Synthesis, characterization and properties of a family of lead(ii)-organic frameworks based on a multi-functional ligand 2-amino-4-sulfobenzoic acid exhibiting auxiliary ligand-dependent dehydration-rehydration behaviours

Article abstract of DOI:10.1039/c4dt00659c

A systematic investigation is reported of the use of the multi-functional ligand 2-amino-4-sulfobenzoate (asba^2-) to construct lead(ii)-organic frameworks in the presence and absence of N-donor auxiliary ligands phen, bipy and bix [phen = 1,10-phenanthroline, bipy = 2,2′-bipyridine and bix = 1,4-(methylene-benzene)bisimidazole]. Under ambient, aqueous conditions the assembly of asba^2- with Pb(ii) and phen or bipy leads to two iso-structural 2D double-layer frameworks, {[Pb₂(asba) ₂(phen)₂(H₂O)]·2H₂O} _n (1) and {[Pb₂(asba)₂(bipy)₂(H ₂O)]·2H₂O}_n (2). [Pb₂(asba) ₂(bix)₂(H₂O)₂]_n (3) is obtained in the presence of the auxiliary ligand bix and possesses a 3D network built up from 2D Pb(ii)-asba^2--bridged double-layer pillared by bix. A 2D (4,4) topological network [Pb(asba)(H₂O)]_n (4) is obtained in the absence of any second ligand or presence of some bistriazole bridging spacers. The coordination modes of the ligand asba^2- in 1-4 are greatly dependent on the type of auxiliary ligand and the compounds exhibit auxiliary ligand-dependent dehydration-rehydration behaviours; 1 shows in situ rapid and reversible dehydration-rehydration behaviour in air, while the iso-structural compound 2 loses crystallinity in air and transforms into {[Pb₂(asba)₂(bipy)₂(H₂O)] ·H₂O}_n (2A) verified by TGA, elemental analysis and powder X-ray diffraction analysis (PXRD). 3 also shows reversible dehydration-rehydration behaviour, but it takes around one week to rehydrate even after exposure to water vapor, while the dehydrated phase of 4 rehydrates to a new crystalline material. 1 and 3 fall within the category of the recoverable collapsing and guest-induced re-formation frameworks. The water molecules in 1 and 3 have some influence on their solid state fluorescent emission intensity. This journal is the Partner Organisations 2014.

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Synthesis, characterization and properties of a
family of lead(II)–organic frameworks based on a
multi-functional ligand 2-amino-4-sulfobenzoic
acid exhibiting auxiliary ligand-dependent
dehydration–rehydration behaviours†
Cite this: Dalton Trans., 2014, 43,
11597
Kou-Lin Zhang,*a Zhao-Yin Zhong,a Lei Zhang,a Chu-Yue Jing,a Luke M. Danielsb
and Richard I. Waltonb
A systematic investigation is reported of the use of the multi-functional ligand 2-amino-4-sulfobenzoate
(asba2−) to construct lead(II)–organic frameworks in the presence and absence of N-donor auxiliary
ligands phen, bipy and bix [phen = 1,10-phenanthroline, bipy = 2,2’-bipyridine and bix = 1,4-(methylene-
benzene)bisimidazole]. Under ambient, aqueous conditions the assembly of asba2− with Pb(II) and phen
or bipy leads to two iso-structural 2D double-layer frameworks, {[Pb2(asba)2(phen)2(H2O)]·2H2O}n (1) and
{[Pb2(asba)2(bipy)2(H2O)]·2H2O}n (2). [Pb2(asba)2(bix)2(H2O)2]n (3) is obtained in the presence of the auxi-
liary ligand bix and possesses a 3D network built up from 2D Pb(II)-asba2−-bridged double-layer pillared
by bix. A 2D (4,4) topological network [Pb(asba)(H2O)]n (4) is obtained in the absence of any second
ligand or presence of some bistriazole bridging spacers. The coordination modes of the ligand asba2− in
1–4 are greatly dependent on the type of auxiliary ligand and the compounds exhibit auxiliary ligand-
dependent dehydration–rehydration behaviours; 1 shows in situ rapid and reversible dehydration–
rehydration behaviour in air, while the iso-structural compound 2 loses crystallinity in air and transforms
into {[Pb2(asba)2(bipy)2(H2O)]·H2O}n (2A) verified by TGA, elemental analysis and powder X-ray diffraction
analysis (PXRD). 3 also shows reversible dehydration–rehydration behaviour, but it takes around one week
to rehydrate even after exposure to water vapor, while the dehydrated phase of 4 rehydrates to a new
crystalline material. 1 and 3 fall within the category of the “recoverable collapsing” and “guest-induced
re-formation” frameworks. The water molecules in 1 and 3 have some influence on their solid state
fluorescent emission intensity.
Received 5th March 2014,
Accepted 24th May 2014
DOI: 10.1039/c4dt00659c
www.rsc.org/dalton
compared with transition metal MOFs, less attention has been
paid to the MOFs of p-block metal ions despite their impor-
Introduction
During the past few decades, metal–organic frameworks
(MOFs) have attracted much interest in supramolecular chem-
istry, coordination chemistry and materials chemistry, not only
because of their intriguing structural and topological novelty,
but also owing to their tremendous potential applications in
adsorption, microelectronics, ion exchange, separations, non-
linear optics, sensing, heterogeneous catalysis, etc.1–6 However,
tance in photovoltaic conversion, organic light-emitting
diodes, electroluminescence and fluorescent sensors, etc.7 Of
these, lead(II)–organic frameworks are of interest for a number
of reasons. Pb(II) has the ability to form diverse framework
structures with interesting topologies not seen for other
metals, due to its large ionic radius, variable coordination
numbers, ranging from 2 to 10, and diverse coordination geo-
metries.8,9 The coordination geometry of Pb(II) is described as
either holodirected or hemidirected. The holodirected geo-
metry is found in Pb(II) complexes with high coordination
numbers and can be understood in terms of the crowding
effect, while the hemidirected geometry is generally observed
in lead(II) compounds with small coordination numbers and is
associated with the impact of the stereochemical activity of the
6s2 lone pair of Pb(II).8f Lead(II)–organic frameworks have been
aKey Laboratory of Environmental Material and Environmental Engineering of
Jiangsu Province, College of Chemistry and Chemical Engineering, Yangzhou University,
Yangzhou 225002, P.R. China. E-mail: klzhang@yzu.edu.cn,
koulinzhang2002@yahoo.com; Tel: +86 514 87975244
bDepartment of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
†Electronic supplementary information (ESI) available. CCDC 835434 (1),
834929 (2), 835435 (3), 835436 (4) and 989589 (H2asba). For ESI and crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/c4dt00659c
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shown to have interesting catalytic activity towards the Knoeve-
nagel condensation reaction9o and photophysical properties
such as luminescence10 and birefringence,11 and may form
multi-dimensional Pb–X–Pb (X = O, N, Cl, S) frameworks
giving rise to a variety of topologies.12 The coordination chem-
istry of Pb(II) in such materials has recently been investigated
and frequently discussed with regard to the coordination and
stereoactivity of the valence shell lone electron pair in relation
to potential uses as functional materials.13–15
The structural architectures of MOFs can be varied by chan-
ging the metal–ligand ratio, solvents, geometry of the auxiliary
ligands, pH, temperature, etc.16 The flexibility of forming
various topological structures may be enhanced by using
p-block metal ions, and in the case of Pb(II), the coordination
preference of Pb(II) and its geometry, size and bridging ability
of the organic ligands are expected to dictate the final topology
of the framework formed.16c
Chart 1 Molecular structure of H2asba·H2O with 50% ellipsoids.
specific coordination arrays; (5) owing to the presence of aro-
matic/hetero rings of asba2− and dipyridyl/bisimidazole-type
auxiliary ligands in the assembly system, delicate π⋯π stacking
The work presented here uses 2-amino-4-sulfobenzoic acid
(H2asba) as the organic ligand precursor (Chart 1). This is
based on the following considerations: (1) as a rigid aromatic interactions are available to play an important role in the for-
carboxylate ligand, asba2− can play the role of a bridging rod,
mation of an extended supramolecular network, well known in
biological systems.17 To the best of our knowledge, there are as
and so structural prediction of the resulting polymeric species
may be possible to some extent; (2) the acid H2asba has excel- yet no complexes reported with asba2− as the ligand, and
indeed the single crystal X-ray structure of H2asba itself has
not been determined.
Herein we describe a systematic study of the preparation,
crystallography and properties of a family of four Pb(II)
frameworks based on asba2−(Scheme 1). {[Pb2(asba)2(phen)2-
lent solubility in water at room temperature, and so the inter-
action between H2asba and Pb(II) ions can take place easily
under close to ambient conditions; (3) the amino functional
group is the potential interaction site for forming N–H⋯O
hydrogen bonding or coordinative bonds with the central
metal ion; (4) a variety of binding modes of the carboxylate (H2O)]·2H2O}n (1) and {[Pb2(asba)2(bipy)2(H2O)]·2H2O}n (2) are
iso-structural and exhibit a 2D double-layered architecture
and sulfonate groups are anticipated, which will offer new
(phen = 1,10-phenanthroline, bipy = 2,2′-bipyridine). [Pb2(asba)2-
insights to develop building blocks for the construction of
Scheme 1 Simplified representation of the synthesis and crystalline architectures of 1–4 showing the rich auxiliary ligand-dependent dehydration–
rehydration behaviours of these four MOFs.
