Three novel zinc(ii) metal-organic frameworks based on three tetrazolate ligands: Synthesis, structures and photoluminescence

Article abstract of DOI:10.1039/c4ra02872d

Three metal-organic frameworks (MOFs), namely [Zn(BPT)H₂O] (JUC-121), [Zn₅(IBT)₆]·8[H₂N(CH ₃)₂]·DMA (JUC-122) and [Zn(TPD)(H ₂O)₂]·0.5H₂O (JUC-123) (JUC = Jilin University, China), H₂BPT = (5-bromo-1,3-phenylene)bis(tetrazole), H₃IBT = 4,5-bis(tetrazol-5-yl)imidazole and H₂TPD = 3,5-di(tetrazol-5-yl)pyridine, were obtained by the reactions of Zn(NO ₃)₂·6H₂O and three tetrazolate ligands, which were characterized by single crystal X-ray diffraction, thermal gravimetric analyses (TGA), Fourier-transform infrared spectra (FT-IR), elemental analysis (CHN) and powder X-ray diffraction (PXRD). From the crystal structures of these complexes and the coordination modes of the ligands, we can see that the tetrazolate ligands have multi-connectivity abilities to obtain intriguing varieties of molecular architectures. JUC-121 displays a three-dimensional (3D) network with the point symbol (4·6 ⁵)₂(4²·8⁴)(6 ⁴·8²). JUC-122 shows a two-dimensional (2D) framework with the point symbol (24³)₂(24)₉ and JUC-123 has a 2D bimodal (3, 3)-connected net with the point symbol (4·8²). The solid-state fluorescent spectra of JUC-121, JUC-122, JUC-123 and the free ligands were measured at room temperature. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra02872d

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Three novel zinc(II) metal–organic frameworks
based on three tetrazolate ligands: synthesis,
structures and photoluminescence†
Cite this: RSC Adv., 2014, 4, 21535
a
a
Hongming He, Fuxing Sun, Nian Zhao,a Rongrong Yuana and Guangshan Zhuab
*
Three metal–organic frameworks (MOFs), namely [Zn(BPT)H2O] (JUC-121), [Zn5(IBT)6]$8[H2N(CH3)2]$DMA
(JUC-122) and [Zn(TPD)(H2O)2]$0.5H2O (JUC-123) (JUC ¼ Jilin University, China), H2BPT ¼ (5-bromo-1,3-
phenylene)bis(tetrazole), H3IBT
¼
4,5-bis(tetrazol-5-yl)imidazole and H2TPD
¼
3,5-di(tetrazol-5-yl)
pyridine, were obtained by the reactions of Zn(NO3)2$6H2O and three tetrazolate ligands, which were
characterized by single crystal X-ray diffraction, thermal gravimetric analyses (TGA), Fourier-transform
infrared spectra (FT-IR), elemental analysis (CHN) and powder X-ray diffraction (PXRD). From the crystal
structures of these complexes and the coordination modes of the ligands, we can see that the
tetrazolate ligands have multi-connectivity abilities to obtain intriguing varieties of molecular
architectures. JUC-121 displays
(4$65)2(42$84)(64$82). JUC-122 shows
(243)2(24)9 and JUC-123 has a 2D bimodal (3, 3)-connected net with the point symbol (4$82). The solid-
state fluorescent spectra of JUC-121, JUC-122, JUC-123 and the free ligands were measured at room
temperature.
a
three-dimensional (3D) network with the point symbol
two-dimensional (2D) framework with the point symbol
Received 1st April 2014
Accepted 2nd May 2014
a
DOI: 10.1039/c4ra02872d
www.rsc.org/advances
properties, such as spin crossover,28,29 selective gas adsorp-
tion,30,31 luminescent,32 and selective ion sensing,33 but also for
their multi-connectivity abilities to obtain fascinating topolog-
ical structures.
Introduction
In the past two decades, metal–organic frameworks (MOFs),1–3
also known as porous coordination polymers (PCPs), have
attracted great interest because of intriguing varieties of
molecular architectures and potential applications as func-
tional materials.4–17 These materials can be applied potentially
in gas storage, separation,4–7 ion exchange,8 sensors,9–12
heterogeneous catalysis,13–15 optical devices16–19 and so on.
