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Hydrothermal synthesis and structural characterization of organically templated zincophosphites: [Zn(C4N3H13)][Zn4(HPO3)6]⋅(C4N3H15) and [Zn5(H2O)4(HPO3)6]⋅(C7NH10)2(H2O)
Solid State Sciences 8 (2006) 192–196 www.elsevier.com/locate/ssscie
Hydrothermal synthesis and structural characterization of organically templated zincophosphites: [Zn(C4 N3H13)][Zn4 (HPO3 )6 ]·(C4N3H15 ) and [Zn5 (H2 O)4(HPO3 )6]·(C7NH10 )2(H2 O) Dong Zhang, Huijuan Yue, Zhan Shi, Min Guo, Shouhua Feng ∗ State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, P.R. China Received 18 October 2005; accepted 31 October 2005 Available online 20 December 2005
Abstract Two organically templated zincophosphites, [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) and [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) were synthesized using diethylenetriamine and benzylamine as templates and characterized by single-crystal X-ray diffraction. [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) crystallizes in orthorhombic Cmca with cell parameters a = 18.9617(7) Å, b = 10.0192(3) Å, c = 16.1415(4) Å. [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) crystallizes in triclinic P -1 with cell parameters a = 10.0039(9) Å, b = 10.2172(9) Å, c = 11.6488(9) Å, and α = 69.646(5)◦ , β = 88.003(5)◦ , γ = 62.994(5)◦ . [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) consist of alternatively linked ZnO4 , ZnO2 N3 and [HPO3 2− ] units. In this structure, the structure-directing amines as ligands to zinc are present in two distinct forms, the free state and bonded state, and the two species occurring in channels. [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) is made up of ZnO4 , ZnO6 and [HPO3 2− ] moieties forming distinct channels, the protonated aromatic amine molecules are located in the intersection of the channels. In the compounds, the connections ZnO2 N3 and ZnO6 of Zn atoms are the first reported in the synthesis of zincophosphite materials. Two zincophosphites, having two-dimensional structures with 4, 6, 8-membered rings channels, were also characterized by IR spectroscopy, thermogravimetric and differential thermal analyses. 2005 Published by Elsevier SAS. Keywords: Hydrothermal synthesis; Organic–inorganic hybrid composites; X-ray diffraction; N ligands; Layered compounds
1. Introduction In the past decades, the preparation and structural chemistry of a number of organically templated metal phosphates were extensively studied for their potential applications in ion exchange, absorption, catalysis, and chemical sensor [1–10]. Structurally, the tetrahedral PO4 are basic building block in the phosphates [11–16]. Since 2001, when Harrison proposed the substitution of P(III) for P(V) and prepared the organically templated zincophosphite [17], some zincophosphites have been reported for replacing zincophosphates [18–22]. Compared to tetrahedral phosphate, the phosphite has a pseudo pyramidal geometry. The hydrogen phosphite group [HPO3 ]2− as a new basic building block led to diversity of novel structures * Corresponding author. Fax: +86-431-5168624; tel.: +86-431-5168661.
E-mail address: [email protected] (S. Feng). 1293-2558/$ – see front matter 2005 Published by Elsevier SAS. doi:10.1016/j.solidstatesciences.2005.10.017
in organically templated zincophosphites. Moreover, openframework metal phosphites have been synthesized, including [C2 H10 N2 ]·[V(HPO3 )2 ], [C2 H10 N2 ]·[Fe(HPO3 )2 ] [23], [C2 H10 N2 ]·[Co3 (HPO3 )4 ] [24], [C2 H10 N2 ]·[Cr(HPO3 )F3 ] [25] and [C2 H10 N2 ]·[Mn3 (HPO3 )4 ] [26], [C2 H10 N2 ]·[Al(OH){H(HPO3 )}2 ] [27], [C4 H12 N2 ]·[(UO2 )2 (PO3 H)2 {PO2 (OH)H2 }] [28]. As an extension of our previous study on the inorganic– organic hybrid phosphates [29,30] and organically templated phosphites [31–35], we continue our research on the investigation of the templating effect by finding a similar synthetic system. In this paper, we describe the syntheses and crystal structures of two two-dimensional zincophosphites, [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) 1 and [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) 2, with four, six, eight-membered rings, containing two types of amine molecules. Compound 1 is composed of alternating ZnO4 tetrahedra, ZnO2 N3 trigonal bipyramid and HPO3 pseudo pyramids. Compound 2 involves
