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New layered functionalized titanium(IV) phenylphosphonates
Journal of Physics and Chemistry of Solids 73 (2012) 1452–1455
Contents lists available at SciVerse ScienceDirect
Journal of Physics and Chemistry of Solids journal homepage: www.elsevier.com/locate/jpcs
New layered functionalized titanium(IV) phenylphosphonates K. Mela´nova´ a,n, J. Klevcov b, L. Beneˇs c, J. Svoboda a, V. Zima a a b c
´ Square 2, 162 06 Prague 6, Czech Republic Institute of Macromolecular Chemistry of Academy of Sciences of the Czech Republic, v.v.i., Heyrovsky ´snohorske´ 2069, Dvu ´love´ nad Labem, Czech Republic ˚r Kra High School of Informatics and Services, Eliˇsky Kra ´ 95, 532 10 Pardubice, Czech Republic University of Pardubice, Faculty of Chemical Technology, Studentska
a r t i c l e i n f o
a b s t r a c t
Available online 25 November 2011
New functionalized layered titanium phenylphosphonates were prepared by reactions of titanium(IV) tetraisopropoxide with corresponding phosphonic acids (phenylphosphonic, 4-carboxyphenylphosphonic, 4-sulfamoylphenylphosphonic, 1,4-benzenediphosphonic and 4-sulfophenylphosphonic acid) and subsequent hydrothermal or solvothermal treatments at 180 1C for 60 h. The compounds prepared were characterized by EDX, elemental analysis, TGA and powder X-ray diffraction. The ability of the compounds prepared to intercalate basic compounds was tested using aliphatic amines and diamines. & 2011 Elsevier Ltd. All rights reserved.
Keywords: B. Chemical synthesis C. Thermogravimetric analysis (TGA) C. X-ray diffraction
1. Introduction Metal phosphonates are a class of hybrid inorganic–organic compounds in which the metal coordinates to phosphonate functional group. Modulation of their organic parts can be done to create required structures or to obtain specific properties. Most stable organophosponates are those of tetravalent metals, especially zirconium phosphonates, which were the most thoroughly investigated [1]. Less attention has been paid to titanium phosphonates. First information about titanium phenylphosphonate was given in the papers of DiGiacomo [2,3]. The influence of the way of the preparation on textural properties of titanium phenylphosphonate was studied [4]. Various mixed titanium phosphate–phenylphosphonates were prepared and their intercalation properties and also electrical conductivity were studied [5,6]. Titanium phosphate–sulfophenylphosphonates were prepared either by sulfonation of titanium phenylphosphonate [7] or by reaction of TiCl4 with a mixture of phosphoric acid and 3-sulphophenylphosphonic acid [8] and their proton conductivity was studied in detail. Intercalation of alkylamines into titanium phenylphosphonate was studied using calorimetrical titration [9,10]. In this paper, we report on the preparation and characterization of new 4-functionalized titanium phenylphosphonates.
2. Experimental All starting chemicals were obtained from commercial sources and were used without further purification. 4-substituted n
Corresponding author. E-mail address: [email protected] (K. Mela´nova´).
0022-3697/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jpcs.2011.11.016
phenylphosphonic acids were prepared as has been described previously [11–13]. 2.1. Preparation of Ti(C6H5PO3)2 (TiPhP) A solution of 0.4 g of phenylphosphonic acid in 20 ml of isopropanol was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. A white gel was immediately formed, which was separated by centrifugation and dried at room temperature. To obtain the crystalline product, this dried gel and 9 ml of water were placed in a Teflon-lined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with water/ethanol (1/1 v/v) mixture and dried in air at room temperature (relative humidity RH¼33%). The yield was 88%. The P/Ti atomic ratio was 2, according to the energy-dispersive X-ray microanalysis (EDX). Anal. Calcd. for C12H10TiO6P2 (360.04): 40.03% C, 2.80% H; found 39.87% C, 2.31% H. 2.2. Preparation of Ti(HOOCC6H4PO3)2 0.5H2O (TiCPhP) A solution of 0.54 g of 4-carboxyphenylphosphonic acid monohydrate in 50 ml of hot water was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. A white gel was immediately formed, which was separated by centrifugation and dried at room temperature. This dried gel and 9 ml of water were placed in a Teflon-lined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with water/ethanol (1/1 v/v) mixture and dried in air at room temperature (RH¼33%). The yield was 67%. The P/Ti atomic ratio was 2, according to EDX. The water content was determined by thermogravimetry (see
´nova ´ et al. / Journal of Physics and Chemistry of Solids 73 (2012) 1452–1455 K. Mela
Table 1 Basal spacings of the compounds prepared and their weight losses during their thermal decomposition. Compound
TiPhP TiCPhP TiNSPhP TiSPhP TiSPhP–PhP TiPPhP
Weight loss (%) found (calc.)
