Interpenetrated and Catenated Zinc Thiosulfates Frameworks with dia

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Interpenetrated and Catenated Zinc thiosulfates frameworks with dia and qtz nets: Synthesis, Structure, and Properties Srinivasan Natarajan, and Rajendran Karthik Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b00051 • Publication Date (Web): 10 Mar 2016 Downloaded from http://pubs.acs.org on March 12, 2016

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Crystal Growth & Design

Interpenetrated and Catenated Zinc thiosulfates frameworks with dia and qtz nets: Synthesis, Structure, and Properties Rajendran Karthik and Srinivasan Natarajan*

Framework solids Laboratory, Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore-560012, India.

*

Corresponding Author, E-mail: [email protected]

1 ACS Paragon Plus Environment


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Abstract Reactions between Zn(NO3)2.6H2O, Na2S2O3, 4,4′-bipyridine (bpy), 1,2-bis(4-pyridyl)ethene (bpe), 1,2-bis(4-pyridyl)ethane (bpa)and 1,3-bis(4-pyridyl)propane (bpp) under solvothermal conditions resulted in four new zinc thiosulfate hybrid compounds. Compound I has 4-membered zinc thiosulfate rings connected by the ligand, 1,3-bis(4-pyridyl)propane (bpp) forming two-dimensional structure. Compound II – IV have onedimensional zinc thiosulfate chains connected by the ligands, bpy, (II) bpe,(III) and bpa (IV) giving rise to three-dimensional structures. All the four-structures exhibit three-fold inter-penetration. Proton conductivity studies indicate reasonable proton mobility at 34 °C and at 98% relative humidity. The compounds also exhibit Lewis acid character and good photocatalytic activity for the decomposition of cationic dyes.


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Introduction Phosphate and silicate based framework compounds, with interconnected channels and cavities have been investigated extensively for their many applications in the area of catalysis, luminescence, sorption and separation processes.1-6 The new family of framework compounds based on carboxylates, known as metalorganic frameworks (MOF) or inorganic coordination polymers (CP), are being studied vigorously during the past two decades for their many potential applications in sorption and catalysis.7-11 The studies on MOFs and related compounds have brought out the usefulness of nitrogen containing aromatics as ligands and structure builders.12-16 The usefulness of 4,4′-bipyridine in extending the dimensionality of the structure was established during the preparation of phosphates and related structures.17-22 This strategy was also adapted for the preparation of many other compounds.23-32 We have been interested in the study of phosphates, phosphites, arsenates and other related compounds over the years to understand the possible pathways of formation of such structures and also for their interesting physical properties such as magnetism.23-32. One of the ways to rationalize the formation of compounds with open structures could be to think in terms of the subtle balance between the acids and bases that are involved in the preparation of such compounds. The hard-soft acids and bases (HSAB) theory of Pearson33 appears to hold some promise towards the understanding of the formation of the framework structures of phosphates, sulfates, carbonates etc. Of the many anions, the borates were explored recently as a framework builder.34-40 We have also investigated the usefulness of thiosulfates in the formation of hybrid structures.41-44 Though modest success has been achieved in the stabilization of thiosulfate as part of the framework, the issue with regard to the synthesis of thiosulfate frameworks are many. Thiosulfate, similar to sulfate, is a tetrahedral ion with identical charge (2). Sulfates were shown to form interesting framework structures during the last decade.45-54 Thiosulfates on the other hand, appear different and the following points may be relevant: (i) thiosulfate is a hetero-anion with three oxygen and one sulfur atoms; (ii) the two distinct sulfur species have different oxidation states (+6 and -2, respectively); (iii) the bond strengths of the S-O and S-S bonds within the (S2O3)2- anion would be different as indicated by the bond distances (S-O ~ 1.45 Å and S-S ~ 2 Å). These factors would make the thiosulfates sensitive under the harsh hydrothermal reactions, normally employed for the synthesis of open-framework phosphates and silicates. The thiosulfate tends to breaks down under high acidic as well as basic pH and also at higher temperatures forming elemental sulfur. The elemental sulfur would be reactive and form metal sulfides



