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A new 3D cadmium coordination polymer containing 3-amino-1H-1,2,4-triazole: Synthesis, structure, and property
Inorganic Chemistry Communications 88 (2018) 38–41
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Short communication
A new 3D cadmium coordination polymer containing 3-amino-1H-1,2,4-triazole: Synthesis, structure, and property Bing Liu a,⁎, Mei-Ting Wen a, Mei-Lin Shen b, Wei-Ni Miao a, Ting-Ting He a, Ling Xu b,⁎ a b
College of Chemistry and Chemical Engineering, Shaanxi University of Sciences and Technology, Xi'an 710021, Shaanxi Province, PR China Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi'an 710062, Shaanxi Province, PR China
a r t i c l e
i n f o
Article history: Received 23 October 2017 Received in revised form 20 November 2017 Accepted 22 November 2017 Available online 2 December 2017 Keywords: Coordination polymer 1,2,4-Triazole Fluorescence Crystal structure
a b s t r a c t Cadmium acetate (Cd(Ac)2) reacted with 3-amino-1H-1,2,4-triazole (Hatr) under hydrothermal conditions to produce a 3D framework, [Cd5(atr)7(Ac)3(H2O)2] (1), which is constructed through the interweaving of the 2D (4′4) layers with the 1D zigzag [Cd3(atr)2(H2O)] chains. Compound 1 was isolated with high phase purity confirmed by PXRD. TGA indicates the thermal decomposition temperature of compound 1 at 343 °C, showing the framework of 1 has high thermal stability. The solid state fluorescence of 1 at ambient temperature exhibits a blue emission at 419 nm, assigned to intraligand π → π⁎ transition of 1,2,4-triazole ring, which is similar to that of free Hatr with emission at 427 nm. The temperature-dependent fluorescence of 1 shows a thermal quenching with 43.78% quenching rate at 200 °C, and the fluorescent intensity can be completely recovered as the temperature decreased to ambient temperature. © 2017 Published by Elsevier B.V.
Coordination polymers (CPs) have made many progresses recently in many fields, such as gas storage and selective separation [1], chemosensor [2], light-emitting devices [3], catalysis [4], drug-delivery [5], gas/liquid detection [6], which aims at the structure constructions and the structure-property relationship [7]. A lot of work have been devoted to the structure design and controlled synthesis of CPs, attributing to understand the structure-property relationship [8]. However, at present, the preparation of a CP with predicted structure and desired property is still a challenge [9]. One of the strategies of CP structure construction is the rational selection of inorganic metal connectors and organic linkers [10]. The organic linkers containing the donor sites of N or O atoms are commonly used to tune the CP structure constructions [11]. The metal azolate frameworks have attracted much interest due to the rich π-electron aromatic N-heterocycles bind to soft transition metal showing charming structures and properties with high stabilities [12]. Compared to the famous diazole ligands of imidazolate and pyrazolate with simple coordination modes to fabricate the predictable structures, 1,2,4-trizaole ligands with one more nitrogen donor exhibit less predictable coordination behaviors and relative weaker coordination abilities. With the bridging fashions of μ3-1κN: 2κN: 4κN, μ2-1κN: 2κN, μ2-2κN: 4κN [13], 1,2,4-triazole ligands demonstrate themselves as versatile linkers to construct “simple, high-symmetry” structures [14]. 3-amino-1H-1,2,4-triazole (Hatr) is a two-connecting neutral or three-connecting anionic (deprotonated) ligand in the constructions of coordination polymers, which vails to achieve open porous ⁎ Corresponding authors. E-mail addresses: [email protected] (B. Liu), [email protected] (L. Xu).
https://doi.org/10.1016/j.inoche.2017.11.016 1387-7003/© 2017 Published by Elsevier B.V.