Owing to their richness and unpredictability architectures in
the structural assembly of these materials, many efforts have
been focused on it. The organic ligands play a signicant role to
tune the structures and topological networks, so a lot of organic
ligands have been synthesised to prepare novel MOFs. Most of
the ligands are multicarboxylic acids and aromatic N-heterocy-
cles such as pyridine, imidazole, triazole, tetrazolate and their
derivatives.20–27 Among the ligands, tetrazolate and their deriv-
atives as ve-membered N-heterocyclic azoles have received
extensive attention not only because of the richness of
Recently, some small tetrazole linkers are applied to build up
novel MOFs.34–36 More structurally complex and functional
molecular architectures and robust functionalities have been
presented. To our knowledge, the largest number of exposed
framework atoms (both metals and nonmetals) would likely
contribute to enhanced small molecules storage capacity such
as CO2. Su et al. have synthesized a novel zeolite-like metal–
organic framework with sodalite topology based on an N-rich
tetrazolate ligand, which exhibits high CO2 uptake and selective
CO2/N2 adsorption capacity.37 On the other hand, the tetrazolate
ligands have multi-connectivity abilities to form very beautiful
framework patterns. Evidently, it is quite interesting and chal-
lenging job to explore the assembly of N-rich tetrazolate ligand
with a metal ion/cluster in crystal engineering.
Herein, we successfully designed and synthesized three
small similar organic ligands with two tetrazole groups, namely,
H2BPT ¼ (5-bromo-1,3-phenylene)bis(tetrazole), H3IBT ¼ 4,5-
bis(tetrazol-5-yl)imidazole and H2TPD ¼ 3,5-di(tetrazol-5-yl)-
pyridine. Three novel MOFs, namely [Zn(BPT)H2O] (JUC-121),
[Zn5(IBT)6]$8[H2N(CH3)2]$DMA (JUC-122) and [Zn(TPD)(H2O)2]$
0.5H2O (JUC-123) (JUC ¼ Jilin University, China), were synthe-
sized by the reactions of Zn(NO3)2$6H2O and these ligands.
Single crystal analysis demonstrates that JUC-121, JUC-122 and
aState Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin
University, Changchun, 130012, P. R. China. E-mail: zhugs@jlu.edu.cn; Fax: +86-
431-85168331; Tel: +86-431-85168887
bQueensland Micro- and Nanotechnology Centre, Griffith University, Queensland 4111,
Australia
† Electronic supplementary information (ESI) available. CCDC 972881–972883.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c4ra02872d
JUC-123 display different structures. JUC-121 displays
a
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three-dimensional (3D) network with the point symbol reux. Aer cooling to room temperature slowly, 40 mL of an
(4$65)2(42$84)(64$82). JUC-122 shows a two-dimensional (2D) aqueous solution of NaOH (1 M) was added to the resulting
framework with the point symbol (243)2(24)9 and JUC-123 also solution under stirring for 1 h at room temperature. Then 1 M
has a 2D bimodal (3, 3)-connected net with the point symbol HCl solution was added to it to get a white precipitation with pH
(4$82). The solid-state uorescent spectra of free ligands, JUC- ¼ 2.0–3.0. Aer stirring it for 1 h, the white precipitation was
121, JUC-122 and JUC-123 were measured at room temperature. ltered and washed with distilled water (3 ꢂ 30 mL) to obtain
3,5-di(tetrazol-5-yl)pyridine of 1.47 g (yield: 91%). 1H NMR (300
MHz, DMSO), d (ppm): 9.37 (d, J ¼ 2.1 Hz, 2H); 9.05 (t, J ¼ 2.1
Experimental section
Materials and methods
Hz, 1H). Selected FT-IR data (KBr pellet, cmꢁ1): 3372 (s), 3153
(s), 3064 (s), 2326 (br), 2142 (s), 1992 (s), 1914 (s), 1860 (s), 1650
(s), 1589 (s), 1448 (s), 1386 (s), 1427 (s), 1210 (m), 971 (br), 912
(s), 790 (s), 748 (s), 688 (s), 649 (s), 511 (s), 428 (s).