Basal spacing
First step
Total
˚ (A)
o1.0(0) 2.0(2.0) 2.0(1.7) 6.5(6.5) 11.0(11.1) 5.9(6.0)
40.0(38.4) 50.5(51.5) 59.1(57.9) 58.3(60.1) 52.2(54.4) 27.0(26.0)
15.02 18.52 19.72 20.15 19.85 9.50
Table 1). Anal. Calcd. for C14H10TiO10P2 0.5H2O (457.06): 36.79% C, 2.43% H; found 36.15% C, 2.38% H.
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2.6. Preparation of Ti(HO3SC6H4PO3)0.9(C6H5PO3)1.1 3H2O (TiSPhP– PhP) A mixture of 0.2 g of phenylphosphonic acid and 5.46 ml of 0.225 M solution of 4-sulfophenylphosphonic acid in 40 ml of isopropanol was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. A white gel was immediately formed, which was separated by centrifugation and dried at room temperature. This dried gel and 9 ml of 1-hexanol were placed in a Teflon-lined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with isopropanol and dried in air at room temperature (RH¼33%). The yield was 80%. The P/Ti atomic ratio was 2.02, P/S ratio was 2.22, according to EDX. The water content was determined by thermogravimetry (see Table 1). Anal. Calcd. for C12H10O8.7S0.9P2Ti 3H2O (486.14) 29.65% C, 3.32% H, 5.94% S; found 30.21% C, 3.58% H, 6.07% S.
2.3. Preparation of Ti(NH2SO2C6H4PO3)2 0.5H2O (TiNSPhP) A solution of 0.64 g of 4-sulfamoylphenylphosphonic acid in 10 ml water and 40 ml of isopropanol was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. A colorless gel was slowly formed, which was separated by centrifugation and dried at room temperature. To obtain crystalline product, this dried gel and 9 ml of water were placed in a Teflon-lined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with water/ethanol (1/1 v/v) mixture and dried in air at room temperature (RH¼33%). The yield was 86%. The P/Ti atomic ratio was 2.1, P/S ratio was 0.97, according to EDX. The water content was determined by thermogravimetry (see Table 1). Anal. Calcd. for C12H12N2O10S2P2Ti 0.5H2O (527.20): 27.34% C, 2.49% H 5.31% N, 12.17% S; found 28.06% C, 2.81% H, 5.52% N, 12.06% S. 2.4. Preparation of Ti(O3PC6H4PO3) H2O (TiPPhP). A solution of 0.293 g of 1,4-benzenediphosphonic acid in 5 ml of water and 40 ml of isopropanol was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. The colloidal solution formed was evaporated in a rotary evaporator to dryness and together with 9 ml of water were placed in a Teflonlined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with water/ethanol (1/1 v/v) mixture and dried in air at room temperature (RH¼33%). The yield was 75%. The P/Ti atomic ratio was 2.03, according to EDX. The water content was determined by thermogravimetry (see Table 1). Anal. Calcd. for C6H4TiO6P2 H2O (299.94) 24.03% C, 2.02% H; found 23.32% C, 1.96% H. 2.5. Preparation of Ti(HO3SC6H4PO3)2 2H2O (TiSPhP) 10.92 ml of 0.225 M solution of 4-sulfophenylphosphonic acid and 40 ml of isopropanol was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. No gel was formed. The solution was evaporated in a rotary evaporator to dryness and together with 9 ml of 1-hexanol was placed in a Teflon-lined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with isopropanol and dried in air at room temperature (RH¼33%). The yield was 67%. The P/Ti atomic ratio was 1.95, P/S ratio was 1.0, according to EDX. The water content was determined by thermogravimetry (see Table 1). Anal. Calcd. for C12H10O12S2P2Ti 2H2O (556.19) 25.91% C, 2.54% H, 11.53% S; found 25.36% C, 2.67% H, 11.27% S.
