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Sonochemical syntheses of one-dimensional silver(I) supramolecular polymer: A precursor for preparation of silver nanostructure
Inorganic Chemistry Communications 44 (2014) 1–5
Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Sonochemical syntheses of one-dimensional silver(I) supramolecular polymer: A precursor for preparation of silver nanostructure Shiva Hojaghani a, Kamran Akhbari b, Moayed Hossaini Sadr a, Ali Morsali c,⁎ a b c
Department of Chemistry, College of Basic Sciences, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran School of Chemistry, College of Science, University of Tehran, P.O. Box 14155-6455, Tehran, Islamic Republic of Iran Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14115-4838, Tehran, Islamic Republic of Iran
a r t i c l e
i n f o
Article history: Received 4 January 2014 Accepted 20 February 2014 Available online 1 March 2014 Keywords: Supramolecular polymer Nano-structure Nanosilver Sonochemical Surfactant Oleic acid
a b s t r a c t Nano-structures of one-dimensional supramolecular polymer, [Ag(Me-8-HqH)(Me-8-Hq)]n (1) [Me-8-HqH = 2-methyl-8-hydroxyquinoline], have been synthesized by the reaction of Me-8-HqH and AgNO3 by sonochemical process. The single-crystal X-ray data of compound 1 shows that both two AgI ions are chelated by two Me-8-HqH and Me-8-Hq− molecules. Coordination number of AgI ions in compound 1 is four and they have AgO2N2 coordination sphere. The AgI complexes in 1 are linked to each other via hydrogen bonding and form a supramolecular chain structure. Thermal decomposition of compound 1 nanostructure in oleic acid results in formation of silver nano-structure. These nano-structures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The thermal stability of compound 1 was studied by thermogravimetric (TG) and differential thermal analyses (DTA). © 2014 Published by Elsevier B.V.
Considerable attentions have been paid to the supramolecular polymers composed of 1D chains, 2D sheets and 3D networks due to the potential applications in separation, catalysis and as conductors, sensors and storage devices [1,2]. Much interest has been focused on the supramolecular polymeric structures constructed by coordination bonds, hydrogen bonding and aromatic π-stacking interactions [3–6]. Several different synthetic approaches have been offered for the preparation of coordination compounds [7]. Some of them are (1) slow diffusion of the reactants into a polymeric matrix, (2) diffusion from the gas phase, (3) evaporation of the solvent at ambient or reduced temperatures, (4) precipitation or recrystallisation from a mixture of solvents, (5) temperature controlled cooling and (6) hydrothermal synthesis. Nanometer-sized structures of supramolecular polymers are fascinating to explore, since their unique properties are controlled by the large number of surface molecules, which experience an entirely different environment than those in a bulk crystal. Controlling the growth of materials at the sub micrometer scale is of central importance in the emerging field of nanotechnology [8–11]. Although considerable effort has been performed to the controlled synthesis of nano-scale structures of metals, oxides, sulfides and ceramic materials, little attention was focused to date on nano-structures of supramolecular compounds. In this paper we describe a simple synthetic sonochemical preparation of AgI supramolecular polymer nano-structures. Sonochemistry is ⁎ Corresponding author. Tel./fax: +98 21 82884416. E-mail address: [email protected] (A. Morsali).
http://dx.doi.org/10.1016/j.inoche.2014.02.030 1387-7003/© 2014 Published by Elsevier B.V.
