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Three new three dimensional Zn(II)-benzenetetracarboxylate coordination polymers: Syntheses, crystal structures and luminescent properties
Polyhedron 123 (2017) 69–74
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Polyhedron journal homepage: www.elsevier.com/locate/poly
Three new three dimensional Zn(II)-benzenetetracarboxylate coordination polymers: Syntheses, crystal structures and luminescent properties Yu-Hui Luo a, Chuan-Zhou Tao a, Dong-En Zhang a, Juan-Juan Ma a, Lin Liu a, Zhi-Wei Tong a,⇑, Xiao-Yang Yu b,⇑ a b
Department of Chemical Engineering, Huaihai Institute of Technology, Jiangsu, Lianyungang 222000, China Jilin Institute of Chemical Technology, Jilin City, Jilin 132022, China
a r t i c l e
i n f o
Article history: Received 2 October 2016 Accepted 27 October 2016 Available online 4 November 2016 Keywords: 1,2,4,5-Benzenetetracarboxylic acid Zinc(II) compounds Coordination polymers Hydrothermal reaction Luminescent property
a b s t r a c t Three novel coordination polymers, namely, [Zn2(betc)(L1)H(H2O)]2H2O (1), [Zn2(btec)(L2)2] (2) and [Zn5(btec)2(L3)1.5(OH)2]2H2O (3) (L1 = 3,5-di(1H-imidazol-1-yl)benzoate, L2 = 1,3-bis((1H-1,2,4-triazol1-yl)methyl)benzene and L3 = 1,3-di(1H-1,2,4-triazol-1-yl)propane), have been hydrothermally synthesized. Compound 1 shows a three dimensional (3D) framework with fsc-3,5-P4/mbm topology. Compound 2 reveals a 3D pillar-layered framework with the presence of 3-fold left- and right-handed helical chains. Compound 3 also exhibits a 3D framework based on 1D zinc chains. In addition, the luminescent properties for 1–3 have also been investigated. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction Coordination polymers (CPs) are attracting more and more interests in recent years, not only due to their intriguing architectures but also due to their wildly potential applications including gas storage, separation, magnetism and catalysis [1]. Although a great effort have been paid to prepare novel CPs, it is still difficult to prepare CPs with expected structures. Because the final structures can be affected by many kinds of factors, such as metal ions, organic ligands, pH value, solvents, reaction temperature, and so on [2]. Among the above mentioned factors, the organic ligand has been considered as one of the most important fact in the self-assembly system. The multi-carboxylate ligands as an important family of O-donor ligands are good choices in the construction of CPs with fascination architectures and properties [3]. In this regard, 1,2,4,5-Benzenetetracarboxylic acid (H4btec) have been widely used for their variety of coordination modes [4]. The four carboxylate groups of H4btec are equally arranged around the benzene ring and can rotate along the C–C bond resulting in kinds of conformations. On the other hand, flexible N-donor ligands have been proved as excellent co-ligands for the construction of novel
⇑ Corresponding authors. E-mail addresses: [email protected] [email protected] (X.-Y. Yu). http://dx.doi.org/10.1016/j.poly.2016.10.045 0277-5387/Ó 2016 Elsevier Ltd. All rights reserved.
(Z.-W.
Tong),
yangyan-
networks [5]. In this work, we are prompted to construct novel CPs by utilizing H4btec and flexible N-donor ligands under hydrothermal condition. Herein we report three Zn(II) CPs, namely, [Zn2(betc)(L1)H(H2O)]2H2O (1), [Zn2(btec)(L2)2] (2) and [Zn5(btec)2(L3)1.5(OH)2]2H2O (3) (L1 = 3,5-di(1H-imidazol-1-yl)benzoate, L2 = 1,3-bis((1H-1,2,4-triazol-1-yl)methyl)benzene and L3 = 1,3-di(1H-1,2,4-triazol-1-yl)propane). All of the title compounds show three dimensional (3D) frameworks. Compound 1 represents a rare example of CP with fsc-3,5-P4/mbm topology. In addition, the luminescent properties for 1–3 have also been investigated. 2. Experimental section 2.1. Materials and general methods All reagents and solvents were purchased from commercial sources and used without further purification. Powder X-ray diffraction (PXRD) patterns were collected on a Rigaku Dmax 2000 X-ray diffractometer with graphite monochromatized Cu Ka radiation (k = 0.154 nm) and 2h ranging from 5° to 50° with an increment of 0.02° and a scanning rate of 5°/min. The FI-IR spectra were measured in KBr pellets in the range 4000–400 cm 1 on a Mattson Alpha-Centauri spectrometer. Elemental analysis (EA) for C, H and N was performed on a Perkin-Elmer 2400 Elemental
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Analyzer. Thermogravimetric analysis (TGA) was performed on a Perkin-Elmer Thermal Analyzer under nitrogen atmosphere at a heating rate of 10 °C min 1. The fluorescent property was measured on a FLS920 Edinburgh Luminescence Spectrometer with a light source of Xenon lamp. The wavelengths for the photoexcitation of each compound were set the maximum of the excitation spectra.
Table 1 Crystal data and structure refinement for 1, 2 and 3.
