Syntheses, structures and photoluminescent properties of a series of divalent nickel and cadmium complexes based on 3-carboxy-1-(4′-(2″- carboxy)biphenylmethyl)-2-oxidopyridinium and structurally different N-donor ligands

Article abstract of DOI:10.1016/j.poly.2012.11.045

Ten new coordination polymers, namely, [Cd(L)(pbib)_0.5] (1), [Ni(L)(pbib)]·2H₂O (2), [Cd₂(L)₂(pytp) ₂]·H₂O (3), [Cd(L)(tbpy)] (4), [Ni(L)(pytp)] (5), [Ni(L)(tbpy)]·0.25H₂O (6), [

Full text of DOI:10.1016/j.poly.2012.11.045

Polyhedron 50 (2013) 556–570
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Syntheses, structures and photoluminescent properties of a series of divalent
nickel and cadmium complexes based on 3-carboxy-1-(40-(200-carboxy)
biphenylmethyl)-2-oxidopyridinium and structurally different N-donor ligands
⇑
⇑
Ai-Ting Pu, Jin Yang , Wei-Qiu Kan, Yan Yang, Jian-Fang Ma
Key Lab of Polyoxometalate Science, Department of Chemistry, Northeast Normal University, Changchun 130024, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Ten new coordination polymers, namely, [Cd(L)(pbib)0.5] (1), [Ni(L)(pbib)]ꢀ2H2O (2), [Cd2(L)2(pytp)2]ꢀH2O
(3), [Cd(L)(tbpy)] (4), [Ni(L)(pytp)] (5), [Ni(L)(tbpy)]ꢀ0.25H2O (6), [Cd(L)(biim-6)0.5] (7), [Cd(L)(phen)] (8),
[Cd3(L)3(H2O)]ꢀH2O (9), and [Cd3(L)3(biim-4)0.5]ꢀ6H2O (10), where biim-4 = 1,10-(1,4-butanediyl)bis
(imidazole), biim-6 = 1,10-(1,6-hexanedidyl)bis(imidazole), pbib = 1,4-bis(imidazol-1-ylmethyl)benzene,
phen = 1,10-phenanthroline, pytp = 2-(60-(pyridin-200-yl)-40-p-tolylpyridin-20-yl)pyridine, tbpy = 2-(40-
(400-tert-butylphenyl)-60-(pyridin-200-yl)pyridin-20-yl)pyridine and H2L = 3-carboxy-1-(40-(200-carboxy)
biphenylmethyl)-2-oxidopyridinium, have been synthesized under hydrothermal conditions. Their struc-
tures have been determined by single-crystal X-ray diffraction analyses and further characterized by
infrared spectra (IR), elemental analyses, powder X-ray diffraction (PXRD) and thermogravimetric (TG)
Received 11 August 2012
Accepted 29 November 2012
Available online 7 December 2012
Keywords:
Coordination polymers
Topological structure
Luminescence
analyses. Compounds 1 and 2 show layer structures. Neighboring layers are further linked by
ing interactions to form 3D supramolecular architectures. Compound 3 consists of two crystallographi-
cally different dimers, which are further linked by and hydrogen-bonding interactions into a 2D
supramolecular architecture. Compounds 4–6 feature chain structures. In 4, neighboring chains are
stacked by interactions to result in a 2D supramolecular architecture. In 5, the adjacent chains are
linked by interactions to yield a 3D supramolecular architecture. In 6, neighboring chains are further
linked by hydrogen-bonding interactions into a 3D supramolecular architecture. Compound 7 exhibits a
2D 63-hcb network. Neighboring networks are further extended by
stacking interactions into a 3D
p–p stack-
p–p
p–p
p–p
p–p
supramolecular architecture. Compound 8 displays a (4,4) sheet. Compound 9 reveals a 2D (4,4) network.
Compound 10 shows a 3D 5-connected framework with (46ꢀ64) topology. The effects of the L anions and
the N-donor ligands on the structures of the coordination polymers have been discussed. In addition, the
luminescent properties of 1, 3, 4 and 7–10 have also been investigated in details.
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
pH values, and reaction temperatures [3,4]. Among these factors,
the anions play a key role in the design and construction of various
Currently, considerable efforts have been focused on the design
and synthesis of novel multidimensional coordination polymers
not only because of their intriguing variety of architectures and
topologies but also because of their enormous potential applica-
tions in the fields of electrical conductivity, magnetism, nonlinear
optics, ion exchange, and gas absorption [1]. Nevertheless, it is still
a great challenge to predict the structures and properties of the tar-
get coordination polymers [2]. Usually, the construction of the
coordination polymers can be influenced by several factors, such
as the nature of the anions, N-donor ligands, the central metals,
coordination polymers. In this regard, the multicarboxylate li-
gands, as an important type of organic anions, have been exten-
sively utilized as multifunctional linkers because of their rich
coordination modes in the assembly of polymeric structures, such
as monodentate, bidentate and tridentate [5]. Up to now, benzene–
polycarboxylate anions such as benzene–tricarboxylic acid and
benzene–tetracarboxylic acid have been widely studied in the con-
struction of coordination polymers [6]. However, flexible pyridine-
carboxylate ligands have received less attention [7].
Based on above consideration, a new flexible dicarboxylic acid
ligand 3-carboxy-1-(40-(200-carboxy)biphenylmethyl)-2-oxidopy-
ridinium (H2L) was synthesized (Scheme 1). The H2L ligand was
chosen as the organic ligand based on the following consider-
ations: (i) The H2L ligand contains a –CH2– spacer at the center
⇑
Corresponding authors. Fax: +86 431 85098620 (J.-F. Ma).
E-mail addresses: yangjinnenu@yahoo.com.cn (J. Yang), jianfangma@yahoo.
com.cn (J.-F. Ma).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.11.045

