Two luminescent d10 metal coordination polymers assembled from a semirigid terpyridyl carboxylate ligand with high selective detecting of Cu2+, Cr2O72- and acetone

Article abstract of DOI:10.1016/j.jssc.2017.04.014

Using a carboxylic oligopyridine ligand, 4′-(4-carboxyphenyl)?4,2′:6′,4″- terpyridine (Hcptpy), and imidazole-4,5-dicarboxylic acid (H₃idc), two metal(II)-cptpy compounds formulated as [Zn₂(cptpy)₄]_n·nH₂

Full text of DOI:10.1016/j.jssc.2017.04.014

Author’s Accepted Manuscript
10
Two luminescent d metal coordination polymers
assembled from a semirigid terpyridyl carboxylate
2+
ligand with high selective detecting of Cu ,
2-
Cr O and acetone
2 7
Fei Yuan, Ting-Ting Wang, Huai-Ming Hu,
Chuan-Ti Li, Chun-Sheng Zhou, Xiaofang Wang,
Ganglin Xue
www.elsevier.com/locate/yjssc
PII:
S0022-4596(17)30124-X
http://dx.doi.org/10.1016/j.jssc.2017.04.014
YJSSC19747
DOI:
Reference:
To appear in:
Journal of Solid State Chemistry
Received date: 23 February 2017
Revised date: 5 April 2017
Accepted date: 12 April 2017
Cite this article as: Fei Yuan, Ting-Ting Wang, Huai-Ming Hu, Chuan-Ti Li,
10
Chun-Sheng Zhou, Xiaofang Wang and Ganglin Xue, Two luminescent d meta
coordination polymers assembled from a semirigid terpyridyl carboxylate ligand
2+
2-
with high selective detecting of Cu , Cr O and acetone, Journal of Solid
2 7
State Chemistry, http://dx.doi.org/10.1016/j.jssc.2017.04.014
This is a PDF file of an unedited manuscript that has been accepted fo
publication. As a service to our customers we are providing this early version o
the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting galley proof before it is published in its final citable form
Please note that during the production process errors may be discovered which
could affect the content, and all legal disclaimers that apply to the journal pertain

Two luminescent d10 metal coordination polymers assembled
from a semirigid terpyridyl carboxylate ligand with high
2-
selective detecting of Cu2+, Cr2O7 and acetone
Fei Yuana,b, Ting-Ting Wangb, Huai-Ming Hub*, Chuan-Ti Lib, Chun-Sheng Zhoua*,
Xiaofang Wangb, Ganglin Xueb
a
Shaanxi Key Laboratory of Comprehensive Utilization of Tailings Resources,
College of Chemical Engineering and Modern Materials, Shangluo University,
Shangluo 726000, China
b
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of
Ministry of Education, College of Chemistry and Materials Science, Northwest
University, Xi'an 710127, China
*To whom correspondence should be addressed.
Prof. Dr. Huai-Ming Hu
College of Chemistry and Materials Science
Northwest University
Xi’an 710127, China
Tel/Fax: +86-29-81535026
Email: ChemHu1@NWU.EDU.CN
1

Abstract: Using a carboxylic oligopyridine ligand, 4′-(4-carboxyphenyl)-4,2′:6′,4″-
terpyridine (Hcptpy), and imidazole-4,5-dicarboxylic acid (H3idc), two
metal(II)-cptpy
compounds
formulated
as
[Zn2(cptpy)4]n·nH2O
(1),
[Zn2(cptpy)2(Hidc)(H2O)2]n·nH2O (2) have been hydrothermally synthesized and
structurally characterized by single-crystal X-ray diffraction. Compound 1 shows a
2D + 2D →3D supramolecular framework structure generated by two-fold
interpenetrating 3-connected 2D framework (2D+2D→2D) with the sql topological
net and the Schläfli symbol of {44·62}. Compound 2 displays a 1D ladder chain
structure. The luminescent properties of 1 and the ones immersed in various kinds of
organic compounds and nitrate@DMF solutions have been investigated. Importantly,
1 shows highly selective and sensitive response to acetone and Cu2+ through
luminescence quenching effects, making it a promising luminescent sensor for
acetone molecule and Cu2+. Meaningwhile, compound 2 shows highly selective
2−
sensitivity for Cr2O7
.
Graphical Abstract
Two luminescent d10 metal coordination polymers assembled
from a semirigid terpyridyl carboxylate ligand with high
2-
selective detecting of Cu2+ ion, Cr2O7 and acetone
Fei Yuana,b, Ting-Ting Wanga, Huai-Ming Hua*, Chuan-Ti Lia, Xiaofang Wanga,
Ganglin Xuea
Two Zn(II) coordination polymers based on 4′-(4-carboxyphenyl)-4,2′:6′,4″-
2

terpyridine have been obtained. Compound 1 shows high selective detecting for Cu2+
ion and acetone molecule. Meaningwhile, compound 2 shows highly selective
2−
sensitivity for Cr2O7
.
Keywords: Coordination polymer; Carboxylate; Luminescence; Sensor
1. Introduction
Currently coordination polymers (CPs) or metal-organic frameworks (MOFs) as a
kind of multifunctional materials still have attracted much interest due to their
potential applications such as molecular separation [1], catalysis [2], gas storage and
3

capture [3], drug delivery [4], and sensor devices [5,6]. In particular, as high
sensitivity and low cost sensors, researches on MOF-based fluorescence sensors have
developed significantly owing to their potential importance in biological and
environmental systems [5-7].
Some representative examples for the selective sensing of metal ions such as Cu2+,
Cr6+ have been successfully studied [7-9]. Among those, luminescent MOFs
containing free Lewis basic pyridyl sites as the potential receptor units to interact with
the target metal ions have also been reported, such as [Eu(pdc)1.5
(DMF)]·(DMF)0.5(H2O)0.5
(pdc=pyridine-3,5-dicarboxylate)
[7a],
[H2N
(Me)2][Ln3(L)2(HCOO)2(DMF)2(H2O)] (H4L=2,6-di(3′,5′-dicarboxylphenyl)pyridine)
[8]. Generally, selectivity and sensitivity mainly depend on the naked interaction
between the host and the guest, and this interaction is highly affected by solvent,
hydrogen bonding capability, π…π stacking and electrostatic interaction. Despite
recent exciting and compelling developments, the design and construction of
MOF-based fluorescence sensors are still a great challenge.
MOFs are constructed from metal ions and bridging organic linkers [10-12]. The
successful synthesis of the target MOFs relies heavily on the organic links, so it is
extremely important to select an appropriate organic linker to construct MOFs. In this
context, 4′-(4-carboxyphenyl)-4,2′:6′,4″-terpyridine (Hcptpy, Scheme 1) was selected
as our ligand according to the following consideration: (a) Hcptpy, as a semi-rigid
bridging ligand, can link metal ions via coordination bond to construct high
dimensional and honeycomb porous coordination polymers. (b) It has a large
π-conjugated nonlinear structure with N, O donors that can offer additional hydrogen
bonding and π–π interactions to consolidate the whole framework structures. (c)
Metal ions prefer binding carboxylate O atoms and N atoms of two terminal pyridine
groups rather than the N atom of the central pyridine in Hcptpy because of steric
effect resulting from two terminal pyridine groups, so this N atom as a functional site
is predicted to recognize small Lewis acidic molecules and metal ions. The incoming
imidazole-4,5-dicarboxylic acid as auxiliary ligand has abundant coordination modes
and is convenient bridging units, which may form much more complicated structures.
4