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readily. From the HSAB theory,33 thiosulfate anions are soft bases and it is preferable to react with soft acids or intermediate acid cations. Our earlier studies on the use of soft acid cations such as Cd2+ was successful in the formation of new thiosulfate frameworks.41-44 As a continuation of this theme of research, we have now investigated the reactivity of intermediate acid cations such as Zn2+ by employing a panoply of strategies. Our efforts have been successful and we have now isolated four new Zinc thiosulfate phases: [Zn(S2O3)(bpp)] I, [Zn2(S2O3)2(bpy)2] II, [Zn(S2O3)(bpe)].H2O III and [Zn3(S2O3)3(bpa)3].3H2O IV. In this paper, we describe the synthesis, structure and properties of the zinc thiosulfate compounds. Experimental Section Synthesis and initial characterization The reagents Zn(NO3)2.6H2O [CDH India, 98%], Na2S2O3,[Fluka, 99%], 4,4′-bipyridine (bpy) [Aldrich, 98%], 1,2-bis(4-pyridyl)ethene (bpe) [Aldrich, 98%], 1,2-bis(4-pyridyl)ethane (bpa) [Aldrich, 98%] and 1,3-bis(4-pyridyl)propane (bpp) [Aldrich, 98%] were used as purchased without any further purification. In a typical synthesis for I, Zn(NO3)2.6H2O (0.297 g, 1mM), Na2S2O3 (0.158 g, 1mM), bpp ( 0.198 g, 1 mM) were taken in a mixture of 4ml of distilled water and 6ml of methanol. The mixture was stirred at room temperature for 30 minutes. The homogenized mixture was transferred and sealed into a 23 mL PTFE lined stainless steel autoclave and heated at 80°C for 72h. On cooling, yellow colored block crystals were filtered under vacuum, washed with deionized water and dried at ambient conditions. Compound II, III and IV were prepared employing similar synthetic procedure (Table 1). Elemental Analysis of the products in each case was carried out using Thermo Finnigan FLASH EA 1112CHN analyzer (Table 1).

The prepared compounds were characterized by powder X-ray diffraction (PXRD), IR, UV-visible and Photo-luminescence (PL) spectroscopic studies. The PXRD patterns were recorded in the 2θ range 5-50° employing Cu Kα radiation (λ=1.5418Å, Philips X′pert). The observed PXRD patterns were found to be consistent with the simulated PXRD patterns generated from the single crystal X-ray structure (ESI, Figure S1S4). The Infrared (IR) spectroscopic studies were carried out using Perkin-Elmer, SPECTRUM 1000.

The IR spectra for all the compounds exhibited characteristic bands (ESI, Figure S5).The IR spectra of compounds I – IV were interpreted in five distinct regions. 1) A broad band centered around 3412, 3495 cm-1 and 3479, 3570 cm-1, respectively for III and IV could be due to the symmetric and anti-symmetric stretching


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of the lattice water molecule; 2) A band at ~ 3072cm-1 indicates aromatic υ(CH) modes of pyridine skeleton; 3) a band in the range of 1660-1200 cm-1 indicates C-H bending vibrations due to symmetric and asymmetric stretching modes of the pyridine ring; 4) a sharp band at 1129cm-1 could be due to S-O; 5) bands in the range of 500 – 800 cm-1 could be due to the bending modes of S-O and S-S of the thiosulfate unit. The observed IR bands were similar to those reported in earlier thiosulfate framework compounds34-40. Thermogravimetric analysis (TGA) was carried out in flowing oxygen atomosphere (flow rate = 20ml min-1) in the temperature range 30 – 850 ºC (heating rate = 5 ºC min-1) (ESI, Figure S6) The TGA studies indicate that compound I exhibits weight loss in two steps. The first weight loss of 52.6% observed in the temperature range of 285 – 310 °C corresponds to the loss of 1,3-bis(4-pyridyl)propane and the second more broader loss of 21.2% observed in the temperature range 490 - 720 °C corresponds to the loss of one thiosulfate unit. The total weight loss of 73.8% corresponds with the loss of the 1,3-bis(4-pyridyl)propane and one thiosulfate unit (calc. 73.9%). Compound II also exhibits one main weight loss followed by a tail. The weight loss in the narrow range of 400 – 410 °C of ~ 62.3% corresponds to the loss of the 4,4′-bipyridine. The tail end temperature range of 575 - 625 °C exhibits a weight loss of 11.4%, which corresponds to the loss of two thiosulfate moieties. The total weight loss of 73.7% corresponds to the loss of two 4,4′-bipyridine molecules and two thiosulfate units (calc. 71.8%). Compound III exhibits an initial weight loss of 4.2% in the temperature range of 30 - 110 °C, which may be due to the loss of the adsorbed and lattice water molecule. The weight loss of 54.3 % in the range 140 - 220 °C, corresponds to the loss of 1,2-bis(4-pyridyl)ethene . A broad weight loss of 14.4% between 220 - 600 °C, may be due to the loss of one thiosulfate unit. The total weight loss of 72.9% corresponds with the loss of 1,2-bis(4-pyridyl)ethene and one thiosulfate units and the lattice water molecule (calc. 75.6%). Compound IV also exhibits similar weight loss of 4.5% in the temperature range of 170 - 220 °C, which would correspond to the loss of three lattice water molecule. The weight loss of 51.1% in the temperature range of 230 – 480 °C which corresponds to the loss of three 1,2-bis(4-pyridyl)ethane. The weight loss of 19.6 % observed in the temperature range of 530 - 770 °C, corresponds to the loss of three thiosulfate unit. The total weight loss of 74.2% corresponds with the loss of three 1,2-bis(4-pyridyl)ethane and three thiosulfate units and three lattice water molecule (calc. 75.6%). In all the cases, the PXRD of the calcined products suggested that the majority of the observed lines correspond to a mixture of ZnSO4 (ICSD: 150578) and ZnO (ICSD: 182358) phases.