the research area in which molecules undergo a reaction due to the application of powerful ultrasound radiation (20 kHz–10 MHz) [12]. Ultrasound induces chemical or physical changes during cavitations, a phenomenon involving the formation, growth and instantaneously implosive collapse of bubbles in a liquid, which can generate local hot spots having temperatures of roughly 5000 °C, pressures of about 500 atm and a lifetime of a few microseconds [13]. These extreme conditions can drive chemical reactions, but they can also promote the formation of nano-sized structures, mostly by the instantaneous formation of a plethora of crystallization nuclei [13,14]. This has been widely used to fabricate nano-sized structures of a variety of compounds and in recent years many kinds of nano-sized materials have been prepared by this method [15–24]. This article focuses on the simple synthetic preparation of AgI supramolecular polymer nano-structures by sonochemical process. In addition, nano-structures of [Ag(Me-8-HqH)(Me-8-Hq)]n (1) [Me-8-HqH = 2-methyl-8-hydroxyquinoline] supramolecular polymer, have been used as new precursors for preparation of silver nanostructures by thermal decomposition in oleic acid. The Scheme 1 shows the reaction between silver(I) nitrate and 2-methyl-8-hydroxyquinoline by two different methods. Single crystal X-ray diffraction analyses (Tables S1 and S2) of compound 1 show that two types of AgI ions exist in this complex. Each of them is chelated by two Me-8-HqH and Me-8-Hq− molecules (Fig. 1). Fig. 1 shows the ORTEP view of both independent molecules. Thermal displacement ellipsoids are shown at 50% probability level in each independent molecule, the H atom of OH group is disordered
2
S. Hojaghani et al. / Inorganic Chemistry Communications 44 (2014) 1–5
Evaporation in MeCN solvent
AgNO3 +[(Me-8-HqH)(Me-8-Hq)]
By sonochemical process
Silver micro-structure Silver nano-structure
Single crystal of compound 1
Nano-structure of compound 1
Calcination at 673 K In OA at 453 K
Scheme 1. The produced materials from the reaction of [(Me-8-HqH)(Me-8-Hq−)], [Me-8-HqH = 2-methyl-8-hydroxyquinoline] with silver(I) nitrate by two different methods and fabrication of silver micro- and nano-structures from compound 1 nano-supramolecular polymer.
over two positions with equal occupancies. So, in each independent molecule, only one OH group presents. The second ligand is Me-8-Hq− anion. Indeed, 2-methyl-8-hydroxyquinoline acts as bidentate chelating ligand with two forms of protonated (Me-8-HqH) and deprotonated (Me-8-Hq−) ligands. The AgI ions in 1 are coordinated by two N and two O atoms of Me-8-HqH and Me-8-Hq − ligand (Fig. 1). The AgI complexes in 1 were linked to each other via hydrogen bonding to form a supramolecular chain structure along the crystallographic b axis (Table S3 and Fig. 2). Our search shows that the AgI ions in compound 1 unlike two polymorphs of [Ag(8HqH)(8-Hq)]n (α and β), (8-HqH: 8-hydroxyquinoline and 8-Hq−: 8-hydroxyquinolate) [25] do not involve in polyhapto Ag⋯C interactions with the phenyl group of neighboring [Ag(Me-8-HqH)(Me-8Hq)] units. Thus the complex could be considered to contain two types of AgI ions with AgO2N2 coordination sphere. No π–π stacking interaction exists in 1, too. Fig. 3b shows the XRD pattern of a typical sample of [Ag(Me-8HqH)(Me-8-Hq)]n (1) prepared by the sonochemical process from 0.1(Me-8-HqH):0.05(Ag+) M solutions of initial reagents under ultrasonic waves. An acceptable match, with slight differences in 2θ, was observed between the simulated pattern from single-crystal X-ray data (Fig. 3a) and the pattern from experimental data (Fig. 3b). Results of XRD powder patterns indicate that the experimental data are in good
Molecule 1
agreement with the simulated XRD powder pattern based on single crystal X-ray data, hence this compound obtained as a mono-phase. The morphology, structure and size of the two samples which were prepared by sonochemical process are investigated by a Scanning Electron Microscopy (SEM). Fig. 4 (up and down) shows the SEM images of compound 1 nano-structures prepared by sonochemical process in ultrasonic bath from the reaction of 0.05:0.1 and 0.1:0.2 M concentrations of initial reagents, respectively. As could be observed from this figure, acceptable results were obtained from this process to fabricate compound 1 nano-structure. But as it is obvious, concentration increase from 0.05:0.1 to 0.1:0.2 M of initial reagents results in agglomeration of nano-structures, thus preparation of compound 1 nanostructure from 0.05:0.1 M concentration of initial reagents is more appropriate than the 0.1:0.2 M concentration of initial reagents. Thermogravimetric (TG) and differential thermal analyses (DTA) of compound 1 nano-structure show that this compound is stable up to 98 °C (Figure S1), at which temperature decomposition of compound 1 nano-structure starts in two steps with two endothermic effects at 130 and 250 °C, respectively. In these two steps, removal of protonated (Me-8-HqH) and deprotonated (Me-8-Hq−) ligands occurs between 98 °C and 700 °C with a mass loss of 80.5% (calcd 74.82%). Mass loss calculations and XRD pattern (Fig. 3c) show that the final decomposition product is metallic silver. It should be mentioned that C. Janiak et al.