Based on above mentioned aspects, we report synthesis and crystal structure of two
new compounds [Zn2(cptpy)4]n·nH2O (1), [Zn2(cptpy)2(Hidc)(H2O)2]n·nH2O (2).
Solid-state luminescent properties of 1 were also examined under ultraviolet
irradiation at ambient temperature. Compounds 1 and 2 show high selectivity and
sensitivity for Cu2+ ion, Cr2O72− anion and acetone molecule due to the quenching
effect, which may be a potential material for detecting these substances. Meanwhile
the mechanisms of the quenching effect and sensing properties of 1 and 2 are
discussed.
[Scheme 1 is here]
2. Experimental section
2.1. Materials and general methods
Hcptpy was prepared according to literature methods with some modifications
[13-15], other chemicals were of reagent grade and used without further purification.
Infrared spectra were obtained from KBr pellets on a Bruker EQUINOX 55 Fourier
transform infrared spectrometer in the 400-4000 cm-1 region. Elemental analyses (C,
H, N) were performed on an elementar Vario EL III elemental analyzer. Thermal
gravimetry analyses (TGA) were carried out with a Universal V2.6 DTA system at a
rate of 10 ℃/min in a nitrogen atmosphere. Powder X-ray diffraction (PXRD)
patterns were carried out by a Bruker D8 ADVANCE X-ray powder diffractometer
(Cu-Kα, λ = 1.5418 Å) with the 2θ from 5 to 50° under the 0.03° scan step.
Photoluminescent spectra of compounds 1 and 2 were measured using a Hitachi
F-7200 Fluorescence Spectrometer for the solid powder samples at room temperature.
Hitachi U-3310 UV-vis spectrometer was selected to perform diffusion reflectance
measurement.
2.2. Synthesis
2.2.1 Synthesis of Mptpy
5

A mixture of 4-acetylpyridine (3.21 g, 26.7 mmol), p-tolualdehyde (3.208 g, 26.7
mmol) and NaOH (20ml, 2.0 mol/L) was dissolved in ethanol (50 mL) and stirred at
0 °C for 2 h, resulted in the formation of a light yellow solution. Then, added
4-acetylpyridine (3.208 g, 26.7 mmol) and excessive ammonium acetate (10.00 g,
129.7 mmol), stirred at 80 °C for 5 h. After the mixture was cooled to room
temperature, the resulting white precipitate was filtered off, recrystallized with
methanol, and dried in a vacuum to give 3.56 g (yield 41.3 % based on p-tolualdehyde)
Mptpy (confirmed by single-crystal X-ray analysis) as colorless block crystals. Anal.
Calcd. (%) for C22H17N3: C, 81.71; H, 5.30; N, 12.99. Found: C, 81.57; H, 5.34; N,
12.39. IR(KBr, cm-1): 3429(w), 3029(m), 1686(w), 1660(m), 1595(vs), 1548(m),
1514(w), 1406(w), 1340(w), 1225(m), 1043(m), 991(s), 812(vs), 656(m), 513(w).
1
ESI-MS: [M+H]+ calcd. for C22H18N3: 324.1495; found: 324.1488. H NMR (400
MHz, (CD3)2SO2) δ: 8.76 -8.75(m, 4H), 8.45 (s, 2H), 8.33-8.30 (m, 4H), 8.02 (d, J =
8.0 Hz, 2H), 7.39 (d, J = 8.0 Hz, 2H), 2.39 (s, 3H). 13C NMR (100 MHz, (CD3)2SO2)
δ: 154.36, 150.34, 150.10, 145.39, 139.54, 133.86, 129.73, 127.35, 121.20, 118.58,
20.86. (Figs. S1 and S2, supporting information)
Synthesis of Hcptpy.
Method 1: A mixture of Mptpy (2.16 g, 6.7 mmol), KMnO4 (4.20 g, 26.7 mmol),
and H2O (100 mL) were added to a round bottom flask and stirred at room
temperature. In this period, the solution was adjusted to pH=10.0 with the addition of
KOH. After stirring for 2h at 100℃, the mixture was filtered and washed with hot
water. And then the filtrate was made slightly acidic (pH=5.0) by the addition of HCl
(aq., conc.), the precipitate was filtered off and dried in vacuo to give a white powder.
Yield: 1.95 g (83%). Anal. Calc. for C22H15O2N3 (Mr = 353.11) (%): C, 74.78; H, 4.28;
N, 11.89. Found (%): C, 74.23; H, 4.92; N, 11.37. IR(KBr, cm−1): 3407(s), 3090(m),
2024(w), 1693(s), 1631(s), 1600(s), 1506(s), 1425(w), 1397(m), 1328(w), 1119(m),
834(m), 778(m), 617(m). ESI-MS: [M-H]- calcd. for C22H14O2N3: 352.1092; found:
352.1090. 1H NMR (400 MHz, (CD3)2SO2) δ: 9.02 (m, 4H), 8.85–8.78 (m, 6H), 8.30
(d, J=8.0, 2H), 8.14 (d, J=8.0, 2H). 13C NMR (100 MHz, (CD3)2SO2) δ: 166.87,
6

152.44, 151.38, 149.91, 143.87, 140.01, 132.10, 129.95, 128.05, 123.93, 122.24. (Figs.
S1 and S2, supporting information)
[Scheme 2 is here]
Method 2: In a typical preparation, 4-acetylpyridine (1.21 g, 10 mmol) was added
to a stirred solution of 4-carboxybenzaldehyde (0.75 g, 5 mmol), KOH (0.8 g, 14
.
mmol) and NH3 H2O (20 mL) in 150 mL ethanol. The reaction mixture was stirred at
room temperature whilst open to air for 48 h, after which the solution was made
slightly acidic (pH=5) with the addition of HCl (aq., conc.). The resulting light yellow
precipitate was filtered off, recrystallized with a mixture of ethanol and methanol, and
dried in vacuo to give white powders. Yield: 1.22 g (69%). ESI-MS: [M-H]- calcd. for
C22H14N3O2: 352.1092; found: 352.1090. 1H NMR (400 MHz, (CD3)2SO2) δ: 9.02 (m,
4H), 8.85–8.78 (m, 6H), 8.30 (d, J=8.0, 2H), 8.14 (d, J=8.0, 2H). 13C NMR (100 MHz,
(CD3)2SO2) δ: 166.87, 152.44, 151.38, 149.91, 143.87, 140.01, 132.10, 129.95,
128.05, 123.93, 122.24. (Figs. S1 and S2, supporting information)
[Scheme 3 is here]
2.2.2 Synthesis of [Zn2(cptpy)4]n·nH2O (1)
Method 1: Compound 1 was prepared by hydrothermal reaction of
Zn(NO3)2·6H2O (0.0136 g, 0.1 mmol) and Hcptpy (0.0277 g, 0.1 mmol) in distilled
water (8 mL) and N,N-dimethylacetamide (DMA) (2 mL) and using 0.5 mol.L-1
NaOH aqueous solution to adjust the pH to 6.0 that was placed in a Teflon-lined
stainless steel vessel (25 mL), heated to 180℃ for 72h and then cooled to room
temperature at a rate of 5℃/h. The yellow block crystalline product was obtained,
washed with distilled water (5 mL), and dried in air to give 0.0484 g, yield 62.2%
based on Zn. Elemental anal. calcd for: C88H56N12Zn2O9 (%): C 67.92, H 3.63, N
10.80; found: C 67.75, H 3.65, N 10.39. IR(KBr, cm−1): 3414(s), 3132(s), 1597(s),
1548(s), 1399(vs), 1221(w), 1138(w), 1066(w), 1021(w), 831(w), 781(m), 700(m),
7