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The solid state diffuse reflectance UV-visible spectroscopic studies were carried at room temperature (Perkin-Elmer model Lambda 35 UV) (ESI, Fig.S7). The reflectance spectra was then converted into a absoption like spectra employing the Kubelka-Munk function. The observed absorbance peaks for the free ligands bpa, bpy, bpe, bpp and Na2S2O3 are ~307nm (4.03 eV), 305 nm (4.06 eV), 324 nm (3.82 eV), 302 nm (4.10 eV) and 290 nm (4.27 eV) respectively. The absorbance peaks for compounds were observed to be centered around ~ 264 and 397 nm (I), ~ 252 and 316 nm (II), ~ 337 and 486 nm (III) and ~ 260 and 312 nm (IV). The peaks around ~260nm (4.76 eV) could be due to the thiosulfate ion and the peaks around ~310 – 340 nm (4 – 3.64 eV) may be due to the intraligand electron transfer and the peaks around ~486 nm (2.55 eV) may be due to the charge transfer from the ligand to the metal. The observed values are similar to those observed for the cadmium thiosulfate phases.41-44 We have also carried out photoluminescence studies for the compounds I - IV along with free bpy, bpe, bpa and bpp ligands in the solid state at room temperature (ESI, Figure S8-11). The main emission peak for free bpy, bpa was centered around ~ 368 nm, for bpp ~ 385nm (λex=310nm) and for bpe ~ 397nm, when excited using 310 nm wavelength. These emissions can be attributed to π* → π or π* → n transitions. The thiosulfate compounds exhibit a red-shift of ~60nm compared to the ligands with the emission peaks centered around 437nm (I and II), 424nm (III) and 440nm (IV) when excited using a wavelength of λex=316nm. This band could be the charge transfer band from the ligand to the metal center (LMCT). Single crystal structure determination A single crystal of each compound was carefully selected under a polarizing optical microscope and glued to a thin glass fiber. The single crystal data was collected at room temperature 293(2)K on a Oxford Xcalibur (Mova) diffractometer equipped with an EOS CCD detector. The X-ray generator was operated at 50 kV and 0.8 mA using Mo Kα (λ -= 0.71073 Å) radiation. The cell refinement and data reduction were carried out using CrysAlis RED.83 The structure was solved by direct methods and refined using SHELX97 present in the WinGX suit of programs (version 1.63.04a).84 The hydrogen positions for the ligands were initially located from the difference Fourier map, and for the final refinement, they were placed in geometrically ideal positions and refined in the riding mode. The hydrogen positions for the water molecules in III, IV however, could not be located from the difference fourier maps. The full matrix least-squares refinement against |F2| was carried out using the WinGx suite of programs.85 The final refinements included atomic positions for all the atoms, anisotropic thermal parameters for all the non-hydrogen atoms, and isotropic thermal parameters for all the