A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
557
Scheme 1. Structures of H2L and the N-donor ligands used in this work.
of the molecule. Therefore, the biphenyl and pyridine rings can
2. Experimental
freely twist to meet the requirements of the coordination geome-
tries of metal cations in different directions, offering various possi-
bilities for construction of frameworks with unique structures. (ii)
The H2L ligand is a multidentate ligand because of the presence of
two carboxylate groups and one hydroxyl group. The carboxylate
and hydroxyl oxygen groups can adopt varied coordination modes
with metal cations (Scheme 2).
2.1. Materials and methods
H2L and the N-donor ligands were prepared by the procedures
reported [9,10]. Other reagents were obtained from commercial
suppliers and used without further purification. The C, H and N ele-
mental analyses was conducted on a Perkin–Elmer 240C elemental
analyzer. The FT-IR spectra were recorded from KBr pellets in the
range 4000–400 cmꢁ1 on a Mattson Alpha-Centauri spectrometer.
Thermogravimetric analyses (TGA) were performed on a Perkin–
Elmer TG-7 analyzer heated from room temperature to 600 °C un-
der nitrogen gas. The solid-state emission/excitation spectra were
recorded on a Perkin–Elmer FLS-920 spectrometer. The powder
X-ray diffraction (PXRD) data of the samples was collected on a
Rigaku Dmax 2000 X-ray diffractometer with graphite monochro-
In this work, ten new compounds based on flexible H2L and dif-
ferent N-donor ligands have been synthesized under hydrothermal
conditions, namely, [Cd(L)(pbib)0.5] (1), [Ni(L)(pbib)]ꢀ2H2O (2),
[Cd2(L)2(pytp)2]ꢀH2O (3), [Cd(L)(tbpy)] (4), [Ni(L)(pytp)] (5),
[Ni(L)(tbpy)]ꢀ0.25H2O (6), [Cd(L)(biim-6)0.5] (7), [Cd(L)(phen)] (8),
[Cd3(L)3(H2O)]ꢀH2O (9), and [Cd3(L)3(biim-4)0.5]ꢀ6H2O (10), where
biim-4 = 1,10-(1,4-butanediyl)bis(imidazole),
biim-6 = 1,10-(1,6-
hexanedidyl)bis(imidazole), pbib = 1,4-bis(imidazol-10-ylmethyl)
benzene, phen = 1,10-phenanthroline, pytp = 2-(60-(pyridin-200-yl)-
40-p-tolylpyridin-20-yl)pyridine, and tbpy = 2-(40-(400-tert-
matized Cu Ka radiation (k = 0.154 nm) and 2h ranging from 5 to
50°. The experimental PXRD patterns are in good agreement with
the corresponding simulated ones (Fig. S7 in the Supporting Infor-
mation). 1H and 13C NMR spectra were recorded on a Bruker UNITY
INOVA-500 instrument.
butylphenyl)-60-(pyridin-200-yl)pyridin-20-yl)pyridine.
All
the
compounds are characterized by X-ray crystallography, infrared
spectra (IR), powder X-ray diffraction (PXRD) and thermogravimet-
ric analyses (TG). The effects of the L anions and the N-donor ligands
on the structures of the coordination polymers have been discussed
[8]. Furthermore, the photoluminescent properties of compounds 1,
3, 4 and 7–10 have also been investigated.
2.2. Synthesis
2.2.1. Synthesis of H2L
A mixture of 2-hydroxyl nicotinic acid (2.78 g, 20 mmol), con-
centrated sulfuric acid (2 mL), and EtOH (100 mL) was heated at
90 °C for 8 h. The solvent was evaporated by rotary evaporation
to 20 mL, then 200 mL water was added. The mixture was adjusted
to pH 7–8 with NaHCO3 powder. The product was extracted by
chloroform for three times. The solvent was removed from the fil-
trate by rotary evaporation, and popcorn solid of 2-hydroxyl nico-
tinic acid ethyl ester formed immediately.
The 2-hydroxyl nicotinic acid ethyl ester (3.30 g, 20 mmol) and
NaOH (0.80 g, 20 mmol) were added to EtOH solution (200 mL),
then white solid formed immediately. The mixture was stirred
for 1 h, 4-bromomethylbiphenyl-20-carboxylic acid methyl ester
(5.62 g, 20 mmol) and DMF (100 mL) was added. After stirring at
90 °C for 6 h, an excess of NaOH (4.8 g, 120 mmol) and water
(50 mL) were added to the mixture stirring at 90 °C for 6 h. The sol-
vent was removed by rotary evaporation, and then 250 mL water
was added. The mixture was adjusted to pH
2 with HCl
(1.0 mol Lꢁ1), and an off-white solid of H2L formed immediately.
The solid was filtered off, washed with water and dried (yield in
94.3%). Anal. Calc. for C20H16NO5 (Mr = 350.34): C, 68.57; H, 4.60;
N, 4.00. Found: C, 68.50; H, 4.45; N, 4.10%. IR data (KBr, cmꢁ1):
3079 (m), 1628 (m), 1559 (w), 1452 (w), 1374 (m), 1304 (s),
Scheme 2. Coordination modes of the L anions in compounds 1–10.