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(bix)2(H2O)2]n (3) is a 3D network constructed from 2D Pb(II)-
asba2−-bridged double-layers pillared by the auxiliary ligand
bix [1,4-(methylene-benzene)bisimidazole]. [Pb(asba)(H2O)]n
(4), a 2D (4,4)-network, was obtained in the absence of any
auxiliary ligands or in the presence of some bistriazole
spacers. The auxiliary ligand-dependent dehydration–rehydra-
tion behaviours of 1–4 and solid-state fluorescent properties
for all compounds have been studied.
Results and discussion
Synthesis of the complexes
The materials 1–4 were obtained under ambient conditions.
An aqueous mixture of lead(II) and H2asba in the presence/
absence of N-donor auxiliary ligands typically results in pre-
cipitation of a polycrystalline powder directly, but single crys-
tals of 1–4 were successfully obtained by keeping the filtrate
under ambient air for several days with the addition of NaOH
to neutralize the acid. The molar ratio of H2asba : NaOH was
found to be important for the growth of single crystals. Molar
ratios of H2asba : NaOH of 1 : 2 for 1 and 4, 1 : 1 for 2 and 3
were necessary when attempts were made to synthesize 1–4 as
single crystals and polycrystalline powder was obtained if
other molar ratios were used. It should be mentioned that 2
and 3 cannot be obtained without the presence of a small
quantity of ethanol and methanol, respectively, to aid the solu-
bility of the ligands bipy and bix. Compound 4 can also be
obtained in the presence of some bistriazole bridging spacers
[bte
= 1,4-bis(1,2,4-triazol-1-yl)ethane, btp = 1,3-bis(1,2,4-
triazol-1-yl)propane, btb = 1,4-bis(1,2,4-triazol-1-yl)butane, bth
= 1,6-bis(1,2,4-triazol-1-yl)hexane and bbtz = 1,4-(methylene-
benzene)bistriazole], indicating that the coordination ability of
these bistriazole bridging auxiliary ligands to Pb(II) is weaker
than that of bix and cannot compete with the ligand asba2− in
this system. All the carboxylate groups of H2asba in 1–4 are
found to be deprotonated as evidenced by FT-IR spectra and
the results of crystallographic analysis (vide infra). The ligand
asba2− exhibits various coordination modes in 1–4 (Scheme 2),
which exert an important influence on the crystalline architec-
tures as described below.
Structure description
{[Pb2(asba)2(phen)2(H2O)]·2H2O}n (1) and {[Pb2(asba)2(bipy)2-
(H2O)]·2H2O}n (2). 1 and 2 are iso-structural and thus we only
describe the structure of 1 in detail (Fig. 1). The detailed struc-
ture of 2 is shown in Fig. S1.†
Scheme 2 Simplified representation of the coordination modes of
asba2− in 1–4.
The hydrous lead(II) framework 1 crystallizes in the triclinic
ˉ
system with the space group P1 (Table 1). There are two crystal-
lographically independent hemidirected Pb(II) ions, two asba2− water. Pb2 is hexa-coordinated (Pb2O4N2) with two nitrogen
anions, two phen chelating ligands, one coordinated water atoms (N4, N5) from another phen, two oxygen atoms (O11,
and two lattice water molecules in the asymmetric unit O12) from the chelating carboxylate group and two sulfonate
(Fig. 1A). The Pb1 sites are heptacoordinated (Pb1O5N2) by two oxygen atoms (O7, O10) from two asba2− ligands. The bond
nitrogen atoms from the phen ligand and five oxygen atoms: distances in the carboxylate group [(1.205(3)–1.317(3) Å] of
two from the carboxylate groups, two from the sulfonate H2asba (see ESI† CIF for H2asba·H2O, also obtained in this
groups of two asba2− ligands and one from the coordinated work) clearly show some differences between single- and
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double-bond character, while almost identical bond lengths in
the carboxylate group in 1 [1.265(11)–1.284(10) Å] are observed,
consistent with delocalization as a result of the coordination
of the carboxylate group to Pb(II).
It is useful to compare our new materials with previous
frameworks that include Pb(II).8f,18 The Pb–N bond distances
for lead(II) complexes with an inactive 6s2 lone pair usually fall
in the range of 2.62–2.88 Å19 and the Pb–N distances [2.497 (7)–
2.623(8) Å] in 1 fall within the ranges usually observed in
Pb(II) complexes containing a phen ligand with an active 6s2
lone pair.8b,9c Furthermore, the distances of Pb–Osulfonate and
Pb–Owater are longer than those of Pb–Ocarboxylate (Table 2).
Therefore, the presence of an active 6s2 lone pair opposite to
Pb–Ocarboxylate and close to Pb–Osulfonate is deduced. So, both
Pb1 and Pb2 exhibit hemidirected geometry with the
(Pb1N2O5) and (Pb2N2O4) chromophores, respectively (Fig. 1A).
One asba2− anion acts as a tridentate ligand in the
η1:η1:η1:μ2-coordination mode (Scheme 2): the carboxylate
group (O1C13O2) exhibits chelating coordination and the sul-
fonate group (S2O5O7O13) shows monodentate coordination.
The other asba2− anion acts as a pentadentate ligand with the
η1:η1:η1:η1:η1:μ4-coordination mode: the carboxylate group
(O11C13O2) also exhibits chelating coordination while the sul-
fonate group (S1O8O9O10) exhibits the tridentate coordi-
nation, linking three lead(II) atoms. These two asba2− anions
coordinate with the lead(II) ion alternatively; as a result, a 26-
membered metallamacrocyclic ring is formed. Furthermore,
the tridentate sulfonate group (S1O8O9O10) and its symmetric
equivalent (S1aO8aO9aO10a) coordinate with two symmetric
Pb1 atoms, resulting in the centrosymmetrical sulfonate-
bridged dinuclear eight-membered (Pb1O8S1O9Pb1aO8a-
S1aO9a) secondary building unit (SBU) [Pb2(SO3)2(phen)2],
which further links the adjacent metallamacrocyclic ring into a
1D necklace-like double chain (Fig. 1B). Within the double
chain, the π⋯π stacking interactions exist between the phen
ligands or between the benzene ring of asba2− and the aro-
matic ring of phen (centeroid–centeroid: 3.675, 3.754 Å). 1D
necklace-like double chains are further linked with each other
by such SBUs along the [100] direction; as a result, a 2D
double-layered framework is formed along the [110] plane
(Fig. 1C).
Hydrogen bonds exist extensively in the structure of 1
(Table 3). The coordinated water O1W together with the lattice
water O2W and O3W form hydrogen-bonded trimers with
average Ow⋯Ow distances of 2.863 Å which matches well the
expected distance of hydrogen bonds between water mole-
cules.20 Interlayer π⋯π stacking interactions exist between the
phen ligands (centeroid–centeroid: 4.030 Å). A 3D supramole-
cular network is thus formed through such weak interactions
(Fig. 1E).
Fig. 1 (A) Top: view of the coordination environment of the Pb(II), the
coordination mode of the asba2− ligand and the centrosymmetrical
dinuclear SBU in 1. #1 x − 1, y − 1, z − 1, #2 x − 1, y − 1, z. Bottom:
polyhedral representation of the hemidirected Pb1 and Pb2. (B) The
26-membered uncoplanar metallamacrocycle, metallacalix[4]arene, was
linked by the SBU, resulting in the formation of a 1D necklace-like
double chain, showing the π⋯π stacking interactions within the double
chain. (C) 2D double-layered framework. (D) 3D supramolecular
network formed through interlayer hydrogen bonds (pink dashed lines)
and π⋯π stacking interactions (green dashed lines).