CPs and new topological nets [15]. In this contribution, we present a 3D atr-containing cadmium CP, [Cd5(atr)7(Ac)3(H2O)2] (1), which was synthesized under hydrothermal condition [16] and characterized by single crystal X-ray diffraction (SCXRD) (Table 1), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), solid-state and temperature-dependent fluorescence, and FT-IR. Compound 1 shows interesting structure features, high thermal stability, blue fluorescence, and fluorescence thermal quenching. 1. Crystal structure The single crystal analysis reveals 1, [Cd5(atr)7(Ac)3(H2O)2], is a 3D architecture, in whose asymmetric unit there are five cadmium atoms, seven atr− ligands, three Ac− anions, and two coordinated water molecules. Compound 1 crystallizes in orthorhombic noncentrosymmetric space group P212121, whose structural flack factor is −0.02(6), indicating the absolute structure is accurate [17]. Five cadmium atoms show two types of coordination geometries: five-coordinated Cd1, Cd2 and Cd5 atoms are in distorted CdN5 and CdN3O2 square pyramids and a CdN3O2 triangular bipyramid respectively; six-coordinated Cd3 and Cd4 are in CdN5O and CdN3O3 octahedra (Supporting information, Fig. S1). All the deprotoned atr− ligands adopt the same coordination mode of μ 3 -1κN: 2κN: 4κN (Supporting information, Scheme S1a). The Ac− anions exhibit three types of coordination modes: μ3-monodentate bridging/monodentate, μ2-monodentate bridging, and monodentate (Supporting information, Scheme S1b–d). Each Cd3 shapes a [Cd(H2O)] subunit with O1W as a terminal ligand, which is further connected into a 1D [Cd(atr)(H2O)] chain along the
B. Liu et al. / Inorganic Chemistry Communications 88 (2018) 38–41
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Table 1 Crystal and structure refinement data for compound 1. Compound
1
Empirical formula Fw Crystal system Space group a/Å b/Å c/Å V/Å3 Z Dc(Mg m−3) μ/mm−1 F(000) Crystal size/mm3 2θ/° Reflections collected Independent reflections S Final R1, wR2 [I N 2σ(I)] R1, wR2 (all data) Δρmax/min/e·Ǻ−3 Flack parameter
C20H31Cd5N29O8 1367.74 orthorhombic P212121 13.3148(7) 15.0801(5) 19.6590(4) 3947.3(3) 4 2.302 2.734 2632.0 0.20 × 0.10 × 0.05 8.24 to 50.046 13,449 6627 [Rint = 0.0768, Rsigma = 0.1307] 1.020 R1 = 0.0682, wR2 = 0.1412 R1 = 0.1064, wR2 = 0.1631 1.82/−1.18 −0.02(6)
Fig. 2. Comparison of the simulated and experimental PXRD patterns of compound 1.
R1 = (Σ||Fo | − |Fc || / Σ|Fo |). wR2 = [Σ(w(F2o − F2c )2) / Σ(w|F2o |2)]1/2.
a-direction by the atr− ligands with N71 connecting neighboring [Cd(H2O)] subunits in μ2-1κN: 4κN mode (Fig. 1). Cd2 and Cd5 are alternately linked by the μ2-atr− ligands with N61 and Ac− bridges into a [Cd2(atr)(Ac)] chain along the a-direction, and its neighboring staggered chain is connected by the μ2-atr− ligands with N12 into a lattice-like chain (Fig. 1). These ladder-like chains fabricate with the [Cd(atr)(H2O)] chain containing Cd3 through two groups of μ2-atr− bridges with N21 and N31 into a 2D (4′4) layer along the ac-plane (Fig. 1; the topological
network in Supporting information, Fig. S2). Cd4 also shapes a similar [Cd(H2O)] subunit. Each Cd1 connects N44 and N51 of two atr− ligands in almost coplanar mode with the dihedral angle of 3.364°. The two atr− ligands continue to bind the [Cd(H2O)] subunits into a 1D zigzag [Cd3(atr)2(H2O)] chain along the c-direction (Fig. 1). The 2D (4′4) layers interweave with the zigzag [Cd 3 (atr)2 (H2 O)] chains through the rest N sites of the atr− ligands and the Ac− to form a 3D architecture (Fig. 1). Considering the structural features of 1, the Cd2(Ac) subunit that is formed by the μ2-monodentate bridging Ac− bridging Cd2 and Cd4
Fig. 1. The structural construction and the topological network of 1.