558
A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
1254 (m), 1168 (s), 777 (w), 695 (s). 1H NMR (500 MHz, DMSO) d/
ppm: 5.36 (s, 2H), 6.80 (t, J = 6.0 Hz, 1H), 7.32–7.39 (m, 5H), 7.45 (d,
J = 7.5 Hz, 1H), 7.55 (d, J = 7.5 Hz, 1H), 7.72 (d, J = 7.5 Hz, 1H),
8.41–8.47 (m, 2H). 13C NMR (125 MHz, DMSO) d/ppm: 52.95,
109.35, 117.48, 127.98, 128.18, 129.25, 129.70, 131.03, 131.47,
132.76, 135.13, 140.93, 141.16, 145.71, 146.21, 164.14, 165.28,
170.07.
cmꢁ1): 3053 (s), 2964 (s), 1644 (w), 1603 (w), 1460 (m), 1440
(m), 1378 (w), 1246 (s), 1217 (s), 820 (s), 792 (m), 751 (m).
2.2.8. Synthesis of [Cd(L)(biim-6)0.5] (7)
A mixture of CdCl2ꢀ2.5H2O (0.011 g, 0.05 mmol), H2L (0.018 g,
0.05 mmol), biim-6 (0.011 g, 0.05 mmol), NaOH (0.004 g,
0.1 mmol), methanol (2.6 mL) and water (5.4 mL) was placed in a
Teflon reactor. The mixture was heated at 140 °C for 4 days, and
then it was gradually cooled to room temperature. Colorless block
crystals were obtained in a 51% yield. Anal. Calc. for C26H22CdN3O5
(Mr = 568.87): C, 54.89; H, 3.90; N, 7.39. Found: C, 54.76; H, 3.99;
N, 7.51%. IR data (KBr, cmꢁ1): 3056 (s), 2936 (s), 1656 (w), 1545
(w), 1515 (m), 1463 (m), 1394 (w), 1368 (m), 1234 (s), 859 (m),
769 (m), 716 (s).
2.2.2. Synthesis of [Cd(L)(pbib)0.5] (1)
A mixture of CdCl2ꢀ2.5H2O (0.011 g, 0.05 mmol), H2L (0.018 g,
0.05 mmol), pbib (0.012 g, 0.05 mmol), NaOH (0.004 g, 0.1 mmol),
methanol (2.6 mL) and water (5.4 mL) was placed in a Teflon reac-
tor, and heated at 140 °C for 3 days. Then it was cooled to room
temperature at 10 °C hꢁ1. Colorless block crystals were obtained
in a 43% yield. Anal. Calc. for C27H20CdN3O5 (Mr = 578.86): C,
56.02; H, 3.48; N, 7.26. Found: C, 56.12; H, 3.38; N, 7.35%. IR data
(KBr, cmꢁ1): 3064 (s), 1649 (w), 1579 (w), 1514 (m), 1462 (s),
1394 (w), 1368 (m), 1242 (s), 859 (s), 776 (m), 733 (m), 714 (s).
2.2.9. Synthesis of [Cd(L)(phen)] (8)
The preparation of 8 was similar to that of 3 except that phen
was used instead of pytp. Colorless crystals of 8 were collected in
a 56% yield. Anal. Calc. for C32H21CdN3O5 (Mr = 639.92): C, 60.06;
H, 3.31; N, 6.57. Found: C, 60.18; H, 3.20; N, 6.69%. IR data (KBr,
cmꢁ1): 3050 (s), 2936 (s), 1652 (w), 1607 (w), 1576 (w), 1547
(w), 1450 (s), 1400 (m), 1365 (m), 774 (s), 746 (m), 707 (s).
2.2.3. Synthesis of [Ni(L)(pbib)]ꢀ2H2O (2)
The preparation of 2 was similar to that of 1 except that
NiCl2ꢀ6H2O was used instead of CdCl2ꢀ2.5H2O. Pale green crystals
of 2 were collected in a 58% yield. Anal. Calc. for C34H31NiN5O7
(Mr = 680.35): C, 60.02; H, 4.59; N, 10.29. Found: C, 59.90; H,
4.64; N, 10.40%. IR data (KBr, cmꢁ1): 3063 (s), 2945 (s), 1648 (w),
1583 (w), 1540 (w), 1445 (m), 1408 (w), 1358 (m), 1210 (s), 861
(m), 800 (s), 771 (m).
2.2.10. Synthesis of [Cd3(L)3(H2O)]ꢀH2O (9)
A mixture of CdCl2ꢀ2.5H2O (0.011 g, 0.05 mmol), H2L (0.018 g,
0.05 mmol), NaOH (0.004 g, 0.1 mmol) and water (8 mL) was
placed in a Teflon reactor. The mixture was heated at 140 °C for
3 days, and then it was gradually cooled to room temperature. Col-
orless block crystals were obtained in a 33% yield. Anal. Calc. for
2.2.4. Synthesis of [Cd2(L)2(pytp)2]ꢀH2O (3)
C
60H43Cd3N3O17 (Mr = 1415.17): C, 50.92; H, 3.06; N, 2.97. Found:
A mixture of CdCl2ꢀ2.5H2O (0.011 g, 0.05 mmol), H2L (0.018 g,
0.05 mmol), pytp (0.015 g, 0.05 mmol), NaOH (0.004 g, 0.1 mmol),
methanol (2.6 mL) and water (5.4 mL) was placed in a Teflon reac-
tor, which was heated at 140 °C for 3 days, and then it was cooled
to room temperature at 10 °C hꢁ1. Colorless block crystals of 3
were obtained in a 30% yield based on Cd(II). Anal. Calc. for C84H62-
Cd2N8O11 (Mr = 1584.22): C, 63.68; H, 3.94; N, 7.07. Found: C,
63.56; H, 3.80; N, 7.19%. IR data (KBr, cmꢁ1): 3061 (s), 1651 (w),
1542 (w), 1443 (m), 1399 (w), 1367 (w), 1249 (m), 1193 (s), 855
(s), 768 (m), 747 (m), 687 (s).
C, 50.79; H, 3.19; N, 2.82%. IR data (KBr, cmꢁ1): 3613 (s), 3078
(s), 2950 (s), 1648 (w), 1599 (m), 1460 (m), 1398 (w), 1233 (s),
1214 (s), 863 (m), 790 (s), 766 (w).
2.2.11. Synthesis of [Cd3(L)3(biim-4)0.5]ꢀ6H2O (10)
The preparation of 10 was similar to that of 9 except that biim-4
was used. Methanol (3 mL) and water (5 mL) were placed in a Tef-
lon reactor. Colorless crystals of 10 were collected in a 57% yield.
Anal. Calc. for C65H58Cd3N5O21 (Mr = 1582.36): C, 49.34; H, 3.69;
N, 4.43. Found: C, 49.46; H, 3.81; N, 4.32%. IR data (KBr, cmꢁ1):
3055 (s), 2950 (s), 1649 (w), 1554 (w), 1460 (m), 1396 (w), 1306
(m), 1233 (m), 879 (s), 861 (m), 763 (m), 720 (s).
2.2.5. Synthesis of [Cd(L)(tbpy)] (4)
The preparation of 4 was similar to that of 3 except that tbpy
(0.018 g) was used instead of pytp. Methanol (4 mL) and water
(4 mL) were placed in a Teflon reactor. Colorless block crystals
were obtained in a 53% yield. Anal. Calc. for C45H36CdN4O5
(Mr = 825.18): C, 65.50; H, 4.40; N, 6.79. Found: C, 65.62; H, 4.25;
N, 6.68%. IR data (KBr, cmꢁ1): 3054 (s), 2964 (m), 1648 (s), 1597
(s), 1545 (s), 1444 (s), 1399 (m), 1364 (m), 1251 (s), 816 (s), 765
(m), 753 (m).
2.3. Crystal structure determination
Crystallographic diffraction data for compounds 1–10 were re-
corded on an Oxford Diffraction Gemini R Ultra diffractometer with
graphite-monochromated Mo
Ka radiation (k = 0.71073 Å) at
293 K. Absorption corrections were applied using a multi-scan
technique. All the structures were solved by direct method of SHEL-
XS-97 and refined by full-matrix least-squares techniques using the
SHELXL-97 program within WINGX [11]. All non-hydrogen atoms were
easily found from the Fourier difference maps and refined with
anisotropic temperature parameters. The disordered atoms C
atoms (C25 and C26) for 7 were split over two sites with a total
occupancy of 1. Hydrogen atoms attached to carbons were gener-
ated geometrically. Hydrogen atoms of the disordered C atoms
for 7 could not be positioned geometrically. Hydrogen atoms of
O1W for 9 were located from difference Fourier maps and refined
with isotropic displacement parameters. Hydrogen atoms of the
free water molecules for 2, 3, 6, 9 and 10 were not included in
the model. The detailed crystallographic data and structure refine-
ment parameters for these compounds are summarized in Table 1.
Selected bond distances and angles and hydrogen bond parameters
for them are listed in Tables S1–S10 (see the Supporting
Information).
2.2.6. Synthesis of [Ni(L)(pytp)] (5)
A mixture of NiCl2ꢀ6H2O (0.012 g, 0.05 mmol), H2L (0.018 g,
0.05 mmol), NaOH (0.004 g, 0.1 mmol), and water (8 mL) was
placed in a Teflon reactor. The mixture was heated at 150 °C for
3 days. Green crystals of 5 were collected in a 57% yield. Anal. Calc.
for C42H30NiN4O5 (Mr = 729.41): C, 69.16; H, 4.15; N, 7.68. Found:
C, 69.29; H, 4.01; N, 7.79%. IR data (KBr, cmꢁ1): 3056 (s), 2951
(s), 1648 (w), 1595 (w), 1461 (m), 1441 (m), 1387 (w), 1248 (m),
1220 (s), 820 (s), 791 (m), 751 (m).
2.2.7. Synthesis of [Ni(L)(tbpy)]ꢀ0.25H2O (6)
The preparation of 6 was similar to that of 5 except tbpy was
used instead of pytp. Green crystals of 6 were collected in a 55%
yield). Anal. Calc. for C45H36.5NiN4O5.25 (Mr = 775.99): C, 69.65; H,
4.74; N, 7.22. Found: C, 69.52; H, 4.65; N, 7.34%. IR data (KBr,