2.7. Reactions of TiCPhP, TiSPhP and TiSPhP–PhP with sodium hydroxide The reactions were carried out at room temperature using a computer-controlled Schott Titronic 97 piston burette. Using the burette, 0.096 M aqueous NaOH was added to a host suspended in water–ethanol mixture. The pH of the solution during the reaction was measured with a glass pH electrode. 2.8. Reactions of TiCPhP, TiSPhP and TiSPhP–PhP with hexylamine The reactions were done under the same experimental arrangement but using a 0.0503 M hexylamine solution in ethanol. 2.9. Instrumentation The titanium, phosphorus and sulfur contents were determined by an electron scanning microscope JEOL JSM-5500LV and energy-dispersive X-ray microanalyser IXRF Systems (detector GRESHAM Sirius 10). The accelerating voltage of the primary electron beam was 20 kV. The thermogravimetric measurements were carried out in air between 30 and 960 1C at a heating rate of 5 1C min 1. Powder X-ray diffraction data were obtained with a D8-Advance diffractometer (Bruker AXS, Germany) with Bragg– Brentano y–y geometry (40 kV, 30 mA) using CuKa radiation with secondary graphite monochromator. The diffraction angles were measured at room temperature from 21 to 501 (2y) in 0.0251 steps with a counting time of 4 s per step.
3. Results and discussion White or colorless gels are formed by the reaction of titanium tetraisopropoxide with phenylphosphonic, 4-carboxyphenylphosphonic, 4-sulfamoylphenylphosphonic and 1,4-benzenediphosphonic acids. Hydrothermal treatment is necessary to obtain crystalline solids. In the case of 4-sulphophenylphosphonic acid, no gel was formed and the crystalline product was obtained by solvothermal treatment in 1-hexanol. Diffractograms of the phenylphosphonates prepared contain series of basal reflections from which the basal spacings given in Table 1 were calculated. Except titanium phenylphosphonate, all substituted phenylphosphonates contain interlayer water molecules. They lose weight in two steps on heating. In the first step from 50 to 230 1C, the interlayer water is released. In the second one, a decomposition of the phenylphosphonate anion occurs. The end product of the thermal decomposition is titanium diphosphate TiP2O7 (JCPDS No. 04-012-4504) [14]. The found and calculated weight losses
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´nova ´ et al. / Journal of Physics and Chemistry of Solids 73 (2012) 1452–1455 K. Mela
are given in Table 1. The amount of interlayer water for substituted titanium phenylphosphonates depends on the relative humidity of the atmosphere. As an example, the dependences of the basal spacing and water content x for TiSPhP and TiSPhP–PhP on the relative humidity are shown in Fig. 1. Samples were stored over solutions with defined RH for one week before the TG and XRD measurements and were covered with a protecting foil during the XRD measurement to avoid spontaneous dehydration. The basal spacing of TiSPhP changes only little from 20.15 at 11% RH to 21 A˚ at 98% RH whereas the water content increases from two to nearly four at 98% RH. On the other hand, TiSPhP–PhP is able to uptake about 8.5 water molecules per formula unit at 98% RH, which is accompanied with a large increase of the basal spacing from 19.8 A˚ ˚ to 25.5 A. The ability of the compounds containing acidic groups (TiCPhP, TiSPhP, TiSPhP–PhP) to interact with basic compounds was tested by their titration with sodium hydroxide and hexylamine solutions. The titration curves are shown in Figs. 2 and 3. In the case of TiSPhP–PhP, all sulfonic groups are neutralized either with sodium hydroxide (with the Na/S ratio of 0.9, as found by EDX) or with hexylamine. On the other hand, only a part of the sulfonic groups is neutralized when TiSPhP is titrated with sodium hydroxide and hexylamine solutions giving products with formulas Ti(C6H4PO3SO3)2H0.6Na1.4 xH2O (based on the Na/S ratio equal to 0.7 found by EDX) and Ti(C6H4PO3SO3H)2 0.86 (C6H13NH2) xH2O, respectively. This phenomenon, that is the lower amounts of the intercalated species than those corresponding to the theoretical amounts in the case of TiSPhP, was also observed on titration of g-Ti(HPO4)2 2H2O with amines [15]. It was explained by steric hindrances in the interlayer space, in which the acidic groups are too close to each other to allow neutralization of all of them. In our case this explanation is supported by the fact that in the case of TiSPhP–PhP the acidic groups are not so closely packed and all of them are neutralized. It is questionable whether this explanation can be applied also for the titration of TiSPhP with NaOH. During this titration the basal spacing decreases from 20.15 A˚ found for TiSPhP to 19.4 A˚ for Ti(C6H4PO3SO3)2H0.6Na1.4. Perhaps this decrease of the basal spacing prevents the movement of the sodium atoms in the interlayer space and thus stops further neutralization of the sulfonic groups. The intercalates of hexylamine have the basal spacings of 31.4 and 32.6 A˚ for TiSPhP–PhP and TiSPhP, respectively. As the basal
Fig. 2. Titration of 4-substituted phenylphosphonates with NaOH.