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B. Liu et al. / Inorganic Chemistry Communications 88 (2018) 38–41
Fig. 3. TG curve of compound 1.
was dummied as a 7-connecting node. Cd1, Cd3 and Cd5 were dummied as 6-, 5- and 4-connecting nodes, respectively. Except the atr− ligand with N21 and Ac− with O1 as a 2-connecting nodes, the other atr− ligands were considered as 3-connecting nodes. The 3D architecture was simplified into a 12-nodal 2,2,3,3,3,3,3,3,4,5,6,7-connected topological network with point symbol of {4.6.8}3{4.62}3{43.62.84.10}{43.66.87.105}{46.64.85}{63.82.10}{6}2 (Fig. 1). 2. PXRD The experimental PXRD pattern for 1 matches well with the simulated one from the single crystal structure data, indicating that the single crystal structure solution is correct and the bulk sample of 1 was isolated as a single crystal pure phase (Fig. 2). 3. TG analysis TG analysis was used to evaluate the thermal behavior of compound 1, which exhibits that compound 1 can keep the
Fig. 5. The solid-state temperature-dependent fluorescence of compound 1.
framework thermal stability up to 343 °C (Fig. 3). The 31.2% weight loss as heating to 422 °C corresponds to the loss of H2O, Ac− anions and part of atr− ligands. In the following heating at 422–900 °C, it was observed that the total weight loss of compound 1 occurred, and the weight loss closes to 100% at ca. 900 °C. This phenomenon is not common because most known coordination compounds will remain some non-volatile inorganic residues such as metal, metal oxides or carbons [18]. The phenomenon of “no residues” may be related with the fact that 1,2,4-triazole-containing compounds are usually explosive. We infer the deflagration of compound 1 caused the residues to lift out of the TGA pan, though we cannot clarify the detailed thermal decomposition procedure with a high-speed camera [19]. Based on the literature analysis on high density energetic materials, we can find out that triazoles, tetrazole, furazan, furoxan, \\NH2, \\NO2, \\N3, \\NNO2 are energetic groups [20], which have been in investigation for energetic materials for decades. Because of the high nitrogen content (66.63%) and the inherently energetic N\\N, C\\N, C_N bonds, atr− ligand is possible to construct
Fig. 4. Solid-state emission spectra of compound 1 (λex = 266 nm) and free Hatr (λex = 360 nm) (left), and the CIE 1931 chromaticity diagram together with the calculated color coordinate of compound 1 (right).
B. Liu et al. / Inorganic Chemistry Communications 88 (2018) 38–41
explosive coordination polymers. Therefore, the thermal behavior of compound 1 after 422 °C cannot reflect the real thermal decomposition of the framework because of the explosion.