[Pb2(asba)2(bix)2(H2O)2]n (3). 3 Crystallizes in the triclinic
ˉ
system with the space group P1. In the asymmetric unit, there
are two crystallographically independent lead(II) ions, two
independent asba2− ligands, two bix and two coordinated
water molecules. The Pb1 is penta-coordinated (Pb1O4N) by
one nitrogen atom (N5) from the bix ligand and four oxygen
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Table 1 Crystallographic data and structure refinement details for 1–4
Complex
1
2
3
4
Empirical formula
Formula weight
Temperature
C
38H32N6O13Pb2S2
C34H32N6O13Pb2S2
1211.20
296(2)
C28H28N6O12Pb2S2
1119.06
296(2)
C7H7NO6PbS
440.39
296(2)
1259.20
296(2)
Wavelength/Å
Crystal system
Space group
0.71073
Triclinic
P1
0.71073
0.71073
0.71073
Monoclinic
P21/c
Triclinic
Triclinic
ˉ
ˉ
ˉ
P1
P1
a/Å
b/Å
c/Å
α/°
9.6177(15)
13.490(2)
15.996(2)
90.087(2)
96.643(2)
105.861(2)
1981.8(5)
2
9.7272(10)
13.4690(14)
15.4478(16)
89.2900(10)
83.6170(10)
70.4760(10)
1895.0(3)
1
5.9314(7)
11.0291(13)
24.939(3)
101.0520(10)
92.705(2)
93.508(2)
1595.3(3)
2
6.6780(11)
14.672(3)
9.7183(17)
90
95.169
90
948.3(3)
4
3.084
18.024
808
β/°
γ/°
V/Å3
Z
Dc/Mg m−3
2.110
8.665
1204
2.123
9.057
1156
2.330
10.745
1060
Absorption coeff./mm−1
F(000)
θ Range for data collection/°
Index ranges
1.28 to 27.58
−12 ≤ h ≤ 12,
−17 ≤ k ≤ 17,
−20 ≤ l ≤ 20
17 376
1.60 to 27.56
−12 ≤ h ≤ 12,
−17 ≤ k ≤ 17,
−17 ≤ l ≤ 20
16 657
1.67 to 27.48
−7 ≤ h ≤ 7,
−14 ≤ k ≤ 14,
−32 ≤ l ≤ 30
14 086
2.52 to 27.55
−8 ≤ h ≤ 8,
−18 ≤ k ≤ 19,
−12 ≤ l ≤ 11
8085
Reflections collected
Unique(Rint
Completeness
)
8952 [R(int) = 0.0432]
97.5%
8555 [R(int) = 0.0504]
97.8%
7182 [R(int) = 0.0436]
97.9%
2177 [R(int) = 0.0450]
99.8%
Max. and min. transmission
0.3564 and 0.1514
1.010
0.404 and 0.154
1.079
0.2956 and 0.1169
1.062
0.067 and 0.019
1.091
Goof on F2
Final R indices [I > 2σ(I)]
R indices (all data)
R1 = 0.0437, wR2 = 0.1038 R1 = 0.0419, wR2 = 0.1175 R1 = 0.0394, wR2 = 0.0963 R1 = 0.0263, wR2 = 0.0688
R1 = 0.0799, wR2 = 0.1297 R1 = 0.0545, wR2 = 0.1294 R1 = 0.0527, wR2 = 0.1085 R1 = 0.0292, wR2 = 0.0705
Largest diff. peak and hole/e Å−3 1.842 and −1.166
1.634 and −2.285
1.826 and −1.643
2.252 and −1.446
Table 2 Selected bond lengths [Å] and angles [°] for 1–4
Complex 1
Pb(1)–N(3)
Pb(1)–N(2)
Pb(1)–O(1W)
Pb(1)–O(6)#1
Pb(2)–N(5)
Pb(2)–N(6)
Pb(2)–O(7)
O(1)–Pb(1)–O(2)
O(1)–Pb(1)–N(2)
O(2)–Pb(1)–N(2)
O(1)–Pb(1)–N(1)
O(2)–Pb(1)–N(1)
N(2)–Pb(1)–N(1)
O(1)–Pb(1)–O(1W)
O(2)–Pb(1)–O(1W)
N(2)–Pb(1)–O(1W)
N(1)–Pb(1)–O(1W)
O(7)–Pb(2)–O(6)
O(7)–Pb(2)–N(3)
O(6)–Pb(2)–N(3)
2.623(8)
2.591(7)
2.754(8)
2.799(7)
2.497(7)
2.597(8)
2.844(6)
52.4(2)
76.1(2)
79.2(2)
93.0(2)
135.3(2)
63.7(2)
72.9(2)
114.7(2)
122.5(2)
70.9(2)
53.8(2)
79.3(2)
77.1(2)
Pb(1)–O(1)
2.455(6)
Pb(1)–O(2)
Pb(1)–O(5)#2
Pb(2)–O(4)
Pb(2)–O(6)
Pb(2)–O(8)
2.526(6)
2.914(7)
2.759(7)
2.455(6)
2.394(6)
O(3)–Pb(2)–C(20)
O(7)–Pb(2)–N(4)
O(6)–Pb(2)–N(4)
N(3)–Pb(2)–N(4)
O(7)–Pb(2)–O(3)
O(6)–Pb(2)–O(3)
N(3)–Pb(2)–O(3)
N(4)–Pb(2)–O(3)
O(7)–Pb(2)–C(20)
O(6)–Pb(2)–C(20)
N(3)–Pb(2)–C(20)
N(4)–Pb(2)–C(20)
105.6(2)
76.3(2)
121.9(2)
65.0(3)
131.2(2)
80.5(2)
73.8(2)
124.3(2)
27.0(2)
26.8(2)
75.7(3)
99.0(3)
Complex 2
Pb(1)–N(2)
2.587(6)
2.424(5)
2.446(5)
2.713(6)
2.529(6)
2.828(5)
2.635(7)
53.83(17)
76.79(19)
80.82(19)
Pb(2)–N(6)
Pb(2)–O(3W)
Pb(2)–O(3)
Pb(2)–O(10)#5
Pb(2)–O(9)#5
Pb(2)–O(5)#3
2.576(6)
2.846(6)
2.965(7)
2.482(5)
2.475(5)
2.776(5)
Pb(1)–O(1)#4
Pb(1)–O(2)#4
Pb(1)–O(6)
Pb(1)–N(3)
Pb(1)–O(4)
Pb(2)–N(5)
O(1)#4–Pb(1)–O(2)#4
O(1)#4–Pb(1)–N(3)
O(2)#4–Pb(1)–N(3)
O(9)#5–Pb(2)–N(5)
O(10)#5–Pb(2)–N(5)
N(6)–Pb(2)–N(5)
91.1(2)
134.7(2)
62.6(2)
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Table 2 (Contd.)
Complex 2
O(1)#4–Pb(1)–N(2)
O(2)#4–Pb(1)–N(2)
N(3)–Pb(1)–N(2)
O(1)#4–Pb(1)–O(6)
O(2)#4–Pb(1)–O(6)
N(3)–Pb(1)–O(6)
N(2)–Pb(1)–O(6)
O(1)#4–Pb(1)–O(4)
O(2)#4–Pb(1)–O(4)
N(3)–Pb(1)–O(4)
N(2)–Pb(1)–O(4)
O(6)–Pb(1)–O(4)
O(9)#5–Pb(2)–O(3)
O(10)#5–Pb(2)–O(3)
N(6)–Pb(2)–O(3)
120.2(2)
76.24(19)
63.5(2)
O(9)#5–Pb(2)–O(5)#3
O(10)#5–Pb(2)–O(5)#3
N(6)–Pb(2)–O(5)#3
N(5)–Pb(2)–O(5)#3
O(9)#5–Pb(2)–O(3W)
O(10)#5–Pb(2)–O(3W)
N(6)–Pb(2)–O(3W)
N(5)–Pb(2)–O(3W)
O(5)#3–Pb(2)–O(3W)
O(9)#5–Pb(2)–O(10)#5
O(9)#5–Pb(2)–N(6)
O(10)#5–Pb(2)–N(6)
N(5)–Pb(2)–O(3)
122.30(17)
73.80(17)
77.89(19)
118.70(18)
74.53(18)
113.74(18)
123.80(19)
72.40(19)
157.24(18)
52.42(18)
74.5(2)
77.84(17)
130.16(16)
76.63(19)
127.97(19)
83.68(17)
79.87(17)
158.21(17)
120.8(2)
108.82(16)
88.53(18)
78.40(18)
158.23(17)
80.4(2)
132.67(19)
100.82(16)
61.96(16)
O(5)#3–Pb(2)–O(3)
O(3W)–Pb(2)–O(3)
Complex 3
Pb(1)–O(6)
Pb(1)–N(5)
Pb(1)–O(8)#1
Pb(1)–O(2W)
Pb(1)–O(7)
Pb(2)–O(2)#2
N(5)–Pb(1)–O(2W)
O(7)–Pb(1)–O(6)
O(7)–Pb(1)–N(5)
O(7)–Pb(1)–O(2W)
N(5)–Pb(1)–O(6)
O(2W)–Pb(1)–O(6)
2.758(6)
2.422(7)
2.947(6)
2.428(6)
2.400(6)
2.873(5)
90.8(2)
49.8(2)
79.2(2)
69.9(2)
75.8(2)
Pb(2)–N(2)
Pb(2)–O(4)
Pb(2)–O(5)
Pb(2)–O(1)
Pb(2)–O(9)#1
Pb(2)–O(1W)
N(2)–Pb(2)–O(5)
N(2)–Pb(2)–O(1W)
O(5)–Pb(2)–O(1W)
N(2)–Pb(2)–O(4)
O(5)–Pb(2)–O(4)
O(1W)–Pb(2)–O(4)
2.466(7)
2.647(6)
2.468(6)
2.954(7)
2.805(8)
2.531(5)
79.4(2)
90.7(2)
69.01(18)
77.8(2)
51.02(18)
119.99(18)
119.5(2)
Complex 4
Pb(1)–O(1W)
Pb(1)–O(3)
2.485(3)
2.754(3)
Pb(1)–O(5)#4
Pb(1)–O(2)#2
2.358(3)
2.629(3)
Pb(1)–N(1)#5
2.767(5)
Pb(1)–O(4)#4
2.713(4)
O(5)#4–Pb(1)–O(1W)
O(5)#4–Pb(1)–O(2)#2
O(1W)–Pb(1)–O(2)#2
O(5)#4–Pb(1)–O(4)#4
O(1W)–Pb(1)–O(4)#4
O(2)#2–Pb(1)–O(4)#4
O(5)#4–Pb(1)–O(3)
O(1W)–Pb(1)–O(3)
70.28(12)
79.73(11)
75.16(11)
50.90(11)
116.73(11)
73.72(11)
91.23(11)
142.52(12)
O(2)#2–Pb(1)–O(3)
O(4)#4–Pb(1)–O(3)
O(5)#4–Pb(1)–N(1)#5
O(1W)–Pb(1)–N(1)#5
O(2)#2–Pb(1)–N(1)#5
O(4)#4–Pb(1)–N(1)#5
O(3)–Pb(1)–N(1)#5
134.91(10)
66.74(11)
75.37(11)
72.02(11)
143.86(10)
108.33(11)
71.85(10)
Symmetry transformations: #1 1 − x, 1 − y, 1 − z, #2 x − 1, y − 1, z for 1; #2 x, y + 1, z, #3 −x + 1, −y + 1, −z, #4 x + 1, y, z, #5 x, y − 1, z for 2;