A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
559
Table 1
Crystal data and structure refinements for compounds 1–10.
1
2
3
4
Formula
C
27H20CdN3O5
C34H31NiN5O7
680.35
C84H62Cd2N8O11
1584.22
C45H36CdN4O5
825.18
monoclinic
P21/n
15.635(2)
14.6280(18)
17.886(3)
90
114.791(16)
90
3713.7(8)
4
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
578.86
monoclinic
C2/c
13.8148(6)
15.8632(6)
21.7690(8)
90
105.131(4)
90
4605.2(3)
8
triclinic
triclinic
ꢀ
ꢀ
P1
P1
10.6610(3)
10.8820(4)
14.4380(6)
109.088(4)
98.976(3)
94.75
1547.35(10)
2
1.460
11.7390(4)
13.3650(6)
23.9190(11)
103.391(4)
90.437(3)
101.737(4)
3568.4(3)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (g/cm3)
1.670
1.474
1.476
F(000)
2328
1.050
0.0323
0.0745
708
1.048
0.0554
0.1528
1612
1.023
0.0486
0.1128
1688
0.999
0.0645
0.1301
Goodness-of-fit GOF on F2
aR1 [I > 2
r
(I)]
bwR2 (all data)
Rint
0.0257
0.0372
0.0383
0.0761
5
6
7
Formula
C
42H30NiN4O5
C45H36.5NiN4O5.25
C26H22CdN3O5
568.87
monoclinic
C2/c
15.6300(8)
13.7610(5)
22.2970(9)
90
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
729.41
monoclinic
P21/n
15.2836(5)
8.8648(2)
25.2366(8)
90
775.99
monoclinic
P21/c
10.7718(4)
15.5626(5)
23.4500(10)
90
a
(°)
b (°)
102.935(3)
90
3332.44(17)
4
101.975(4)
90
3845.5(3)
4
98.446(4)
90
4743.7(4)
8
c
(°)
V (Å3)
Z
Dcalc (g/cm3)
1.454
1.340
1.593
F(000)
1512
1.019
0.0434
0.0950
1618
1.011
0.0540
0.1342
2296
1.034
0.0410
0.1016
Goodness-of-fit GOF on F2
aR1 [I > 2
r
(I)]
bwR2 (all data)
Rint
0.0389
0.0434
0.0315
8
9
10
Formula
C
32H21CdN3O5
C60H43Cd3N3O17
1415.17
triclinic
C65H58Cd3N5O21
1582.36
triclinic
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
639.92
orthorhombic
Pbca
ꢀ
ꢀ
P1
P1
11.5379(4)
16.2173(5)
27.8815(8)
90
90
90
5217.0(3)
8
1.629
13.982(5)
14.039(5)
14.557(5)
101.286(5)
101.660(5)
99.890(5)
2677.1(16)
2
14.4840(5)
15.2760(6)
17.6280(7)
112.514(4)
105.357(3)
93.378(3)
3417.7(2)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (g/cm3)
1.756
1.538
F(000)
2576
1.010
0.0378
0.0766
1408
1.049
0.0381
0.0982
1590
1.016
0.0529
0.1614
Goodness-of-fit GOF on F2
aR1 [I > 2
r
(I)]
bwR2 (all data)
Rint
0.0512
0.0269
0.0388
aR1
=
R
||Fo| ꢁ |Fc||/
R
|Fo|. bwR2 = |
R
R .
w(|Fo|2 ꢁ |Fc|2)|/ |w(Fo2)2|1/2
one N atom from one pbib ligand (Cd1–N2 = 2.314(3) Å) in a dis-
torted octahedral coordination environment. The N2, O2#2, O4 and
O5 atoms comprise the basal plane, whereas the O3#2 and O1#1
atoms occupy the axial positions. L anions bridge neighboring Cd(II)
3. Results and discussion
3.1. Crystal structures
cations adopting a l3- : : : :g
g1 g1 g1 g1 1 coordination mode (mode I,
3.1.1. Structure of [Cd(L)(pbib)0.5] (1)
Scheme 2) to generate an infinite double chain (Fig. 1b). The chains
are further linked by pbib ligands to yield a wave-like layer (Fig. S1).
As shown in Fig. 1a, each Cd(II) cation is coordinated by four oxy-
gen atoms from two carboxylate and one phenolic hydroxyl of three
L
anions (Cd1–O1#1 = 2.228(2), Cd1–O2#2 = 2.305(2), Cd1–
Moreover, adjacent layers are extended by face-to-face
p–pstacking
O3#2 = 2.310(2), Cd1–O4 = 2.326(2) and Cd1–O5 = 2.388(2) Å) and
interactions between imidazole rings with interplanar separation