632(m), 489(w).
Method 2: Compound 1 was synthesized in a similar procedure as Method 1, by
using ZnCl2 (0.0166 g, 0.1 mmol) in place of Zn(NO3)2·6H2O. The yellow block
crystalline product was obtained, washed with distilled water (5 mL), and dried in air
to give 0.0383 g, yield 49.2% based on Zn. Elemental anal. calcd for: C88H56N12Zn2O9
(%):C 67.92, H 3.63, N 10.80; found: C 67.75, H 3.65, N 10.39. IR(KBr, cm−1):
3414(s), 3132(s), 1597(s), 1548(s), 1399(vs), 1221(w), 1138(w), 1066(w), 1021(w),
831(w), 781(m), 700(m), 632(m), 489(w).
2.2.3. Synthesis of [Zn2(cptpy)2(Hidc)(H2O)2]n·nH2O (2)
Method 1: A mixture of Zn(NO3)2·6H2O (0.0291 g, 0.1 mmol), Hcptpy (0.0277 g,
0.05 mmol), and H3idc (0.0126 g, 0.1 mmol) in distilled water (10 mL) that adjusted
the pH value to 4.5 with 0.5 mol.L-1 NaOH aqueous solution was placed in a
Teflon-lined tainless steel vessel (25 mL), heated to 180℃ for 72 h and then cooled to
room temperature at a rate of 5℃/h. The yellow sheet crystalline products of 2 were
obtained, washed with distilled water (5 mL), and dried in air to give 0.0321 g (yield
61.8% based on Zn). Anal. Calc. for C49H31N8Zn2O11 (%): C, 56.67; H, 3.00; N, 10.79.
Found: C, 56.52; H, 3.08; N, 10.32%. IR(KBr, cm−1): 3133(s), 1596(m), 1548(m),
1401(vs), 1251(w), 1132(w), 870(w), 829(m), 784(m), 707(m), 634(w), 517(w).
Method 2: Compound 2 was synthesized in a similar procedure as Method 1, by
using distilled water (8 mL) and N, N-dimethylacetamide (DMA) (2 mL) in place of
distilled water (10 mL). The yellow sheet crystalline product was obtained, washed
with distilled water (5 mL), and dried in air to give 0.0281 g, yield 54.1% based on Zn.
Anal. calcd for: C49H31N8Zn2O11 (%):C, 56.67; H, 3.00; N, 10.79. Found: C, 56.52; H,
3.08; N, 10.32%. IR(KBr, cm−1): 3133(s), 1596(m), 1548(m), 1401(vs), 1251(w),
1132(w), 870(w), 829(m), 784(m), 707(m), 634(w), 517(w).
2.2.4. Crystal structure determinations
Suitable single crystals of compounds 1–2 were tested on a Bruker SMART
APEXII CCD diffractometer equipped with graphite-monochromated Mo-Kα
8

radiation (λ = 0.71073 Å) at room temperature. The structures were solved by direct
methods and refined by a full-matrix, least-squares refinement on F2 with
SHELXL-97 and SHELXS-97 [16]. The hydrogen atoms were calculated and
assigned their ideal positions with isotropic displacement factors and included in the
final refinement by use of geometric restraints. The relevant crystallographic data are
summarized in Table 1. Selected bond lengths and angles are listed in Table S1 (ESI†).
CCDC numbers are 1478584-1478586 for Mptpy and compounds 1-2, respectively.
2.3. Quantum-chemical calculation
The optimized geometry and natural bond orbital (NBO) charge distributions of
the free ligand Hcptpy were given by the GAUSSIAN 03 suite of programs [17]. And
all calculations were carried out at the B3LYP/6-31G(d, p) level of theory.
3. Results and discussion
3.1. Synthesis
The optimized geometry and natural bond orbital (NBO) charge distributions of
Hcptpy have been calculated by the B3LYP/6-311G(d, p) level [17]. The calculated
results reveal that Hcptpy has one characteristics: The negative NBO charges mainly
distribute on the oxygen and nitrogen atoms. The NBO charges are -0.598 and -0.716
for two carboxylate oxygen atoms, -0.455, -0.455 and -0.455 for three pyridyl
nitrogen atoms in the free ligand Hcptpy (Scheme 1). These values show that the N
and O atoms may have strong coordination abilities under appropriate reaction
conditions, which are confirmed by our present experimental results. In 1 and 2, the
carboxyl group from Hcptpy is deprotonated to form the (cptpy)- unit. These findings
further confirm our views about the coordination ability of Hcptpy.
It is well-known that the purposeful design and controllable synthesis of
functional MOFs are influenced by many factors. The effect of the N, O-donor
auxiliary ligands has also attracted increasing interest in recent years because the
auxiliary ligands used in the assembly processes may play an important role in
directing the construction of MOFs. Obviously, compared with compound 1, the
9

auxiliary ligand (H3idc) has a significant influence on the structure formation of 2.
Interestingly, In the two preparation methods of 1, when using ZnCl2 (0.0166 g, 0.1
mmol) in place of Zn(NO3)2·6H2O under similar condition, the crystals of 1 are also
obtained. The results indicate that anions has no influnce on crystal strucuture of 1.
3.2. Structure description of crystalline polymer [Zn2(cptpy)4]n·nH2O (1)
X-ray single crystal structural analysis reveals compound 1 shows a two-fold
interpenetrating 2D framework. The asymmetric unit of 1 contains two
crystallographically independent Zn(II) (Zn1 and Zn2) ions, four (cptpy)- anions and
one lattice water molecule. As shown in Fig. 1a, Zn1 center is four-coordinated to two
oxygen atoms (O1, O3A) from different (cptpy)- anions and two nitrogen atoms (N1A,
N4) from two different (cptpy)- anions, respectively. The coordination geometry of
Zn1 center can be described as a distorted tetrahedron, the O1, O3A, N1A atoms
comprise the basal plane and N4 occupies vertex position. The coordination geometry
of Zn2 center can be described as a distorted trigonal bipyramid geometry (Fig. 1a),
the O5, O8B and N7A atoms comprise the equatorial plane, and the N10, O7B atoms
occupy the axial positions [N10-Zn2-O7B=149.8(2)°], the Zn–N distances fall in the
range of 2.065(6) Å to 2.086(6) Å, and the Zn–O bond lengths vary from 1.917(7) to
2.210(6) Å, which is similar to previously reported values [18a]. In compound 1, the
three pyridyl rings of (cptpy)- ligand are non-planar, each outer pyridyl group is
twisted with respect to the central one, the dihedral angles between the central and
outer pyridyl rings are 20.28° (N1 pyridyl ring), 34.96° (N2 pyridyl ring), 1.90° (N4
pyridyl ring), 23.42° (N6 pyridyl ring), 9.36° (N7 pyridyl ring), 21.43° (N9 pyridyl
ring), 10.40° (N10 pyridyl ring) and 34.58° (N12 pyridyl ring), respectively. The
rotation of the N1, N4, N7 and N10 pyridyl ring with the central pyridyl ring is larger
than that of N2, N6, N9 and N12 pyridyl ring, the reason for this phenomenon is the
repulsion force arising from the central pyridyl-β-hydrogen atoms and the formation
of intermolecular bridging hydrogen bonds to stabilize the complexes [18b, c].
Notably, the Zn1 ions are connected by two pyridyl nitrogen atoms and two
carboxylate oxygen atoms of the different (cptpy)- ligands with a μ2-η1:η1 bridging
10