Fig. 3. Titration of 4-substituted phenylphosphonates with hexylamine.
Fig. 1. Dependence of the basal spacing and water content x on the relative humidity of the atmosphere (RH) for TiSPhP (squares) and TiSPhP–PhP (circles).
spacings of the hexylamine intercalates are about 12 A˚ higher than those of the pure hosts and the length of the hexylamine ˚ we suppose that the hexylamine molemolecule is about 9.2 A, cules are arranged in a bilayer way. In the case of TiCPhP, only a quarter of the carboxy groups was neutralized by sodium hydroxide (confirmed by Na/P ratio of 0.4 found by EDX) and no reaction was observed in the case of the hexylamine solution. Intercalations of butylamine and 1,12-diaminododecane were done by shaking the solid TiSPhP–PhP and TiSPhP with an eightfold excess of the guest in an ethanol solution at room temperature. The TiSPhP intercalates are stable at ambient condition. The butylamine intercalate has the basal spacing of 28.95 A˚ and contains about 0.6 butylamine per formula unit as follows from thermogravimetry (see Fig. 4). The 1,12-diaminododecane intercalate has the basal spacing of 32.4 A˚ and contains about 0.4 diamine per formula unit. In contrast to the TiSPhP intercalates, the TiSPhP–PhP intercalates are not stable (see Fig. 4); during washing and drying their basal spacings decrease (from 28.5 to 19.9 A˚ and from 32.08 to 24.95 A˚ for the butylamine and diaminododecane intercalates, respectively) probably due to a loss of the intercalated
´nova ´ et al. / Journal of Physics and Chemistry of Solids 73 (2012) 1452–1455 K. Mela
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Acknowledgment This work was supported by the Czech Science Foundation (Grant no. 203/08/0208). J. Klevcov participated in the work in the frame of the ’’Open Science II’’ project.
Appendix A. Supplementary Information Supplementary data associated with this article can be found in the online version at doi:10.1016/j.jpcs.2011.11.016.
References
Fig. 4. Diffractograms of the TiSPhP intercalate with butylamine and the TiSPhP– PhP intercalate with 1,12-diaminododecane: (a) as prepared with excess of the guest and (b) washed and dried.
guest and/or water. Similar instability of the amine intercalates was observed for the intercalates of mixed zirconium sulfophenyl– phenylphosphonate [16]. Other amines and diamines can be also intercalated into both TiSPhP and TiSPhP–PhP. A more thorough study of these intercalations is now under way.
[1] G. Alberti, in: J.L. Atwood, J.E. Davies, D.D. MacNicol, F. V¨ogtle (Eds.), Comprehensive Supramolecular Chemistry, 7, Pergamon Press, Oxford, 1996, pp. 151–187. [2] M.B. Dines, P.M. DiGiacomo, Inorg. Chem. 20 (1981) 92–97. [3] P.M. DiGiacomo, Patent Europe no. 00 10 857 (1982). [4] A.A. Anillo, M.A. Villa-Garcıa, R. Llavona, M. Suarez, J. Rodriguez, Mater. Res. Bull. 34 (1999) 627–640. [5] E. Jaimez, A. Bortun, G.B. Hix, J.R. Garcia, J. Rodriguez, R.C.T. Slade, J. Chem. Soc. Dalton Trans. (1996) 2285–2292. [6] E. Jaimez, A.I. Bortun, S.G. Khainakov, I.I. Voitko, J.R. Garcia, J. Rodriguez, J. Mater. Res. 13 (1998) 323–328. [7] E.W. Stein, A. Clearfield, M.A. Subramanian, Solid State Ionics 83 (1996) 113–124. [8] G. Alberti, U. Costantino, M. Casciola, S. Ferroni, L. Massinelli, P. Staiti, Solid State Ionics 145 (2001) 249–255. [9] V.S.O. Ruiz, C. Airoldi, J. Therm. Anal. Calorim. 71 (2003) 459–465. [10] V.S.O. Ruiz, S.L.P. Dias, Y. Gushikem, R.E. Bruns, C. Airoldi, J. Solid State Chem. 177 (2004) 675–680. [11] V. Zima, J. Svoboda, K. Mela´nova´, L. Beneˇs, M. Casciola, M. Sganappa, J. Brus, M. Trchova´, Solid State Ionics 181 (2010) 705–713. [12] G.O. Doak, L.D. Freedman, J. Am. Chem. Soc. 73 (1951) 5658–5660. [13] P. Tavs, Chem. Ber. 103 (1970) 2428–2436. [14] Joint Committee on Powder Diffraction Standards, International Centre of Diffraction Data, Swarthmore, PA. [15] U. Costantino, J. Inorg. Nucl. Chem. 43 (1981) 1895–1902. [16] L. Beneˇs, K. Mela´nova´, J. Svoboda, V. Zima, E-MRS Spring Meeting, Symposium T: Advanced hybrid materials: stakes and concepts, June 7–11, 2010, Strasbourg, France. Program T, P112, /http://www.emrs-strasbourg.com/ files/USB%2010/symposium_t.pdfS.