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a network of ZnO4 tetrahedra, ZnO6 octahedral and HPO3 pseudo pyramids with shared vertices. The connections of Zn in the two compounds, ZnO2 N3 and ZnO6 , are the first mentioned in zincophosphite materials. And we have discovered in compound 1 of open-framework structure where the organic amine plays the dual space-filling agent. The structure-directing amine is present in two distinct forms, in the free state and the bonded state as a ligand to zinc, the two species occurring in distinct channels. In compound 2, using aromatic molecules as template is also seldom reported in the synthesis of the zinc phosphate or zincophosphite. Two compounds were characterized by IR spectroscopy, thermogravimetric and differential thermal analyses. 2. Experimental 2.1. Synthesis and characterization In a typical synthesis for compound 1, a mixture of Zn(ac)2 · 2H2 O (0.219 g), H3 PO3 (0.410 g), diethylenetriamine (0.35 mL), and water (5.0 mL) in a molar ratio of 1 : 5 : 3 : 166 was stirred under ambient conditions until it was homogeneous. The final reaction mixture with pH = 5.0 was heated in a sealed Teflon-lined steel autoclave at 160 ◦ C for 96 h. Compound 2 was prepared from a mixture of Zn(ac)2 ·2H2 O (0.219 g), H3 PO3 (0.410 g), benzylamine (0.5 mL), and water (5.0 mL) in a molar ratio of 1 : 5 : 5 : 166 and it was stirred under ambient conditions until it was homogeneous. The final reaction mixture with pH = 6.0 was heated in a sealed Teflon-lined steel autoclave at 160 ◦ C for 120 h. The resulting products, consisting of colorless block single crystals, were filtered, washed with distilled water and dried under ambient conditions (75% yield based on Zn for 1 and 85% yield based on Zn for 2). The elemental analyses were performed on a Perkin–Elmer 2400 element analyzer. The inductively couple plasma (ICP) analysis was carried out on a Perkin–Elmer Optima 3300DV ICP instrument. The ICP and elemental analysis results of the bulk products were also consistent with the theoretical values. Anal. calcd. for 1: C, 9.46; H, 3.35; N, 8.28%. Found: C, 9.7; H, 3.30; N, 8.37%. Calcd. for 2: C, 15.09; H, 3.23; N, 2.52%. Found: C, 15.39; H, 3.26; N, 2.58%. The IR spectra of the compounds showed typical peaks, with very little differences in the spectra. Strong absorption bands at 3413 cm−1 for N–H and 2500–3300 cm−1 for C– H bending stretching vibrations are observed. The bands at 2412 cm−1 for 1 and 2399 cm−1 for 2 were attributed to the terminal P–H stretch and deformation. The intense bands in the range 1087 cm−1 for 1 and 1150 cm−1 for 2 were attributed to the asymmetric and symmetric stretching vibrations of O– P–O. The bonds at 1382.7, 1457.9, 1542.7, 1616.1 cm−1 were assigned to the benzene ring stretching vibrations for 2. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) were carried out on a Perkin–Elmer DTA 1700 differential thermal analyzer and a Perkin–Elmer TGA 7 thermogravimetric analyzer in air with a heating rate of 10 ◦ C min−1 .
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Table 1 Crystal data and structure refinement parameters for [Zn4 Zn·(C4 N3 H13 )· (HPO3 )6 ]·(C4 N3 H15 ) 1 and [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) 2 1
2
Empirical formula Fw T (K) λ (Å)
C8 H34 N6 O18 P6 Zn5 1015.08 293(2) 0.71073
C14 H36 N2 O23 P6 Zn5 1113.12 293(2) 0.71073
Space group a (Å) b (Å) c (Å)
Cmca 18.9617(7) 10.0192(3) 16.1415(4)
P -1 10.0039(9) 10.2172(9) 11.6488(9) α = 69.646(5) β = 88.003(5) γ = 62.994(5) 983.72(15) 1 1.879 3.327 0.0595 0.1671
V (Å3 ) 3066.58(16) Z 4 Dcalc. (g cm−3 ) 2.199 µ (mm−1 ) 4.249 R1 a [I > 2θ(I )] 0.0463 wR2 b [I > 2θ(I )] 0.1499 a R = F | − |F / |F |. o c o 1 b wR = {[w(F 2 − F 2 )2 ]/ [w(F 2 )2 ]}1/2 . 2 o c o