# 1 − x, 1 − y, z, #2 x − 1, y − 1, z for 3; #2 −x, −y + 1, −z + 2, #4 x, y, z + 1, #5 x, −y + 1/2, z + 1/2 for 4.
atoms: one sulfonate oxygen atom O8 from one asba2− ligand atom while the sulfonate group coordinates with Pb2 through
and two carboxylate oxygen atoms (O6, O7) from one asba2− the Pb2–O2 bond, leading to the formation of 1D asba2−
-
ligand and one coordinated water O2W with the Pb1–O dis- bridged linear chains which are further pillared alternatively
tances ranging from 2.427(6) to 2.947(6) Å and the Pb1–N5 dis- by bix in the TT (trans–trans) conformation and zigzag asba2−
-
tance being the shortest [2.422(7) Å], indicating that Pb1 Pb1-bix-Pb1-asba2−- units in which the asba2− ligand exhibits
exhibits hemidirected geometry and the 6s2 active lone pair the η1:η1:η1:η1:μ3-coordination mode (Scheme 2). As a result, a
lies opposite to the bond Pb1–N5 and near the bond Pb1–O10. 2D network with point symbol (82)(42·82) is formed.16a There
Pb2 is heptacoordinated (Pb2O6N) with one nitrogen atom are two metallamacrocyclic rings: uncoplanar metallacalix[8]
(N2) from the other bix ligand, two oxygen atoms (O4, O5) arene and metallacalix[4]arene within the 2D network
from the chelating carboxylate group and two sulfonate oxygen (Fig. 2B). The adjacent 2D layers were further linked to each
atoms (O1, O2) from two different asba2− ligands with Pb2–O other by the bonds Pb1–O8 [2.947(6) Å] and Pb2–O1 [2.957(7) Å],
distances ranging from 2.468(6) to 2.954(7) Å to furnish a resulting in
a 3D pillared-layered architecture in which
hemidirected geometry and the 6s2 lone pair lies opposite to the 2D Pb(II)-asba2−-bridged double-layer is pillared by bix
the Pb2–N2 bond [2.465(6) Å] (Fig. 2A).8f
(Fig. 2C).
Hydrogen bonds exist extensively in the lattice of 3 between
The overall 3D architecture of 3 can be described as follows.
The carboxylate group of one asba2− chelates with the Pb2 the coordinated water molecules and the oxygen atoms of
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Table 3 Hydrogen bonds for 1–4
D–H⋯A
d(D–H)
d(H⋯A)
d(D⋯A)
<DHA
Symmetry of A
Complex 1
O1W–H1WA⋯O2W
N1–H1A⋯O2
N1–H1B⋯O2W
O2W–H2WA⋯O3W
O2W–H2WB⋯O1
N4–H4A⋯O9
N4–H4B⋯O10
O3W–H3WB⋯O3
O1W–H1WB⋯O8
0.8500
0.8600
0.8600
0.8500
0.8500
0.8600
0.8600
0.8500
0.8500
2.0600
2.0600
2.3600
2.0300
2.0400
2.1100
2.3600
2.1200
1.9400
2.887(10)
2.686(11)
3.165(12)
2.838(12)
2.806(11)
2.729(11)
3.081(12)
2.886(12)
2.785(9)
164.00
129.00
155.00
158.00
149.00
128.00
142.00
149.00
169.00
−1 + x, y, z
1 + x, y, z
−x, 1 − y, −z
x, −1 + y, z
Complex 2
O1W–H1WA⋯O9
N1–H1A⋯O2W
N1–H1A⋯O8
0.8500
0.8600
0.8600
0.8600
0.8500
0.8500
0.8500
0.8600
0.8500
0.8500
1.9800
2.5200
2.5800
2.0700
1.9900
2.3700
2.1500
2.0400
2.1000
2.0300
2.764(9)
3.189(11)
3.326(11
2.700(10)
2.824(9)
3.160(9)
2.892(9)
2.680(10)
2.901(8)
2.806(9)
152.00
135.00
145.00
129.00
167.00
155.00
146.00
130.00
158.00
152.00
x, −1 + y, z
−1 + x, 1 + y, z
N1–H1B⋯O1
O1W–H1WB⋯O2W
O2W–H2WB⋯O7
O2W–H2WA⋯O7
N4–H4B⋯O10
O3W–H3WB⋯O2
O3W–H3WA⋯O1W
1 + x, −1 + y, z
1 − x, 1 − y, 1 − z
1 + x, y, z
Complex 3
O1W–H1WA⋯O4
O1W–H1WB⋯O3
O2W–H2WA⋯O6
N3–H3B⋯O4
0.8500
0.8500
0.8500
0.8600
0.8500
0.8600
0.8600
1.9600
1.9600
1.9100
2.1100
2.0600
2.3200
2.0100
2.773(8)
2.770(8)
2.744(9)
2.737(10)
2.720(9)
3.167(10)
2.644(11)
158.00
158.00
164.00
130.00
134.00
170.00
130.00
−1 + x, y, z
−1 + x, −1 + y, z
−1 + x, y, z
O2W–H2WB⋯O9
N6–H6A⋯O3
−1 + x, −1 + y, z
−1 + x, y, z
N6–H6B⋯O7
Complex 4
O1W–H1WB⋯O3
O1W–H1WB⋯O4
N1–H1A⋯O1
0.8500
0.8500
0.9000
0.9000
0.8500
2.3900
2.2100
2.4500
1.9700
1.9900
2.949(5)
2.998(5)
3.299(5)
2.718(5)
2.771(5)
124.00
154.00
157.00
139.00
152.00
1 + x, y, z
1 + x, y, 1 + z
1 + x, y, z
N1–H1B⋯O5
O1W–H1WA⋯O1
1 + x, 1/2 − y, 1/2 + z
both carboxylate (O5⋯O1W 2.833 Å, O7⋯O2W 2.766 Å) and formed (Fig. 3C), in which the asba2− ligand exhibits the
sulfonate groups (O3⋯O1W 2.770 and O9⋯O2W 2.720 Å) of η1:η1:η1:η1:η1:μ4-coordination mode (Scheme 2).
the asba2− ligand with an average O–H⋯O hydrogen bond dis-
If pseudo atoms are placed at the centre of the SBUs, which
tance of 2.758 Å, which further stabilizes the 3D framework.
are then further treated as nodes, with the distances between
[Pb(asba)(H2O)]n (4). 4 Crystallizes in the monoclinic system the pseudo atoms as linkers (8.7993 and 9.7183 Å), then the
with the space group P21/c. In the asymmetric unit, there is net can be simplified as a 2D (4,4) topological net.1k
one crystallographically independent lead(II), one asba2− and
The interlayer hydrogen bonds between the coordinated
one coordinated water molecule. The lead(II) atom is hexa- water molecules and both coordinated and uncoordinated sul-
coordinated by one nitrogen atom (N1) from one asba2− ligand fonate oxygen atoms [O1, O3] further extend the 2D layer in
and five oxygen atoms, among which two carboxylate oxygen “ABAB” packing mode into a 3D supramolecular network
atoms (O4, O5) from one asba2− ligand and two sulfonate [O1W–H1WA⋯O1 2.771(5); O1W–H1WB⋯O3 2.949(5) Å]
oxygen atoms (O2, O3) from two asba2− ligands and one (Fig. 3D).
oxygen atom (O1W) from the water molecule to furnish a
hemidirected [PbN1O5] geometry (Fig. 3A). The sulfonate
FT-IR spectra and thermal stability
group coordinates with the lead(II) ion in the syn–syn coordi- The FT-IR spectral data show features attributable to the car-
nation mode, resulting in an eight-membered S1O2O3Pb- boxylate stretching vibrations of 1, 2A, 3 and 4. The absence of
S1O2aO3aPba secondary building unit (SBU) [Pb2(SO3)2] and bands in the range of 1680–1760 cm−1 indicates the complete
these are further linked by the asba2− bridge, leading to the deprotonation of H2asba in these four compounds. The
formation of 1D double-chains (Fig. 3B) further linked to each characteristic bands of the carboxylate groups appear in the
other through the Pb–N bonds; as a result, a 2D network is range of 1613–1649 cm−1 for the asymmetric stretching and
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Fig. 3 (A) Top: the diagram showing the coordination geometry of the
Pb(II) ion in 4. Symmetry transformations: #1 −x + 3/2, y − 1/2, z − 1/2;
#2 x, 1/2 − y, 1/2 + z; #3 x, y, 1 + z. Bottom: polyhedral representation
of the hemidirected Pb(II). (B) View of the [Pb2(SO3)2] SBU and 1D asba2−
-
bridged double chain with a 21 rotation axis. (C) View of the 2D network
formed through the 1D double chains linked by Pb–N bonds and sche-
matic representation of the 2D (4,4) topological network. (D) 3D supra-
molecular network formed through the interlayer hydrogen bonds (red
dashed lines).