mode to form a 2D layers, and the Zn2 ions are connected by two pyridyl nitrogens
atom and three carboxylate oxygen atoms of the different (cptpy)- ligands with a
μ2-η1:η1 and μ2-η1:η2 bridging mode to form a similar 2D layer. The through-space
apertures within a single layer motif measure 15.102 × 15.117 Å (Fig. 1b). The large
rectangular windows within the layers allow interpenetration of parallel sets of layers
with each other. Therefore, each individual 2D layer is parallel-interpenetration with
another generating a 2D+2D→2D interpenetration bi-layer structure (Fig. 1c). From
the topological perspective, if each Zn(II) ion acts as 4-connected node and (cptpy)-
anion is also severed as 4-connected node, the architecture of 1 is simplified to a (4,
4)-connected 2D sql topological network with the Schläfli symbol of {44·62}. The
π…π stacking interaction between the pyridyl rings and phenyl rings in adjacent
layers sustains the system of interpenetrated bi-layers (Fig. S4). Interestingly, the
uncoordinated pyridyl rings of (cptpy)− anion ligands serve as side arms hanging on
the opposite side of the layer. As a result, the bi-layer networks generate a 2D + 2D
→ 2D tetra-layer structure (Fig. S5) through π…π stacking interaction between
pyridyl rings (centroid-to-centroid distances of 3.738 Å and 3.882 Å), and then the
tetra-layer structures are further superimposed by π…π stacking interaction between
pyridyl rings and phenyl rings (centroid-to-centroid distances of 3.631 Å to 3.866 Å)
to form a 2D + 2D → 3D interdigitation architecture (Fig. S6). To the best of our
knowledge, example of 2D+2D→2D parallel interpenetration, 2D+2D→2D
interdigitation and 2D+2D→3D interdigitation based on both 2D+2D→2D parallel
interpenetration and 2D+2D→2D interdigitation have been reported [18-21]. ‘
Comparing with the reported Cd(II) compound [18a], the ionic radius of Cd(II) is
longer than that of Zn(II), which means the Cd(II) center can adopt a higher
coordination number and different coordination geometry, while leading to a similar
polymeric framework. The result indicates that metal ions have no remarkable
influence on the formation of target coordination polymeric frameworks.
[Fig. 1 is here]
11

3.3. Structure description of [Zn2(cptpy)2(Hidc)(H2O)2]n·nH2O (2)
Compound 2 crystallizes in the monoclinic system with P21/n space group and
exhibits a 1D ladder chain structure. The asymmetric unit of 2 contains one Zn ion,
one (cptpy)- anion and half a (Hidc)2- anion. As shown in Fig. 2a, Zn1 center is
six-coordinated with four oxygen atoms (O1A, O2A, O3, O5) from one (cptpy)- anion,
one (Hidc)- anion and water molecule and two nitrogen atoms (N1, N4) from one
(cptpy)- anion and one (Hidc)- anion, respectively. The coordination geometry of Zn1
center can be described as a distorted ZnN2O4 octahedron, the O2A, O3, O5, N1
atoms comprise the equatorial plane, and the O1A and N4 atoms occupy the axial
positions (N4-Zn1-O1A=159.0(2)°). In 2, the Zn-N bond lengths are 2.046(6) Å and
2.075(6) Å, and the Zn-O distances are in the range of 2.068(7) Å to 2.312(7) Å,
which are slightly longer than the corresponding values of 1. The three pyridyl rings
of the (cptpy)- anion ligand are non-planar, each terminal pyridine group is twisted
with respect to the central one, and the dihedral angles between the central and
terminal pyridyl rings are 4.60° (N1 pyridyl ring) and 18.19° (N3 pyridyl ring),
respectively.
As shown in Fig. 2b, the (Hidc)2- anion adopts µ4-η2:η2 bridging mode to link two
Zn(II) centers to form a binuclear Zn unit with the Zn...Zn distance of 6.280 Å.
Furthermore, these binuclear units are linked by (cptpy)- anion (µ2-η2:η1) to form a 1D
chain structure. The chains are connected through hydrogen bonding interactions
between the coordination water molecule and uncoordinated oxygen atoms from
carboxylate of (Hidc)2- anion (O5-H...O4i, 2.702 Å, symmetric code i, (x, 1+y, z)) to
form a 2D supramolecular structure (Figs. 2c and S7). The 2D structure is further
piled up through π…π interactions between pyridyl rings and phenyl rings
(centroid-to-centroid distances of 3.984 Å and 4.071 Å) to form a 3D supramolecular
structure (Fig. 2d).
[Fig. 2 is here]
3.4. PXRD and thermogravimetric analyses
12

The powder X-ray diffraction (PXRD) experiments for the two MOFs were
carried out carefully to check phase purity at room temperature. The patterns show
that the main peaks of the synthesized CPs are closely consistent with those of the
simulations from the single-crystal X-ray diffraction data, which imply high quality of
the obtained products (Figs. S8 and S9, Supporting information). Moreover, the
thermal stabilities of compounds 1 and 2 were also detected via thermogravimetric
analysis (TGA) (Fig. S10, Supporting information). For 1, the weight loss of 1.56%
below 150 ℃ (calculated: 1.16%) corresponds to the loss of one lattice water
molecule. After about 440 ℃, the whole framework structure begins to collapse with
continous weight loss until heating to 1000 ℃. The TGA curve of 2 reveals that the
weight loss of 5.64% below 180 ℃ (calculated: 5.20%) corresponds to the loss of
one lattice and two coordination water molecules. After about 395 ℃, the whole
framework structure begins to collapse with continuous weight loss until heating to
1000 ℃. TGA results reveal the compounds possess good thermal stability.
3.5. Optical band gaps
The UV-Vis absorption spectra of the ligands (Hcptpy, H3idc) and complexes 1
and 2 were conducted in the crystalline sample at room temperature (Fig. S11). The
Hcptpy ligand exhibits strong absorption bands from 200 nm to 340 nm with two
peaks at 262 and 311 nm. Meanwhile, The H3idc ligand displays absorption bands
with maxima at 226 nm, which can be ascribed to π-π* transitions of the ligands.
Furthermore, the higher energy absorption bands in the Hcptpy ligand is higher than
that of H3idc in the energy level, indicating that it might be more influenced when
coordinated with the transition metal ion. With this regard, it’s notable that the lowest
energy absorption bands of complexes 1 (λmax = 334 nm, 29940 cm-1) and 2 (λmax
=
331 nm, 30211 cm-1) are red-shifted when compared with the corresponding Hcptpy
ligand (λmax = 311 nm, 30487 cm-1), which may be attributed to the decreased energy
gap of the intraligand (IL) transition when coordinated to the metal center ion [22].
The optical band gap (Eg) have been reported to be one of the principal factors to
affect the photocatalysis degradation process of the organic dye in previous literature
13