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associated with this article can be found in the online version, at doi: https://doi.org/10.1016/j.inoche.2017.11.016. References
4. Fluorescence The solid state fluorescence of compound 1 and free Hatr ligand at ambient temperature and temperature-dependent fluorescence of 1 were investigated. The free Hatr ligand shows a strong blue emission at 427 nm with the excitation at 360 nm, which can be assigned to intraligand π → π⁎ transition of 1,2,4-triazole ring. Compared to the free Hatr, compound 1 exhibits a similar blue fluorescence at 419 nm excited by 266 nm UV-light with a small blue shift of 8 nm (Fig. 4), which is related with the intraligand π → π⁎ transition of 1,2,4-triazole ring. The analysis of CIE 1931 chromaticity diagram together with the calculated color coordinates of 1 and Hatr suggests the emission colors are blue (Fig. 4). The temperature-dependent emission intensities of compound 1 were investigated with increasing 25–200 °C and decreasing 200–30 °C (Fig. 5). Compound 1 showed a thermal quenching that the fluorescence intensity decreased depending on temperature, whose fluorescence intensity was quenched at 200 °C about 43.78%. As the temperature was back to 30 °C from 200 °C, the fluorescence intensity can be totally recovered, which agrees with the TGA data that the framework stays stable before 343 °C. The hydrothermal reaction of Cd(Ac)2 with Hatr produced a 3D framework, [Cd5(atr)7(Ac)3(H2O)2] (1), which is constructed by 2D (4′4) layers interweaving with the 1D zigzag [Cd3(atr)2(H2O)] chains. The 3D framework can be simplified into a 12-nodal 2,2,3,3,3,3,3,3,4,5,6,7-connected topological network with point symbol of {4.6.8}3{4.62}3{43.62.84.10}{43.66.87.105}{46.64.85}{63.82.10}{6}2. The consistency of the experimental and simulated PXRD patterns confirms that the bulk sample of 1 has high phase purity. The thermal decomposition of 1 starts at 343 °C, showing the 3D framework has high thermal stability. The solid state fluorescence of 1 at ambient temperature exhibits blue fluorescence at 419 nm, close to 427 nm of free Hatr, which is assigned to intraligand π → π⁎ transition of 1,2,4-triazole ring. The temperature-dependent fluorescence of 1 shows a thermal quenching with 43.78% quenching rate at 200 °C, and a complete recovery occurred with the temperature decreasing to ambient temperature. Acknowledgments The work was sponsored by the National Natural Science Foundation of China (21401122), the Fundamental Research Funds for the Central Universities (GK201603050), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, Shaanxi University of Science and Technology (BJ14-02). Appendix A. Supplementary data Crystallographic data (excluding structure factors) for compound 1 in this paper has been deposited with the Cambridge Crystallographic Data Centre (the CCDC deposition number: 1574931. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
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Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Short communication
A new 3D cadmium coordination polymer containing 3-amino-1H-1,2,4-triazole: Synthesis, structure, and property Bing Liu a,⁎, Mei-Ting Wen a, Mei-Lin Shen b, Wei-Ni Miao a, Ting-Ting He a, Ling Xu b,⁎ a b
College of Chemistry and Chemical Engineering, Shaanxi University of Sciences and Technology, Xi'an 710021, Shaanxi Province, PR China Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi'an 710062, Shaanxi Province, PR China
a r t i c l e
i n f o
Article history: Received 23 October 2017 Received in revised form 20 November 2017 Accepted 22 November 2017 Available online 2 December 2017 Keywords: Coordination polymer 1,2,4-Triazole Fluorescence Crystal structure
a b s t r a c t Cadmium acetate (Cd(Ac)2) reacted with 3-amino-1H-1,2,4-triazole (Hatr) under hydrothermal conditions to produce a 3D framework, [Cd5(atr)7(Ac)3(H2O)2] (1), which is constructed through the interweaving of the 2D (4′4) layers with the 1D zigzag [Cd3(atr)2(H2O)] chains. Compound 1 was isolated with high phase purity confirmed by PXRD. TGA indicates the thermal decomposition temperature of compound 1 at 343 °C, showing the framework of 1 has high thermal stability. The solid state fluorescence of 1 at ambient temperature exhibits a blue emission at 419 nm, assigned to intraligand π → π⁎ transition of 1,2,4-triazole ring, which is similar to that of free Hatr with emission at 427 nm. The temperature-dependent fluorescence of 1 shows a thermal quenching with 43.78% quenching rate at 200 °C, and the fluorescent intensity can be completely recovered as the temperature decreased to ambient temperature. © 2017 Published by Elsevier B.V.