2.2. Structural determination Crystals were carefully selected for X-ray diffraction analysis. The intensity data were collected on a Siemens SMART CCD diffractometer with graphite-monochromated Mo Kα (λ = 0.71073 Å) radiation at a temperature of 293 ± 2 K. A hemisphere of data was collected using a narrow-frame method with scan widths of 0.30◦ in ω and an exposure time of 30 s/frame. Data processing was accomplished with the SAINT processing program [36]. The structure was solved by Direct Methods, which use the SHELXTL crystallographic software package [37]. The zinc and phosphorus atoms were first located, whereas the carbon, nitrogen, and oxygen atoms were found in the difference Fourier maps. In compound 1, O(5) splits to O(5 ), N(1) splits to N(1 ). The hydrogen atoms residing on the phosphorus were located by Fourier maps. And the hydrogen atoms residing on the amine molecules were placed geometrically except compound 1. Hydrogen atoms associated with the hydrogen phosphite moieties (P–H) and template molecules (N–H and C–H) were refined by riding on their parent atoms. All non-hydrogen atoms were refined anisotropically. Details of the final refinement are given in Table 1. 3. Results and discussion 3.1. Crystal structure of [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) 1 Compound 1 contains ZnO4 tetrahedra, ZnO2 N3 trigonal bipyramid and HPO3 pseudo pyramids as the polyhedralbuilding units (Fig. 1(a)). In this structure, two independent zinc atoms present two different coordination geometries. The Zn(1) is tetrahedrally coordinated by four oxygen atoms, with Zn– O bond distances from 1.914 to 1.963 Å. The O–Zn–O bond
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(a)
(b)
angles are in the range of 105.90–117.97◦ . Zn(2) has a symmetrically equivalent point Zn(2A) by the symmetry operation 1 − x, 1 − y, 1 − z. From the knowledge of thermal vibration and crystallography, Zn(2) and Zn(2A) occupy two split positions of one Zn atom. Thus, the coordination of Zn(2) should be divided into two parts, Figs. 1(b) and 1(c). The five-coordinated Zn(2) or Zn(2A) is composed of two oxygen donors from each of two adjacent phosphite groups and three nitrogen atoms from a diethylenetriamine ligand to form a distorted trigonal bipyramid geometry. The Zn–O(N) bond distances are in the average value of 2.042 Å. The zinc atom is connected to the phosphorus atoms via Zn–O–P links. Two distinct P atoms form the centers of pseudo pyramid with average P–O bond distances of 1.531 Å for P(1), 1.519 Å for P(2). The O–P–O bond angles are in the range of 105.1–117.3◦ (av. O–P(1)–O = 110.76◦ , O–P(2)–O = 111.55◦ ). The framework structure of 1 is consists of alternating inorganic and organic layers stacked along [010] direction. Fig. 2 shows the inorganic layer viewed down the [001] direction. The sheet structure consists of four, six, eight-membered rings that form a network of alternatively linked corner-sharing ZnO4 tetrahedra, ZnO2 N3 trigonal bipyramid and HPO3 pseudo pyramids. The linkages between Zn(1)O4 and HP(2)O3 units form four-membered rings that are shared edge-wise forming the ladders. These ladders are further linked together by the two oxygen atoms of HP(1)O3 groups to generate 2D structure with the channels of eight-membered rings window. Zn(2) is connected to the P(1) via the third oxygen atom. And the linkages among three Zn(1)O4 , two HP(2)O3 , two HP(1)O3 and one Zn(2)O2 N3 units which are connected to each other by sharing vertices form another type of eight-membered rings. In this structure, the organic amine plays the dual space-filling agent. The structure-directing amine is present in two distinct forms, in the free state and the bonded state as a ligand to zinc, the two species located above and below the sheet. The free diprotonated diethylenetriamine molecules locate in the interlayer region and balance the overall negative electrostatic charge of the layers.
(c) Fig. 1. (a) Show the asymmetric unit of [Zn4 Zn·(C4 N3 H13 )·(HPO3 )6 ]· (C4 N3 H15 ) 1 with thermal ellipsoids shown at 50% probability. Zn(2) has a symmetrically equivalent point Zn(2A). (a) Can be divided into (b) and (c) (in (b) and (c), some atoms are omitted for clarity).
Fig. 2. The layer of compound 1 viewed along the [001] direction. All H atoms are omitted for clarity.