2.2. Preparation of [Zn2(betc)(L1)H(H2O)]2H2O (1) The pH of the mixture of Zn(NO3)26H2O (0.1 mmol, 30.0 mg), H4btec (0.04 mmol, 10.0 mg), 3,5-Di(1H-imidazol-1-yl)benzonitrile (0.04 mmol, 9.0 mg) and H2O (10 ml) was adjusted to about 3.5 with HCl (aq. 0.1 M) and NaOH (aq. 0.1 M). The resulting mixture was transferred into a 23 ml Teflon-lined stainless steel autoclave reactor and then heated at 160 °C for 72 h. After cooled to room temperature at a rate of 3 °C h 1, colorless crystals suitable for X-ray structural analysis were isolated by filtrating, washing with water several times, and drying in air. Yield: ca. 20% (based on Zn). Anal. calc. for C23H18N4O13Zn2: C, 40.08; H, 2.63; N, 8.13. Found: C, 39.98; H, 2.59; N, 8.09%. IR (KBr, cm 1): m = 3450 (m), 3120 (m), 3070 (m), 1600 (s), 1520 (s), 1410 (m), 1350 (s), 1260 (s), 1130 (m), 1080 (s), 1010 (m), 949 (m), 812 (s), 732 (m), 667 (m), 611 (s), 503 (m). 2.3. Preparation of [Zn2(btec)(L2)2] (2) The preparation of 2 (colorless crystals) is similar to that of 1 except that L2 (0.04 mmol, 10.0 mg) was used instead of 3,5-Di (1H-imidazol-1-yl)benzonitrile. Yield: ca. 35% (based on Zn). Anal. calc. for C17H13N6O4Zn: C, 47.41; H, 3.04; N, 19.51. Found: C, 47.38; H, 2.95; N, 19.46%. IR (KBr, cm 1): m = 3150 (m), 1620 (m), 1580 (m), 1530 (m), 1480 (s), 1417 (s), 1360 (s), 1310 (s), 1280 (m), 1140 (s), 1020 (m), 997 (s), 904 (m), 864 (s), 816 (s), 739 (s), 671 (s), 606 (s), 515(s). 2.4. Preparation of [Zn5(btec)2(L3)1.5(OH)2]2H2O (3) The preparation of 3 (colorless crystals) is similar to that of 1 except that L3 (0.04 mmol, 7.0 mg) was used instead of 3,5-Di (1H-imidazol-1-yl)benzonitrile and the pH of the mixture was adjusted to about 5.5. Yield: ca. 15% (based on Zn). Anal. calc. for C61H42N18O40Zn10: C, 31.57; H, 1.82; N, 10.86. Found: C, 31.38; H, 1.79; N, 10.79%. IR (KBr, cm 1): m = 3450 (m), 3130 (m), 1620 (m), 1550 (m), 1510 (s), 1400 (s), 1340 (s), 1290 (s), 1250 (s), 1140 (m), 1020 (m), 925 (m), 890 (m), 858 (m), 795 (m), 756 (m), 710 (s), 638 (m), 563 (m), 501 (m). 2.5. Single-crystal X-ray crystallography Crystallographic diffraction dates for 1 and 2 were performed on a Bruker Apex CCD diffractometer and those of compound 3 were recorded on an Oxford Diffraction Gemini R Ultra diffractometer at 293 k, using a graphite monochromated Mo Ka radiation (k = 0.71073 Å). All the structures were solved by Direct Method of SHELXS-97 and refined by full-matrix least-squares techniques using the SHELXL-97 program. [6] All non-hydrogen atoms were refined with anisotropic temperature parameters. All hydrogen atoms on organic ligands (except for C23A and C23B of 3) were placed in geometrically idealized position as a riding mode. The water hydrogen atoms (except for O3WA and O3WB of 1, O1W and O2W of 3) were located from difference Fourier maps. The disordered atoms (O3WA and O3WB of 2; C23A, C28A, C29A, C23B, C28B and C29B of 3) were split over two sites with a total occupancy of 1 and restricted by SIMU and ISOR. The atoms with ADP
a
1
2
3
Formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z l (mm 1) F(0 0 0) Reflections collected Reflections unique Rint Goodness-of-fit (GOF) on F2 R1, wR2 [I > 2r(I)]a
C23H18N4O13Zn2 689.15 monoclinic P2(1)/n 7.0878(10) 34.978(5) 11.9500(14) 90 125.259(9) 90 2419.1(6) 4 2.066 1392 8242 4208 0.0767 1.089
C17H13N6O4Zn 430.7 monoclinic P2(1)/c 10.355(3) 8.977(3) 18.237(6) 90 100.548(4) 90 1666.6(9) 4 1.515 876 8093 2867 0.0658 1.08
C61H42N18O40Zn10 2320.83 triclinic P-1 11.9764(5) 12.2491(5) 14.5512(6) 68.795(4) 67.582(4) 85.387(4) 1835.63(13) 1 3.322 1154 12 916 7706 0.0286 1.07
0.0795, 0.1869
0.0452, 0.1088
R1, wR2 (all data)a
0.1040, 0.2040
0.0623, 0.1533 0.0855, 0.1664
R1 =
P ||Fo|
P P |Fc||/ |Fo|, wR2 = {w(F2o
F2c )2]/
0.0654, 0.1207
P [w(F2o)]2}1/2.