[23, 24]. Inspired by this, we obtain the band gaps (Eg) of compounds 1 and 2 through
transforming the diffuse reflectance data into a Kubelka-Munk function [25-27]. As
depicted in Fig. S12, the Eg values evaluated from the steep absorption edge for 1 and
2 are 2.42 eV and 1.92 eV, respectively, indicating that compounds 1 and 2 are
potential wide gap semiconductive materials [28, 29].
3.6. Luminescence measurements and discussions
The luminescence of compounds 1 and 2 and Hcptpy ligand was evaluated in the
solid state at room temperature, and their emission spectra are given in Fig. S13.
Hcptpy ligand exhibits a strong emission at 415 nm upon excitation at 300 nm, which
maybe assigned to the π*-π transitions. Compounds 1 and 2 exhibit broad emission
banks at 405 nm and 378 nm, respectively, at the same excitation condition, which
mean blue-shifts of ca. 10 nm and ca. 37 nm relative to the free Hcptpy ligand. The
slight blue-shift maybe mainly originated from the coordination interactions between
the metal atom and the ligand [30]. Interestingly, compound 2 exhibts stronger
luminescence, which maybe result from stronger hydrogen-bonding interactions
between 1D chains. As 1 keeps one protonated carboxylic group in every (Hidc)2−
anion ligand, whether the carboxyl group will affect luminescence properties has
aroused our great interest. To explore the luminescent responses of 1 under
protonation and deprotonation conditions, the luminescence emission spectra of 5 mg
1 in 5 mL H2O were recorded with gradual addition of NaOH (0.03 M). As shown in
Figs. 3a and 3b, with the increase of NaOH, the maximum emission wavelength slight
moved from 377 to 373 nm gradually. Obviously, the emission intensity also
decreased gradually. The phenomenon should be related to the free carboxylic groups
and their deprotonation process. Structure analysis shows that there exist significant
hydrogen bonds between the adjacent 1D chains. The addition of bases into the
system will gradually react with the carboxylic groups in 2, leading to the breaking of
hydrogen bonds, accompanied by increasing instability and reduced conjugation in 2,
resulting in luminescence decay. The instability and reduced conjugation of the
system should be responsible for the blue shifts of the maximum emission wavelength
14

[8]. PXRD after NaOH titration (Fig. S9) was measured and the patterns showed that
the basic framework of 2 was kept and added new peak. Then the sample was titrated
with HNO3 (1:60) straight after NaOH titration to see whether the process is
reversible. However, along with the increase of HNO3, the emission intensity
decreased sharply (Figs. 3a and 3c), the suspension gradually turned clear. As a result,
HNO3 titration proved nonreversible, and the reason may be the instability of 2 in
base condition where the structure may have been broken down, which has been
confirmed by powder X-ray diffraction (PXRD) patterns after NaOH titration.
The most interesting feature is that its luminescence spectrum in 1 is largely
dependent on the solvent molecules, particularly in the case of acetone, which exhibit
the most significant quenching effects (Fig. 4). PXRD pattern performed after solvent
immersion (Fig. S14a) proves the structure is well preserved. Such solvent-dependent
luminescence properties are of interest for the sensing of acetone solvent molecules.
When the acetone solvent content was gradually added and increased to 1-DMF
standard emulsion, the fluorescence intensity of the 1 emulsion gradually decreased
with the addition of acetone solvent (Fig. 5a). The fluorescence decrease was nearly
proportional to the acetone concentration. The decreasing trend of the fluorescence
intensity of 1 at 405 nm versus the volume ratio of acetone could be well fitted with a
first-order exponential decay (Fig. 5b), indicating that fluorescence quenching of 1 by
acetone is diffusion-controlled [31].
[Fig. 3 is here]
[Fig. 4 is here]
[Fig. 5 is here]
3.7. Detection of Metal Ions-Photoinduced Electron Transfer.
The most significant structural feature of 1 is the presence of free Lewis basic
pyridyl and carboxyl sites on the framework structure, highlighting the potential for
15

sensing functions and recognizing metal ions. Therefore, in order to research the
luminescent responses of 1 to different metal ions, the products of 1 were ground into
powder and suspended in DMF solution containing the same concentration of
different nitrate (Na(NO3)2, K(NO3)2, Ca(NO3)2, Mn(NO3)2, Pb(NO3)2, Zn(NO3)2,
Cd(NO3)2, Co(NO3)2, Ni(NO3)2, Cu(NO3)2) for 48h, and then their luminescent
spectra are recorded. Interestingly, the Cu2+ ion shows a significant quenching effect
on the luminescence intensity of 1; in contrast, luminescence intensity for 1 in other
metal ions system are little enhance or decreased to a degree, indicating highly
selective sensing of 1 for Cu2+ ions (Fig. 6a).
To gain more insight into the quenching effect resulted from Cu2+, titration
experiments were carried out via changing the concentration of Cu2+ cations in
solution. The titration experiments indicated that the luminescent intensities at 415 nm
were gradually weakened by increasing the amount of Cu2+ ions (Fig. 6b), and the
intensity was reduced to 50% at a concentration about 0.42 mM for Cu(NO3)2.
Importantly, the luminescence intensity of the suspension follows the first-order
exponential decay formula I=779.66×exp(-CV/0.50)+116.92 (insert of Fig. 6b), by
which Cu2+ could be detected quantitatively (I=luminescence intensity of
1-Cu(NO3)2@DMF suspensions, CV=Cu2+ volume concentration, R2=0.99),
displaying the diffusion-controlled quenching process for the Cu2+ ions [32, 33]. The
excellent result indicate that the crystalline products of 1 can be used as the excellent
luminescent sensor to detect Cu2+ ions as highly selective luminescent crystalline
materials (Fig. 6c).
In order to further evaluate the selectivity of complex 1 toward the Cu2+ ion, we
studied the quenching effect of Cu2+ ion and all the other mixed transition metal ions
(Na+, K+, Ca2+, Mn2+, Pb2+, Zn2+, Cd2+, Co2+, Ni2+) on the luminescent intensity of 1.
As illustrated in Fig. 7a, Cu2+ ion exhibited much more significant quenching effect
on 1 than the mixed ions. Furthermore, when Cu2+ ion was incorporated in the mixed
ions, the luminescence intensity of 1 is nearly complete quenching, which
demonstrated the high selectivity of 1 toward the Cu2+ ion. To further examine the
sensing sensitivity for Cu2+ ion, 1 was immersed in DMF solutions with gradually
16