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hydrogen atoms. The details of the structure solution and final refinement parameters are given in Table 2. The crystallographic data for the compounds I - IV were deposited with the Cambridge Crystallographic Data Center (CCDC). The CCDC numbers for the compounds are: I – 940249, II – 940248, III – 940250, IV 940251. Results and Discussion Structure of [Zn(S2O3)(C13H14N2)], I The asymmetric unit of I contains 21 non-hydrogen atoms, comprising of one crystallographically independent Zn(II) ion, one thiosulfate and one 1,3-bis(4-pyridyl)propane (bpp). The Zn(II) ions are tetrahedrally coordinated with one oxygen and a sulfur atom from the thiosulfate unit and two nitrogen atoms from the 1,3-bis(4-pyridyl)propane unit. The average Zn-S, Zn-O and Zn-N bond distances are 2.296, 1.981 and 2.043 Å, respectively. The S-Zn-O and N-Zn-N bond angles are 105.4(9)° and 104.0(1)° suggesting tetrahedral coordination. The thiosulfate unit has an average bond angle of 109.4°. The various bond lengths and angles observed in I are comparable to those observed for the cadmium thiosulfate compounds.41-44 Selected bond distances are listed in Table 3. The ZnN2OS and S2O3 tetrahedral units are connected through their vertices forming a simple fourmembered ring. The four-membered ring units are connected by bpp units forming a two-dimensional layer structure (Figure 1a). Two such layers are arranged in a way that they are in a direction perpendicular to each other as shown in Figure 1b. The arrangements of the layers are such that they are catenated to each other (Figure 1b). To the best of our knowledge, this is the first observation of catenated layered structure involving thiosulfate hybrids. In addition, it may be noted that the structure of I has the basic building unit, the 4membered ring, formulated to be the fundamental building unit in the tetrahedral structures of aluminosilicate and aluminophosphates.55-60 The observation of the simple 4-membered ring structure in the present compounds suggests that it may be possible to prepare compounds that are similar to the phosphates and silicates.1-6 From a topological view, if we considered the 4-membered ring as a node, then it would result in a simple 4-connected net (Figure 1c). The 4-connected nets here are catenated by two perpendicular rhombus grids as shown in Figure 1c.



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Structure of [Zn2(S2O3)2(C10H10N2)2], II The asymmetric unit of II contains 36 non-hydrogen atoms comprising of two Zn(II) ions, two thiosulfate unit and two 4,4′-bipyridine (bpy) ligands. The zinc atoms Zn(1) and Zn(2), are tetrahedrally coordinated with one oxygen and one sulfur atom from the thiosulfate units and two nitrogen atoms from the bpy ligand. The average Zn-O, Zn-S and Zn-N distances are 1.989 Å, 2.260 Å and 2.018 Å, respectively. The thiosulfate units S-S and S-O have average bond distances of 2.044 and 1.459 Å. The average bond angles surrounding Zn(1) is 107.4° and for Zn(2) it is 107.9°. The thiosulfate unit has an average angle of 109.7°. The bond angles suggest that the participating tetrahedral units are slightly distorted. The Zn(II) ion is connected with two thiosulfate units via the oxygen and sulfur atoms forming a onedimensional chain (Figure 2a). The Zinc thiosulfate chain is arranged in a helical fashion around the 21 screw axis. The 4,4′-bipyridine (bpy) units connect the chains by bonding with alternate Zn(II) ion forming a twodimensional sheet (Figure 2b). The bpy units were twisted around the central C-C bond with an average torsion angle of 26.4°. The 2D sheets are further connected by another bpy units giving rise to a three-dimensional structure with large channels (18.7 Х 15.8 Å) (atom-atom contact distance not including the vander Waals radii). (Figure 2c) The large voids in this structure are not sustainable and give rise to interpenetration. In II, we observed a three-fold interpenetration of the 3D structure (Figure 3b). From a topological perspective, II can be viewed as a diamondoid net as the participating ligands are tetrahedral in nature. The diamondoid structure is generally observed where the participating nodes are tetrahedral in nature. The diamondoid structures have been observed commonly in many metal-organic framework hybrid compounds.61-66 Here, the Zn(II) ions acts as the tetrahedral node (coordinated with two bpy and two S2O32- units). The connectivity between Zn, S2O3 and bpy gives rise to an adamentane type unit, which is common for all the diamondoid networks. (Figure 3a) The schlafli symbol is 66. The present structure appears to be the first observation of a diamond net in a thiosulfate structure. Structure of [Zn(S2O3)(C12H10N2)].H2O, III The asymmetric unit of III contains 21 non-hydrogen atoms comprising of one Zn(II) ion, one thiosulfate unit, one 1,2-bis(4-pyridyl)ethylene ligand (bpe) and one lattice water molecule. Similar to compound I and II, the Zn(II) ions are tetrahedrally coordinated with one oxygen and one sulfur atom from thiosulfate units and two nitrogen atoms from the bpe units. The various observed bond distances and angles between the participating species are in the ranges expected for this type of bonding (Table 3)