Molecule 2
Fig. 1. ORTEP view of both independent molecules. Thermal displacement ellipsoids are shown at 50% probability level in each independent molecule, The H atom of OH group is disordered over two positions with equal occupancies. So, in each independent molecule, only one OH group presents that the second ligand is anion.
S. Hojaghani et al. / Inorganic Chemistry Communications 44 (2014) 1–5
3
Fig. 2. Showing the formation of one-dimensional supramolecular structure via hydrogen bonding interaction in compound 1.
also showed that supramolecular Ag compounds can given rise to elemental silver by temperature induced [26] or light-induced [27] processes. Fig. 3c attributed to the XRD pattern of the residue obtained from calcination of compound 1 nanostructure at 673 K. The obtained pattern matches with the standard patterns of cubic silver with the lattice parameters (a = 4.0862 Å and z = 4) which are close to the reported values, (JCPDS card number 04–0783). SEM image (Fig. 5, up) of the residue obtained from the calcination of compound 1 nano-structure at 673 K shows that micro-structure of metallic silver were agglomerated to form this spongy solid. This spongy metallic silver structure has agglomerated from 0.15 to 1.0 μm size of micro-particles (with the average diameter of about 0.55 μm). Formation of this spongy solid is
Fig. 3. XRD patterns; a) simulated pattern based on single crystal data of compound 1, b) nano-structure of compound 1 prepared by sonochemical process from 0.1(Me-8HqH):0.05(Ag+) M solutions of initial reagents, c) silver micro-structure prepared by the calcination of compound 1 nanostructure and d) silver nano-structure prepared by thermal decomposition of compound 1 nanostructure in oleic acid at 453 K.
due to decomposition of Me-8-HqH ligand which accompanied with removal of resulting gas such as CO2. In order to obtain silver nanostructure from nano-structure of compound 1 and to prevent from agglomeration, oleic acid was used as a surfactant until the thermal decomposition of compound 1 occurs in the resulting micelles [28]. XRD pattern of residue (Fig. 3d), shows that the resulting residue was cubic silver with the lattice parameters mentioned above. SEM images of the resulting residue show the formation of silver nano-structure agglomerated from nano-particles having diameters between 40 and
Fig. 4. SEM images of compound 1 nano-structures prepared by sonochemical process from 0.1:0.05 M (up) and 0.2:0.1 M (down) concentrations of initial reagents.
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studies of other polymers with different metal ions are ongoing in our laboratory, which may offer new insights into metal–organic supramolecular assembly and nano-chemistry. Acknowledgments The support of this investigation by Islamic Azad University, University of Tehran, and Tarbiat Modares University is gratefully acknowledged. Appendix A. Supplementary material Complete bond lengths and angles, co-ordinates and displacement parameters have been deposited at Cambridge Crystallography Data Center. Supplementary data are available from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK on request, quoting the deposition number 935401 for compound 1. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10. 1016/j.inoche.2014.02.030. References
Fig. 5. SEM images of spongy silver micro-structure prepared by the calcination of compound 1 nano-structure at 673 K (up) and silver nano-structure prepared by OA at 453 K (down).