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3.2. Crystal structure of [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) 2 The asymmetric unit of 2 contains 27 non-hydrogen atoms, of which 17 atoms belong to the framework and 10 atoms to the guest amine molecule. Compound 2 contains ZnO4 tetrahedra, ZnO6 octahedral and HPO3 pseudo pyramids as the polyhedralbuilding units (Fig. 3). Three independent zinc atoms present two different coordination geometries. The Zn(2) and Zn(3) atoms are tetrahedrally coordinated by four oxygen atoms, with Zn–O bond average distances of 1.939 Å for Zn(2), 1.944 Å for Zn(3). The O–Zn–O bond angles are in the range of 106.2– 116.2◦ (av. O–Zn(2)–O = 109.43◦ , O–Zn(3)–O = 109.39◦ ). The six-coordinated zinc site Zn(1) exhibits the distorted octahedral geometry with the basal positions defined by oxygen donors from each of two adjacent phosphite groups and four water molecule. The Zn–O bond distances are in the range of 1.945–2.172 Å with an average value of 2.108 Å. The Zn atom is connected to the P atoms via Zn–O–P links. All of the phosphite groups adopt the µ3 -coordination mode. Three distinct P atoms form the centers of pseudo pyramid with P–O bond distances of 1.512 Å for P(1), 1.515 Å for P(2), 1.516 Å for P(3), respectively. The O–P–O bond angles are in the range of 108.3–114.5◦ (av. O–P(1)–O = 111.2◦ , O–P(2)–O = 112.7◦ , O–P(3)–O = 112.3◦ ). The framework structure of 2 has the similar inorganic frameworks of compound 1 with the different compositions along [001] direction (Fig. 4). The linkages between Zn(2)O4 , HP(2)O3 and Zn(3)O4 , HP(3)O3 units form two types of fourmembered rings that are shared edge-wise forming the ladders. These ladders are further linked together by HP(1)O3 groups to generate 2D structure with the channels of eight-membered ring window. Zn(1) is connected to the P(1) via the third oxygen atom. As the result, one eight-membered ring comes into being that is enclosed by two P(1), one Zn(1) and the fourmembered rings ladders. The water molecules and the templates
Fig. 4. The layer of compound 2 viewed along the [001] direction. All H atoms are omitted for clarity.
locate in the channel. The protonated benzylamine amines exit as charge-balanced cations and the nitrogen atom of each template molecule interacts with the host framework through extensive H-bonding interactions. The representative hydrogen bonds are O(3)· · ·H(1A), O(9)· · ·H(1B), O(10)· · ·H(1C), whose lengths are 2.04, 2.19, 1.99 Å, respectively. Thus the sheets are hold together by multipoint hydrogen bonds. The layer structures of the two compounds are similar with each other, but the connections of the Zn atoms are different. In compound 1, diethylenetriamine, which has three nitrogen atoms, binds to Zn as a terminal tridentate ligand. But, in compound 2, one dentate amine benzylamine is difficult to chelated to Zn atoms, which coordinated by four water molecules. As a result, organic templates are sensitive to the formation of the zincophosphites. 3.3. Thermogravimetric (TG) analysis
Fig. 3. The asymmetric unit of [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) 2 with thermal ellipsoids shown at 50% probability.
The TGA studies indicate that the weight loss occurred in two mass losses for 1 and three mass losses for 2 in the range 30–800 ◦ C. In the case of 1, the first mass loss of 10.52% in the range 250–400 ◦ C corresponds to the loss of the free amine molecules (calcd. 10.15%). The second mass loss with a broad tail amounts to a total loss of 10.31% in the range 400–750 ◦ C and corresponds to the loss of the bond amine molecules (calcd. 10.34%). In the case of 2, the first mass loss of 1.80% in the range 100–150 ◦ C corresponds to the loss of the free water molecules (calcd. 1.62%). The second mass loss of 7.75% in the range 150–250 ◦ C corresponds to the loss of the water molecules, which bond to zinc atoms (calcd. 7.47%). And the mass loss of 17.71% in the range 250–400 ◦ C corresponds to the loss of the amine (calcd. 17.6%). Each of the decomposed samples was found to be poorly crystalline (powder XRD) and corresponds to a dense zinc phosphate, Zn2 P2 O7 (JCPDS: 43-0488), indicating destruction of the framework structure upon loss of the amine.