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The Zn(II) ions are bound to the thiosulfate units giving rise to one-dimensional chains, similar to that observed in II (Figure 4a). The bpe ligand connects alternate Zn centers forming a two-dimensional layer (Figure 4b). The 2D hybrid layers are further cross-linked by another bpe unit giving rise to a three-dimensional structure (ESI, Figure S19(d)) The bpe ligand in inorganic-organic hybrid structures has been subject an intense study as it provides opportunities to investigate possible photodimerization of the C=C bonds.68 Our previous studies on the use of bpe resulted in a family of cadmium thiosulfate compounds that satisfied the Schmidt’s criterion,67 and allowed us to investigate the photodimerization.44 In the present case, however, the C=C bond pairs are at a larger distance of ~ 11.4 Å, which precludes the possibility of photo-dimerisation studies in the present compound. The extra-framework water molecules occupy the one-dimensional channels of width16 Х 24 Å; (atom-atom contact distance not including the vander Waals radii). Similar to the structure of II, the large open 1D channels gave rise to three-fold interpenetration in the structure (Figure 4c). The structure of III also has the same diamondoid net (ESI, Figure S20(c)) with a schlafli symbol of 66 (Zn = tetrahedral node).

Structure of [Zn3(S2O3)3(C12H12N2)3].3H2O, IV The asymmetric unit of IV consists of 60 non-hydrogen atoms, of which three Zn, three thiosulfate unit, three 1,2-bis(4-pyridyl)ethane and three water molecule are unique. Both the Zn(II) ions are tetrahedrally coordinated with similar connectivity to that observed in I – III the compounds. The selected bond distances and angles are comparable to those observed before (Table 3).41-44 In IV, the Zn(II) ions and [S2O3]2- ions are connected to form a helical chain due to the 61 screw axis (Figure 5a). In the helical chains, two consecutive Zn atoms Zn(1) and Zn(2) are connected by bpa ligand forming a two-dimensional sheet (Figure 5b). The Zn(3) atom connects the two-dimensional sheets through the bpa ligand forming a three-dimensional structure (Figure 5c).The extra-framework water molecules occupies the one-dimensional channel. The structure also exhibits three-fold interpenetration (Figure 6a) From a topological point of view, the present structure appears to be closely related to the structure of β-quartz (qtz). Interestingly both Zn2+ and (S2O3)2- are tetrahedrally coordinated and are arranged in a hexagonal fashion similar to that observed in β–quartz (Figure 6b). The schalfli symbol of the structure, 64, 82, was also similar to that observed for qtz net.



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Structural comparison: Four new Zinc thiosulfate phases (I - IV) have been prepared by varying the length of the nitrogen containing secondary ligands. While compound I has a catenated two-dimensional arrangement, the compounds II – IV have one-dimensional Zinc thiosulfate chains cross-linked by the pyridine ligands giving rise to interpenetrated three-dimensional structures. In I, a simple 4-membered ring of Zinc thiosulfate connected by the bpp ligand. As mentioned before, the observation of a 4-membered ring in I is encouraging and may lead to the formation of newer thiosulfate structures similar to the sulfate and phosphate structures. It has been known that three important structures, viz, the diamond (dia), the SrAl2 (sra) and the quartz (qtz) net represent hybrid structures based on tetrahedral node.61-66 Presently, we have isolated the diamond net (II and III, (ESI, Figure S24(a,b)) and the quartz net (IV). In addition, it can be noted that the compositions of III and IV are the same, but a closer look at the connectivity within the structure reveal subtle differences. In III, the bpe ligand connects two zinc thiosulfate one dimensional chains through alternate Zn centers, whereas in IV, the bpa ligand connects through the Zn(3) center (Figure 5c). The difference in the connectivity is also reflected in the different net structures observed for the compounds III and IV. It is also known that the formation of tetrahedral node depends not only on the metal, but also the coordinating ability. Zn centers, normally, have octahedral coordination in many inorganic-organic hybrid structures.69-71 In the present structure, the zinc species exhibits only tetrahedral coordination, which resulted in the 4-connected net structures. Proton Conductivity: The presence of lattice water molecules in the structures of III and IV prompted us to investigate the possible proton migration in these compounds. Proton mobility is one of the important properties that is being actively investigated in the area of inorganic-organic hybrid compounds.72-79 Proton conductivity measurements on III and IV were carried out by employing AC-impedance spectroscopy studies (Alpha, Novocontrol). The samples were scanned in the frequency range of 0.1−106 Hz (signal amplitude: 0.12 V). For the studies, the samples were pelletised and placed in between the two steel electrodes at 98% relative humidity and at room temperature. Proton conductivity values of ~ 6.24 × 10-6 and 9.38 × 10-5 Ω-1cm-1 (34 °C and 98% RH) were observed for the compounds III and IV, respectively (Figure.7(i)). The proton conductivity values, though not very high, are within the ranges exhibited by many hybrid compounds.72-79 The activation energy for the proton