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A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
Fig. 1. (a) Coordination environment of the Cd(II) center in compound 1 (thermal ellipsoids are at the 30% probability level). Symmetry codes: #1x + 1, y, z; #2ꢁx + 1, ꢁy + 1,
#3
ꢁz + 1; ꢁx + 1, y, ꢁz + 1/2; #4x ꢁ 1, y, z. (b) View of the infinite double-chain structure constructed by L anions and Cd(II) cations. (c) View of the 3D supramolecular
assembly formed by p–p stacking interactions.
being 3.77 Å [12] (the centroid–centroid and slippage distances of
3.89 and 0.94 Å) into a 3D supramolecular architecture (Fig. 1c).
cations in a l2- : : : :
g1 g1 g0 g1 g1 coordination mode (mode VII,
Scheme 2) to form a dimeric unit [Ni2L2] with the Niꢀ ꢀ ꢀNi separa-
tion of 9.320 Å. Neighboring [Ni2L2] dimers are linked by one kind
of pbib ligand to generate an infinite chain structure (Fig. S2a). The
adjacent chains are bridged by another kind of pbib ligand to yield
a 2D network (Fig. S2b). The 2D network of 2 can be viewed as a
(44)-sql network structure (Fig. 2b). In addition, the 2D networks
are further extended into a 3D supramolecular architecture by
3.1.2. Structure of [Ni(L)(pbib)]ꢀ2H2O (2)
X-ray crystallography reveals that the asymmetric unit of 2 con-
sists one Ni(II) cation, two halves of pbib ligands, one L anion, and
two lattice water molecules (Fig. 2a). Each Ni(II) cation is six-coor-
dinated by two N atoms from two pbib ligands (Ni1–N = 2.078(3)–
2.086(3) Å) and four oxygen atoms from two carboxylate and one
phenolic hydroxyl of two L anions. The Ni1–O bond lengths are
in the range of 2.038(3)–2.236(3) Å, and the O–Ni1–O angles vary
from 85.13(11)° to 163.93(11)°. Each L anion bridges two Ni(II)
p–p
stacking interactions between imidazole and benzene rings
of
L anions with interplanar separation being 3.83 Å (the
centroid–centroid and slippage distances of 4.13 and 1.55 Å)
(Fig. 2c).

A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
561
Fig. 2. (a) ORTEP view of 2 showing the local coordination environment of Ni(II) cation with hydrogen atoms and solvent water molecule omitted for clarity (30% probability
displacement ellipsoids). Symmetry codes: #1ꢁx + 2, ꢁy + 1, ꢁz + 1; #2ꢁx, ꢁy, ꢁz; #3ꢁx + 2, ꢁy + 1, ꢁz. (b) Schematic view of the (44)-sql network structure. (c) View of the 3D
supramolecular architecture of 2 formed by p–p stacking interactions.

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A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
Fig. 3. (a) ORTEP view of 3 showing the local coordination environments of Cd(II) cations with hydrogen atoms omitted for clarity (30% probability displacement ellipsoids).
#1
#2
Symmetry codes: ꢁx + 1, ꢁy + 1, ꢁz + 1; ꢁx + 2, ꢁy + 1, ꢁz + 2. (b) View of the two types of [Cd2(L)2] dimeric units (green and red spheres represent Cd(II) and O atoms,
respectively). (c) View of the supramolecular layer formed by hydrogen-bonding interactions in 3. (Color online.)
3.1.3. Structure of [Cd2(L)2(pytp)2]ꢀH2O (3)
2.375(4) Å and 2.211(3) to 2.391(3) Å, respectively. Cd1 and its
symmetry-related species are chelated by two L ligands in l2
g0 coordination mode to form one type of [Cd2(L)2] di-
mer (mode II, Scheme 2), whereas Cd2 and its symmetry-related
species are linked by two L ligands in l2
0 coordina-
tion mode (mode III, Scheme 2) to yield another type of [Cd2(L)2]
dimer. The two types of [Cd2(L)2] dimers show ‘‘O’’ shaped
conformations (Fig. 3b). It is noteworthy that adjacent [Cd2(L)2] di-
As illustrated in Fig. 3a, the asymmetric unit of 3 contains two
unique Cd(II) cations, two L anions, two pytp ligands and two halves
of lattice water molecules. Cd1 cation is seven-coordinated by four
oxygen atoms from two carboxylate groups of two L anions (Cd1–
O1#1 = 2.469(3), Cd1–O2#1 = 2.323(3), Cd1–O4 = 2.371(3), Cd1–
O5 = 2.392(3) Å), and three nitrogen atoms from one pytp ligand
(Cd1–N2 = 2.367(4), Cd1–N3 = 2.344(3), Cd1–N4 = 2.384(4) Å) in a
distorted pentagonal bipyramid coordination environment.
However, Cd2 cation exhibits a distorted octahedral coordination
geometry, completed by three oxygen atoms from two carboxylate
groups of two L anions and three nitrogen atoms from one pytp li-
gand. The Cd2–N and Cd2–O bond lengths range from 2.340(4) to
-
g1-
:
g1 g1 g1
: : :
-
g1 g1 g0 g1
: : : :g
mers are linked by two types of face-to-face
p–p interactions be-
tween pyridine rings of pytp ligands and benzene rings of L
anions (face-to-face distances of 3.54 and 3.52 Å, respectively) to
generate two unique supramolecular double chain structures
(Fig. S3).

A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
563
In addition, there exist intermolecular C5–H5ꢀ ꢀ ꢀO5#3
,
l2
-
g1
:
g1
:
g0
:
g1
:
g0 coordination mode (mode III, Scheme 2) to
C32–H32ꢀ ꢀ ꢀO8#2
,
C47–H47ꢀ ꢀ ꢀO10#4
and
C83–H83ꢀ ꢀ ꢀO3#1
form a polymeric helical chain propagating along the crystallo-
graphic c-axis with a pitch of 14.63 Å (Fig. 4b). The tbpy ligands
are attached to the helical chain as tridentate ligands. As shown
in Fig. 4c, the tbpy ligands from two neighboring helical chains
hydrogen-bonding interactions (Table S3b), which extend the
supramolecular chains into a supramolecular layer (Fig. 3c).
are well-matched to furnish strong p–p stacking interactions (cen-
troid-to-centroid distance of 3.58 Å and face-to-face distance of
3.30 Å), yielding a supramolecular layer (Fig. 4c). Clearly, the
strong p–p stacking interactions play an important role in stabiliz-
3.1.4. Structure of [Cd(L)(tbpy)] (4)
The asymmetric unit of 4 contains one crystallographically
independent Cd(II) cation, one L anion, one tbpy ligand. As shown
in Fig. 4a, each Cd(II) cation is coordinated by three nitrogen atoms
from one tbpy ligand (Cd1–N2 = 2.349(5), Cd1–N3 = 2.323(5) and
Cd1–N4 = 2.344(5) Å), and three carboxylate oxygen atoms from
ing the 2D supramolecular network.
Notably, there are intramolecular and intermolecular hydrogen
bonds (C7–H7Bꢀ ꢀ ꢀO3, C3–H3ꢀ ꢀ ꢀO1#3, C32–H32ꢀ ꢀ ꢀO5#4 and C34–
H34ꢀ ꢀ ꢀO3#4) between the carbon and oxygen atoms of L anions
(Table S4b), which further stabilize the supramolecular layer of 4.
two
L
anions (Cd1–O2 = 2.176(5), Cd1–O4#1 = 2.289(5) and
Cd1–O5#1 = 2.529(5) Å), showing a distorted octahedral coordina-
tion environment. Each L anion bridges two Cd(II) cations in a
#1
Fig. 4. (a) Coordination environment of the Cd(II) center in compound 4 (30% probability displacement ellipsoids). Symmetry codes for the generated atoms: ꢁx + 3/2,
#2
y ꢁ 1/2, ꢁz + 3/2; ꢁx + 3/2, y + 1/2, ꢁz + 3/2. (b) View of the helical chain structure. (c) View of the supramolecular layer formed by
p–p stacking interactions.