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4. Conclusions Two 2D zincophosphites with the formulas [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) 1 and [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) 2 have been hydrothermally synthesized with 4, 6, 8-membered rings channel. In the compounds, the connections ZnO2 N3 and ZnO6 of Zn atoms are the first reported in the synthesis of zincophosphite materials. Furthermore, in the structure of 1, the structure-directing amine is present in two distinct forms, free state and bonded state. In compound 2, we use aromatic molecules as template, which is also seldom reported. The current study shows the sensitivity of the formation of the zincophosphites to the organic templates, similarly to the cases of the zincophosphate, and the further possibility for hydrothermally preparing novel organically templated phosphites by the use of different organic templates. Acknowledgements We thank the National Science Foundation of China (No. 20071013 and 20301007) and the State Basic Research Project of China (G2000077507) for support. References [1] [2] [3] [4] [5] [6] [7] [8] [9]
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Hydrothermal synthesis and structural characterization of organically templated zincophosphites: [Zn(C4 N3H13)][Zn4 (HPO3 )6 ]·(C4N3H15 ) and [Zn5 (H2 O)4(HPO3 )6]·(C7NH10 )2(H2 O) Dong Zhang, Huijuan Yue, Zhan Shi, Min Guo, Shouhua Feng ∗ State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, P.R. China Received 18 October 2005; accepted 31 October 2005 Available online 20 December 2005
Abstract Two organically templated zincophosphites, [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) and [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) were synthesized using diethylenetriamine and benzylamine as templates and characterized by single-crystal X-ray diffraction. [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) crystallizes in orthorhombic Cmca with cell parameters a = 18.9617(7) Å, b = 10.0192(3) Å, c = 16.1415(4) Å. [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) crystallizes in triclinic P -1 with cell parameters a = 10.0039(9) Å, b = 10.2172(9) Å, c = 11.6488(9) Å, and α = 69.646(5)◦ , β = 88.003(5)◦ , γ = 62.994(5)◦ . [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) consist of alternatively linked ZnO4 , ZnO2 N3 and [HPO3 2− ] units. In this structure, the structure-directing amines as ligands to zinc are present in two distinct forms, the free state and bonded state, and the two species occurring in channels. [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) is made up of ZnO4 , ZnO6 and [HPO3 2− ] moieties forming distinct channels, the protonated aromatic amine molecules are located in the intersection of the channels. In the compounds, the connections ZnO2 N3 and ZnO6 of Zn atoms are the first reported in the synthesis of zincophosphite materials. Two zincophosphites, having two-dimensional structures with 4, 6, 8-membered rings channels, were also characterized by IR spectroscopy, thermogravimetric and differential thermal analyses. 2005 Published by Elsevier SAS. Keywords: Hydrothermal synthesis; Organic–inorganic hybrid composites; X-ray diffraction; N ligands; Layered compounds
1. Introduction In the past decades, the preparation and structural chemistry of a number of organically templated metal phosphates were extensively studied for their potential applications in ion exchange, absorption, catalysis, and chemical sensor [1–10]. Structurally, the tetrahedral PO4 are basic building block in the phosphates [11–16]. Since 2001, when Harrison proposed the substitution of P(III) for P(V) and prepared the organically templated zincophosphite [17], some zincophosphites have been reported for replacing zincophosphates [18–22]. Compared to tetrahedral phosphate, the phosphite has a pseudo pyramidal geometry. The hydrogen phosphite group [HPO3 ]2− as a new basic building block led to diversity of novel structures * Corresponding author. Fax: +86-431-5168624; tel.: +86-431-5168661.
E-mail address: [email protected] (S. Feng). 1293-2558/$ – see front matter 2005 Published by Elsevier SAS. doi:10.1016/j.solidstatesciences.2005.10.017