1384–1490 cm−1 for the symmetric stretching. The character-
istic stretching vibrations for the sulfonate group in 1, 2A, 3
and 4 are seen at 1200, 1211, 1250 and 1200 cm−1, respectively.
The broad band centered at 3400 cm−1 corresponds to the
mixed vibrations of both H2O and –NH2 in 1, 2A, 3 and 4.21
To study the thermal stability of the compounds, a thermo-
gravimetric analysis (TGA) was performed under flowing N2
with a heating rate of 10 °C min−1 (Fig. 4). The TGA curve of 1
Fig. 2 (A) Top: view of the coordination environment of the Pb(II)
atoms, the coordination mode of the asba2− ligand in 3. #1 − x, 1 − y, z;
#2 x − 1, y − 1, z. Bottom: polyhedral representation of the hemidirected
Pb1 and Pb2. (B) 2D (82)(42·82) topological network with two kinds of
uncoplanar metallamacrocyclic rings: metallacalix[8]arene and metalla-
calix[4]arene. (C) Top: the adjacent 2D layers were linked by the covalent
bonds Pb1–O8 and Pb2–O1 (blue lines) into a 3D network. Bottom:
polyhedral representation of the final 3D framework in which 2D Pb(II)-
asba2−-bridged double-layers were pillared by bix (hydrogen bonds:
red dashed lines).
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(calcd: 4.09%). The second step of weight loss from 390 °C cor-
responds to the combustion of the organic groups.
Dehydration–rehydration behaviours of 1, 3 and 4
The thermogravimetric analysis (TGA) shows clearly that both
the interstitial and coordinated water molecules in 1, 3 and 4
could be removed upon heating. To study the dehydration–
rehydration properties of 1, 3 and 4, an in situ variable temp-
erature powder X-ray diffraction analysis (VT-PXRD) was per-
formed in the static air over the temperature ranges
30–120–30 °C for 1 (Fig. 6), r.t.–215 °C–r.t. for 3 (Fig. 8) and
r.t.–260 °C–r.t. (r.t. = room temperature) for 4 (Fig. 9), respect-
ively. It should be pointed out that the dehydrated phases of 1,
3 and 4 retain crystallinity after the loss of water molecules,
but the structures of the desolvated materials are changed, as
supported by the in situ VT-PXRD patterns at 120 °C for 1,
215 °C for 3 and 260 °C for 4, respectively. Remarkably, the
VT-PXRD patterns clearly show that the dehydrated phase of 1
rehydrates rapidly in the air, resulting in the re-establishment
of the original structure. So, 1 undergoes in situ rapid and
reversible dehydration–rehydration behaviour just in the static
air. In order to study the stability of the dehydrated phase of 1
and determine whether the reverse structural transformation
can occur just on cooling, we measured XRD data under dry
nitrogen. The water is removed at a slightly lower temperature
and then on cooling the phase remains dehydrated (Fig. 7).
This proves that the water is removed and the dehydrated
phase is stable in the absence of atmospheric water.
Fig. 4 TGA curves of 1 (blue), 2A (green), 3 (red) and 4 (black).
shows a gradual weight decrease of 3.86% from 100 to 120 °C
that corresponds to the loss of one coordinated and two lattice
water molecules (calcd: 4.29%). A sharp weight loss beginning
at 350 °C indicates decomposition of the framework.
The weight loss of 2.39% from 234 to 273 °C corresponds to
the release of one coordinated and one lattice water molecule,
which further reveals that the formula of the partly dehydrated
phase of {[Pb2(asba)2(bipy)2(H2O)]·2H2O}n (2) is {[Pb2(asba)2-
(bipy)2(H2O)]·H2O}n (2A) (calcd: 3.02%). The second step begins
from 351 °C and the whole decomposition process is incom-
plete at 800 °C. Powder X-ray diffraction further shows that the
structure of 2A is different from that of 2 (Fig. 5).
It should be noted that it takes about one week for the de-
hydrated phase of 3 to absorb the water molecules and revert
to the original structure even in the presence of water vapor.
For 3, the first step weight loss of 3.22% (calcd: 3.40%) in
the temperature range 114–215 °C corresponds to the removal
of two coordinated water molecules. A sharp weight loss begin-
ning at 354 °C indicates the decomposition of the framework.
The TGA of 4 exhibits two main steps of weight loss. A
weight loss of 4.66% in the temperature range 228–260 °C is in
agreement with the release of the coordinated water molecules
Fig. 6 VT-XRPD patterns recorded during the heating of 1 showing the
complete departure of the water molecules at 120 °C (red line) for 1,
leading to a new dehydrated phase which further shows rapid in situ
reversible dehydration–rehydration just in static air.
Fig. 5 PXRD patterns: (red) simulated from the single-crystal data of 2
with Mercury 1.4.2, (green) for the powder sample 2A.
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Fig. 9 XRPD patterns for 4: (1) the simulated XRPD pattern calculated
from single-crystal data of 4 with Mercury 1.4.2; (2) as-synthesized 4
measured at room temperature; (3) after removal of the water molecules
at 260 °C; (4) after in situ introduction of the water molecules in the
static air into the desolvated material at room temperature; (5) after
exposure of the dehydrated material of 4 to water vapor for two weeks;
and (6) for one month at room temperature. (The dashed lines are used
to denote the positions of some new peaks appearing in the rehydrated
material of 4.)
Fig. 7 VT-XRPD patterns recorded during the heating of 1 under a dry
nitrogen atmosphere showing the complete departure of the water
molecules at 120 °C (red line) for 1, leading to a new dehydrated phase
which on cooling remains dehydrated.
4 shows quite different dehydration–rehydration behaviour
from 1 and 3: the dehydrated phase of 4 rehydrates to a new
crystalline phase whose structure is different from the original
structure, verified by the different PXRD patterns compared
with those of both the original bulk sample and the simulated
ones (Fig. 9). So, this dehydration of 4 is irreversible.
The framework integrity of 1 and 3 can be maintained after
a number of desorption–adsorption cycles, which indicates
that these two compounds may possibly have potential use as
water adsorbents.
Desorption/adsorption to gases
In order to test the ability of all the dehydrated materials to
host molecules other than water, several sorption experiments
were carried out. We considered molecules that are currently
of interest for storage, for example, carbon dioxide (CO2) and
nitrogen (N2). Further, gas sorptions were performed at 278 K
to give more reliable results related to crystal structures deter-
mined at room temperature. The dehydrated materials of 1,
2A, 3 and 4 show almost no uptake capacity to N2 molecules at
278 K. Only the dehydrated material of 1 showed a weak
adsorption capacity in CO2 uptake with a final uptake of 10 mg
g−1 (1.0 wt%) at 38 atm (Fig. 10); the other three materials
show almost no adsorption to CO2. The adsorption of CO2 by 1
may be attributed to the fact that among the materials we have
studied it contains the largest conjugated delocalization
system phen, which may strengthen the electric interaction
between the guest small molecules and the host framework.
Furthermore, it should be noted that the dehydrated 1 showed
Fig. 8 XRPD patterns for 3: (1) the simulated XRD pattern calculated
from single-crystal data of 3 with Mercury 1.4.2; (2) as-synthesized 3
measured at room temperature, (3) after removal of the water molecules
at 215 °C; (4) after exposure of the dehydrated material of 3 to water
vapor at room temperature for two days; (5) after exposure of the
dehydrated material of 3 to water vapor at room temperature for
one week.
The reversible dehydration–rehydration behaviours of 1 and
3 are further verified by the TGA analysis of the rehydrated
materials of 1 and 3. The first step mass loss corresponding to
water molecules in TGA of the rehydrated materials is 4.23%
(calcd: 4.29%) for 1 and 2.83% (calcd: 3.40%) for 3, respect-
ively (see Fig. S2†), showing that complete rehydration had
been achieved.
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Fig. 10 Sorption isotherm of CO2 measured at 278 K for 1 (black:
adsorption, red: desorption).