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Fig. 5. (a) Coordination environment of the Ni(II) cation in 5 showing 30% thermal probability ellipsoids. Symmetry codes for the generated atoms: #1ꢁx + 1/2, y + 1/2, ꢁz + 3/
#2
2; ꢁx + 1/2, y ꢁ 1/2, ꢁz + 3/2. (b) View of the infinite chain in 5. (c) View of the 3D supramolecular architecture of 5 formed via
p–p stacking interactions.
3.1.5. Structure of [Ni(L)(pytp)] (5)
pytp ligands are attached on both sides of the chain (Fig. 5b). Adja-
cent chains are further linked by two types of face-to-face inter-
actions between two pyridine rings of pytp ligands and two benzene
rings of L ligands (face-to-face distances of 3.57 and 3.38 Å, respec-
tively), resulting in a 3D supramolecular architecture (Fig. 5c).
As illustrated in Fig. 5a, the asymmetric unit of 5 contains one
Ni(II) cation, one L anion and one pytp ligand. Each Ni(II) is six-coor-
p–p
dinated by three oxygen atoms from two L anions (Ni1–O2#1
=
2.0501(18), Ni1–O3#1 = 2.0194(18), Ni1–O5 = 2.0287(18) Å), and
three nitrogen atoms from one pytp ligand (Ni1–N2 = 2.131(2),
Ni1–N3 = 2.001(2) and Ni1–N4 = 2.095(2) Å), exhibiting a distorted
3.1.6. Structure of [Ni(L1)(tbpy)]ꢀ0.25H2O (6)
octahedral geometry. Each L anion, adopting a l2
coordination mode (mode IV, Scheme 2), bridges two Ni(II) atoms
to form an infinite chain structure. It is interesting to note that the
-
g1
:
g0
:
g0
:
g1
:
g1
The asymmetric unit of 6 consists of one Ni(II) cation, one L anion,
one tbpy ligand, and a quarter of water molecule. As shown in Fig. 6a,
each Ni(II) cation displays a distorted octahedral coordination

A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
565
Fig. 6. (a) Coordination environment of the Ni(II) cation in 6 (30% probability displacement ellipsoids). Symmetry codes: #1ꢁx + 2, y ꢁ 1/2, ꢁz + 1/2; #2ꢁx + 2, y + 1/2, ꢁz + 1/2.
(b) View of the infinite helical-chain constructed by L anions and Ni(II) cations along the a-axis. (c) View of the 3D supramolecular architecture of 6 formed via hydrogen-
bonding interactions.
geometry, surrounded by three nitrogen atoms from one tbpy ligand
(Ni1–N2 = 2.119(3), Ni1–N3 = 1.998(3), Ni1–N4 = 2.110(3) Å) and
three oxygen atoms from two L anions (Ni1–O2#2 = 2.007(2), Ni1–
O3#2 = 2.072(2) and Ni1–O5 = 2.042(2) Å). Each L anion links two
In addition, C29 and C32 from pyridine ring of tbpy ligand donate
H atoms to oxygen atoms from carboxyl groups to yield intermolec-
ular C29–H29ꢀ ꢀ ꢀO4#5 and C32–H32ꢀ ꢀ ꢀO4#5 hydrogen-bonding
interactions. Besides, C4 and C5 from pyridine ring of L ligand donate
H atoms to O5#3 and O2#4 atoms to generate intramolecular C4–
H4ꢀ ꢀ ꢀO5#3 and C5–H5ꢀ ꢀ ꢀO2#4 hydrogen-bonding interactions
(Table S6b). These hydrogen bonds join the neighboring chains to
from a 3D supramolecular architecture (Fig. 6c).
Ni(II) cations in a l2- : : : :
g1 g0 g0 g1 g1 coordination mode (mode
IV, Scheme 2) to generate an infinite helical chain along the a-axis
(Fig. 6b). The tbpy ligands, as the dangling arms, are attached on both
sides of the chain.

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3.1.7. Structure of [Cd(L)(biim-6)0.5] (7)
The topology of this network can be described as a 3-connected
hexagonal honeycomb 63-hcb net (Figs. S4b and 7b).
As shown in Fig. 7a, the asymmetric unit 7 contains one Cd(II)
cation, one-half biim-6 ligand and one L anion. Each Cd(II) cation
is six-coordinated by four oxygen atoms from three carboxylate
In addition, those wavelike layers are further extended into a 3D
supramolecular architecture by the face-to-face
p–p stacking
and one phenolic hydroxyl groups of three
L
anions (Cd1–
interactions between imidazole rings of the adjacent layers with
the interplanar separation being 3.57 Å (the centroid–centroid
and slippage distances of 3.73 and 1.05 Å, respectively). Obviously,
the non-covalent p–p stacking interactions play an important role
in the formation of the 3D supramolecular structure of 7 (Fig. 7c).
O1#1 = 2.236(3), Cd1–O2 = 2.277(3), Cd1–O3 = 2.326(3), Cd1–
O4#2 = 2.322(3) and Cd1–O5#2 = 2.388(3) Å) and one N atom from
one biim-6 ligand (Cd1–N2 = 2.270(4) Å) in a distorted octahedral
coordination geometry. As shown in Fig. S4a, adjacent Cd(II) cat-
ions are bridged by L anions in l3- : : : :
g1 g1 g1 g1 g1 coordination
mode (mode I, Scheme 2) to yield a double-chain structure. The
chains are linked by the biim-6 ligands to furnish a wave-like layer.
Fig. 7. (a) Coordination environment of the Cd(II) cation in 7 showing 30% thermal
probability ellipsoids. Symmetry codes for the generated atoms: #1ꢁx + 1/2, ꢁy + 1/
Fig. 8. (a) ORTEP diagram showing the coordination environment for Cd(II) cation in
8. All H atoms are omitted for clarity. (Symmetry codes: #1ꢁx + 1/2, y + 1/2, z; #2ꢁx,
ꢁy, ꢁz + 1; #3ꢁx + 1/2, y ꢁ 1/2, z). (b) View of the 2D (4,4) network of 8. (c) View of
the intramolecular hydrogen-bonding interactions in the 2D structure of 8.
#2
#3
2, ꢁz + 1;
ꢁx + 1/2, ꢁy + 3/2, ꢁz + 1;
ꢁx + 1, y, ꢁz + 1/2. (b) Topological
representation of the 63-hcb net. (c) View of the 3D supramolecular structure of
7 formed via interactions.
p–p