Coordination polymers (CPs) have made many progresses recently in many fields, such as gas storage and selective separation [1], chemosensor [2], light-emitting devices [3], catalysis [4], drug-delivery [5], gas/liquid detection [6], which aims at the structure constructions and the structure-property relationship [7]. A lot of work have been devoted to the structure design and controlled synthesis of CPs, attributing to understand the structure-property relationship [8]. However, at present, the preparation of a CP with predicted structure and desired property is still a challenge [9]. One of the strategies of CP structure construction is the rational selection of inorganic metal connectors and organic linkers [10]. The organic linkers containing the donor sites of N or O atoms are commonly used to tune the CP structure constructions [11]. The metal azolate frameworks have attracted much interest due to the rich π-electron aromatic N-heterocycles bind to soft transition metal showing charming structures and properties with high stabilities [12]. Compared to the famous diazole ligands of imidazolate and pyrazolate with simple coordination modes to fabricate the predictable structures, 1,2,4-trizaole ligands with one more nitrogen donor exhibit less predictable coordination behaviors and relative weaker coordination abilities. With the bridging fashions of μ3-1κN: 2κN: 4κN, μ2-1κN: 2κN, μ2-2κN: 4κN [13], 1,2,4-triazole ligands demonstrate themselves as versatile linkers to construct “simple, high-symmetry” structures [14]. 3-amino-1H-1,2,4-triazole (Hatr) is a two-connecting neutral or three-connecting anionic (deprotonated) ligand in the constructions of coordination polymers, which vails to achieve open porous ⁎ Corresponding authors. E-mail addresses: [email protected] (B. Liu), [email protected] (L. Xu).
https://doi.org/10.1016/j.inoche.2017.11.016 1387-7003/© 2017 Published by Elsevier B.V.
CPs and new topological nets [15]. In this contribution, we present a 3D atr-containing cadmium CP, [Cd5(atr)7(Ac)3(H2O)2] (1), which was synthesized under hydrothermal condition [16] and characterized by single crystal X-ray diffraction (SCXRD) (Table 1), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), solid-state and temperature-dependent fluorescence, and FT-IR. Compound 1 shows interesting structure features, high thermal stability, blue fluorescence, and fluorescence thermal quenching. 1. Crystal structure The single crystal analysis reveals 1, [Cd5(atr)7(Ac)3(H2O)2], is a 3D architecture, in whose asymmetric unit there are five cadmium atoms, seven atr− ligands, three Ac− anions, and two coordinated water molecules. Compound 1 crystallizes in orthorhombic noncentrosymmetric space group P212121, whose structural flack factor is −0.02(6), indicating the absolute structure is accurate [17]. Five cadmium atoms show two types of coordination geometries: five-coordinated Cd1, Cd2 and Cd5 atoms are in distorted CdN5 and CdN3O2 square pyramids and a CdN3O2 triangular bipyramid respectively; six-coordinated Cd3 and Cd4 are in CdN5O and CdN3O3 octahedra (Supporting information, Fig. S1). All the deprotoned atr− ligands adopt the same coordination mode of μ 3 -1κN: 2κN: 4κN (Supporting information, Scheme S1a). The Ac− anions exhibit three types of coordination modes: μ3-monodentate bridging/monodentate, μ2-monodentate bridging, and monodentate (Supporting information, Scheme S1b–d). Each Cd3 shapes a [Cd(H2O)] subunit with O1W as a terminal ligand, which is further connected into a 1D [Cd(atr)(H2O)] chain along the
B. Liu et al. / Inorganic Chemistry Communications 88 (2018) 38–41
39
Table 1 Crystal and structure refinement data for compound 1. Compound
1
Empirical formula Fw Crystal system Space group a/Å b/Å c/Å V/Å3 Z Dc(Mg m−3) μ/mm−1 F(000) Crystal size/mm3 2θ/° Reflections collected Independent reflections S Final R1, wR2 [I N 2σ(I)] R1, wR2 (all data) Δρmax/min/e·Ǻ−3 Flack parameter
C20H31Cd5N29O8 1367.74 orthorhombic P212121 13.3148(7) 15.0801(5) 19.6590(4) 3947.3(3) 4 2.302 2.734 2632.0 0.20 × 0.10 × 0.05 8.24 to 50.046 13,449 6627 [Rint = 0.0768, Rsigma = 0.1307] 1.020 R1 = 0.0682, wR2 = 0.1412 R1 = 0.1064, wR2 = 0.1631 1.82/−1.18 −0.02(6)
Fig. 2. Comparison of the simulated and experimental PXRD patterns of compound 1.