100 nm (with the average diameter of about 54 nm), (Fig. 5 down). Thus compound 1 nano-structures are good precursors for preparation of silver nano-structure by thermal decomposition in oleic acid. Conclusions The nano-structures of [Ag(Me-8-HqH)(Me-8-Hq)]n (1) supramolecular polymer with one-dimensional chain structure, as a result of hydrogen bonding interaction, were synthesized by sonochemical process. Concentration increase of initial reagents results in agglomeration of compound 1 nano-structure. Coordination number of AgI ions in compound 1 is four and they have AgO2N2 coordination sphere. Compound 1 is a new precursor for preparation of metallic silver. The calcination of compound 1 nano-structure, which obtained from sonochemical process, leads to formation of agglomerated silver micro-structure. Thus calcination is not an appropriate process for the preparation of silver nano-structure from compound 1. We successfully prepared silver nano-structure with the average diameter of 54 nm from the thermal decomposition of compound 1 nano-structure in oleic acid at 453 K. Indeed, thermal treatment of sonochemically synthesized nano-structure of compound 1 with oleic acid led to formation of nano-structure of metallic silver. This paper is one of the few samples using sonication as an alternative synthetic procedure to form supramolecular polymers. This method for preparation of supramolecular polymers may be had some advantages such as: it takes places in shorter reaction times, produces better yields and also it may produce the polymers at nano-size. From this perspective, further systematic
[1] B. Moulton, M.J. Zaworotko, From molecules to crystal engineering: supramolecular isomerism and polymorphism in network solids, Chem. Rev. 101 (2001) 1629–1658. [2] M. Eddaoudi, D.B. Moler, H. Li, B. Chen, T.M. Reineke, M. O'Keeffe, O.M. Yaghi, Acc. modular chemistry: secondary building units as a basis for the design of highly porous and robust metal−organic carboxylate frameworks, Acc. Chem. Res. 34 (2001) 319–330. [3] T.J. Barton, L.M. Bull, W.G. klemperer, D.A. Loy, B. McEnancy, M. Misono, P.A. Monson, G. Pez, G.W. Scherer, J.C. Vartuli, O.M. Yaghi, Tailored porous materials, Chem. Mater. 11 (1999) 2633–2656. [4] L. Pan, T. Frydel, M.B. Sander, X.-Y. Huang, J. Li, The effect of pH on the dimensionality of coordination polymers, Inorg. Chem. 40 (2001) 1271–1283. [5] J. Dai, M. Yamamoto, T. Kuroda-Sowa, M. Maekawa, Y. Suenaga, M. Munakata, Double hydrogen bond- and π–π-stacking-assembled two-dimensional copper(I) complex of 2-hydroxyquinoxaline, Inorg. Chem. 36 (1997) 2688–2690. [6] C.B. Aakeröy, N.R. Champness, C. Janiak, Recent advances in crystal engineering, CrystEngComm 12 (2010) 22–43. [7] A.K. Hall, J.M. Harrowfield, A. Morsali, A.A. Soudi, A. Yanovsky, Bonds and lone pairs in the flexible coordination sphere of lead(II), CrystEngComm 2 (2000) 82–85. [8] C. Janiak, A critical account on π–π stacking in metal complexes with aromatic nitrogen-containing ligands, J. Chem. Soc. Dalton Trans. (2000) 3885–3896. [9] K. Akhbari, A. Morsali, Silver nanofibers from the nanorods of one-dimensional organometallic coordination polymers, Cryst. Eng. Comm. 12 (2010) 3394–3396. [10] T.M. Barclay, A.W. Cordes, J.R. Mingie, R.T. Oakley, K.E. Preuss, A bis(1,2,3-dithiazole) charge transfer salt with 2: 1 stoichiometry; inhibition of association and generation of slipped -stacks, Cryst. Eng. Comm. 15 (2000) 89–91. [11] C.A. Hunter, J.K.M. Sanders, The nature of.pi–pi. interactions, J. Am. Chem. Soc. 112 (1990) 5525–5534. [12] K.S. Suslick, S.B. Choe, A.A. Cichowlas, M.W. Grinstaff, Sonochemical synthesis of amorphous iron, Nature 353 (1991) 414–416. [13] M. Martos, J. Morales, L. Sanchez, R. Ayouchi, D. Leinen, F. Martin, J.R. RamosBarrado, Electrochemical properties of lead oxide films obtained by spray pyrolysis negative electrodes for lithium secondary batteries, Electrochim. Acta 46 (2001) 2939–2948. [14] M. Sugimoto, Amorphous characteristics in spinel ferrites containing glassy oxides, J. Magn. Magn. Mater. 