Fig. 11 Solid state fluorescent spectra for 1 (cyan), 2A (blue), 3 (red), 4
(red) and H2asba (black) (λex = 300 nm).
selective uptake of CO2 over N2 at 278 K, which may be attribu-
ted to the smaller kinetic diameter of CO2 compared to that of
N2 (CO2, 3.3; N2, 3.6 Å) and the significant quadrupole
moment of CO2 (−1.4 × 10−39 cm2), which generates specific
interactions with the host framework.1j,22
2-amino-5-sulfobenzoate perturbed by the lead(II) ion.8b,23 An
even more blue-shifted emission with the maximum emission
peak around 436 nm was observed in 3, which indicates that
the auxiliary flexible bridging ligand bix has a great influence
on the positions and strengths of fluorescent emission. Such a
large blue shift may likely be caused by the coordination
of asba2− and an interaction between ligands perturbed by
Pb(II).8b,23 The maximum emission intensity of 2A among the
four compounds may be attributed to the fact that 2A contains
the least content of water molecules (calcd: 3.02%). It should
be noted that, after removal of the water molecules, the
maximum emissions of the dehydrated materials of 1 and 3
(Fig. S5 and S6†) become stronger than those of the corres-
ponding hydrated materials 1 and 3, indicating that the water
molecules in 1 and 3 have some influence on their fluorescent
intensity.
To determine whether the adsorption of CO2 by 1 is reversi-
ble, in situ XRD patterns were measured under a flow of pure
CO2 at atmospheric pressure. First, we noted that the addition
of CO2 to the hydrated phase gave no change in the powder
XRD patterns. However, addition of CO2 to the dehydrated
phase of 1 resulted in an increase in the background of the
pattern immediately. This is reversible if N2 is then added, and
then repeatable upon switching back to CO2 (Fig. S3†). The
Bragg peaks remain in the same place, suggesting that the
framework of the structure is unaffected by the addition of
gas. Our conclusion is that the CO2 is taken up by the solid in
a disordered way at ambient pressure and so gives diffuse scat-
tering that is responsible for the increased background of the
patterns.
Fluorescent properties
Conclusion
To compare the relative fluorescent intensities of the materials
1, 2A, 3 and 4 we measured the emission spectra of all the In summary, the present study shows that the ligand asba2−
complexes and free acid with the same excitation wavelength and the Pb(II) ion can act as convenient building blocks for the
(Fig. 11). The free acid H2asba exhibits a maximum fluorescent construction of MOFs with interesting properties. In this way,
emission at 502 nm upon excitation at λex = 300 nm. Excitation the first examples of a family of four lead(II) MOFs with
of the microcrystalline samples 1, 2A, 3 and 4 also at λex
=
H2asba were generated, their structures being greatly depen-
300 nm leads to the generation of similar blue-shifted fluo- dent on the type of used auxiliary ligand (or its absence). 1
rescent emissions for 1, 2A and 4 with the maximum emission and 2, exhibiting iso-structural 2D double-layered frameworks,
centered around 472 nm, indicating that the auxiliary ligands are formed in the presence of auxiliary chelating ligands phen
bipy and phen almost have no influence on the emission and bipy, respectively. In the case of using the auxiliary flexible
mechanism since the free ligands bipy and phen show the ligand bix, a novel 3D pillared-layered framework 3 was
maximum emission at 400 and 392 nm (λex = 300 nm), respect- obtained successfully. 4, a 2D (4,4) topological network, is
ively (see Fig. S4†). So the blue shifts for 1, 2A and 4 are likely formed in the absence of any auxiliary ligands or in the pres-
caused by the coordination of the multi-functional ligand ence of some bis(triazole) bridging spacers. The most interest-
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ing property of 1 is its in situ rapid and reversible dehydration– formed. All non-hydrogen atoms were refined anisotropically.
rehydration behaviour simply in air, while the iso-structural The carbon/nitrogen-bound hydrogen atoms of all the com-
compound 2 loses crystallinity under the same conditions. 1 plexes were added geometrically and allowed to ride on their
and 3 show guest-induced structural recovery, which falls respective parent atoms. The oxygen-bound hydrogen atoms of
within the category of “recoverable collapsing” and “guest- water molecules were firstly located in the difference Fourier
induced re-formation” framework materials, while 4 shows map and then kept fixed. The contribution of these hydrogen
irreversible dehydration–rehydration behaviour and rehydrates atoms was included in the structure factor calculations. Details
to a new crystalline phase. Thus the type of auxiliary ligands of crystal data, collection and refinement are listed in Table 1.
appears to be a key factor that affects the dehydration–rehydra-
Synthesis of {[Pb2(asba)2(phen)2(H2O)]·2H2O}n (1). A
tion properties of the resulting framework. To the best of our mixture of Pb(NO3)2 (0.033 g, 0.100 mmol) and phen (0.020 g,
knowledge, 1 also represents the first lead(II)–organic frame- 0.100 mmol) in water (12 ml) was added to a mixture of
work that shows in situ rapid and reversible dehydration– H2asba (0.022 g, 0.100 mmol) and NaOH (0.008 g,
rehydration behavior just in the air, so it may possibly be used 0.200 mmol) in water (6 ml). The filtrate was kept at ambient
as a potential adsorbent and sensing material to water vapor. temperature for several days to yield pale yellow needle-like
The materials 1, 2A, 3 and 4 have been found to exhibit blue crystals (yield: 43 mg; 69% based on H2asba). Anal. calcd (%)
fluorescence in the solid state. The water molecules in 1 and 3 for C38H32N6O13Pb2S2: C, 36.24; H, 2.56; N, 6.68. Found: C,
have a great influence on their fluorescent emission intensity. 36.14; H, 2.45; N, 6.57. Selected IR data (KBr pellet, cm−1):
This work will give impetus to further investigation of the 3436(s), 3050(w), 1606(s), 1570(s), 1505(s), 1417(s), 1396(s),
coordination chemistry of asba2−. Further work is in progress 1309(w), 1193(vs), 1128(w), 1040(s), 837(s), 722(s), 618(m).
in our laboratory to prepare other novel MOFs based on the
ligand asba2− with interesting tunable functional properties.
Synthesis of {[Pb2(asba)2(bipy)2(H2O)]·2H2O}n (2). A mixture
of Pb(NO3)2 (0.033 g, 0.100 mmol) and bipy (0.008 g,
0.050 mmol) in water–CH3CH2OH = 1 : 1 (6 ml) was added to a
mixture of H2asba (0.022 g, 0.100 mmol) and NaOH (0.004 g,
0.100 mmol) in water (5 ml). The filtrate was kept at ambient
temperature for several days to yield pale yellow needle-like
crystals. The crystal loses crystallinity in air and transforms
into {[Pb2(asba)2(bipy)2(H2O)]·H2O}n (2A) (yield: 21 mg; 71%
based on bipy). Anal. calcd (%) for C34H30N6O12Pb2S2: C,
34.21; H, 2.51; N, 7.03. Found: C, 34.09; H, 2.43; N, 6.89.
Selected IR data (KBr pellet, cm−1): 3390(s), 3312(w), 1613(s),
1563(s), 1505(s), 1439(s), 1417(s) 1374(vs) 1324(s), 1223(vs),
1148(vs), 1004(w), 830(s), 749(s), 706 (s), 648(w).
Synthesis of [Pb2(asba)2(bix)2(H2O)2]n (3). A mixture of
H2asba (0.011 g, 0.050 mmol) and NaOH (0.002 g,
0.050 mmol) in water (5 ml) and Pb(NO3)2 (0.033 g, 0.1 mmol)
was added to a solution of bix (0.014 g, 0.050 mmol) in
CH3OH (3 ml). The filtrate was kept at ambient temperature
for several days to yield pale yellow needle-like crystals (yield:
17 mg; 59% based on H2asba). Anal. calcd (%) for
C28H28N6O12Pb2S2: C: 30.05; H, 2.52; N, 7.51. Found: C, 30.25;
H, 2.59; N, 7.41. Selected IR data (KBr pellet, cm−1): 3400(s),
3066(w), 1649(s), 1584(s), 1482(vs), 1426(s), 1338(s), 1214(s),
1142(s), 1083(w), 851(vs), 752(vs), 675 (w), 605(s).
Experimental section
Materials and measurements
The auxiliary ligand 1,4-(methylene-benzene)bisimidazole (bix)
was prepared according to the literature method.24 The other
reagents were purchased commercially and used without
further purification. Elemental analyses (C, H and N) were
carried out on a 240C Elemental analyzer. FT-IR spectra
(400–4000 cm−1) were recorded from KBr pellets in a Magna
750 FT-IR spectrophotometer. Solid state fluorescent spectra
were recorded using an F 4500 fluorescence spectrometer
equipped with a phosphorescence device. Both the excitation
and emission pass widths are 5.0 nm. Thermogravimetric
analysis was performed on a NETZSCH STA 409 PG/PC instru-
ment from room temperature to 800 °C at a heating rate of
10 °C min−1 in N2. X-ray powder diffraction data were collected
on a computer controlled Bruker D8 Advanced XRD diffracto-
meter operating with Cu-Kα1/2 (λ = 1.5418 Å) radiation at a
scanning rate of 0.024° s−1 from 5° to 20° using a VÅNTEC
solid-state detector. The diffractometer was fitted with an
Anton-Parr XRK900 heating stage for variable temperature
studies. Thermogravimetric analysis (TGA) was performed on
a NETZSCH STA 409 PG/PC instrument under a stream of N2
(10 ml min−1).