All the chemical reagents and solvents in this work for
syntheses and analyses were purchased from commercial
sources without further purication. The TGA were performed
in the range of 30–800 ꢀC under air ow at a heating rate of 10
ꢀC minꢁ1 with a Perkin-Elmer TGA thermogravimetric analyzer.
Powder X-ray diffraction (PXRD) data were obtained on a Scin-
[Zn(BPT)H2O] (JUC-121). A mixture of H2BPT (40 mg, 0.14
mmol), Zn(NO3)2$6H2O (60 mg, 0.2 mmol) and water–ethanol
(1.6–0.4 mL) was sealed in a 20 mL Teon-lined autoclave and
heated at 130 ꢀC for 24 h. Aer cooling to room temperature
slowly, yellow block crystals were obtained by ltration, washed
with distilled water and dried in air. Yield: 28 mg (54% based on
H2BPT). EA (%) calc. for C8H5N8OBrZn: C, 25.50; H, 1.33; N,
29.75. Found: C, 25.36; H, 1.25; N, 29.21. Selected FT-IR data
(KBr pellet, cmꢁ1): 3468 (br), 3056 (s), 2950 (s), 2213 (br), 1774
(s), 1712 (s), 1608 (s), 1589 (s), 1498 (s), 1442 (s), 1415 (s), 1392
(s), 1338 (s), 1259 (s), 1155 (s), 1112 (s), 1029 (br), 916 (s), 889 (s),
782 (s), 769 (s), 746 (s), 732 (s), 682 (s), 590 (br), 534 (s), 457 (s).
˚
tag X1 diffractometer at 50 kV, 200 mA for Cu-Ka (l ¼ 1.5418 A)
at room temperature. Elemental analyses were performed on a
Perkin-Elmer 240 analyzer. Fourier-transform infrared spec-
troscopy (FT-IR) spectra were obtained on a Nicolet Impact
410 FT-IR spectrometer in the 4000–400 cmꢁ1 range by using
KBr pellets. All uorescence measurements for the solid
samples were recorded on a Fluoromax-4 spectrouorometer at
room temperature. The 300 MHz 1H NMR spectra were recorded
on a Bruker AV 400 spectrometer at 298 K with Me4Si as the
internal standard.
[Zn5(IBT)6]$8[H2N(CH3)2]$DMA (JUC-122).
A mixture of
H3IBT (5 mg, 0.025 mmol), Zn(NO3)2$6H2O (15 mg, 0.05 mmol),
DMA–ethanol (3.5–1.5 mL) and concentrated nitric acid was
sealed into a 20 mL capped vessel. The vessel was heated at
60 ꢀC. The crystals were obtained aer 2 days, washed with DMA
Synthesis
(5-Bromo-1,3-phenylene)bis(tetrazole)
(H2BPT). Firstly, and dried in air. Colourless block crystals were collected. Yield:
5-bromo-1,3-benzenedicarbonitrile was prepared according to 4 mg (48% based on H3IBT); EA (%) calc. for C50H79N69OZn5: C,
the literature procedure.38 A mixture of 5-bromo-1,3-benzene- 30.06; H, 3.96; N, 48.40. Found: C, 29.46; H, 3.26; N, 49.21.
dicarbonitrile (1.55 g, 7.5 mmol), NaN3 (1.95 g, 45 mmol) and Selected FT-IR data (KBr pellet, cmꢁ1): 3442 (br), 3064 (s), 3012
triethylamineꢀhydrochloride (6.175 g, 30 mmol) was stirred for (s), 2863 (br), 1625 (s), 1569 (s), 1504 (s), 1446 (s), 1409 (s), 1361
3 days at 100 C in an oil-bath in a mixture system of toluene– (s), 1249 (s), 1220 (s), 1186 (s), 1122 (s), 1062 (s), 1027 (m),
methanol (50–10 mL). Aer cooling to room temperature, 40 mL 985 (s), 962 (s), 854 (br), 754 (s), 696 (s), 646 (s), 601 (s), 561 (s),
of an aqueous solution of NaOH (1 M) was added dropwise over 501 (s).