(O1, O3 and C6 for 1; C4 for 2; C24 for 3) were restricted by ISOR. The crystallographic data for 1–3 are summarized in Table 1. 3. Results and discussion 3.1. Crystal structure of 1 Single crystal X-ray structural analysis reveals that 1 is crystalline in monoclinic P21/c space group. A proton has been added to the formula directly to balance the charge. The 3,5-Di(1H-imidazol-1-yl)benzonitrile is hydrolyzed into L1 under hydrothermally condition. The asymmetric unit of 1 contains two Zn2+ ions, one btec4 anions and one L1 ligands. As shown in Fig. 1a, Zn1 and Zn2 are both four-coordinated in ZnO2N2 tetrahedral geometries, but with different coordination environments. Zn1 is coordinated by two carboxylate oxygen atoms (O1 and O7#1; #1 x + 1, y, z + 1), one nitrogen atom (N1) from L1 and one water oxygen atom (O1 W). Zn2 is coordinated by three carboxylate oxygen atoms (O3, O6#1 and O9#3; #1 x + 1, y, z + 1; #3 x, -y + 3/2, z + 1/2) and one nitrogen atom (N3#2; #2 x + 1, y 1/2, z + 1/2) from L1. The Zn–O and Zn–N bond lengths vary from 1.927(4) to 2.035 (5) Å and from 1.979(5) to 1.986(5) Å, respectively. Zn1 and Zn2 ions are connected by btec4 to form 1D chains, which are further connected by L1 ligands through Zn1–N1 and Zn2–N3 bonds to form 2D layered structure (Fig. 1b and c). Then, L1 ligands coordinated to Zn2+ ions through Zn2–O9 bonds to connect the 2D layers into a 3D framework (Fig. 1d). The remaining blank of the 3D structure is occupied by the lattice water molecules. Topologically, if Zn1 and Zn2 are considered as a bimetal center, it connects three L1 and two other bimetal centers can be regarded as a 5-connected node. L1 connect three bimetal centers can be regarded as a 3-connected node. Thereafter, the framework of 1 can be described as a bi-nodal (3,5)-connected framework with fsc-3,5-P4/mbm topology (Fig. 2b) [7]. As far as we know, the CPs with fsc-3,5-P4/mbm topology is still rare [8]. 3.2. Crystal structure of 2 Single crystal X-ray structural analysis reveals that 2 is crystalline in monoclinic P21/c space group. The asymmetric unit of
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Fig. 1. (a) Coordination environments of Zn ions. Symmetry codes: #1 x + 1, y, z + 1; #2 x + 1, y 1/2, View of 2D layer of 1. (d) 2D layers of 1 are connected into 3D framework through Zn2–O9 bonds.
z + 1/2; #3 x,
71
y + 3/2, z + 1/2. (b) View of 1D Zn-btec chain of 1. (c)
ions are connected by btec4 to form a 2D layered structure, in which 30-membered macrocycles constructed by four btec4 ligands and four Zn2+ ions can be found (Fig. 3b). L2 ligands coordinated to Zn2+ ions to connect the 2D layers into a 3D pillar-layered framework (Fig. 3c). Furthermore, btec4 and L2 ligands of 2 connect Zn2+ ions to form 3-fold left- and right-handed helical chains along the b axis (Fig. 3d and e). The number of left-handed helical chains is equal to that of right-handed ones. Topologically, each btec4 connects four Zn2+ atoms can be regarded as a 4-connected node, and each Zn2+ atom connects two btec4 and two other Zn2+ atoms can also be regarded as a 4-connected node. Then the framework of 2 can be described as a new type of bi-nodal (4,4)-connected framework with (6284)(6482)2 topology (Fig. 4). 3.3. Crystal structure of 3
Fig. 2. Schematic description of the fsc-3,5-P4/mbm topology of 1.
2 contains one Zn2+ ion, half btec4 anions and one L2 ligands. As shown in Fig. 3a, Zn1 shows a ZnO2N2 tetrahedral geometry with the coordination of two carboxylate oxygen atoms (O1 and O3) and two nitrogen atoms (N1 and N4) (Zn1–O1 1.930(4) Å, Zn1– O3 1.969(4) Å, Zn1–N1 2.010(5) Å and Zn1–N4 2.016(5) Å). Zn2+
Single crystal X-ray structural analysis reveals that 3 is crys space group. The asymmetric unit of 3 contalline in triclinic P1 tains five Zn2+ ions, two btec4 anions, one and a half L3 ligands, two l3-OH anions and two lattice water molecules. As shown in Fig. 5a, Zn1, Zn2 and Zn5 are six-coordinated in octahedral coordination geometries, but with different coordination environments. Zn1 is coordinated by four carboxylate oxygen atoms (O3, O5, O9 and O14), one oxygen atom (O2) from l3-OH anion and one nitrogen atom (N1) from L3 ligand. Zn2 is coordinated by four carboxylate oxygen atoms (O5, O8, O13 and O17) and two oxygen atoms (O1 and O2) from l3-OH anions. Zn5 is coordinated by four carboxylate oxygen atoms (O3#2, O4#2, O10 and O18; #2 x + 1, y + 1, z + 1), one oxygen atom (O2) from l3-OH anion and one nitrogen atom (N7) from L3. Zn3 and Zn4 are five-coordinated in triangular bipyramidal coordination geometries, but also with different coordination environments. Zn3 is coordinated by three carboxylate oxygen atoms (O11, O16#1 and O17;
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Fig. 3. (a) Coordination environments of Zn1 ion. (b) View of 2D layer of 2. The 30-membered ring is highlighted in green. (c) View of 3D pillar-layered structure of 2. (d) and (e) Represent right- and left-handed 3-fold helical chains of 2, respectively.
atom (O1) from l3-OH anion. The Zn–O and Zn–N bond lengths vary from 1.990(3) to 2.246(3) Å and from 2.021(4) to 2.099(4) Å, respectively. Zn2+ ions are connected by carboxylate oxygen atoms to form 1D chains, which are further connected by btec4 ligands to form a 3D framework with 1D channels along the c axis (Fig. 5b and c). L3 are filling in the channels of the framework through coordinated to Zn ions (Fig. 5d). There are two types of L3 ligands, one is coordinated with the coplanar Zn–O chains of the channel, and the other is coordinated with the diagonal Zn-O chains of the channel. The remaining blank of the 3D structure is occupied by the lattice water molecules. Fig. 4. Schematic description of the (6284)(6482)2 topology of 2.