Synthesis of [Pb(asba)(H2O)]n (4). A mixture of H2asba
(0.011 g, 0.050 mmol) and NaOH (0.004 g, 0.100 mmol) was
dissolved in water (5 ml) and then an aqueous solution of
Pb(NO3)2 (0.033 g, 0.100 mmol) in water (5 ml) was added whilst
stirring. The filtrate was kept at ambient temperature for
several days and pale yellow block crystals were formed (yield:
Crystal structure determination
Crystallographic data for 1–4 were collected with a Siemens 15 mg; 70% based on H2asba). Anal. calc. for C7H7NO6PbS1: C,
SMART CCD diffractometer using graphite-monochromated 19.08; H, 1.60; N, 3.18. Found: C, 18.89; H, 1.48; N, 3.06%.
(Mo-Kα) radiation (λ = 0.71073 Å), ψ and ω scan modes. The Selected IR data (KBr pellet, cm−1): 3365(s), 3083(w), 1622(s),
structures were solved by direct methods and refined by the 1582(s), 1513(s), 1430(ws), 1362(vs), 1219(vs), 1115(vs), 1062(vs),
full-matrix least-squares on F2 method using SHELXL-97 896(s), 827(s), 793(w), 704(s), 636(w).We found that 4 could
program.25 Intensity data were corrected for Lorenz and polari- also be obtained in the presence of bte, btp, btb, bth or bbtz
zation effects and a multi-scan absorption correction was per- with the same molar amount as H2asba.
11608 | Dalton Trans., 2014, 43, 11597–11610
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Paper
(e) W. G. Lu, C. Y. Su, T. B. Lu, L. Jiang and J. M. Chen,
J. Am. Chem. Soc., 2006, 128, 34; (f) M. D. Allendorf,
C. A. Bauer, R. K. Bhakta and R. J. T. Houk, Chem. Soc. Rev.,
2009, 38, 1330.
4 (a) O. M. Yaghi, M. O’Keeffe, N. W. Ockwig, H. K. Chae,
M. Eddaoudi and J. Kim, Nature, 2003, 423, 705;
(b) S. Kitagawa, R. Kitaura and S. I. Noro, Angew. Chem., Int.
Ed., 2004, 43, 2334; (c) C. N. R. Rao, S. Natarajan and
R. Vaidhyanathan, Angew. Chem., Int. Ed., 2004, 43, 1466;
(d) B. H. Ye, M. L. Tong and X. M. Chen, Coord. Chem. Rev.,
2005, 249, 545.
5 (a) I. V. Mitchell, Pillared Layered Structures: Current Trends
and Applications, Elsevier, London, 1990; (b) K. T. Holman,
A. M. Pivowar, J. V. Swift and M. D. Ward, Acc. Chem. Res.,
2001, 34, 107; (c) J. L. Song, H. H. Zhao, J. G. Mao and
K. R. Dunbar, Chem. Mater., 2004, 16, 1884; (d) B. Y. Lou,
F. L. Jiang, B. L. Wu, D. Q. Yuan and M. C. Hong, Cryst.
Growth Des., 2006, 6, 989.
6 (a) A. M. Beatty, Coord. Chem. Rev., 2003, 246, 131;
(b) X.-P. Li, J.-Y. Zhang, M. Pan, S.-R. Zheng, Y. Liu and
C.-Y. Su, Inorg. Chem., 2007, 46, 4617.
Acknowledgements
We gratefully acknowledge the Natural Science Foundation of
Jiangsu Province (BK2012680), the Analysis Center of Yangzhou
University, the Priority Academic Program Development of
Jiangsu Higher Education Institutions (PAPD), and the Key
Laboratory of Environmental Material and Environmental
Engineering of Jiangsu Province.
References
1 (a) G. Férey, C. Mellot-Draznieks, C. Serre, F. Millange,
J. Dutour, S. Surble and I. Margiolaki, Science, 2005, 309,
2040; (b) F. Millange, C. Serre, N. Guillou, G. Férey and
R. I. Walton, Angew. Chem., Int. Ed., 2008, 47, 4100;
(c) S. Kitagawa and K. Uemura, Chem. Soc. Rev., 2005, 34,
109; (d) J. W. Steed and J. L. Atwood, Supramolecular
Chemistry, Wiley and Sons, New York, 2000; (e) S. R. Batten
and R. Robson, Angew. Chem., Int. Ed., 1998, 37, 1460;
(f) G.-X. Liu, Y.-Q. Huang, Q. Chu, T. Okamura, W.-Y. Sun,
H. Liang and N. Ueyama, Cryst. Growth Des., 2008, 8, 3233;
(g) F.-Q. Wang, X.-J. Zheng, Y.-H. Wan, C.-Y. Sun,
Z.-M. Wang, K.-Z. Wang and L.-P. Jin, Inorg. Chem., 2007,
46, 2956; (h) G. J. Halder and C. J. Kepert, J. Am. Chem. Soc.,
2005, 127, 7891; (i) I. Grobler, V. J. Smith, P. M. Bhatt,
S. A. Herbert and L. J. Barbour, J. Am. Chem. Soc., 2013,
135, 6411; ( j) L. Du, Z. Lu, K. Zheng, J. Wang, X. Zheng,
Y. Pan, X. You and J. Bai, J. Am. Chem. Soc., 2013, 135, 562;
(k) D.-S. Li, Y.-P. Wu, J. Zhao, J. Zhang and J. Y. Lu, Coord.
Chem. Rev., 2014, 261, 1.
2 (a) Y. Y. Niu, H. G. Zheng, H. W. Hou and X. Q. Xin, Coord.
Chem. Rev., 2004, 248, 169; (b) J. Heo, Y. M. Jeon and
C. A. Mirkin, J. Am. Chem. Soc., 2007, 129, 7712; (c) J. Luo,
H. Xu, Y. Liu, Y. Zhao, L. L. Daemen, C. Brown,
T. V. Timofeeva, S. Ma and H.-C. Zhou, J. Am. Chem. Soc.,
2008, 130(30), 9626; (d) O. R. Evans and W. Lin, Acc. Chem.
Res., 2002, 35, 511; (e) X. H. Bu, W. Chen, S. L. Lu,
R. H. Zhang, D. Z. Liao, W. M. Shionoya, M. Bu, F. Brisse
and J. Ribas, Angew. Chem., Int. Ed., 2001, 40, 3201;
(f) X.-H. Zhou, Y.-H. Peng, X.-D. Du, C.-F. Wang, J.-L. Zuo
and X.-Z. You, Cryst. Growth Des., 2009, 9, 1028;
(g) L. J. Murray, M. Dincã and J. R. Long, Chem. Soc. Rev.,
2009, 38, 1294; (h) B. Moulton and M. J. Zaworotko,
Chem. Rev., 2001, 101, 1629; (i) H. Furukawa, J. Kim,
N. W. Ockwig, M. O’Keeffe and O. M. Yaghi, J. Am. Chem.
Soc., 2008, 130(35), 11650; ( j) L. Han, Y. Zhou, W.-N. Zhao,
X. Li and Y.-X. Liang, Cryst. Growth Des., 2009, 9, 660;
(k) D. Liu, K. Lu, C. Poon and W. Lin, Inorg. Chem., 2014,
53, 1916.
7 (a) A. Strasser and A. Vogler, J. Photochem. Photobiol., A,
2004, 165, 115; (b) A. Vogler and H. Nikol, Pure Appl. Chem.,
1992, 64, 1311.
8 (a) J. Yang, J. F. Ma, Y. Y. Liu, J. C. Ma and S. R. Batten,
Inorg. Chem., 2007, 46, 6542; (b) S. R. Fan and L. G. Zhu,
Inorg. Chem., 2007, 46, 6785; (c) Y. H. Zhao, H. B. Xu,
Y. M. Fu, K. Z. Shao, S. Y. Yang, Z. M. Su, X. R. Hao,
D. X. Zhu and E. B. Wang, Cryst. Growth Des., 2008, 8,
3566; (d) J. Yang, J. F. Ma, Y. Y. Liu, J. C. Ma and
S. R. Batten, Cryst. Growth Des., 2009, 9, 1894; (e) J. Yang,
G. D. Li, J. J. Cao, Q. Yue, G. H. Li and J. S. Chen,
Chem. – Eur. J., 2007, 13, 3248; (f) L. Shimoni-Livny,
J. P. Glusker and C. W. Bock, Inorg. Chem., 1998, 37,
1853.