5 minutes to the solution, which was stirred at room tempera-
[Zn(TPD)(H2O)2]$0.5H2O (JUC-123). A mixture of H2TPD
ture for 1 h. Then 40 mL of diluted HCl (1 M) was added until no (30 mg, 0.14 mmol), Zn(NO3)2$6H2O (74 mg, 0.25 mmol) and
further white precipitate formed. The white precipitation water–ethanol (1.6–0.4 mL) was sealed in a 20 mL Teon-lined
product was collected by ltration, washed with distilled water autoclave, which was heated at 160 ꢀC for 24 h and then cooled
(3 ꢂ 10 mL) and methanol (3 ꢂ 10 mL), then dried to give 1.93 g to room temperature, yellow block crystals were obtained by
(yield: 88%). 1H NMR (300 MHz, DMSO), d (ppm): 8.76 (t, J ¼ 1.5 ltration, washed with distilled water, and dried in air. Yield:
Hz, 1H); 8.35 (d, J ¼ 1.4 Hz, 2H). Selected FT-IR data (KBr pellet, 34 mg (76% based on H2TPD). EA (%) calc. for C14H16N18O5Zn2:
cmꢁ1): 3435 (s), 3066 (m), 2942 (m), 2873 (s), 2730 (m), 2634 (s), C, 25.95; H, 2.47; N, 38.93. Found: C, 25.16; H, 2.66; N, 37.93.
2520 (m), 1826 (s), 1554 (s), 1457 (s), 1386 (s), 1247 (s), 1166 (s), Selected FT-IR data (KBr pellet, cmꢁ1): 3214 (br), 3083 (br), 2267
1097 (s), 1008 (m), 922 (m), 887 (m), 771 (s), 736 (s), 674 (s), 524 (m), 1677 (m), 1664 (m), 1452 (s), 1427 (s), 1305 (s), 1236 (s),
(s), 447 (s).
1207 (m), 1137 (m), 1054 (s), 1033 (s), 925 (s), 808 (s), 755 (s), 696
4,5-Bis(tetrazol-5-yl)imidazole (H3IBT). 4,5-Bis(tetrazol-5-yl)- (s), 607 (br), 530 (s), 439 (s).
imidazole (H3IBT) was prepared according to the literature
procedure.39
X-ray structure determination and structure renement
3,5-Di(tetrazol-5-yl)pyridine (H2TPD). Firstly, pyridine-3,5-
dicarbonitrile was prepared according to the literature proce- Crystallographic data collections for JUC-121, JUC-122 and JUC-
dure.40
mixture of pyridine-3,5-dicarbonitrile (0.97 g, 123 were taken on Bruker SMART APEX II CCD-based diffrac-
A
7.5 mmol), NaN3 (1.95 g, 45 mmol) and triethylamine hydro- tometer with graphite monochromatized Mo-Ka radiation (l ¼
˚
chloride (6.175 g, 30 mmol) was added to a 100 mL ask with 0.71073 A) at 298 K. Corrections for incident and diffracted
toluene–methanol (40–8 mL), which was stirred for 3 days with beam absorption effects were applied to the date using the
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Table 1 Crystal data and structure refinements for JUC-121, JUC-122 and JUC-123
Compound
JUC-121
JUC-122
JUC-123
Empirical formula
Formula weight
Crystal system
Space group
C8H3N8OBr Zn
372.47
C30H6N60Zn5
1533.90
Hexagonal
ꢀ
R3c
C14H14N18O5Zn2
645.21
Monoclinic
P21/c
11.9967(11)
13.2295(12)
7.0045(7)
90.00
90.472(1)
90.00
1110.65(18)
2
1.929
2.234
2712
Tetragonal
P42/ncm
13.280(2)
13.280(2)
13.533(3)
90.00
90.00
90.00
2386.7(7)
8
2.073
˚
a (A)
18.8708(7)
18.8708(7)
52.615(4)
90.00
90.00
120.00
16 226.3(15)
6
0.942
1.140
4515
˚
b (A)
˚
c (A)
a (ꢀ)
b (ꢀ)
g (ꢀ)
3
˚
V (A )
Z
rcalc g cmꢁ3
m (mmꢁ1
Nref
)
5.411
1561
F(000)
R(int)
1439.0
0.0356
1.079
0.0331, 0.0871
0.0496, 0.0954
4533.0
0.0562
1.133
0.0498, 0.1621
0.0799, 0.1749
648.0
0.0198
1.056
0.0284, 0.0738
0.0373, 0.0794
Goodness-of-t on F2
R1, wR2 [I > 2s(I)]
R1, wR2 (all data)