#1 x + 1, y + 1, z), one oxygen atom (O1) from l3-OH anion and one nitrogen atom (N4) from L3. Zn4 is coordinated by four carboxylate oxygen atoms (O6, O7, O12 and O15) and one oxygen
3.4. Structural comparison From the structural description above, we can see that btec4 ligand adopts three different coordination modes in compounds
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Fig. 5. (a) Coordination environments of Zn ions. Symmetry codes: #1 x + 1, y + 1, z; #2 x + 1, y + 1, z + 1. (b) Polyhedron description of 1D Zn-O chain of 3. (c) View of 3D framework connected by btec4 and Zn-O chains. (d) Two types of L3 (highlighted in blue and green, respectively) are filling in the channels of the framework. (Colour online.)
Fig. 6. Coordination modes of btec4 in 1–3: (a) for 1 and 2; (b) and (c) for 3.
1–3 as shown in Fig. 6. In 1 and 2, although all btec4 ligands show l8:g1:g0:g1:g0:g1:g0:g1:g0 coordination modes, the conformations of them are slightly different (Fig. S1). The btec4 ligands of 1 bridge Zn2+ ions to form 1D chains and the btec4 of 2 link Zn2+ ions to give 2D network. In 3, btec4 coordinate with eight Zn2+ ions and adopt two type of coordination modes: l8:g1:g2:g2:g1: g1:g2:g2:g1 and l8:g1:g1:g1:g1:g1:g1:g1:g1. The Zn2+ ions are connected by btec4 to form 3D framework. As it is wildly mentioned that the geometries of N-donor ligands show remarkable influences on the structures of the compounds, the different conformations of btec4 in compounds 1–3 may be attribute to the investigate of different N-donor ligands in the synthesis process [5]. These results confirm the multitudinous conformations of H4btec, which makes it better adaptability in the assembly system.
3.5. PXRD and thermal analysis The PXRD patterns of the as-synthesized 1–3 matched well with the simulated patterns, respectively, indicating its crystalline phase purity (Fig. S2). TGA experiment was performed from 45 to 600 °C under N2 atmosphere to examine the thermal stability of 1–3 (Fig. S3). For 1, the weight loss from 45 to 100 °C corresponds to the release of lattice water molecules (obsd 5.20%, calcd 5.22%). The second weight loss from 105 to 130 °C is attributed to the release of coordinated water molecules (obsd 1.97%, calcd 2.61%). The third weight loss from 360 to 500 °C corresponds to the decomposing gradually of the organic groups of 1. For 2, only one weight loss is observed from 280 to 530 °C which can be attributed to the decomposition of organic components. For 3, the first
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nodal (4,4)-connected framework with the presence of 3-fold leftand right-handed helical chains. The results of solid-state luminescent measurements indicate that the title compounds may be candidates for fluorescent materials. Acknowledgements We gratefully acknowledge financial support by the National Natural Science Foundation of China (Nos. 21301048 and 21401062), the Natural Science Fund of Jiangsu Province (BK20140447, BK20141247, BK20130404, SBK201220654) and the University Science Research Project of Jiangsu Province (13KJB430005, 15KJB430004, 16KJB150004). Appendix A. Supplementary data
Fig. 7. Excitation and emission spectra of 1–3 in the solid state at room temperature.