9 (a) M. J. Katz, P. M. Aguiar, R. J. Batchelor, A. A. Bokov,
Z.-G. Ye, S. Kroeker and D. B. Leznoff, J. Am. Chem. Soc.,
2006, 128(11), 3669; (b) F. Bonhomme, T. M. Alam,
A. J. Celestian, D. R. Tallant, T. J. Boyle, B. R. Cherry,
R. G. Tissot, M. A. Rodriguez, J. B. Parise and M. Nyman,
Inorg. Chem., 2005, 44, 7394; (c) S.-R. Fan and L.-G. Zhu,
Inorg. Chem., 2006, 45, 7935; (d) R. Sasai and
H. Shinomura, J. Solid State Chem., 2013, 198, 452;
(e) S. H. Deo and A. Godwin, J. Am. Chem. Soc., 2000, 122,
174; (f) J. Li and Y. Lu, J. Am. Chem. Soc., 2000, 122, 10466;
(g) M. H. Jack, M. Saeed and A. S. Ali, Inorg. Chem., 2004,
43, 1810; (h) L. K. Li, Y. L. Song, H. W. Hou, Y. T. Fan and
Y. Zhu, Eur. J. Inorg. Chem., 2005, 3238; (i) X.-Y. Yu, R. Xin,
W.-P. Gao, N. Wang, X. Zhang, Y.-Y. Yang and X.-S. Qu,
J. Solid State Chem., 2013, 204, 314; ( j) Y. H. Yeom, Y. Kim
and K. Seff, Microporous Mesoporous Mater., 1999, 28, 103;
(k) Y. H. Yeom, Y. Kim and K. Seff, J. Phys. Chem., 1997,
B101, 5314; (l) F. Frostemark, L. A. Bengtsson and
B. Holmberg, J. Chem. Soc., Faraday Trans., 1994, 90, 2531;
(m) L. Li, S. Q. Zhang, L. Han, Z. H. Sun, J. H. Luo and
M. C. Hong, Cryst. Growth Des., 2013, 13, 106; (n) D.-S. Li,
3 (a) D. T. de Lill, N. S. Gunning and C. L. Cahill, Inorg.
Chem., 2005, 44, 258; (b) K. Biradha, Y. Hongo and
M. Fujita, Angew. Chem., Int. Ed., 2000, 39, 3843;
(c) X. Zhao, G. Zhu, Q. Fang, Y. Wang, F. Sun and S. Qiu,
Cryst. Growth Des., 2009, 9, 737; (d) D. N. Dybtsev, H. Chun
and K. Kim, Angew. Chem., Int. Ed., 2004, 43, 5033;
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 11597–11610 | 11609

View Article Online
Paper
Dalton Transactions
Y.-P. Wu, P. Zhang, M. Du, J. Zhao, C.-P. Li and Y.-Y. Wang,
(d) F. Fredoueil, M. Evain, D. Massiot, M. Bujoli-Doeuff,
P. Janvier, A. Clearfield and B. Bujoli, J. Chem. Soc., Dalton
Trans., 2002, 1508; (e) B. Chen, S. Ma, F. Zapata,
F. R. Fronczek, E. B. Lobkovsky and H.-C. Zhou, Inorg.
Chem., 2007, 46, 1233.
Cryst. Growth Des., 2010, 10, 2037; (o) X.-M. Lin, T.-T. Li,
L.-F. Chen, L. Zhang and C.-Y. Su, Dalton Trans., 2012, 41,
10422.
10 (a) F. J. M. Casado, L. Cañadillas-Delgado, F. Cucinotta,
A. Guerrero-Martínez, M. R. Riesco, L. Marchese and 16 (a) S. R. Batten, S. M. Neville and D. R. Turner, Coordination
J. A. R. Cheda, CrystEngComm, 2012, 14, 2660; (b) Y.-H. Zhao,
H.-B. Xu, K.-Z. Shao, Y. Xing, Z.-M. Su and J.-F. Ma, Cryst.
Growth Des., 2007, 7, 513; (c) K.-L. Zhang, F. Zhou, R. Wu,
B. Yang and S. W. Ng, Inorg. Chim. Acta, 2009, 362, 4255;
(d) K.-L. Zhang, Y. Chang, C. T. Hou, R. Wu, G. W. Diao
and S. W. Ng, CrystEngComm, 2010, 12, 1194;
(e) K.-L. Zhang, Z.-C. Pan, W. Liang, W.-L. Liu and S. W. Ng,
Mater. Lett., 2009, 63, 2136; (f) K.-L. Zhang, Y. Chang,
Polymers: Design, Analysis and Applications, RSC Publishing,
Cambridge, 2009; (b) W. L. Leong and J. J. Vittal, Chem.
Rev., 2011, 111, 688; (c) P. Diaz, J. Benet-Buchholz, R. Vilar
and A. J. P. White, Inorg. Chem., 2006, 45, 1617;
(d) K.-L. Zhang, C. T. Hou, J.-J. Song, Y. Deng, L. Li,
S. W. Ng and G.-W. Diao, CrystEngComm, 2012, 14, 590;
(e) C. Gabriel, M. Perikli, C. P. Raptopoulou and A. Terzis,
Inorg. Chem., 2012, 51, 9282.
J.-B. Zhang, Y. Deng, T.-T. Qiu, L. Li and S. W. Ng, CrystEng- 17 (a) K. M. Guckian, B. A. Schweitzer, R. X.-F. Ren,
Comm, 2012, 14, 2926.
C. J. Sheils, D. C. Tahmassebi and E. T. Kool, J. Am. Chem.
Soc., 2000, 122, 2213; (b) Y. Kim, J. H. Geiger, S. Hahn and
P. B. Sigler, Nature, 1993, 365, 512; (c) J. L. Kim,
D. B. Nikolov and S. K. Burley, Nature, 1993, 365, 520;
(d) C. A. Hunter and J. K. M. Sanders, J. Am. Chem. Soc.,
1990, 112, 5525.
11 (a) M. J. Katz, P. M. Aguiar, R. J. Batchelor, A. A. Bokov,
Z.-G. Ye, S. Kroeker and D. B. Leznoff, J. Am. Chem.
Soc., 2006, 128, 3669; (b) M. J. Katz, H. Kaluarachi,
R. J. Batchelor, A. A. Bokov, Z.-G. Ye and D. B. Leznoff,
Angew. Chem., Int. Ed., 2007, 46, 8804.
12 (a) K. P. Rao, A. Thirumurugan and C. N. R. Rao, 18 (a) M. Arfa, R. Olier and M. Privat, J. Phys. Chem. A, 2008,
Chem. – Eur. J., 2007, 13, 3193; (b) A. Thirumurugan,
R. A. Sanguramath and C. N. R. Rao, Inorg. Chem., 2008,
47, 823.
112, 6004; (b) C. Gourlaouen and O. Parisel, Angew. Chem.,
Int. Ed., 2007, 46, 553; (c) R. D. Hancock, J. H. Reibenspies
and H. Maumela, Inorg. Chem., 2004, 43, 2981; (d) V. Mah
and F. Jalilehvand, Inorg. Chem., 2012, 51, 6285.
13 (a) M. A. R. Dakers, M. N. S. Hill, J. C. Lockhart and
D. J. Rushton, J. Chem. Soc., Dalton Trans., 1994, 209; 19 R. D. Hancock, M. S. Shaikjee, S. M. Dobson and
(b) P. Schwerdtheger, G. A. Heath, M. Dolg and J. C. A. Boeyens, Inorg. Chim. Acta, 1988, 154, 229.
M. A. Bennett, J. Am. Chem. Soc., 1992, 114, 7518; 20 D. Eisenberg and W. Kauzmann, The Structure and
(c) K. Byriel, K. R. Dunster, L. R. Gahan, C. H. L. Kennard, Properties of Water, Oxford University Press, Oxford, 1969.
J. L. Latten, I. L. Swann and P. A. Duckworth, Polyhedron, 21 K. Nakamoto, Infrared and Raman Spectra of Inorganic and
1992, 11, 1205; (d) P. Pyykko, Chem. Rev., 1988, 88, 563.
Coordination Compounds, Wiley, New York, 4th edn, 1986,
14 (a) A. Bashall, M. Mcpartlin, B. P. Murphy, D. E. Fenton,
p. 231.
S. J. Kitchen and P. A. Tasker, J. Chem. Soc., Dalton Trans., 22 S. Coriani, A. Halkier, A. Rizzo and K. Ruud, Chem. Phys.
1990, 505; (b) A. K. Cheetham, G. Férey and T. Loiseau, Lett., 2000, 326, 269.
Angew. Chem., Int. Ed., 1999, 38, 3268; (c) N. Stock, 23 (a) A. Vogler and H. Kunkely, Coord. Chem. Rev., 2007, 251,
S. A. Férey, G. D. Stucky and A. K. Cheetham, J. Chem. Soc.,
Dalton Trans., 2000, 4292; (d) X. Luo, L. Liu, F. Deng and
S. Luo, J. Mater. Chem. A, 2013, 1, 8280.
577; (b) D. Rendell, Fluorescence and Phosphorescence, John
Willey & Sons, New York, 1987; (c) P. C. Ford and A. Vogler,
Acc. Chem. Res., 1993, 26, 220; (d) A. Vogler, A. Paukner and
H. Kunkely, Coord. Chem. Rev., 1980, 33, 227.
15 (a) V. Safarifard, A. Morsali and S. W. Joo, Ultrason. Sono-
chem., 2013, 20, 1254; (b) M. L. Hu, A. Morsali and 24 B. F. Hoskins, R. Robson and D. A. Slizys, J. Am. Chem. Soc.,
L. Aboutorabi, Coord. Chem. Rev., 2011, 255, 2821; 1997, 119, 2952.
(c) O. Sadeghzadeh, A. Morsali, V. T. Yilmaz and 25 G. M. Sheldrick, SHELXL 97. Programs for Crystal Structure
O. Büyükgüngör, Inorg. Chim. Acta, 2010, 363, 841;
Analysis (Release 97-2), University of Göttingen, Germany, 1997.
11610 | Dalton Trans., 2014, 43, 11597–11610
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