SADBAS program.41 The structures were solved by a combina- Zn2 ion, a half BPT2ꢁ ligand and a half coordinated water
tion of direct methods and rened by the full matrix least- molecule. As shown in Fig. 1a, it shows the coordination envi-
squares against F2 values using the SHELXTL program.42 All ronments of Zn(II) ions. There are two independent Zn(II) ions in
non-hydrogen atoms were rened anisotropically and located the structure, which adopt different geometries. Zn1 shows an
˚
successfully from Fourier maps. Because a large region of octahedral ZnN4O2 with four N3 atoms (Zn1–N ¼ 2.131 A)
disordered solvent molecules in JUC-122, the PLATON/ originating from four tetrazolate rings of different ligands and
SQUEEZE was employed to remove their diffraction contribu- two oxygen atoms from coordinated water molecules (Zn1–O ¼
tions.43,44 The solvent-free structure of JUC-122 was obtained by 2.137 A), while Zn2 is coordinated by four N1 atoms from four
˚
˚
the SQUEEZE routine. Hydrogen atoms bonded to carbon were tetrazoles of different ligands (Zn2–N ¼ 2.016 A) to form a
placed geometrically using a riding mode with an isotropic highly distorted tetrahedral geometry. As shown in Fig. 1b and
displacement parameter xed at 1.2 times Ueq of the parent c, each BPT2ꢁ ligand can be regarded as a four-bridged linker to
atoms. Hydrogen atoms of aqua or solvates of JUC-123 were rst bridge two ZnN4O2 cores and two ZnN4 cores through the 1, 3-N
located in difference Fourier maps and then xed in the given atoms (N1, N3) of one tetrazole to form a 3D coordination
positions. The detailed crystallographic data and structure network with no any channels. Therefore, the two Zn(II) ions
renement parameters of JUC-121, JUC-122 and JUC-123 are and the BPT2ꢁ ligand can be regarded as 4-connected nodes
reported in Table 1 and the selected bond lengths and angles
data are listed in Table S1,† respectively.
Results and discussion
Coordination modes of the ligands
Single crystal X-ray diffraction reveal that coordination modes
of the ligands in JUC-121, JUC-122 and JUC-123 during the self-
assembly process. As shown in Scheme 1, the ligands of H2BPT,
H3IBT, and H2TPD are coordinated to four, two, and three metal
ions respectively and the tetrazole groups of different ligands
show different coordination modes.
Crystal structure descriptions
[Zn(BPT)H2O] (JUC-121). A single-crystal X-ray diffraction
analysis reveals that JUC-121 crystallizes in the tetragonal
P42/ncm space group and shows a 3D coordination framework.
Scheme 1 The coordination modes of H2BPT (a), H3IBT (b) and
In the asymmetric unit, there is one fourth Zn1 ion, one fourth H2TPD (c).
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Fig. 1 (a) Coordination environments of Zn(II) atoms (symmetry code:
#1 y + 1/2, x ꢁ 1/2, ꢁz + 2; #2 ꢁx + 1, ꢁy, ꢁz + 2; #3 ꢁy + 1/2, ꢁx + 1/2,
z; #4 ꢁx + 3/2, ꢁy + 1/2, z; #5 ꢁy + 1, x ꢁ 1/2, ꢁz + 3/2; #6 y + 1/2, ꢁx
+ 1, ꢁz + 3/2; #7 y, x, z). (b) View of 3D coordination framework along
the c-axis. (c) View of 3D coordination framework along the a-axis (the
hydrogen atoms are omitted for clarity). (d) The simplified network of
the 3D coordination framework with the point symbol
(4$65)2(42$84)(64$82).