weight loss corresponding to the release of lattice water molecule is observed from 90 to 120 °C (obsd 1.55%, calcd 1.82%). And the further weight loss from 360 to 550 °C can be attributed to the decomposition of organic components of 3. 3.6. Luminescent properties The solid-state luminescent spectra of compounds 1–3 and the free ligands have been investigated at room temperature (Fig. 7). The main emission peaks of the free ligands H4btec, L2 and L3 are at 410 (kex = 340 nm), 458 nm (kex = 372 nm) and 451 (kex = 327 nm), respectively. No emission is observed either for the free L1 ligand or its sodium salt, which consists with the previously reports [9]. The emission peaks of 1–3 occur at 399 nm (kex = 320 nm) for 1, 456 nm (kex = 343 nm) for 2 and 440 nm (kex = 330 nm) for 3, respectively. For compound 1, the emission peaks may be attributed to the intraligand transitions of H4btec due to their similarity. [10] For compounds 2 and 3, the emission of p⁄ ? n transition of H4btec is much weaker than that of the p⁄ ? p transition of the N-donor ligand, so it almost have no contribution to the fluorescent emission of compounds 2 and 3 [11]. The emission peaks of 2 and 3 can be attributed to the intraligand transitions of the N-donor ligands due to their similarity [9]. The blue-shift of the emission band of 1–3 may be due to the coordination interactions of the ligand [12]. These results suggest that 1–3 will be candidates for fluorescent materials. 4. Conclusions In summary, we have successfully synthesized and characterized three novel Zn(II) CPs. All of the title compounds show 3D framework. Compound 1 represents a rare example of CP with fsc-3,5-P4/mbm topology. Compound 2 reveals a new type of bi-
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Three new three dimensional Zn(II)-benzenetetracarboxylate coordination polymers: Syntheses, crystal structures and luminescent properties Yu-Hui Luo a, Chuan-Zhou Tao a, Dong-En Zhang a, Juan-Juan Ma a, Lin Liu a, Zhi-Wei Tong a,⇑, Xiao-Yang Yu b,⇑ a b
Department of Chemical Engineering, Huaihai Institute of Technology, Jiangsu, Lianyungang 222000, China Jilin Institute of Chemical Technology, Jilin City, Jilin 132022, China
a r t i c l e
i n f o
Article history: Received 2 October 2016 Accepted 27 October 2016 Available online 4 November 2016 Keywords: 1,2,4,5-Benzenetetracarboxylic acid Zinc(II) compounds Coordination polymers Hydrothermal reaction Luminescent property
a b s t r a c t Three novel coordination polymers, namely, [Zn2(betc)(L1)H(H2O)]2H2O (1), [Zn2(btec)(L2)2] (2) and [Zn5(btec)2(L3)1.5(OH)2]2H2O (3) (L1 = 3,5-di(1H-imidazol-1-yl)benzoate, L2 = 1,3-bis((1H-1,2,4-triazol1-yl)methyl)benzene and L3 = 1,3-di(1H-1,2,4-triazol-1-yl)propane), have been hydrothermally synthesized. Compound 1 shows a three dimensional (3D) framework with fsc-3,5-P4/mbm topology. Compound 2 reveals a 3D pillar-layered framework with the presence of 3-fold left- and right-handed helical chains. Compound 3 also exhibits a 3D framework based on 1D zinc chains. In addition, the luminescent properties for 1–3 have also been investigated. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction Coordination polymers (CPs) are attracting more and more interests in recent years, not only due to their intriguing architectures but also due to their wildly potential applications including gas storage, separation, magnetism and catalysis [1]. Although a great effort have been paid to prepare novel CPs, it is still difficult to prepare CPs with expected structures. Because the final structures can be affected by many kinds of factors, such as metal ions, organic ligands, pH value, solvents, reaction temperature, and so on [2]. Among the above mentioned factors, the organic ligand has been considered as one of the most important fact in the self-assembly system. The multi-carboxylate ligands as an important family of O-donor ligands are good choices in the construction of CPs with fascination architectures and properties [3]. In this regard, 1,2,4,5-Benzenetetracarboxylic acid (H4btec) have been widely used for their variety of coordination modes [4]. The four carboxylate groups of H4btec are equally arranged around the benzene ring and can rotate along the C–C bond resulting in kinds of conformations. On the other hand, flexible N-donor ligands have been proved as excellent co-ligands for the construction of novel
⇑ Corresponding authors. E-mail addresses: [email protected] [email protected] (X.-Y. Yu). http://dx.doi.org/10.1016/j.poly.2016.10.045 0277-5387/Ó 2016 Elsevier Ltd. All rights reserved.
(Z.-W.
Tong),
yangyan-
networks [5]. In this work, we are prompted to construct novel CPs by utilizing H4btec and flexible N-donor ligands under hydrothermal condition. Herein we report three Zn(II) CPs, namely, [Zn2(betc)(L1)H(H2O)]2H2O (1), [Zn2(btec)(L2)2] (2) and [Zn5(btec)2(L3)1.5(OH)2]2H2O (3) (L1 = 3,5-di(1H-imidazol-1-yl)benzoate, L2 = 1,3-bis((1H-1,2,4-triazol-1-yl)methyl)benzene and L3 = 1,3-di(1H-1,2,4-triazol-1-yl)propane). All of the title compounds show three dimensional (3D) frameworks. Compound 1 represents a rare example of CP with fsc-3,5-P4/mbm topology. In addition, the luminescent properties for 1–3 have also been investigated. 2. Experimental section 2.1. Materials and general methods All reagents and solvents were purchased from commercial sources and used without further purification. Powder X-ray diffraction (PXRD) patterns were collected on a Rigaku Dmax 2000 X-ray diffractometer with graphite monochromatized Cu Ka radiation (k = 0.154 nm) and 2h ranging from 5° to 50° with an increment of 0.02° and a scanning rate of 5°/min. The FI-IR spectra were measured in KBr pellets in the range 4000–400 cm 1 on a Mattson Alpha-Centauri spectrometer. Elemental analysis (EA) for C, H and N was performed on a Perkin-Elmer 2400 Elemental
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Analyzer. Thermogravimetric analysis (TGA) was performed on a Perkin-Elmer Thermal Analyzer under nitrogen atmosphere at a heating rate of 10 °C min 1. The fluorescent property was measured on a FLS920 Edinburgh Luminescence Spectrometer with a light source of Xenon lamp. The wavelengths for the photoexcitation of each compound were set the maximum of the excitation spectra.
Table 1 Crystal data and structure refinement for 1, 2 and 3.