in organically templated zincophosphites. Moreover, openframework metal phosphites have been synthesized, including [C2 H10 N2 ]·[V(HPO3 )2 ], [C2 H10 N2 ]·[Fe(HPO3 )2 ] [23], [C2 H10 N2 ]·[Co3 (HPO3 )4 ] [24], [C2 H10 N2 ]·[Cr(HPO3 )F3 ] [25] and [C2 H10 N2 ]·[Mn3 (HPO3 )4 ] [26], [C2 H10 N2 ]·[Al(OH){H(HPO3 )}2 ] [27], [C4 H12 N2 ]·[(UO2 )2 (PO3 H)2 {PO2 (OH)H2 }] [28]. As an extension of our previous study on the inorganic– organic hybrid phosphates [29,30] and organically templated phosphites [31–35], we continue our research on the investigation of the templating effect by finding a similar synthetic system. In this paper, we describe the syntheses and crystal structures of two two-dimensional zincophosphites, [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) 1 and [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) 2, with four, six, eight-membered rings, containing two types of amine molecules. Compound 1 is composed of alternating ZnO4 tetrahedra, ZnO2 N3 trigonal bipyramid and HPO3 pseudo pyramids. Compound 2 involves
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a network of ZnO4 tetrahedra, ZnO6 octahedral and HPO3 pseudo pyramids with shared vertices. The connections of Zn in the two compounds, ZnO2 N3 and ZnO6 , are the first mentioned in zincophosphite materials. And we have discovered in compound 1 of open-framework structure where the organic amine plays the dual space-filling agent. The structure-directing amine is present in two distinct forms, in the free state and the bonded state as a ligand to zinc, the two species occurring in distinct channels. In compound 2, using aromatic molecules as template is also seldom reported in the synthesis of the zinc phosphate or zincophosphite. Two compounds were characterized by IR spectroscopy, thermogravimetric and differential thermal analyses. 2. Experimental 2.1. Synthesis and characterization In a typical synthesis for compound 1, a mixture of Zn(ac)2 · 2H2 O (0.219 g), H3 PO3 (0.410 g), diethylenetriamine (0.35 mL), and water (5.0 mL) in a molar ratio of 1 : 5 : 3 : 166 was stirred under ambient conditions until it was homogeneous. The final reaction mixture with pH = 5.0 was heated in a sealed Teflon-lined steel autoclave at 160 ◦ C for 96 h. Compound 2 was prepared from a mixture of Zn(ac)2 ·2H2 O (0.219 g), H3 PO3 (0.410 g), benzylamine (0.5 mL), and water (5.0 mL) in a molar ratio of 1 : 5 : 5 : 166 and it was stirred under ambient conditions until it was homogeneous. The final reaction mixture with pH = 6.0 was heated in a sealed Teflon-lined steel autoclave at 160 ◦ C for 120 h. The resulting products, consisting of colorless block single crystals, were filtered, washed with distilled water and dried under ambient conditions (75% yield based on Zn for 1 and 85% yield based on Zn for 2). The elemental analyses were performed on a Perkin–Elmer 2400 element analyzer. The inductively couple plasma (ICP) analysis was carried out on a Perkin–Elmer Optima 3300DV ICP instrument. The ICP and elemental analysis results of the bulk products were also consistent with the theoretical values. Anal. calcd. for 1: C, 9.46; H, 3.35; N, 8.28%. Found: C, 9.7; H, 3.30; N, 8.37%. Calcd. for 2: C, 15.09; H, 3.23; N, 2.52%. Found: C, 15.39; H, 3.26; N, 2.58%. The IR spectra of the compounds showed typical peaks, with very little differences in the spectra. Strong absorption bands at 3413 cm−1 for N–H and 2500–3300 cm−1 for C– H bending stretching vibrations are observed. The bands at 2412 cm−1 for 1 and 2399 cm−1 for 2 were attributed to the terminal P–H stretch and deformation. The intense bands in the range 1087 cm−1 for 1 and 1150 cm−1 for 2 were attributed to the asymmetric and symmetric stretching vibrations of O– P–O. The bonds at 1382.7, 1457.9, 1542.7, 1616.1 cm−1 were assigned to the benzene ring stretching vibrations for 2. Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) were carried out on a Perkin–Elmer DTA 1700 differential thermal analyzer and a Perkin–Elmer TGA 7 thermogravimetric analyzer in air with a heating rate of 10 ◦ C min−1 .
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Table 1 Crystal data and structure refinement parameters for [Zn4 Zn·(C4 N3 H13 )· (HPO3 )6 ]·(C4 N3 H15 ) 1 and [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) 2 1
2
Empirical formula Fw T (K) λ (Å)
C8 H34 N6 O18 P6 Zn5 1015.08 293(2) 0.71073
C14 H36 N2 O23 P6 Zn5 1113.12 293(2) 0.71073
Space group a (Å) b (Å) c (Å)
Cmca 18.9617(7) 10.0192(3) 16.1415(4)
P -1 10.0039(9) 10.2172(9) 11.6488(9) α = 69.646(5) β = 88.003(5) γ = 62.994(5) 983.72(15) 1 1.879 3.327 0.0595 0.1671