decreased Cu2+ concentration in the range of 10−1-10−5 mol/L. Noteworthy, the
luminescence intensity of Cu2+@1 is heavily relied on the concentration of Cu2+ ion.
As shown in Fig. 7b, the luminescence intensity of 1 is almost completely quenched at
a Cu2+ concentration of 10-2 M. It is remarkable that complex 1 features such highly
sensitive sensing for Cu2+ ions in DMF solution.
Additionally, multiple cycles of Cu2+ sensing experiments have been conducted
and the material could greatly regain its intensity after filtration and washing by DMF
(Fig. 8). PXRD pattern performed after Cu(NO3)2 immersion (Fig. S14b) proves the
structure is well preserved. UV-Vis absorption spectra for Cu(NO3)2 solutions has
been recorded. The absorption spectrum of Cu2+ solution has no obvious overlap with
the emission spectrum of 1 (Fig. S15). Therefore, the quenching should origin from
the electron transfer from 1 to Cu2+, instead of the resonance energy transfer [34].
Moreover, the quenching effect of Cu2+ on the luminescence intensity of 1 has been
further examined by fluorescence lifetime studies of 1 and 1@Cu2+. The fluorescence
lifetime of τ1=2.76 ns and τ2=8.64 ns in the 1 is significantly reduced to τ1=1.80 ns
and τ2=3.45 ns in the presence of Cu2+ (see the Supporting Information, Fig. S16),
which maybe result from an interaction between Cu2+ ions and compound 1. XPS
(X-ray photoelectron spectroscopy) experiment on 1-Cu(NO3)2@DMF sample (Figs.
9a and S17) founds that the peak at 933.9 eV especially, which accordance with the
standard value of Cu···O (933.9 eV), suggesting the existence of interaction between
Cu2+ and the terminal carboxyl groups [35]. To explore the possible mechanism for
such luminescence quenching by metal cations, N1s and O1s X-ray photoelectron
spectroscopy (XPS) studies were carried out on Cu2+-incorporated 1 (Figs. 9b and 9c).
The N 1s peak from nitrogen atoms at 398.2 eV and O1s peaks from oxygen atoms at
531.0 eV and in 1 are respective shifted to 399.2 eV (N 1s) and 513.5 eV (O1s)
induced by the addition of Cu2+ in 1, indicating the probable weak binding of pyridyl
nitrogen atoms and carboxylate oxygen atoms to Cu2+ in Cu2+-incorporated 1. Such
binding of the pyridyl nitrogen atoms and carboxylate oxygen atoms to Cu2+ maybe
cause the electrons of Hcptpy ligands to transfer from 1 to Cu2+ ions as electron
acceptors, thus resulting in quenching of the luminescence. In addition, the well
17

recovered intensities after multiple cycles of Cu2+ sensing experiments may provide
proof that Cu2+ ions are mainly absorbed on the surface.
[Fig. 6 is here]
[Fig. 7 is here]
[Fig. 8 is here]
[Fig. 9 is here]
−
−
Finally, aqueous solutions containing sodium salts of Cl−, Br−, I−, ClO4 , NO3 ,
2−
3−
2−
CO3 , PO4 , and Cr2O7 at the same concentration (1.0 × 10−3 M) were also
prepared, and their effects on the fluorescence intensity of 2 were explored. The most
interesting feature is that the PL intensities of the different suspensions are strongly
−
−
dependent on the various anions. The analytes, such as halide ions, ClO4 , NO3 , and
2−
CO3 , have negligible effects on the PL intensity, whereas other anions, in particular
2−
Cr2O7 , significantly decrease the luminescence intensity (Fig. 10). The unusually
selective quenching of Cr2O72− prompted us to apply 2 in the detection of trace Cr6+ in
water. To further evaluate the sensitivity of 2 to Cr6+, we carried out measurements in
2−
the presence of varying concentrations of Cr2O7 . This result indicates that the
fluorescence intensity of 2 is remarkably suppressed with increasing amounts of
Cr2O72− (Fig. 11). The quenching of 2 in the presence of Cr2O72− is most likely due to
a decrease in energy transfer between the π and π* orbitals of (Hidc)2− because of
2−
electron-transfer transitions of Cr2O7 [36]. The highly selective and sensitive
detection of Cr6+ in aqueous solutions by compound 2 is remarkable; therefore, it may
2−
be considered as a MOF sensor for the quantitative detection of Cr2O7 with the
highest sensitivity.
[Fig. 10 is here]
18

[Fig. 11 is here]
4. Conclusion
In summary, two new Zn(II)-MOFs were solvothermally synthesized in solvent
systems. It was found that the Hcptpy ligands displayed three different coordination
modes in the obtained MOFs and thus gave rise to the various MOF structural
diversities. The luminescent properties of two products were studied via ultraviolet
light at room temperature, especially for 1, which showed highly selective sensitivity
for Cu2+ ions and acetone. The 1-MOF can potentially be used to detect these
poisonous substances. We also discussed the mechanisms for the quenching effect and
sensing properties of 1. Importantly, complex 2 shows highly selective sensitivity for
2−
Cr2O7 . The fluorescence quenching caused by Cu2+ can be ascribed to a binding
interaction between the uncoordinated pyridine motif of (cptpy)− and Cu2+ in the
Cu2+-incorporated compounds, whereas the fluorescence depression caused by Cr6+
2−
may be associated with electron-transfer transitions of Cr2O7 . This work provides an
easy and facile route to design and yield the new luminescent MOFs as promising
functional materials. Further research into the sensing materials is underway in our
group. Meanwhile, the optical absorption spectra show that the title compounds may
be a potential wide gap semiconductor material.
Acknowledgements
This work was supported by the Technology Plan Projects of Shangluo (No.
SK2016-44) and the Natural Science Foundation of Shangluo University (No.
16SKY019).
References
[1] (a) J. R. Li, J. Sculley and H. C. Zhou, Chem. Rev. 112 (2012) 869;
(b) R. Matsuda, R. Kitaura, S. Kitagawa, Y. Kubota, R. V. Belosludov, T. C.
Kobayashi, H. Sakamoto, T. Chiba, M. Takata, Y. Kawazoe and Y. Mita, Nature
436 (2005) 238;
19

(c) L. Pan, B. Parker, X. Y. Huang, D. H. Olson, J. Y. Lee and J. Li, J. Am. Chem.
Soc. 128 (2006) 4180.
[2] (a) A. M. Shultz, O. K. Farha, J. T. Hupp and S. T. Nguyen, J. Am. Chem. Soc.
131(2009) 4204;
(b) L. Q. Ma, C. Abney and W. B. Lin, Chem. Soc. Rev. 38 (2009) 1248;
(c) M. Yoon, R. Srirambalaji and K. Kim, Chem. Rev. 112 (2012) 1196.
[3] (a) M. P. Suh, H. J. Park, T. K. Prasad and D. W. Lim, Chem. Rev. 112 (2012) 782;
(b) G. Férey, C. Serre, T. Devic, G. Maurin, H. Jobic, P. L. Llewellyn, G.
D.Weireld, A. Vimont, M. Daturif and J. S. Chang, Chem. Soc. Rev. 40 (2011)
550;
(c) X. H. Bu, M. L. Tong, H. C. Chang, S. Kitagawa and S. R. Batten, Angew.
Chem., Int. Ed. 43 (2004) 192;
(d) K. Konstas, T. OsI, Y. Yang, M. Batten, N. Burke, A. J. Hill and M. R. Hill, J.
Mater. Chem. 22 (2012) 16698.
[4] (a) P. Horcajada, R. Gref, T. Baati, P. K. Allan, G. Maurin, P. Couvreur, G. Férey, R.
E. Morris and C. Serre, Chem. Rev. 112 (2012) 1232;
(b) J. D. Rocca, D. M. Liu and W. B. Lin, Acc. Chem. Res. 44 (2011) 957.
(c) F. Ke, Y. -P. Yuan, L. -G. Qiu, Y. -H. Shen, A. -J. Xie, J. -F. Zhu, X. -Y. Tian
and L. -D. Zhang, J. Mater. Chem. 21 (2011) 3843.
(d) K. Matsuyama, N. Hayashi, M. Yokomizo, T. Kato, K. Ohara and T. Okuyama,
J. Mater. Chem. B 2 (2014) 7551.
[5] (a) L. E. Kreno, K. Leong, O. K. Farha, M. Allendorf, R. P. Van Duyne and J. T.
Hupp, Chem. Rev. 112 (2012) 1105;
(b) Y. J. Cui, Y. F. Yue, G. D. Qian and B. L. Chen, Chem. Rev. 112 (2012) 1126;
(c) X. L. Qi, R. B. Lin, Q. Chen, J. B. Lin, J. P. Zhang and X. M. Chen, Chem.
Sci. 2 (2011) 2214;
(d) H. Xu, S. Zhou, L. Xiao, H. Wang, S. Li and Q. Yuan, J. Mater. Chem. C 3
(2015) 291;
(e) K. S. Asha, K. Bhattacharyya and S. Mandal, J. Mater. Chem. C 2 (2014)
10073.
20