2.2. Preparation of [Zn2(betc)(L1)H(H2O)]2H2O (1) The pH of the mixture of Zn(NO3)26H2O (0.1 mmol, 30.0 mg), H4btec (0.04 mmol, 10.0 mg), 3,5-Di(1H-imidazol-1-yl)benzonitrile (0.04 mmol, 9.0 mg) and H2O (10 ml) was adjusted to about 3.5 with HCl (aq. 0.1 M) and NaOH (aq. 0.1 M). The resulting mixture was transferred into a 23 ml Teflon-lined stainless steel autoclave reactor and then heated at 160 °C for 72 h. After cooled to room temperature at a rate of 3 °C h 1, colorless crystals suitable for X-ray structural analysis were isolated by filtrating, washing with water several times, and drying in air. Yield: ca. 20% (based on Zn). Anal. calc. for C23H18N4O13Zn2: C, 40.08; H, 2.63; N, 8.13. Found: C, 39.98; H, 2.59; N, 8.09%. IR (KBr, cm 1): m = 3450 (m), 3120 (m), 3070 (m), 1600 (s), 1520 (s), 1410 (m), 1350 (s), 1260 (s), 1130 (m), 1080 (s), 1010 (m), 949 (m), 812 (s), 732 (m), 667 (m), 611 (s), 503 (m). 2.3. Preparation of [Zn2(btec)(L2)2] (2) The preparation of 2 (colorless crystals) is similar to that of 1 except that L2 (0.04 mmol, 10.0 mg) was used instead of 3,5-Di (1H-imidazol-1-yl)benzonitrile. Yield: ca. 35% (based on Zn). Anal. calc. for C17H13N6O4Zn: C, 47.41; H, 3.04; N, 19.51. Found: C, 47.38; H, 2.95; N, 19.46%. IR (KBr, cm 1): m = 3150 (m), 1620 (m), 1580 (m), 1530 (m), 1480 (s), 1417 (s), 1360 (s), 1310 (s), 1280 (m), 1140 (s), 1020 (m), 997 (s), 904 (m), 864 (s), 816 (s), 739 (s), 671 (s), 606 (s), 515(s). 2.4. Preparation of [Zn5(btec)2(L3)1.5(OH)2]2H2O (3) The preparation of 3 (colorless crystals) is similar to that of 1 except that L3 (0.04 mmol, 7.0 mg) was used instead of 3,5-Di (1H-imidazol-1-yl)benzonitrile and the pH of the mixture was adjusted to about 5.5. Yield: ca. 15% (based on Zn). Anal. calc. for C61H42N18O40Zn10: C, 31.57; H, 1.82; N, 10.86. Found: C, 31.38; H, 1.79; N, 10.79%. IR (KBr, cm 1): m = 3450 (m), 3130 (m), 1620 (m), 1550 (m), 1510 (s), 1400 (s), 1340 (s), 1290 (s), 1250 (s), 1140 (m), 1020 (m), 925 (m), 890 (m), 858 (m), 795 (m), 756 (m), 710 (s), 638 (m), 563 (m), 501 (m). 2.5. Single-crystal X-ray crystallography Crystallographic diffraction dates for 1 and 2 were performed on a Bruker Apex CCD diffractometer and those of compound 3 were recorded on an Oxford Diffraction Gemini R Ultra diffractometer at 293 k, using a graphite monochromated Mo Ka radiation (k = 0.71073 Å). All the structures were solved by Direct Method of SHELXS-97 and refined by full-matrix least-squares techniques using the SHELXL-97 program. [6] All non-hydrogen atoms were refined with anisotropic temperature parameters. All hydrogen atoms on organic ligands (except for C23A and C23B of 3) were placed in geometrically idealized position as a riding mode. The water hydrogen atoms (except for O3WA and O3WB of 1, O1W and O2W of 3) were located from difference Fourier maps. The disordered atoms (O3WA and O3WB of 2; C23A, C28A, C29A, C23B, C28B and C29B of 3) were split over two sites with a total occupancy of 1 and restricted by SIMU and ISOR. The atoms with ADP
a
1
2
3
Formula Formula weight Crystal system Space group a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z l (mm 1) F(0 0 0) Reflections collected Reflections unique Rint Goodness-of-fit (GOF) on F2 R1, wR2 [I > 2r(I)]a
C23H18N4O13Zn2 689.15 monoclinic P2(1)/n 7.0878(10) 34.978(5) 11.9500(14) 90 125.259(9) 90 2419.1(6) 4 2.066 1392 8242 4208 0.0767 1.089
C17H13N6O4Zn 430.7 monoclinic P2(1)/c 10.355(3) 8.977(3) 18.237(6) 90 100.548(4) 90 1666.6(9) 4 1.515 876 8093 2867 0.0658 1.08
C61H42N18O40Zn10 2320.83 triclinic P-1 11.9764(5) 12.2491(5) 14.5512(6) 68.795(4) 67.582(4) 85.387(4) 1835.63(13) 1 3.322 1154 12 916 7706 0.0286 1.07
0.0795, 0.1869
0.0452, 0.1088
R1, wR2 (all data)a
0.1040, 0.2040
0.0623, 0.1533 0.0855, 0.1664
R1 =
P ||Fo|
P P |Fc||/ |Fo|, wR2 = {w(F2o
F2c )2]/
0.0654, 0.1207
P [w(F2o)]2}1/2.