R1 = (Σ||Fo | − |Fc || / Σ|Fo |). wR2 = [Σ(w(F2o − F2c )2) / Σ(w|F2o |2)]1/2.
a-direction by the atr− ligands with N71 connecting neighboring [Cd(H2O)] subunits in μ2-1κN: 4κN mode (Fig. 1). Cd2 and Cd5 are alternately linked by the μ2-atr− ligands with N61 and Ac− bridges into a [Cd2(atr)(Ac)] chain along the a-direction, and its neighboring staggered chain is connected by the μ2-atr− ligands with N12 into a lattice-like chain (Fig. 1). These ladder-like chains fabricate with the [Cd(atr)(H2O)] chain containing Cd3 through two groups of μ2-atr− bridges with N21 and N31 into a 2D (4′4) layer along the ac-plane (Fig. 1; the topological
network in Supporting information, Fig. S2). Cd4 also shapes a similar [Cd(H2O)] subunit. Each Cd1 connects N44 and N51 of two atr− ligands in almost coplanar mode with the dihedral angle of 3.364°. The two atr− ligands continue to bind the [Cd(H2O)] subunits into a 1D zigzag [Cd3(atr)2(H2O)] chain along the c-direction (Fig. 1). The 2D (4′4) layers interweave with the zigzag [Cd 3 (atr)2 (H2 O)] chains through the rest N sites of the atr− ligands and the Ac− to form a 3D architecture (Fig. 1). Considering the structural features of 1, the Cd2(Ac) subunit that is formed by the μ2-monodentate bridging Ac− bridging Cd2 and Cd4
Fig. 1. The structural construction and the topological network of 1.
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B. Liu et al. / Inorganic Chemistry Communications 88 (2018) 38–41
Fig. 3. TG curve of compound 1.
was dummied as a 7-connecting node. Cd1, Cd3 and Cd5 were dummied as 6-, 5- and 4-connecting nodes, respectively. Except the atr− ligand with N21 and Ac− with O1 as a 2-connecting nodes, the other atr− ligands were considered as 3-connecting nodes. The 3D architecture was simplified into a 12-nodal 2,2,3,3,3,3,3,3,4,5,6,7-connected topological network with point symbol of {4.6.8}3{4.62}3{43.62.84.10}{43.66.87.105}{46.64.85}{63.82.10}{6}2 (Fig. 1). 2. PXRD The experimental PXRD pattern for 1 matches well with the simulated one from the single crystal structure data, indicating that the single crystal structure solution is correct and the bulk sample of 1 was isolated as a single crystal pure phase (Fig. 2). 3. TG analysis TG analysis was used to evaluate the thermal behavior of compound 1, which exhibits that compound 1 can keep the
Fig. 5. The solid-state temperature-dependent fluorescence of compound 1.