Fig. 2 (a) Coordination environments of Zn(II) atoms (symmetry code:
#1 ꢁy, x ꢁ y, z; #2 ꢁx + y, ꢁx, z; #3 x ꢁ y + 1/3, ꢁy + 2/3, ꢁz + 1/6). (b)
View of the single 2D network along the c-axis. (c) View of the packed
layers of JUC-122 along the c-axis. (d) The 2D networks are packed
topologically. The result network could be concerned a 3D together with ABC fashion to form a 3D supramolecular architecture
network with the point symbol (4$65)2(42$84)(64$82).
[Zn5(IBT)6]$8[H2N(CH3)2]$DMA (JUC-122). X-ray crystallog-
raphy conrms that JUC-122 has a 2D framework and crystal-
along the b-axis (the hydrogen atoms and solvent molecules are
omitted for clarity). (e) The simplified network of the single 2D network
along the c-axis with the point symbol (243)2(24)9.
ꢀ
lizes in the hexagonal R3c space group. There is one third Zn1
molecule. Each Zn(II) is ve-coordinated by N2, N5 and N7 from
ion, one second Zn2 ion and one IBT3ꢁ ligand in the asym-
˚
three different ligands (Zn–N ¼ 2.003–2.059 A) and two oxygen
metric unit. There are two crystallographically different Zn(II)
(Fig. 2a). The Zn1 ion is bound with six nitrogen atoms, which
atoms originating from two coordinated water molecules (Zn–O
˚
¼ 2.149–2.154 A) (Fig. 3a). Each ligand is deprotonated to
are three pairs of N1 and N5 atoms from three independent
furnish a TPD2ꢁ anion, which links three Zn ions in a three-
IBT3ꢁ ligands to form a distorted octahedral geometry (Zn1–N ¼
bridged fashion to yield a 2D supramolecular layer (Fig. 3b). As
˚
2.162 A). Meanwhile, the Zn2 ion exhibits a distorted tetrahe-
shown in Fig. 3c and d, the 2D layers are packed together with
dral ZnN4 geometry with two pairs of N4 and N10 atoms
AB fashion by p–p stacking between arene cores of two inde-
belonging to the tetrazolate rings from two independent IBT3ꢁ
pendent TPD2ꢁ (3.611 A) and weak intermolecular van der
˚
3ꢁ
˚
ligands (Zn2–N ¼ 1.982–1.990 A). Each IBT ligand connects
with two Zn(II) ions to form a 2D framework (Fig. 2b) with
triangular lattice, involving twelve ligands and twelve Zn(II) ions.
The 2D networks are packed together with ABC fashion by weak
intermolecular van der Waals interactions to form a 3D supra-
molecular architecture (Fig. 2c and d). The guest solvent
molecules included in the frameworks could be rened, which
can be conrmed by the TGA and elemental analyses. From the
topologic point of view, the Zn1 ion, Zn2 ion can be regarded as
3-connected and 2-connected nodes, respectively, and the
ligand can be simplied into a 2-connected linker to achieve a
2D network with the point symbol (243)2(24)9 (Fig. 2e). This
topology can be regarded as one augmented form of honeycomb
(hcb) topology.
Waals interactions to yield a 3D framework. Topologically, by
considering TPD2ꢁ anions and Zn(II) ions as 3-connected nodes,
the 2D framework can be symbolized as a (3, 3)-connected net
with the point symbol (4$82) (Fig. 3e).
Thermal analysis
PXRD analyses of JUC-121, JUC-122 and JUC-123 were carried
out at room temperature (Fig. 4a and c). The results show that
the experimental PXRD patterns are closely matched those in
the simulated patterns from single crystal structures, which
reveal that the phase purity of the bulk crystalline materials.
From the thermal gravimetric analyses (Fig. 4d), JUC-121 shows
a slow weight loss of 4.89% (calculated: 4.78%) in the range 30–
280 ꢀC, corresponds to loss one coordinated water molecule.