A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
567
#2
#3
Fig. 9. (a) Coordination environments of the Cd(II) cations in 9 (30% probability displace ellipsoids). Symmetry codes: #1x ꢁ 1, y, z; ꢁx + 1, ꢁy + 1, ꢁz + 2; ꢁx + 1, ꢁy,
ꢁz + 1; #4x + 1, y, z. (b) Topological representation of the (44)-sql network.
3.1.8. Structure of [Cd(L)(phen)] (8)
As shown in Fig. 8a, the asymmetric unit 8 contains one Cd(II)
cation, one phen ligand and one L anion. Each Cd(II) cation shows
anions and one water molecule (Cd3–O 2.236(4)–2.640(3) Å) in
slightly distorted pentagonal bipyramid coordination sphere. Each
L anion in a l3- : : : :
g1 g1 g1 g2 g1 coordination mode (mode VI,
a
distorted octahedral coordination geometry {CdN2O4}, sur-
Scheme 2) links three Cd(II) cations to form a wave-like layer
rounded by four oxygen atoms from three carboxylate and one
phenolic hydroxyl of three L anions (Cd1–O1#2 = 2.325(3), Cd1–
O2 = 2.257(3), Cd1–O3 = 2.405(2) and Cd1–O4#1 = 2.221(3) Å) and
two nitrogen atoms from one phen ligand (Cd1–N2 = 2.325(3),
(Fig. S6).
From a topological perspective, if three Cd(II) cations can be re-
garded as a 4-connected node, L anions can be considered as con-
nectors, the layer can be described as a 4-connected (4,4) network
(Fig. 9b).
Cd1–N3 = 2.342(3) Å). Each L anion in a l3- : : : :
g0 g1 g1 g1 g1 coor-
dination mode (mode V, Scheme 2), links Cd(II) cations to generate
a (4,4) sheet (Figs. 8b and S5). The phen ligands are decorated on
two sides of the layer.
3.1.10. Structure of [Cd3(L)3(biim-4)0.5]ꢀ6H2O (10)
As illustrated in Fig. 10a, the asymmetric unit of 10 contains
three Cd(II) cations, half a biim-4 ligand, three L anions and six
water molecules. Each Cd(II) cation is six-coordinated in a trigonal
prismatic coordination environment. Cd1 is coordinated by six
oxygen atoms from three carboxylates and two phenolic hydroxyl
groups of three L anions. Cd1–O bond lengths vary from 2.245(4) to
2.313(5) Å. Cd2 is surrounded by five oxygen atoms from three car-
Furthermore, there exist intramolecular C31–H31ꢀ ꢀ ꢀO1#5 and
C3–H3ꢀ ꢀ ꢀO5#4 hydrogen-bonding interactions between pyridine
groups from phen ligands and carboxylate oxygen atoms from L
anions. Besides, the methylene group of L anion donates H atom
to O3 atom of phenolic hydroxyl group, generating intramolecular
C7–H7Bꢀ ꢀ ꢀO3 hydrogen-bonding interaction (Table S8b), which
further stabilizes the 2D structure of 8 (Fig. 8c).
boxylate groups of three
L anions (Cd2–O1 = 2.222(5), Cd2–
O9#1 = 2.374(5), Cd2–O10#1 = 2.365(5), Cd2–O11#6 = 2.345(5),
Cd2–O12#6 = 2.544(4) Å), and one nitrogen atom from one biim-4
ligand (Cd2–N4 = 2.253(6) Å). Cd3 is six-coordinated by six oxygen
atoms from three carboxylates and one phenolic hydroxyl of three
L anions. Cd3–O bond lengths are all within the normal range. As
shown in Fig. 10b, three carboxylates link three Cd(II) cations to
3.1.9. Structure of [Cd3(L)3(H2O)]ꢀ2H2O (9)
The asymmetric unit of 9 consists of three Cd(II) cations, three L
anions, one coordinated water molecule and two lattice water mol-
ecules. As shown in Fig. 9a, Cd1 cation is six-coordinated by six oxy-
gen atoms from three carboxylate and two phenolic hydroxyl of
three L anions (Cd1–O = 2.251(3)–2.336(3) Å) in a trigonal pris-
matic [13] coordination environment. Cd2 cation is six-coordinated
by six oxygen atoms from three L anions (Cd2–O = 2.214(3)–
2.403(3) Å) in a distorted octahedral coordination geometry. Cd3
cation is seven-coordinated by six oxygen atoms from three L
form
a
:
trinuclear unit. anions bridge trinuclear units in
L
l3-
g1
g1
:
g1
:
g1
:
g1 and l3 g1 g1 g1 g2 g1 coordination modes
- : : : :
(modes I and IV, Scheme 2) to generate a undulated layer. The
layers are further linked by the biim-4 ligands to furnish a compli-
cated 3D framework (Fig. 10c).