133 (1994) 460–462. [15] M.V. Landau, L. Vradman, M. Herskowitz, Y. Koltypin, Ultrasonically controlled deposition–precipitation: Co–Mo HDS catalysts deposited on wide-pore MCM material, J. Catal. 201 (2001) 22–36. [16] H. Wang, Y.N. Lu, J.J. Zhu, H.Y. Chen, Sonochemical fabrication and characterization of stibnite nanorods, Inorg. Chem. 42 (2003) 6404–6411. [17] J.H. Zhang, Z. Chen, Z.L. Wang, N.B. Ming, Sonochemical method for the synthesis of antimony sulfide microcrystallites with controllable morphology, J. Mater. Res. 18 (2003) 1804–1808. [18] T. Ding, J.J. Zhu, J.M. Hong, Sonochemical preparation of HgSe nanoparticles by using different reductants, Mater. Lett. 57 (2003) 4445–4449. [19] M.A. Alavi, A. Morsali, Syntheses and characterization of Sr(OH)2 and SrCO3 nanostructures by ultrasonic method, Ultrason. Sonochem. 17 (2010) 132–138. [20] A. Askarinejad, A. Morsali, Direct ultrasonic-assisted synthesis of sphere-like nanocrystals of spinel Co3O4 and Mn3O4, Ultrason. Sonochem. 16 (2009) 124–131. [21] M.A. Alavi, A. Morsali, Syntheses and characterization of Mg(OH)2 and MgO nanostructures by ultrasonic method, Ultrason. Sonochem. 17 (2010) 441–446. [22] M.J.S. Fard-Jahromi, A. Morsali, Sonochemical synthesis of nanoscale mixed-ligands lead(II) coordination polymers as precursors for preparation of Pb2(SO4)O and PbO nanoparticles; thermal, structural and X-ray powder diffraction studies, Ultrason. Sonochem. 17 (2010) 435–440. [23] A. Askarinejad, A. Morsali, Synthesis of cadmium(II) hydroxide, cadmium(II) carbonate and cadmium(II) oxide nanoparticles: investigation of intermediate products, Chem. Eng. J. 150 (2009) 569–571.
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Contents lists available at ScienceDirect
Inorganic Chemistry Communications journal homepage: www.elsevier.com/locate/inoche
Sonochemical syntheses of one-dimensional silver(I) supramolecular polymer: A precursor for preparation of silver nanostructure Shiva Hojaghani a, Kamran Akhbari b, Moayed Hossaini Sadr a, Ali Morsali c,⁎ a b c
Department of Chemistry, College of Basic Sciences, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran School of Chemistry, College of Science, University of Tehran, P.O. Box 14155-6455, Tehran, Islamic Republic of Iran Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14115-4838, Tehran, Islamic Republic of Iran
a r t i c l e
i n f o
Article history: Received 4 January 2014 Accepted 20 February 2014 Available online 1 March 2014 Keywords: Supramolecular polymer Nano-structure Nanosilver Sonochemical Surfactant Oleic acid
a b s t r a c t Nano-structures of one-dimensional supramolecular polymer, [Ag(Me-8-HqH)(Me-8-Hq)]n (1) [Me-8-HqH = 2-methyl-8-hydroxyquinoline], have been synthesized by the reaction of Me-8-HqH and AgNO3 by sonochemical process. The single-crystal X-ray data of compound 1 shows that both two AgI ions are chelated by two Me-8-HqH and Me-8-Hq− molecules. Coordination number of AgI ions in compound 1 is four and they have AgO2N2 coordination sphere. The AgI complexes in 1 are linked to each other via hydrogen bonding and form a supramolecular chain structure. Thermal decomposition of compound 1 nanostructure in oleic acid results in formation of silver nano-structure. These nano-structures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The thermal stability of compound 1 was studied by thermogravimetric (TG) and differential thermal analyses (DTA). © 2014 Published by Elsevier B.V.