V (Å3 ) 3066.58(16) Z 4 Dcalc. (g cm−3 ) 2.199 µ (mm−1 ) 4.249 R1 a [I > 2θ(I )] 0.0463 wR2 b [I > 2θ(I )] 0.1499 a R = F | − |F / |F |. o c o 1 b wR = {[w(F 2 − F 2 )2 ]/ [w(F 2 )2 ]}1/2 . 2 o c o
2.2. Structural determination Crystals were carefully selected for X-ray diffraction analysis. The intensity data were collected on a Siemens SMART CCD diffractometer with graphite-monochromated Mo Kα (λ = 0.71073 Å) radiation at a temperature of 293 ± 2 K. A hemisphere of data was collected using a narrow-frame method with scan widths of 0.30◦ in ω and an exposure time of 30 s/frame. Data processing was accomplished with the SAINT processing program [36]. The structure was solved by Direct Methods, which use the SHELXTL crystallographic software package [37]. The zinc and phosphorus atoms were first located, whereas the carbon, nitrogen, and oxygen atoms were found in the difference Fourier maps. In compound 1, O(5) splits to O(5 ), N(1) splits to N(1 ). The hydrogen atoms residing on the phosphorus were located by Fourier maps. And the hydrogen atoms residing on the amine molecules were placed geometrically except compound 1. Hydrogen atoms associated with the hydrogen phosphite moieties (P–H) and template molecules (N–H and C–H) were refined by riding on their parent atoms. All non-hydrogen atoms were refined anisotropically. Details of the final refinement are given in Table 1. 3. Results and discussion 3.1. Crystal structure of [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) 1 Compound 1 contains ZnO4 tetrahedra, ZnO2 N3 trigonal bipyramid and HPO3 pseudo pyramids as the polyhedralbuilding units (Fig. 1(a)). In this structure, two independent zinc atoms present two different coordination geometries. The Zn(1) is tetrahedrally coordinated by four oxygen atoms, with Zn– O bond distances from 1.914 to 1.963 Å. The O–Zn–O bond
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(a)
(b)
angles are in the range of 105.90–117.97◦ . Zn(2) has a symmetrically equivalent point Zn(2A) by the symmetry operation 1 − x, 1 − y, 1 − z. From the knowledge of thermal vibration and crystallography, Zn(2) and Zn(2A) occupy two split positions of one Zn atom. Thus, the coordination of Zn(2) should be divided into two parts, Figs. 1(b) and 1(c). The five-coordinated Zn(2) or Zn(2A) is composed of two oxygen donors from each of two adjacent phosphite groups and three nitrogen atoms from a diethylenetriamine ligand to form a distorted trigonal bipyramid geometry. The Zn–O(N) bond distances are in the average value of 2.042 Å. The zinc atom is connected to the phosphorus atoms via Zn–O–P links. Two distinct P atoms form the centers of pseudo pyramid with average P–O bond distances of 1.531 Å for P(1), 1.519 Å for P(2). The O–P–O bond angles are in the range of 105.1–117.3◦ (av. O–P(1)–O = 110.76◦ , O–P(2)–O = 111.55◦ ). The framework structure of 1 is consists of alternating inorganic and organic layers stacked along [010] direction. Fig. 2 shows the inorganic layer viewed down the [001] direction. The sheet structure consists of four, six, eight-membered rings that form a network of alternatively linked corner-sharing ZnO4 tetrahedra, ZnO2 N3 trigonal bipyramid and HPO3 pseudo pyramids. The linkages between Zn(1)O4 and HP(2)O3 units form four-membered rings that are shared edge-wise forming the ladders. These ladders are further linked together by the two oxygen atoms of HP(1)O3 groups to generate 2D structure with the channels of eight-membered rings window. Zn(2) is connected to the P(1) via the third oxygen atom. And the linkages among three Zn(1)O4 , two HP(2)O3 , two HP(1)O3 and one Zn(2)O2 N3 units which are connected to each other by sharing vertices form another type of eight-membered rings. In this structure, the organic amine plays the dual space-filling agent. The structure-directing amine is present in two distinct forms, in the free state and the bonded state as a ligand to zinc, the two species located above and below the sheet. The free diprotonated diethylenetriamine molecules locate in the interlayer region and balance the overall negative electrostatic charge of the layers.
(c) Fig. 1. (a) Show the asymmetric unit of [Zn4 Zn·(C4 N3 H13 )·(HPO3 )6 ]· (C4 N3 H15 ) 1 with thermal ellipsoids shown at 50% probability. Zn(2) has a symmetrically equivalent point Zn(2A). (a) Can be divided into (b) and (c) (in (b) and (c), some atoms are omitted for clarity).
Fig. 2. The layer of compound 1 viewed along the [001] direction. All H atoms are omitted for clarity.