framework thermal stability up to 343 °C (Fig. 3). The 31.2% weight loss as heating to 422 °C corresponds to the loss of H2O, Ac− anions and part of atr− ligands. In the following heating at 422–900 °C, it was observed that the total weight loss of compound 1 occurred, and the weight loss closes to 100% at ca. 900 °C. This phenomenon is not common because most known coordination compounds will remain some non-volatile inorganic residues such as metal, metal oxides or carbons [18]. The phenomenon of “no residues” may be related with the fact that 1,2,4-triazole-containing compounds are usually explosive. We infer the deflagration of compound 1 caused the residues to lift out of the TGA pan, though we cannot clarify the detailed thermal decomposition procedure with a high-speed camera [19]. Based on the literature analysis on high density energetic materials, we can find out that triazoles, tetrazole, furazan, furoxan, \\NH2, \\NO2, \\N3, \\NNO2 are energetic groups [20], which have been in investigation for energetic materials for decades. Because of the high nitrogen content (66.63%) and the inherently energetic N\\N, C\\N, C_N bonds, atr− ligand is possible to construct
Fig. 4. Solid-state emission spectra of compound 1 (λex = 266 nm) and free Hatr (λex = 360 nm) (left), and the CIE 1931 chromaticity diagram together with the calculated color coordinate of compound 1 (right).
B. Liu et al. / Inorganic Chemistry Communications 88 (2018) 38–41
explosive coordination polymers. Therefore, the thermal behavior of compound 1 after 422 °C cannot reflect the real thermal decomposition of the framework because of the explosion.
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associated with this article can be found in the online version, at doi: https://doi.org/10.1016/j.inoche.2017.11.016. References
4. Fluorescence The solid state fluorescence of compound 1 and free Hatr ligand at ambient temperature and temperature-dependent fluorescence of 1 were investigated. The free Hatr ligand shows a strong blue emission at 427 nm with the excitation at 360 nm, which can be assigned to intraligand π → π⁎ transition of 1,2,4-triazole ring. Compared to the free Hatr, compound 1 exhibits a similar blue fluorescence at 419 nm excited by 266 nm UV-light with a small blue shift of 8 nm (Fig. 4), which is related with the intraligand π → π⁎ transition of 1,2,4-triazole ring. The analysis of CIE 1931 chromaticity diagram together with the calculated color coordinates of 1 and Hatr suggests the emission colors are blue (Fig. 4). The temperature-dependent emission intensities of compound 1 were investigated with increasing 25–200 °C and decreasing 200–30 °C (Fig. 5). Compound 1 showed a thermal quenching that the fluorescence intensity decreased depending on temperature, whose fluorescence intensity was quenched at 200 °C about 43.78%. As the temperature was back to 30 °C from 200 °C, the fluorescence intensity can be totally recovered, which agrees with the TGA data that the framework stays stable before 343 °C. The hydrothermal reaction of Cd(Ac)2 with Hatr produced a 3D framework, [Cd5(atr)7(Ac)3(H2O)2] (1), which is constructed by 2D (4′4) layers interweaving with the 1D zigzag [Cd3(atr)2(H2O)] chains. The 3D framework can be simplified into a 12-nodal 2,2,3,3,3,3,3,3,4,5,6,7-connected topological network with point symbol of {4.6.8}3{4.62}3{43.62.84.10}{43.66.87.105}{46.64.85}{63.82.10}{6}2. The consistency of the experimental and simulated PXRD patterns confirms that the bulk sample of 1 has high phase purity. The thermal decomposition of 1 starts at 343 °C, showing the 3D framework has high thermal stability. The solid state fluorescence of 1 at ambient temperature exhibits blue fluorescence at 419 nm, close to 427 nm of free Hatr, which is assigned to intraligand π → π⁎ transition of 1,2,4-triazole ring. The temperature-dependent fluorescence of 1 shows a thermal quenching with 43.78% quenching rate at 200 °C, and a complete recovery occurred with the temperature decreasing to ambient temperature. Acknowledgments The work was sponsored by the National Natural Science Foundation of China (21401122), the Fundamental Research Funds for the Central Universities (GK201603050), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, Shaanxi University of Science and Technology (BJ14-02). Appendix A. Supplementary data Crystallographic data (excluding structure factors) for compound 1 in this paper has been deposited with the Cambridge Crystallographic Data Centre (the CCDC deposition number: 1574931. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
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