Upon further heating, the framework decomposed gradually at
380 ꢀC. The TGA of JUC-122 exhibits an initial weight loss
[Zn(TPD)(H2O)2]$0.5H2O (JUC-123). The X-ray crystallo-
graphic study shows that JUC-123 crystallizes in the monoclinic
space group P21/c and possesses a 2D framework. The asym-
metric unit of JUC-123 contains one Zn ion, one TPD2ꢁ ligand,
two coordinated water molecules and a half guest water
ꢀ
23.23% (calculated: 23.15%) before 157 C and the framework
collapsed at 300 ꢀC. JUC-123 losses a half guest and two
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Fig. 5 Excitation (dot lines) and emission (solid lines) spectra of (a)
H2BPT (blue) and JUC-121 (red), (b) H3IBT (blue) and JUC-122 (red), (c)
H2TPD (blue) and JUC-123 (red).
As shown in Fig. 5, a broad photoluminescence emission band
at 452, 440 and 480 nm under an excitation of 397, 380 and 396
nm for the H2BPT, H3IBT, H2TPD ligands, respectively, which
are probably attributable to the p* / p or p* / n transi-
Fig. 3 (a) Coordination environment of Zn(II) atoms (symmetry code:
#1 ꢁy, ꢁy, ꢁz; #2 x ꢁ 1, ꢁy + 0.5, z ꢁ 0.5). (b) View of the single 2D
network along the c-axis. (c) View of the packed double-layers of tions.45,46 The luminescence properties of JUC-121, JUC-122 and
JUC-123 along the c-axis. (d) The 2D networks are packed together
with AB fashion to form a 3D framework along the b-axis. (the
hydrogen atoms and solvent molecules are omitted for clarity). (e) The
JUC-123 in the solid state were also investigated at room
temperature. These complexes show emission bands at 468 nm
(lem ¼ 396 nm) for JUC-121, 412 nm (lem ¼ 356 nm) for JUC-122
simplified network of the single 2D network along the c-axis with a 2D
bimodal (3, 3)-connected net with the point symbol (4$82).
and 495 nm (lem ¼ 411 nm) for JUC-123, respectively. Compared
to the excitation and emission spectra of the free ligands, the
observed emissions of JUC-121 and JUC-123 are red-shied 16
nm and 15 nm, respectively. It indicates that the luminescent
properties are mainly attributed to the intraligand transition
and ligand-to-metal, which are in good agreement with litera-
ture examples on this class of Zn(II) coordination
compounds.47,48 Furthermore, JUC-122 is different from the
others. The emission band of JUC-122 exhibits blue-shied 28
nm, which may be presumably attributed to the coordination of
the IBT3ꢁ ligand to the central Zn(II) ions. It leads to less
vibrations of the skeleton and reduces the loss of energy by
radiationless decay of the intraligand emission excited state.49,50
Conclusions
In summary, three novel metal–organic frameworks based on
Zn(II) and three different tetrazolate ligands were synthesized.
JUC-121 features a 3D supramolecular network with the point
symbol (4$65)2(42$84)(64$82). Meanwhile, JUC-122 exhibits a 2D
Fig. 4 The simulated (black) and as-synthesized (red) powder X-ray
network with the point symbol (243)2(24)9 and JUC-123 has a 2D
diffraction of JUC-121 (a), JUC-122 (b) and JUC-123 (c). (d) The TGA
curves of JUC-121, JUC-122 and JUC-123.
bimodal (3, 3)-connected net with the point symbol (4$82). From
the crystal structures of these complexes and the coordination
modes of the ligands, the four N atoms of the tetrazolate and
terminal water molecules before 270 ꢀC, which is about 15.73%
their derivatives all have good coordination abilities with metal
(calculated: 13.91%).
ions to generate unpredictable structures and fascinating
topologies. It is expected that more extensive researches to
explore and develop more kinds of ligands with tetrazole groups
Photoluminescence properties
The solid-state luminescent properties of the free ligands, JUC- to generate the richness and unpredictability of structures and
121, JUC-122 and JUC-123 were measured at room temperature. topologies.
This journal is © The Royal Society of Chemistry 2014
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We are grateful to the nancial support from National Basic
Research Program of China (973 Program, grant nos
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(Regional) Joint Research Project of NSFC (grant nos
21120102034), NSFC (grant nos 20831002) and the Australian
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