(O1, O3 and C6 for 1; C4 for 2; C24 for 3) were restricted by ISOR. The crystallographic data for 1–3 are summarized in Table 1. 3. Results and discussion 3.1. Crystal structure of 1 Single crystal X-ray structural analysis reveals that 1 is crystalline in monoclinic P21/c space group. A proton has been added to the formula directly to balance the charge. The 3,5-Di(1H-imidazol-1-yl)benzonitrile is hydrolyzed into L1 under hydrothermally condition. The asymmetric unit of 1 contains two Zn2+ ions, one btec4 anions and one L1 ligands. As shown in Fig. 1a, Zn1 and Zn2 are both four-coordinated in ZnO2N2 tetrahedral geometries, but with different coordination environments. Zn1 is coordinated by two carboxylate oxygen atoms (O1 and O7#1; #1 x + 1, y, z + 1), one nitrogen atom (N1) from L1 and one water oxygen atom (O1 W). Zn2 is coordinated by three carboxylate oxygen atoms (O3, O6#1 and O9#3; #1 x + 1, y, z + 1; #3 x, -y + 3/2, z + 1/2) and one nitrogen atom (N3#2; #2 x + 1, y 1/2, z + 1/2) from L1. The Zn–O and Zn–N bond lengths vary from 1.927(4) to 2.035 (5) Å and from 1.979(5) to 1.986(5) Å, respectively. Zn1 and Zn2 ions are connected by btec4 to form 1D chains, which are further connected by L1 ligands through Zn1–N1 and Zn2–N3 bonds to form 2D layered structure (Fig. 1b and c). Then, L1 ligands coordinated to Zn2+ ions through Zn2–O9 bonds to connect the 2D layers into a 3D framework (Fig. 1d). The remaining blank of the 3D structure is occupied by the lattice water molecules. Topologically, if Zn1 and Zn2 are considered as a bimetal center, it connects three L1 and two other bimetal centers can be regarded as a 5-connected node. L1 connect three bimetal centers can be regarded as a 3-connected node. Thereafter, the framework of 1 can be described as a bi-nodal (3,5)-connected framework with fsc-3,5-P4/mbm topology (Fig. 2b) [7]. As far as we know, the CPs with fsc-3,5-P4/mbm topology is still rare [8]. 3.2. Crystal structure of 2 Single crystal X-ray structural analysis reveals that 2 is crystalline in monoclinic P21/c space group. The asymmetric unit of
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Fig. 1. (a) Coordination environments of Zn ions. Symmetry codes: #1 x + 1, y, z + 1; #2 x + 1, y 1/2, View of 2D layer of 1. (d) 2D layers of 1 are connected into 3D framework through Zn2–O9 bonds.
z + 1/2; #3 x,
71
y + 3/2, z + 1/2. (b) View of 1D Zn-btec chain of 1. (c)
ions are connected by btec4 to form a 2D layered structure, in which 30-membered macrocycles constructed by four btec4 ligands and four Zn2+ ions can be found (Fig. 3b). L2 ligands coordinated to Zn2+ ions to connect the 2D layers into a 3D pillar-layered framework (Fig. 3c). Furthermore, btec4 and L2 ligands of 2 connect Zn2+ ions to form 3-fold left- and right-handed helical chains along the b axis (Fig. 3d and e). The number of left-handed helical chains is equal to that of right-handed ones. Topologically, each btec4 connects four Zn2+ atoms can be regarded as a 4-connected node, and each Zn2+ atom connects two btec4 and two other Zn2+ atoms can also be regarded as a 4-connected node. Then the framework of 2 can be described as a new type of bi-nodal (4,4)-connected framework with (6284)(6482)2 topology (Fig. 4). 3.3. Crystal structure of 3
Fig. 2. Schematic description of the fsc-3,5-P4/mbm topology of 1.
2 contains one Zn2+ ion, half btec4 anions and one L2 ligands. As shown in Fig. 3a, Zn1 shows a ZnO2N2 tetrahedral geometry with the coordination of two carboxylate oxygen atoms (O1 and O3) and two nitrogen atoms (N1 and N4) (Zn1–O1 1.930(4) Å, Zn1– O3 1.969(4) Å, Zn1–N1 2.010(5) Å and Zn1–N4 2.016(5) Å). Zn2+
Single crystal X-ray structural analysis reveals that 3 is crys space group. The asymmetric unit of 3 contalline in triclinic P1 tains five Zn2+ ions, two btec4 anions, one and a half L3 ligands, two l3-OH anions and two lattice water molecules. As shown in Fig. 5a, Zn1, Zn2 and Zn5 are six-coordinated in octahedral coordination geometries, but with different coordination environments. Zn1 is coordinated by four carboxylate oxygen atoms (O3, O5, O9 and O14), one oxygen atom (O2) from l3-OH anion and one nitrogen atom (N1) from L3 ligand. Zn2 is coordinated by four carboxylate oxygen atoms (O5, O8, O13 and O17) and two oxygen atoms (O1 and O2) from l3-OH anions. Zn5 is coordinated by four carboxylate oxygen atoms (O3#2, O4#2, O10 and O18; #2 x + 1, y + 1, z + 1), one oxygen atom (O2) from l3-OH anion and one nitrogen atom (N7) from L3. Zn3 and Zn4 are five-coordinated in triangular bipyramidal coordination geometries, but also with different coordination environments. Zn3 is coordinated by three carboxylate oxygen atoms (O11, O16#1 and O17;
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Fig. 3. (a) Coordination environments of Zn1 ion. (b) View of 2D layer of 2. The 30-membered ring is highlighted in green. (c) View of 3D pillar-layered structure of 2. (d) and (e) Represent right- and left-handed 3-fold helical chains of 2, respectively.
atom (O1) from l3-OH anion. The Zn–O and Zn–N bond lengths vary from 1.990(3) to 2.246(3) Å and from 2.021(4) to 2.099(4) Å, respectively. Zn2+ ions are connected by carboxylate oxygen atoms to form 1D chains, which are further connected by btec4 ligands to form a 3D framework with 1D channels along the c axis (Fig. 5b and c). L3 are filling in the channels of the framework through coordinated to Zn ions (Fig. 5d). There are two types of L3 ligands, one is coordinated with the coplanar Zn–O chains of the channel, and the other is coordinated with the diagonal Zn-O chains of the channel. The remaining blank of the 3D structure is occupied by the lattice water molecules. Fig. 4. Schematic description of the (6284)(6482)2 topology of 2.