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3.2. Crystal structure of [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) 2 The asymmetric unit of 2 contains 27 non-hydrogen atoms, of which 17 atoms belong to the framework and 10 atoms to the guest amine molecule. Compound 2 contains ZnO4 tetrahedra, ZnO6 octahedral and HPO3 pseudo pyramids as the polyhedralbuilding units (Fig. 3). Three independent zinc atoms present two different coordination geometries. The Zn(2) and Zn(3) atoms are tetrahedrally coordinated by four oxygen atoms, with Zn–O bond average distances of 1.939 Å for Zn(2), 1.944 Å for Zn(3). The O–Zn–O bond angles are in the range of 106.2– 116.2◦ (av. O–Zn(2)–O = 109.43◦ , O–Zn(3)–O = 109.39◦ ). The six-coordinated zinc site Zn(1) exhibits the distorted octahedral geometry with the basal positions defined by oxygen donors from each of two adjacent phosphite groups and four water molecule. The Zn–O bond distances are in the range of 1.945–2.172 Å with an average value of 2.108 Å. The Zn atom is connected to the P atoms via Zn–O–P links. All of the phosphite groups adopt the µ3 -coordination mode. Three distinct P atoms form the centers of pseudo pyramid with P–O bond distances of 1.512 Å for P(1), 1.515 Å for P(2), 1.516 Å for P(3), respectively. The O–P–O bond angles are in the range of 108.3–114.5◦ (av. O–P(1)–O = 111.2◦ , O–P(2)–O = 112.7◦ , O–P(3)–O = 112.3◦ ). The framework structure of 2 has the similar inorganic frameworks of compound 1 with the different compositions along [001] direction (Fig. 4). The linkages between Zn(2)O4 , HP(2)O3 and Zn(3)O4 , HP(3)O3 units form two types of fourmembered rings that are shared edge-wise forming the ladders. These ladders are further linked together by HP(1)O3 groups to generate 2D structure with the channels of eight-membered ring window. Zn(1) is connected to the P(1) via the third oxygen atom. As the result, one eight-membered ring comes into being that is enclosed by two P(1), one Zn(1) and the fourmembered rings ladders. The water molecules and the templates
Fig. 4. The layer of compound 2 viewed along the [001] direction. All H atoms are omitted for clarity.
locate in the channel. The protonated benzylamine amines exit as charge-balanced cations and the nitrogen atom of each template molecule interacts with the host framework through extensive H-bonding interactions. The representative hydrogen bonds are O(3)· · ·H(1A), O(9)· · ·H(1B), O(10)· · ·H(1C), whose lengths are 2.04, 2.19, 1.99 Å, respectively. Thus the sheets are hold together by multipoint hydrogen bonds. The layer structures of the two compounds are similar with each other, but the connections of the Zn atoms are different. In compound 1, diethylenetriamine, which has three nitrogen atoms, binds to Zn as a terminal tridentate ligand. But, in compound 2, one dentate amine benzylamine is difficult to chelated to Zn atoms, which coordinated by four water molecules. As a result, organic templates are sensitive to the formation of the zincophosphites. 3.3. Thermogravimetric (TG) analysis
Fig. 3. The asymmetric unit of [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) 2 with thermal ellipsoids shown at 50% probability.
The TGA studies indicate that the weight loss occurred in two mass losses for 1 and three mass losses for 2 in the range 30–800 ◦ C. In the case of 1, the first mass loss of 10.52% in the range 250–400 ◦ C corresponds to the loss of the free amine molecules (calcd. 10.15%). The second mass loss with a broad tail amounts to a total loss of 10.31% in the range 400–750 ◦ C and corresponds to the loss of the bond amine molecules (calcd. 10.34%). In the case of 2, the first mass loss of 1.80% in the range 100–150 ◦ C corresponds to the loss of the free water molecules (calcd. 1.62%). The second mass loss of 7.75% in the range 150–250 ◦ C corresponds to the loss of the water molecules, which bond to zinc atoms (calcd. 7.47%). And the mass loss of 17.71% in the range 250–400 ◦ C corresponds to the loss of the amine (calcd. 17.6%). Each of the decomposed samples was found to be poorly crystalline (powder XRD) and corresponds to a dense zinc phosphate, Zn2 P2 O7 (JCPDS: 43-0488), indicating destruction of the framework structure upon loss of the amine.
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4. Conclusions Two 2D zincophosphites with the formulas [Zn(C4 N3 H13 )][Zn4 (HPO3 )6 ]·(C4 N3 H15 ) 1 and [Zn5 (H2 O)4 (HPO3 )6 ]·(C7 NH10 )2 (H2 O) 2 have been hydrothermally synthesized with 4, 6, 8-membered rings channel. In the compounds, the connections ZnO2 N3 and ZnO6 of Zn atoms are the first reported in the synthesis of zincophosphite materials. Furthermore, in the structure of 1, the structure-directing amine is present in two distinct forms, free state and bonded state. In compound 2, we use aromatic molecules as template, which is also seldom reported. The current study shows the sensitivity of the formation of the zincophosphites to the organic templates, similarly to the cases of the zincophosphate, and the further possibility for hydrothermally preparing novel organically templated phosphites by the use of different organic templates. Acknowledgements We thank the National Science Foundation of China (No. 20071013 and 20301007) and the State Basic Research Project of China (G2000077507) for support. References [1] [2] [3] [4] [5] [6] [7] [8] [9]
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