Considerable attentions have been paid to the supramolecular polymers composed of 1D chains, 2D sheets and 3D networks due to the potential applications in separation, catalysis and as conductors, sensors and storage devices [1,2]. Much interest has been focused on the supramolecular polymeric structures constructed by coordination bonds, hydrogen bonding and aromatic π-stacking interactions [3–6]. Several different synthetic approaches have been offered for the preparation of coordination compounds [7]. Some of them are (1) slow diffusion of the reactants into a polymeric matrix, (2) diffusion from the gas phase, (3) evaporation of the solvent at ambient or reduced temperatures, (4) precipitation or recrystallisation from a mixture of solvents, (5) temperature controlled cooling and (6) hydrothermal synthesis. Nanometer-sized structures of supramolecular polymers are fascinating to explore, since their unique properties are controlled by the large number of surface molecules, which experience an entirely different environment than those in a bulk crystal. Controlling the growth of materials at the sub micrometer scale is of central importance in the emerging field of nanotechnology [8–11]. Although considerable effort has been performed to the controlled synthesis of nano-scale structures of metals, oxides, sulfides and ceramic materials, little attention was focused to date on nano-structures of supramolecular compounds. In this paper we describe a simple synthetic sonochemical preparation of AgI supramolecular polymer nano-structures. Sonochemistry is ⁎ Corresponding author. Tel./fax: +98 21 82884416. E-mail address: [email protected] (A. Morsali).
http://dx.doi.org/10.1016/j.inoche.2014.02.030 1387-7003/© 2014 Published by Elsevier B.V.
the research area in which molecules undergo a reaction due to the application of powerful ultrasound radiation (20 kHz–10 MHz) [12]. Ultrasound induces chemical or physical changes during cavitations, a phenomenon involving the formation, growth and instantaneously implosive collapse of bubbles in a liquid, which can generate local hot spots having temperatures of roughly 5000 °C, pressures of about 500 atm and a lifetime of a few microseconds [13]. These extreme conditions can drive chemical reactions, but they can also promote the formation of nano-sized structures, mostly by the instantaneous formation of a plethora of crystallization nuclei [13,14]. This has been widely used to fabricate nano-sized structures of a variety of compounds and in recent years many kinds of nano-sized materials have been prepared by this method [15–24]. This article focuses on the simple synthetic preparation of AgI supramolecular polymer nano-structures by sonochemical process. In addition, nano-structures of [Ag(Me-8-HqH)(Me-8-Hq)]n (1) [Me-8-HqH = 2-methyl-8-hydroxyquinoline] supramolecular polymer, have been used as new precursors for preparation of silver nanostructures by thermal decomposition in oleic acid. The Scheme 1 shows the reaction between silver(I) nitrate and 2-methyl-8-hydroxyquinoline by two different methods. Single crystal X-ray diffraction analyses (Tables S1 and S2) of compound 1 show that two types of AgI ions exist in this complex. Each of them is chelated by two Me-8-HqH and Me-8-Hq− molecules (Fig. 1). Fig. 1 shows the ORTEP view of both independent molecules. Thermal displacement ellipsoids are shown at 50% probability level in each independent molecule, the H atom of OH group is disordered
2
S. Hojaghani et al. / Inorganic Chemistry Communications 44 (2014) 1–5
Evaporation in MeCN solvent
AgNO3 +[(Me-8-HqH)(Me-8-Hq)]
By sonochemical process
Silver micro-structure Silver nano-structure
Single crystal of compound 1
Nano-structure of compound 1
Calcination at 673 K In OA at 453 K
Scheme 1. The produced materials from the reaction of [(Me-8-HqH)(Me-8-Hq−)], [Me-8-HqH = 2-methyl-8-hydroxyquinoline] with silver(I) nitrate by two different methods and fabrication of silver micro- and nano-structures from compound 1 nano-supramolecular polymer.