#1 x + 1, y + 1, z), one oxygen atom (O1) from l3-OH anion and one nitrogen atom (N4) from L3. Zn4 is coordinated by four carboxylate oxygen atoms (O6, O7, O12 and O15) and one oxygen
3.4. Structural comparison From the structural description above, we can see that btec4 ligand adopts three different coordination modes in compounds
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Fig. 5. (a) Coordination environments of Zn ions. Symmetry codes: #1 x + 1, y + 1, z; #2 x + 1, y + 1, z + 1. (b) Polyhedron description of 1D Zn-O chain of 3. (c) View of 3D framework connected by btec4 and Zn-O chains. (d) Two types of L3 (highlighted in blue and green, respectively) are filling in the channels of the framework. (Colour online.)
Fig. 6. Coordination modes of btec4 in 1–3: (a) for 1 and 2; (b) and (c) for 3.
1–3 as shown in Fig. 6. In 1 and 2, although all btec4 ligands show l8:g1:g0:g1:g0:g1:g0:g1:g0 coordination modes, the conformations of them are slightly different (Fig. S1). The btec4 ligands of 1 bridge Zn2+ ions to form 1D chains and the btec4 of 2 link Zn2+ ions to give 2D network. In 3, btec4 coordinate with eight Zn2+ ions and adopt two type of coordination modes: l8:g1:g2:g2:g1: g1:g2:g2:g1 and l8:g1:g1:g1:g1:g1:g1:g1:g1. The Zn2+ ions are connected by btec4 to form 3D framework. As it is wildly mentioned that the geometries of N-donor ligands show remarkable influences on the structures of the compounds, the different conformations of btec4 in compounds 1–3 may be attribute to the investigate of different N-donor ligands in the synthesis process [5]. These results confirm the multitudinous conformations of H4btec, which makes it better adaptability in the assembly system.
3.5. PXRD and thermal analysis The PXRD patterns of the as-synthesized 1–3 matched well with the simulated patterns, respectively, indicating its crystalline phase purity (Fig. S2). TGA experiment was performed from 45 to 600 °C under N2 atmosphere to examine the thermal stability of 1–3 (Fig. S3). For 1, the weight loss from 45 to 100 °C corresponds to the release of lattice water molecules (obsd 5.20%, calcd 5.22%). The second weight loss from 105 to 130 °C is attributed to the release of coordinated water molecules (obsd 1.97%, calcd 2.61%). The third weight loss from 360 to 500 °C corresponds to the decomposing gradually of the organic groups of 1. For 2, only one weight loss is observed from 280 to 530 °C which can be attributed to the decomposition of organic components. For 3, the first
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nodal (4,4)-connected framework with the presence of 3-fold leftand right-handed helical chains. The results of solid-state luminescent measurements indicate that the title compounds may be candidates for fluorescent materials. Acknowledgements We gratefully acknowledge financial support by the National Natural Science Foundation of China (Nos. 21301048 and 21401062), the Natural Science Fund of Jiangsu Province (BK20140447, BK20141247, BK20130404, SBK201220654) and the University Science Research Project of Jiangsu Province (13KJB430005, 15KJB430004, 16KJB150004). Appendix A. Supplementary data
Fig. 7. Excitation and emission spectra of 1–3 in the solid state at room temperature.
weight loss corresponding to the release of lattice water molecule is observed from 90 to 120 °C (obsd 1.55%, calcd 1.82%). And the further weight loss from 360 to 550 °C can be attributed to the decomposition of organic components of 3. 3.6. Luminescent properties The solid-state luminescent spectra of compounds 1–3 and the free ligands have been investigated at room temperature (Fig. 7). The main emission peaks of the free ligands H4btec, L2 and L3 are at 410 (kex = 340 nm), 458 nm (kex = 372 nm) and 451 (kex = 327 nm), respectively. No emission is observed either for the free L1 ligand or its sodium salt, which consists with the previously reports [9]. The emission peaks of 1–3 occur at 399 nm (kex = 320 nm) for 1, 456 nm (kex = 343 nm) for 2 and 440 nm (kex = 330 nm) for 3, respectively. For compound 1, the emission peaks may be attributed to the intraligand transitions of H4btec due to their similarity. [10] For compounds 2 and 3, the emission of p⁄ ? n transition of H4btec is much weaker than that of the p⁄ ? p transition of the N-donor ligand, so it almost have no contribution to the fluorescent emission of compounds 2 and 3 [11]. The emission peaks of 2 and 3 can be attributed to the intraligand transitions of the N-donor ligands due to their similarity [9]. The blue-shift of the emission band of 1–3 may be due to the coordination interactions of the ligand [12]. These results suggest that 1–3 will be candidates for fluorescent materials. 4. Conclusions In summary, we have successfully synthesized and characterized three novel Zn(II) CPs. All of the title compounds show 3D framework. Compound 1 represents a rare example of CP with fsc-3,5-P4/mbm topology. Compound 2 reveals a new type of bi-
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