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migration in these compounds were found to be 0.26 eV (III) and 0.49 eV(IV). (Figure. 7(ii)) which suggest a Grotthus mechanism. Heterogeneous and photocatalytic studies: The inorganic-organic hybrid compounds generally exhibits Lewis acid behavior. During our investigations of cadmium thiosulfate hybrid compounds, we have established the Lewis acid character by the cyanosilylation studies.41 The present compounds were also explored for Lewis acidity by a simple ketal formation studies. The results of the study are summarized in Table 4. For the Lewis acid catalytic reaction, 100 mg of the catalyst (compound I - IV) was taken in a 10mL round-bottom flask along with 5mL of toluene as the solvent. 7mM of ethylene glycol and 7mM of aliphatic ketone were added to this and the reaction mixture was refluxed at 60°C for 12h. The catalyst was separated from the reaction mixture by simple filtration, washed with water and dried at amibient conditions. The spent catalytic compounds were examined using PXRD, which suggested no appreciable changes. The products were analysed using 1H NMR spectra (ESI, Figure S12-14). In all the cases, we observed near quantitative conversion of the ketones to ketals. This study confirms that the zinc thiosulfate hybrid compounds could be useful as a Lewis catalyst. The catalyst was found to be active with similar conversions for upto 4 cycles. The band gap values for these compounds were found to be ~ 3.12 eV, 3.92 eV, 3.67 eV and 3.97 eV for I, II, III and IV, respectively. The observed band gap values correspond to the bipyridine to metal energy transfer (LMCT) and slightly higher than the conventional semi-conductors such as TiO2 and ZnO.80-82 Since TiO2 and ZnO have been examined as a possible photocatalyst under the UV-light (λmax = 365 nm), we examined the present compounds for the photocatalytic decomposition of organic dyes. To this end, we have examined two cationic dyes, methylene blue (MB) and methyl violet (MV) as the model pollutants. In a typical experiment, 100ppm (MB) and 50 ppm (MV) solution of the dyes in water was taken along with the catalyst (I - IV) (2g/L). The experiemental conditions were similar to those reported earlier.42 The compounds I - IV exhibits photocatalytic activity and we observed ~ 75 % decomposition of the dyes (ESI, Fig.S15, 16). After photocatalytic studies,the compounds I - IV were examined using PXRD, which indicated that the compounds have similar PXRD with a slight reduction in the crystallinity. Repeat reactions on the same used catalysts suggest that the compounds are active with similar results.



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Conclusion Four new zinc thiosulfate based hybrid compounds have been successfully synthesized and characterized. All the compounds exhibit 3-fold interpenetration in their structures. The compounds exhibit reasonable proton mobility at room temperature, photocatalytic activity under UV-radiation and Lewis acidic character. The number of available thiosulfate based hybrid structures is limited and the present solids provide important members to this class of compounds. The present study indicates that it may be profitable to investigate other unusual anions such as dichromate, chromate etc. Work towards this theme is currently under progress. Acknowledgement SN thanks the Department of Science and Technology (DST), and Council of Scientific and Industrial Research (CSIR) Government of India, for the award of research grants. S.N. also thanks DST for a J. C. Bose National Fellowship.


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure Captions Fig. 1.

(a) Figure shows the two-dimensional layers in [Zn(S2O3)(bpp)] I (b) Figure shows the catenation in the structure (sticks represent bpp). (c) The topological view of the structure of I showing the interpenetration

Fig. 2.

(a) View of the -Zn-S2O3-Zn- 1D infinite chains in [Zn2(S2O3)2(bpy)2] II (b) Figure shows the connectivity between bpy and -Zn-S2O3-Zn- chains (c) View of the 3D structure of II

Fig.3.