[6] (a) J. An, C. M. Shade, D. A. Chengelis-Czegan, S. Petoud and N. L. Rosi, J. Am.
Chem. Soc. 133 (2011) 1220;
(b) Y. Takashima, V. Martínez, S. Furukawa, M. Kondo, S. Shimomura, H.
Uehara, M. Nakahama, K. Sugimoto and S. Kitagawa, Nat. Commun. 2 (2011)
168;
(c) L. Wen, X. Zheng, K. Lv, C. Wang, and X. Xu, Inorg. Chem. 54 (2015) 7133;
(d) J. -N Hao and B. Yan, J. Mater. Chem. C 2 (2014) 6758.
[7] (a) B. L. Chen, L. B.Wang, Y. Q. Xiao, F. R. Fronczek, M. Xue, Y. J. Cui, G. D.
Qian, Angew. Chem. Int. Ed. 48 (2009) 500;
(b) G. -P. Li, G. Liu, Y. -Z. Li, L. Hou, Y. -Y Wang, and Z. Zhu, Inorg. Chem. 55
(2016) 3952;
(c) L. -Y. Du, H. Wang, G. Liu, D. Xie, F. -S. Guo, L. Hou and Y. -Y. Wang,
Dalton Trans. 44 (2015) 1110.
[8] L. -Y. Pang, G. -P. Yang, J. -C. Jin, M. Kang, A. -Y. Fu, Y. -Y. Wang and Q. -Z. Shi,
Cryst. Growth Des. 14 (2014) 2954.
[9] B. Liu, W. -P. Wu, L. Hou and Y. -Y. Wang, Chem. Commun. 50 (2014) 8731.
[10] M. Li, D. Li, M. O'Keeffe, O. M. Yaghi, Chem. Rev. 114 (2014) 1343.
[11] Y. He, B. Li, M. O'Keeffe, B. Chen, Chem. Soc. Rev. 43 (2014) 5618.
[12] W. G. Lu, Z. W. Wei, Z. -Y. Gu, T. -F. Liu, J. Park, J. Park, J. Tian, M. W. Zhang,
Q. Zhang, T. G. III, M. Boscha, H. -C. Zhou, Chem. Soc. Rev. 43 (2014) 5561.
[13] E. C. Constable, E. L. Dunphy, C. E. Housecroft, M. Neuburger, S. Schaffner, F.
Schapera and S. R. Batten, Dalton Trans. (2007) 4323.
[14] M. W. Cooke, P. Tremblay and G. S. Hanan, Inorg. Chim. Acta 361 (2008) 2259.
[15] B. C. Wang, Q. R. Wu, H. M. Hu, X. L. Chen, Z. H. Yang, Y. Q. Shangguan, M.
L. Yang and G. L. Xue, Inorg. Chem. Commun. 13 (2010) 715.
[16] G. M. Sheldrick, SHELXL-97, Program for Solution of Crystal Structures,
University of Gottingen, Gottingen, Germany, 1997.
[17] B. -B. Shi, S. -F. Liu, L. Guo, X. -Q. Li, G. Li, Polyhedron 83 (2014) 77.
[18] (a) F. Yuan, R. An, H. -M. Hu, S. -S. Shen, X. Wang, M. -L.Yang, G. Xue, Inorg.
Chem. Comm. 56 (2015) 1;
21

(b) F. Yuan, S. -S. Shen, H.-M. Hu, R. An, X. Wang, Z. Chang, G. Xue, Inorg.
Chim. Acta 430 (2015) 17;
(c) L. A. Barrios, J. Ribas, G. Aromı, J. Ribas-Ariño, P. Gamez, O. Roubeau, S. J.
Teat, Inorg. Chem. 46 (2007) 7154.
[19] (a) Y. L. Gai, F. L. Jiang, L. Chen, Y. Bu, M. Y. Wu, K. Zhou, J. Pan, M. C. Hong,
Dalton Trans. 42 (2013) 9954;
(b) N. -Y. Li, Y. Ge, T. Wang, S. -J. Wang, X. -Y. Jia, D. Liu, CrystEngComm 16
(2014) 2168.
[20] P. Ayyappan, O. R. Evans,W. B. Lin, Inorg. Chem. 41 (2002) 3328.
[21] (a) X. L. Wang, C. Qin, E. B. Wang, L. Xu, Eur. J. Inorg. Chem. 2005 (2005)
3418;
(b) J. Q. Liu, Y. Y. Wang, L. F. Ma, G. L.Wen, Q. Z. Shi, S. R. Batten, D. M.
Proserpio, CrystEngComm 10 (2008) 1123;
(c) L. Han, Y. Zhou, W. N. Zhao, X. Li, Y. X. Liang, Cryst. Growth Des. 9 (2009)
660;
(d) H. D. Guo, D. F. Qiu, X. M. Guo, S. R. Batten, H. J. Zhang, CrystEngComm,
11 (2009) 2611;
(e) X. Y. Cao, Y. G. Yao, S. R. Batten, E. Ma, Y. Y. Qin, J. Zhang, R. B. Zhang, J.
K. Cheng, CrystEngComm 11 (2009) 1030.
[22] X. -Q. Yao, M. -D. Zhang, J. -S. Hu, Y. -Z. Li, Z. -J. Guo, H. -G. Zheng, Cryst.
Growth Des.11 (2011) 3039.
[23] W. -Q. Kan, B. Liu, J. Yang, Y. -Y. Liu, J. -F. Ma, Cryst. Growth Des. 12 (2012)
2288.
[24] W. -L. Liu, L. -H. Ye, X. -F. Liu, L. -M. Yuan, J. -X. Jiang, C. -G. Yan,
CrystEngComm 10 (2008) 1395.
[25] C. -Y. Xu, L. -K. Li, Y. -P. Wang, Q. -Q. Guo, X. -J. Wang, H. -W. Hou, Y. -T.
Fan, Cryst. Growth Des. 11 (2011) 4667.
[26] M. D. Allendorf, C. A. Bauer, R. K. Bhaktaa, R. J. T. Houka, Chem. Soc. Rev. 38
(2009) 1330.
[27] X. -L. Sun, Z. -J. Wang, S. -Q. Zang, W. -C. Song, C. -X. Du, Cryst. Growth Des.
22