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A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
From a topological view, the trinuclear units can be considered
obtained. In 1, the L anions bridge the Cd(II) cations to yield an infi-
nite double-chain. The chains are further linked by pbib ligands to
furnish a layer. In 10, the L anions bridge the Cd(II) cations to yield
a undulated layer. The layers are further bridged by the biim-4 li-
gands to furnish a complicated 3D framework. Obviously, the phe-
nyl group of the pbib ligand increases the steric hindrance when
coordinated with the metal atoms.
as 5-connected nodes, and L anion and biim-4 ligand are regarded
as linkers, respectively, the whole framework of 10 can be de-
scribed as a 3D 5-connected net with the point symbol of (46ꢀ64).
3.2. Discussion
When the rigid or chelating N-donor ligands were used, the com-
pounds are inclined to form low dimensional structures [14]. Com-
pounds 3, 4 and 8 display the effects of chelating ligands on the
structures. The introduction of pytp, tbpy and phen ligands hinders
the propagation of metal–L linkages, and leads to 0D dimeric struc-
ture of compound 3, an infinite chain structure of compound 4 and
the (4,4) sheet of compound 8. Compounds 2, 5 and 6 also show
the effect of the N-donor ligands on the structures of the complexes.
Tack compounds [Ni(L)(pbib)]ꢀ2H2O (2) and [Ni(L)(tbpy)]ꢀ0.25H2O
(6) for example. In 2, the L anions bridgethe Ni(II) cations to generate
dimeric units, which are further linked by two kinds of pbib ligands
to form a 2D network. While, in 6, the L anions link the Ni(II) cations
to generate an infinite helicalchain. The tbpy ligands, as the dangling
arms, are attached on both sides of the chain.
3.2.1. Effects of the N-donor ligands on the structures of the
compounds
The N-donor ligands have a remarkable effect on the construc-
tion of the compounds. Compound [Cd3(L)3(H2O)]ꢀH2O (9) shows a
2D network. However, when the N-donor ligands were introduced
into the reaction system of 9, structurally-different compounds 1,
3, 4, 7, 8 and 10 were obtained. For example, compounds
[Cd(L)(biim-6)0.5] (7) and [Cd3(L)3(biim-4)0.5]ꢀ6H2O (10) display
the effect of the lengths of the bis(imidazole) ligands on the struc-
tures. Compared with biim-4, biim-6 has a longer alkyl spacer. In 7,
the L anions bridge the Cd(II) cations to form an infinite double-
chain. The chains are further linked by the biim-6 ligands to fur-
nish a 2D 63-hcb network. Whereas, in 10, the L anions link the
Cd(II) cations to form layers, which are extended by the biim-4 li-
gands to generate a 3D framework with the (46ꢀ64) topology. Com-
pounds 1 and 10 show the effects of the spacers on the structures.
When two central carbon atoms of the biim-4 ligand are replaced
by the phenyl group, a structurally different pbib ligand was
3.2.2. PXRD results and thermal analysis
To confirm whether the crystal structures are truly representa-
tive of the bulk materials, PXRD experiments were carried out for
Fig. 10. (a) ORTEP view of 10 showing the local coordination environments of Cd(II) cations with hydrogen atoms omitted for clarity (30% probability displacement ellipsoids).
Symmetry codes: #1ꢁx, ꢁy ꢁ 1, ꢁz; #2x, y ꢁ 1, z ꢁ 1; #3ꢁx ꢁ 1, ꢁy ꢁ 1, ꢁz; #4ꢁx, ꢁy, ꢁz + 1; #5ꢁx, ꢁy ꢁ 1, ꢁz ꢁ 1; #6x, y + 1, z + 1. (b) View of the trinuclear unit. (c) Topological
representation of the 5-connected framework of 10. In this network, red spheres represent trinuclear units, the purple and dark green lines represent the biim-4 ligands and L
anions, respectively. (Color online.)

A.-T. Pu et al. / Polyhedron 50 (2013) 556–570
569
1–10. The PXRD experimental and computer-simulated patterns of
the corresponding complexes are shown in the Supporting Infor-
mation (Fig. S7). They show that the synthesized bulk materials
and the measured single crystals are the same.
7, 402 nm (kex = 354 nm) for 8, 403 nm (kex = 324 nm) for 9 and
403 nm (kex = 324 nm) for 10. The emissions of compounds 1, 3,
4 and 7–10 are neither metal-to-ligand charge transfer (MLCT)
nor ligand-to-metal charge transfer (LMCT) in nature since the
Cd2+ cations are difficult to oxidize or to reduce because of their
d10 configuration [18]. The emission peaks of compounds 1, 3, 4
and 7–10 should originate from the corresponding L anion, because
similar emissions have been observed for the H2L ligand [19,20].
Thermogravimetric analyses were carried out for compounds
1–10 in order to characterize the compounds more fully in terms
of thermal stability. The experiments were performed under N2
atmosphere with a heating rate of 10 °C/min, as shown in Fig. S8
(see the Supporting Information). For compound 2, the weight loss
corresponding to the release of two lattice water molecules are ob-
served from 33 to 127 °C (observed 6.2%, calculated 5.3%). The
anhydrous compound begins to decompose at 351 °C. The remain-
ing weight corresponds to the formation of NiO (observed 13.9%,
calculated 11.0%). Compound 3 shows a 1.3% weight loss from 72
to 148 °C, corresponding to the loss of one free water molecule
(calculated 1.2%). The second weight loss from 315 to 567 °C corre-
sponds to the collapse of the framework. The remaining residue is
18.8%, which can be assigned to the formation of CdO (calculated
16.2%). Compound 6 loses its lattice water in the range of 53–
93 °C (observed 0.7%, calculated 0.6%). After removal of the water
molecules, the remaining solid is stable up to 394 °C. In the tem-
perature range of 394–513 °C, the weight loss can be attributed
to the decomposition of the organic ligand. The remaining weight
corresponds to the formation of NiO (observed 10.4%, calculated
9.6%). For compound 9, the weight loss corresponding to the re-
lease of the one lattice water molecule is observed from 50 to
76 °C (observed 1.4%, calculated 1.3%). The weight loss correspond-
ing to the release of the one coordinated water molecule is ob-
served from 161 to 175 °C (observed 1.5%, calculated 1.3%).
Decomposition of the residual composition occurs from 348 to
536 °C, leading to the formation of CdO as the residue (observed
28.3%, calculated 27.2%). For 10, the first weight loss corresponding
to the release of water molecule is observed before 105 °C (ob-
served 7.0%, calculated 6.8%). The departure of the organic compo-
nents occurs from 311 °C (observed 27.13%, calculated 24.3%). For
1, 4, 5 and 8, the decomposition of organic components occurs at
314–519, 315–534, 394–478 and 312–574 °C, respectively.
4. Conclusion
In summary, ten new coordination compounds were success-
fully synthesized under hydrothermal conditions by varying the
N-donor ligands and central metals. These compounds display fas-
cinating 0D, 1D, 2D and 3D structures. The structural differences of
the compounds indicate that the organic ligands and the N-donor
ligands have important effects on the resultant complex structures.
The results also indicate that the H2L ligand is a good candidate for
the construction of coordination compounds with aesthetic struc-
tures. The photoluminescent emissions indicate that compounds
1, 3, 4 and 7–10 may be good candidates for optical materials.
Acknowledgments
We thank the National Natural Science Foundation of China
(Grant Nos. 21071028, 21001023, 21277022), the Science Founda-
tion of Jilin Province (201215005, 20100109) and the Fundamental
Research Funds for the Central Universities for support.
Appendix A. Supplementary material
Selected bond lengths and angles, PXRD patterns, thermogravi-
metric (TG) of the compounds 1–6 and 8–10, emission spectra of
the H2L and the N-donor ligands are given in Supplementary Infor-
mation. CCDC 884320–884329 contain the supplementary crystal-
lographic data for compounds 1–10. These data can be obtained
free of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk. Supplementary data associated
with this article can be found, in the online version, at http://
dx.doi.org/10.1016/j.poly.2012.11.045.
3.2.3. Luminescent properties
Luminescent properties of compounds with d10 metal centers
have attracted much attention because of their potential applica-
tions in chemical sensors, photochemistry, and electroluminescent
display [15]. Solid-state luminescent studies were carried out for
ligands H2L, phen, biim-4, biim-6, pbib, pytp and tbpy, as well as
compounds 1, 3, 4 and 7–10 in the solid state at room temperature
(Fig. S9 and Table 2). The emission bands for the free ligands are
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