(a) The connectivity showing the adamentane unit in II (b) The three-fold interpenetrated structure of II

Fig. 4. (a) The 1D infinite chains observed in [Zn(S2O3)(bpe))].H2O III (b) Figure shows the connectivity between bpe and the Zinc thiosulfate 1D chains in III (c) View of the three-dimensional structure. Note the three-fold interpenetration. The lines are the guides to the eye Fig. 5. (a) The Zinc thiosulfate 1D chains in [Zn3(S2O3)3(C12H12N2)3].3H2O IV Note the formation of helical arrangement. (b) Figure shows the connectivity between -Zn-S2O3-Zn- helical chains and the bpa ligand in IV (c) The three-dimensional view of the structure of IV Fig.6

(a) Figure shows the three-fold interpenetration in the structure of IV (b) The node and net connectivity showing the qtz structure.

Fig. 7.

Nyquist plot for the (a) compound III and (b) compound IV The Arrhenius plot for the proton conductivity studies of (c) compound III and (d) IV



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Page 20 of 31

Table 1. Synthetic conditions employed for the preparation of the compounds I -IV

S.

Composition

No 1.

1mM Zn(NO3)2 + 1mM Na2S2O3 + 1mM bpp +

Producta

Time

Temp

Yield

(h)

(°C)

72

80

[Zn(S2O3)(C13H14N2)], I

77

72

80

[Zn(S2O3)(C10H10N2)]2, II

75

72

80

[Zn(S2O3)(C12H10N2)].H2O, III

76

72

80

[Zn3(S2O3)3(C12H12N2)3].3H2O,

74

(%)

MeOH (6ml) + H2O(4ml) 2.

1mM Zn(NO3)2 + 1mM Na2S2O3 + 2 mM bpy + MeOH (6ml) + H2O(4ml)

3.

1mM Zn(NO3)2 + 1mM Na2S2O3 + 1mM bpe + MeOH (6ml) + H2O(4ml)

4.

1mM Zn(NO3)2 + 1mM Na2S2O3 + 1mM bpa + MeOH (6ml) + H2O(4ml)

IV

bpy = 4,4′-bipyridine, bpp = 1,3-bis(4-pyridyl)propane, bpe = 1,2-bis(4-pyridyl)ethene , bpa = 1,2-bis(4pyridyl)ethane a

CHN analysis for I calc (%) C 41.5%; H 3.7%; N 7.4%; Found(%): C 41.6%; H 3.7%; N 7.5%; For II calc (%) C 35.9%; H 2.4%; N 8.3%; Found(%): C 35.0%; H 2.6 %; N 8.3%; For III calc (%) C 38.3%; H 2.6%; N 7.4%; Found(%): C 37.6; H 2.5%; N 7.1%; For IV calc (%) C 38.1%; H 3.2%; N 7.4%; Found(%): C 36.9%; H 3.5%; N 6.9%; byields are calculated based on the respective metals. Compositions are given in millimoles.


Page 21 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 2. Crystallographic data and structure refinement of parameters for compound [Zn(S2O3)(C13H14N2)] I, [Zn2(S2O3)2(C10H10N2)2] II, [Zn(S2O3)(C12H10N2)].H2O III, [Zn3(S2O3)3(C12H12N2)3].3H2O IV. Structural

I

II

III

IV

parameter Empirical formula

ZnS2O3N2C13H14

Zn2S4O6N4C20H16

ZnS2O4N2C12H10

Zn3S6O12N6C36H36

Formula weight

374.65

671.43

377.77

1139.43

Crystal system

Orthorhombic

Orthorhombic

Monoclinic

Hexagonal

Space group

Pcab (no. 61)

Pbc21 (no. 29)

P21/n (no. 14)

P61

a (Å)

12.165(2)

15.7740(3)

9.260(5)

16.3547(15)

b (Å)

12.189(2)

13.1191(2)

15.959(5)

16.3547(15)

c (Å)

19.303(3)

11.9058(2)

10.379(5)

29.085(3)

α (°)

90

90

90

90

β (°)

90

90

109.375(5)

90

90

90

90

120

V (Å )

2862.2(8)

2463.79(7)

1446.9(11)

6737.4(11)

Z

8

4

4

6

T/K

293

293

293

293

ρ (calc/mgm-3)

1.683

1.976

1.725

1.704

-1

µ (mm )

2.015

2.621

2.001

2.495

λ (Mo Kα/Å)

0.71073

0.71073

0.71073

0.71073

θ range ( °)

1.67 to 28.34

2.58 to 26.00

2.39 to 27.56

1.44 to 27.57

Rint

0.0837

0.0576

0.0261

0.0823

R indexes [ I > 2σ

R1 = 0.0406

R1 = 0.0293

R1 =0.0563

R1 = 0.0571

(I)]

wR2 = 0.0955

wR2 = 0.0719

wR2 = 0.1544

wR2 = 0.1388

R indexes (all data)