over two positions with equal occupancies. So, in each independent molecule, only one OH group presents. The second ligand is Me-8-Hq− anion. Indeed, 2-methyl-8-hydroxyquinoline acts as bidentate chelating ligand with two forms of protonated (Me-8-HqH) and deprotonated (Me-8-Hq−) ligands. The AgI ions in 1 are coordinated by two N and two O atoms of Me-8-HqH and Me-8-Hq − ligand (Fig. 1). The AgI complexes in 1 were linked to each other via hydrogen bonding to form a supramolecular chain structure along the crystallographic b axis (Table S3 and Fig. 2). Our search shows that the AgI ions in compound 1 unlike two polymorphs of [Ag(8HqH)(8-Hq)]n (α and β), (8-HqH: 8-hydroxyquinoline and 8-Hq−: 8-hydroxyquinolate) [25] do not involve in polyhapto Ag⋯C interactions with the phenyl group of neighboring [Ag(Me-8-HqH)(Me-8Hq)] units. Thus the complex could be considered to contain two types of AgI ions with AgO2N2 coordination sphere. No π–π stacking interaction exists in 1, too. Fig. 3b shows the XRD pattern of a typical sample of [Ag(Me-8HqH)(Me-8-Hq)]n (1) prepared by the sonochemical process from 0.1(Me-8-HqH):0.05(Ag+) M solutions of initial reagents under ultrasonic waves. An acceptable match, with slight differences in 2θ, was observed between the simulated pattern from single-crystal X-ray data (Fig. 3a) and the pattern from experimental data (Fig. 3b). Results of XRD powder patterns indicate that the experimental data are in good
Molecule 1
agreement with the simulated XRD powder pattern based on single crystal X-ray data, hence this compound obtained as a mono-phase. The morphology, structure and size of the two samples which were prepared by sonochemical process are investigated by a Scanning Electron Microscopy (SEM). Fig. 4 (up and down) shows the SEM images of compound 1 nano-structures prepared by sonochemical process in ultrasonic bath from the reaction of 0.05:0.1 and 0.1:0.2 M concentrations of initial reagents, respectively. As could be observed from this figure, acceptable results were obtained from this process to fabricate compound 1 nano-structure. But as it is obvious, concentration increase from 0.05:0.1 to 0.1:0.2 M of initial reagents results in agglomeration of nano-structures, thus preparation of compound 1 nanostructure from 0.05:0.1 M concentration of initial reagents is more appropriate than the 0.1:0.2 M concentration of initial reagents. Thermogravimetric (TG) and differential thermal analyses (DTA) of compound 1 nano-structure show that this compound is stable up to 98 °C (Figure S1), at which temperature decomposition of compound 1 nano-structure starts in two steps with two endothermic effects at 130 and 250 °C, respectively. In these two steps, removal of protonated (Me-8-HqH) and deprotonated (Me-8-Hq−) ligands occurs between 98 °C and 700 °C with a mass loss of 80.5% (calcd 74.82%). Mass loss calculations and XRD pattern (Fig. 3c) show that the final decomposition product is metallic silver. It should be mentioned that C. Janiak et al.
Molecule 2
Fig. 1. ORTEP view of both independent molecules. Thermal displacement ellipsoids are shown at 50% probability level in each independent molecule, The H atom of OH group is disordered over two positions with equal occupancies. So, in each independent molecule, only one OH group presents that the second ligand is anion.