12 (2012) 4431.
[28] L. Zhang, L. Liu, M. Li, C. Huang, H. Xu, H. -W. Hou, Y. -T. Fan, Polyhedron 83
(2014) 197.
[29] S. -N. Wang, H. Xing, Y. -Z. Li, J. -F. Bai, Y. Pan, M. Scheer, X. -Z. You, Eur. J.
Inorg. Chem. (2006) 3041.
[30] S. L. Zheng, J. H. Yang, X. L. Yu, X. M. Chen, W. T. Wong, Inorg. Chem. 43
(2004) 830.
[31] Z. Guo, H. Xu, S. Su, J. Cai, S. Dang, S. Xiang, G. Qian, H. Zhang, M.
O’Keeffed and B. Chen, Chem. Commun. 47 (2011) 5551.
[32] Z. M. Hao, X. Z. Song, M. Zhu, X. Meng, S. N. Zhao, S. Q. Su, W. T. Yang, S. Y.
Song, H. J. Zhang, J. Mater. Chem. A 1 (2013) 11043.
[33] B. L. Chen, Y. Yang, F. Zapata, G. Lin, G. Qian, E. B. Lobkovsky, Adv. Mater. 19
(2007) 1693.
[34] Z. C. Hu, B. J. Deibert, J. Li, Chem. Soc. Rev. 43 (2014) 5815.
[35] K. Jayaramulu, R. P. Narayanan, S. J. George, T. K. Maji, Inorg. Chem. 51 (2012)
10089.
[36] (a) X. X. Li, H. Y. Xu, F. Z. Kong, R. H. Wang, Angew. Chem., Int. Ed. 52 (2013)
13769;
(b) J. M. Zhou, W. Shi, H. M. Li, H. Li, P. Cheng, J. Phys. Chem. C 118 (2014)
416.
Table 1. Crystallographic data and structural refinement parameters for Mptpy
and 1–2a
Compound
Mptpy
1
2
Empirical formula
C22H17N3
323.39
C88H56N12Zn2O9
1556.23
C49H31N8Zn2O11
1038.56
Formula weight
23

Crystal system
Space group
A /Å
Triclinic
P-1
Triclinic
P-1
Monoclinic
C2/c
8.5524(16)
9.5677(18)
11.444(2)
89.151(2)
69.103(2)
73.378(2)
834.3(3)
2
15.102(6)
15.117(6)
17.397(7)
86.631(5)
69.642(4)
79.346(5)
3659(3)
4
35.07(2)
7.469(5)
21.491(14)
90
B /Å
C /Å
α/°
β/°
γ/°
120.585(11)
90
V/Å3
4847(5)
4
Z
ρcalc (g ·cm-3)
1.287
1.412
1.423
F (000)
340
1600
2116
Reflections collected
S on F2
4209
26012
11431
1.068
1.040
1.052
Rint
0.0190
0.0493
0.1311
R1, wR2a [I>2σ(I)]
0.0472, 0.1268
0.0655, 0.1437
0.0847, 0.2263
0.1221, 0.2490
0.0883, 0.1991
0.1701, 0.2443
a
R1, wR2 (all data)
2
2 2 1/2
aR1 = Σ||Fo| – |Fc||/Σ|Fo|, wR2=[Σw(Fo –Fc2)2/Σw(Fo ) ]
Figure captions:
Scheme 1. The optimized geometry and NBO charge distributions of the free ligand
Hcptpy (the blue ball represents N atom, the red ball represents O atom and
the gray ball represents C atom).
Scheme 2. Synthetic route I to the Hcptpy ligand
Scheme 3. Synthetic route II to the Hcptpy ligand
24

Fig. 1.
(a) The coordination environments of Zn1 and Zn2 ions in 1 with 30%
thermal ellipsoids (all hydrogen atoms and solvent molecules are omitted
for clarity). (b) 2D layer structures based on the Zn1 and Hcptpy in 1 (blue
ball:N atom, green ball:oxygen atom in Zn1 layer. All ball atoms represent
Lewis base sites). (c) Perspective view of the parallel penetration of the
layers constructed by the Zn1 and Zn2 motifs in 1.
Fig. 2. (a) The coordination environment of Zn1 ions in 2 with 30% thermal
ellipsoids (all hydrogen atoms and solvent molecules are omitted for
clarity). (b) 1D ladder chain in 2. (c) 2D supramolecular layer in 2. (d)
3D supramolecular structure based on π..π stacking interaction in 2.
Fig. 3.
Fig. 4.
Fig. 5.
(a) Emission spectra of 1 in H2O on (b) NaOH titration and (c) HNO3
titration.
(a) The photoluminescence spectra and (b) the luminescence intensities of 1
introduced into various pure solvent emulsions when excited at 300 nm.
(a) The photoluminescence spectra of 1@DMF emulsion in the presence of
various content acetone solvent (excited at 300 nm). (b) The fluorescence
intensity of 1@DMF emulsion as a function of acetone
content.
Fig. 6.
Fig. 7.
Fig. 8.
(a) Comparison of the relative luminescence intensities of various 1-
M(NO3)x@DMF suspensions. (b) Luminescence spectra of 1 in DMF in
the presence of different amounts of Cu2+ (excited at 300 nm) (inset: the
plot of intensity versus Cu2+ concentration). (c) Visual change upon the
addition of various M(NO3)x.
(a) Luminescence intensity at 405 nm of 1-Zn dispersed in DMF and 1-Zn
dispersed in DMF with Cu2+ (10-2 M), mixed ions (Na2+, K2+, Ca2+, Mn2+,
Pb2+, Zn2+, Cd2+, Co2+, Ni2+, 10-2 M), mixed ions+Cu2+ (10-2 M). (b)
Luminescence spectra of 1 in DMF solutions with Cu(NO3)2 at different
concentrations.
Multiple cycles for the quenching by Cu(NO3)2 and the recovery after
filtration and ultrasonic washing by DMF for a few times. The red bars
show the pristine intensity and regenerated ones after washing; while the
25

green bars show the intensities after addition of Cu(NO3)2@DMF solutions.
(a) X-ray photoelectron spectroscopy for complex 1 and Cu2+ incorporated
complex 1; (b) N 1s XPS for complex 1 and Cu2+ incorporated complex 1. (c)
O 1s XPS for complex 1 and Cu2+ incorporated complex 1.
Fig.9.
Fig. 10.
Fig. 11.
(a) The photoluminescence spectra and (b) the luminescence intensities of
1 introduced into various pure solvent emulsions when excited at 300 nm.
(a) The photoluminescence spectra of 2@H2O emulsion in the presence of
various content Cr2O72−. (b) The fluorescence intensity of 2@H2O
2−
emulsion as a function of Cr2O7 .
26

Scheme 1.
Scheme 2.
Scheme 3.
27

Fig. 1.
(a)
(b)
(c)
28

Fig. 2.
(a)
(b)
29