R1 = 0.0758

R1 = 0.0348

R1 =0.00701

R1 = 0.0698

γ (°) 3

wR2 = 0.1080 R1 =∑ | FO| - | FC ||/∑ | FO |; wR2 = {∑ [w

wR2 = 0.0752 (FO2

2

wR2 = 0.1672 2 2

1/2

2

wR2 = 0.1446 2

- FC )]/ ∑ [w (FO ) ]} . w = 1/[ρ (FO) + (aP)2 + bP]. P = [max

(FO2, O) + 2 (FC2)/3, where a= 0.0932 and b=0.0000 for I, a= 0.1000 and b= 0.0000 for II, a= 0.1270 and b= 6.9285 for III, where a= 0.0789 b= 28.7117 for IV.



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Page 22 of 31

Table 3. Selected bond distances in Zinc thiosulfate compounds [Zn(S2O3)(C13H14N2)] I, [Zn2(S2O3)2(C10H10N2)2] II, [Zn(S2O3)(C12H10N2)].H2O III, [Zn3(S2O3)3(C12H12N2)3].3H2O IV. Bond

Distance (Å)

Bond

Distance (Å)

Bond

Distance (Å)

Zn(1)-S(1)

2.2956(11)

Zn(1)-N(2)

2.059(3)

S(2)-O(2)

1.444(3)

Zn(1)-O(1)

1.981(3)

S(1)-S(2)

2.0378(14)

S(2)-O(3)

1.433(3)

Zn(1)-N(1)

2.027(3)

S(2)-O(1)#1

1.477(3)

I

II Zn(1)-S(1)

2.2660(17)

Zn(1)-N(3)

2.048(4)

S(2)-O(3)#1

1.476(4)

Zn(2)-S(3)

2.2548(17)

Zn(2)-N(4)

2.067(4)

S(4)-O(4)#2

1.492(4)

Zn(2)-O(4)

1.981(4)

S(1)-S(2)

2.036(2)

S(4)-O(5)

1.436(3)

Zn(1)-O(3)

1.997(4)

S(3)-S(4)

2.051(2)

S(4)-O(6)

1.461(4)

Zn(1)-N(1)

2.055(4)

S(2)-O(1)

1.447(3)

Zn(2)-N(2)

2.031(4)

S(2)-O(2)

1.446(4) III

Zn(01)-S(1)

2.2936(16)

Zn(01)-N(2)

2.028(4)

S(2)-O(2)#1

1.438(4)

Zn(01)-O(2)

1.984(4)

S(1)-S(2)

2.029(2)

S(2)-O(3)

1.497(6)

Zn(01)-N(1)

2.018(4)

S(2)-O(1)

1.371(6) IV

Zn(1)-S(3)

2.274(2)

Zn(2)-N(2)#1

2.021(5)

S(1)-O(2)

1.404(7)

Zn(2)-S(2)#3

2.282(2)

Zn(2)-N(4)#2

2.027(6)

S(1)-O(3)

1.465(7)

Zn(3)-S(6)

2.284(2)

Zn(3)-N(5)

1.998(6)

S(4)-O(4)

1.345(7)

Zn(1)-O(1)

2.006(7)

Zn(3)-N(6)

2.020(5)

S(4)-O(5)

1.461(10)

Zn(2)-O(6)

2.005(7)

S(1)-S(2)

2.043(3)

S(4)-O(6)

1.411(7)

Zn(3)-O(9)#4

2.014(6)

S(3)-S(4)

2.029(3)

S(5)-O(7)

1.450(6)

Zn(1)-N(1)

2.034(6)

S(5)-S(6)

2.047(3)

S(5)-O(8)

1.467(6)

Zn(1)-N(3)

2.020(6)

S(1)-O(1)

1.454(6)

S(5)-O(9)

1.463(6)

Symmetry transformations used to generate equivalent atoms: For I: #1 -x,-y+1,-z+1; For II: #1 -x+1,-y+1,z-1/2; #2 x,-y+5/2,z+1/2; For III: #1 x-1/2,-y+3/2,z-1/2; For IV: #1 -x+y,-x,z-1/3; #2 x,y+1,z; #3 -x+y+1,-x+1,z-1/3; #4 y+1,-x+y+1,z-1/6


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Table 4. Cyclic ketal formation reactions employing for the compounds I - IV Reactant

Product

Yield (%) Blank

I

II

III

IV

Interpenetrated and Catenated Zinc Thiosulfates Frameworks with dia

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