S. Hojaghani et al. / Inorganic Chemistry Communications 44 (2014) 1–5
3
Fig. 2. Showing the formation of one-dimensional supramolecular structure via hydrogen bonding interaction in compound 1.
also showed that supramolecular Ag compounds can given rise to elemental silver by temperature induced [26] or light-induced [27] processes. Fig. 3c attributed to the XRD pattern of the residue obtained from calcination of compound 1 nanostructure at 673 K. The obtained pattern matches with the standard patterns of cubic silver with the lattice parameters (a = 4.0862 Å and z = 4) which are close to the reported values, (JCPDS card number 04–0783). SEM image (Fig. 5, up) of the residue obtained from the calcination of compound 1 nano-structure at 673 K shows that micro-structure of metallic silver were agglomerated to form this spongy solid. This spongy metallic silver structure has agglomerated from 0.15 to 1.0 μm size of micro-particles (with the average diameter of about 0.55 μm). Formation of this spongy solid is
Fig. 3. XRD patterns; a) simulated pattern based on single crystal data of compound 1, b) nano-structure of compound 1 prepared by sonochemical process from 0.1(Me-8HqH):0.05(Ag+) M solutions of initial reagents, c) silver micro-structure prepared by the calcination of compound 1 nanostructure and d) silver nano-structure prepared by thermal decomposition of compound 1 nanostructure in oleic acid at 453 K.
due to decomposition of Me-8-HqH ligand which accompanied with removal of resulting gas such as CO2. In order to obtain silver nanostructure from nano-structure of compound 1 and to prevent from agglomeration, oleic acid was used as a surfactant until the thermal decomposition of compound 1 occurs in the resulting micelles [28]. XRD pattern of residue (Fig. 3d), shows that the resulting residue was cubic silver with the lattice parameters mentioned above. SEM images of the resulting residue show the formation of silver nano-structure agglomerated from nano-particles having diameters between 40 and
Fig. 4. SEM images of compound 1 nano-structures prepared by sonochemical process from 0.1:0.05 M (up) and 0.2:0.1 M (down) concentrations of initial reagents.
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studies of other polymers with different metal ions are ongoing in our laboratory, which may offer new insights into metal–organic supramolecular assembly and nano-chemistry. Acknowledgments The support of this investigation by Islamic Azad University, University of Tehran, and Tarbiat Modares University is gratefully acknowledged. Appendix A. Supplementary material Complete bond lengths and angles, co-ordinates and displacement parameters have been deposited at Cambridge Crystallography Data Center. Supplementary data are available from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK on request, quoting the deposition number 935401 for compound 1. Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10. 1016/j.inoche.2014.02.030. References
Fig. 5. SEM images of spongy silver micro-structure prepared by the calcination of compound 1 nano-structure at 673 K (up) and silver nano-structure prepared by OA at 453 K (down).
100 nm (with the average diameter of about 54 nm), (Fig. 5 down). Thus compound 1 nano-structures are good precursors for preparation of silver nano-structure by thermal decomposition in oleic acid. Conclusions The nano-structures of [Ag(Me-8-HqH)(Me-8-Hq)]n (1) supramolecular polymer with one-dimensional chain structure, as a result of hydrogen bonding interaction, were synthesized by sonochemical process. Concentration increase of initial reagents results in agglomeration of compound 1 nano-structure. Coordination number of AgI ions in compound 1 is four and they have AgO2N2 coordination sphere. Compound 1 is a new precursor for preparation of metallic silver. The calcination of compound 1 nano-structure, which obtained from sonochemical process, leads to formation of agglomerated silver micro-structure. Thus calcination is not an appropriate process for the preparation of silver nano-structure from compound 1. We successfully prepared silver nano-structure with the average diameter of 54 nm from the thermal decomposition of compound 1 nano-structure in oleic acid at 453 K. Indeed, thermal treatment of sonochemically synthesized nano-structure of compound 1 with oleic acid led to formation of nano-structure of metallic silver. This paper is one of the few samples using sonication as an alternative synthetic procedure to form supramolecular polymers. This method for preparation of supramolecular polymers may be had some advantages such as: it takes places in shorter reaction times, produces better yields and also it may produce the polymers at nano-size. From this perspective, further systematic
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