds.
[4] R. Cao, Q. Shi, D. Sun, M. Hong, W. Bi, Y. Zhao, Inorg. Chem. 41
(2002) 6161.
[5] I. Kumagai, M. Akita-Tanaka, K. Inoue, M. Kurmoo, J. Mater. Chem.
11 (2001) 2146.
` ´
[6] M. Riou-Cavellec, C. Albinet, J.-M. Greneche, G. Ferey, J. Mater.
Chem. 11 (2001) 3166.
[7] C.-Z. Lu, C.-D. Wu, S.-F. Lu, J.-C. Liu, Q.-J. Wu, H.-H. Zhuang, J.-S.
Huang, Chem. Commun. (2002) 152.
[8] K.S. Min, M.P. Suh, J. Am. Chem. Soc. 122 (2000) 6834.
[9] O.M. Yaghi, H. Li, J. Am. Chem. Soc. 118 (1996) 295.
´
[10] B. Gomez-Lor, E. Gutierrez-Puebla, M. Iglesias, M.A. Monge, C.
Ruiz-Valero, N. Snejko, Inorg. Chem. 41 (2002) 2429.
[11] C. Reinhard, H.U. Gu¨del, Inorg. Chem. 41 (2002) 1048.
[12] D. Sun, R. Cao, J. Weng, M. Hong, Y. Liang, J. Chem. Soc., Dalton
Trans. (2002) 291.
4. Conclusions
[13] R. Murugavel, D. Krishnamurthy, M. Sathiyendiran, J. Chem. Soc.,
Dalton Trans. (2002) 34.
Three new complexes [Ln(Hoba)(oba)(phen)]n (Ln ¼ Er
(1) and Yb (2)) and [Er2(bpndc)3(phen)]n (3) were obtained
through hydrothermal methods and characterized by single
crystal X-ray diffraction. The data of crystal structure reveal
that 1 and 2 are isomorphous with 3D supramolecular
structure constructed by 1D chains through hydrongen
bonds and p–p stacking, while 3 is a 3D structure built up
by coordination bonds. It follows that the similar organic
ligands may give rise to completely different crystal
structures because of the different coordination modes of
ligands to lanthanide ions.
[14] L. Pan, N. Ching, X. Huang, J. Li, Chem. Eur. J. 7 (2001) 4431.
[15] Y. Wan, L. Zhang, L. Jin, S. Gao, S. Lu, Inorg. Chem. 42 (2003) 4985.
[16] Y. Wan, L. Jin, K. Wang, L. Zhang, X. Zheng, S. Lu, New J. Chem. 26
(2002) 1590.
[17] X. Zheng, L. Jin, S. Lu, Eur. J. Inorg. Chem. 12 (2002) 3356.
[18] Y. Wang, X. Zheng, W. Zhang, L. Jin, Eur. J. Inorg. Chem. 7 (2003)
1355.
[19] Y. Wang, X. Zheng, W. Zhuang, L. Jin, Eur. J. Inorg. Chem. 19 (2003)
3572.
[20] G.F. Liu, Z.-P. Qiao, H.-Z. Wang, X.-M. Chen, G. Yang, New
J. Chem. 26 (2002) 791.
¨
[21] Sheldrick GM, SHELX-97, PC-version, University of Gottingen,
Germany, 1997.