Contents lists available at SciVerse ScienceDirect
Journal of Physics and Chemistry of Solids journal homepage: www.elsevier.com/locate/jpcs
New layered functionalized titanium(IV) phenylphosphonates K. Mela´nova´ a,n, J. Klevcov b, L. Beneˇs c, J. Svoboda a, V. Zima a a b c
´ Square 2, 162 06 Prague 6, Czech Republic Institute of Macromolecular Chemistry of Academy of Sciences of the Czech Republic, v.v.i., Heyrovsky ´snohorske´ 2069, Dvu ´love´ nad Labem, Czech Republic ˚r Kra High School of Informatics and Services, Eliˇsky Kra ´ 95, 532 10 Pardubice, Czech Republic University of Pardubice, Faculty of Chemical Technology, Studentska
a r t i c l e i n f o
a b s t r a c t
Available online 25 November 2011
New functionalized layered titanium phenylphosphonates were prepared by reactions of titanium(IV) tetraisopropoxide with corresponding phosphonic acids (phenylphosphonic, 4-carboxyphenylphosphonic, 4-sulfamoylphenylphosphonic, 1,4-benzenediphosphonic and 4-sulfophenylphosphonic acid) and subsequent hydrothermal or solvothermal treatments at 180 1C for 60 h. The compounds prepared were characterized by EDX, elemental analysis, TGA and powder X-ray diffraction. The ability of the compounds prepared to intercalate basic compounds was tested using aliphatic amines and diamines. & 2011 Elsevier Ltd. All rights reserved.
Keywords: B. Chemical synthesis C. Thermogravimetric analysis (TGA) C. X-ray diffraction
1. Introduction Metal phosphonates are a class of hybrid inorganic–organic compounds in which the metal coordinates to phosphonate functional group. Modulation of their organic parts can be done to create required structures or to obtain specific properties. Most stable organophosponates are those of tetravalent metals, especially zirconium phosphonates, which were the most thoroughly investigated [1]. Less attention has been paid to titanium phosphonates. First information about titanium phenylphosphonate was given in the papers of DiGiacomo [2,3]. The influence of the way of the preparation on textural properties of titanium phenylphosphonate was studied [4]. Various mixed titanium phosphate–phenylphosphonates were prepared and their intercalation properties and also electrical conductivity were studied [5,6]. Titanium phosphate–sulfophenylphosphonates were prepared either by sulfonation of titanium phenylphosphonate [7] or by reaction of TiCl4 with a mixture of phosphoric acid and 3-sulphophenylphosphonic acid [8] and their proton conductivity was studied in detail. Intercalation of alkylamines into titanium phenylphosphonate was studied using calorimetrical titration [9,10]. In this paper, we report on the preparation and characterization of new 4-functionalized titanium phenylphosphonates.
2. Experimental All starting chemicals were obtained from commercial sources and were used without further purification. 4-substituted n
Corresponding author. E-mail address: [email protected] (K. Mela´nova´).
0022-3697/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jpcs.2011.11.016
phenylphosphonic acids were prepared as has been described previously [11–13]. 2.1. Preparation of Ti(C6H5PO3)2 (TiPhP) A solution of 0.4 g of phenylphosphonic acid in 20 ml of isopropanol was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. A white gel was immediately formed, which was separated by centrifugation and dried at room temperature. To obtain the crystalline product, this dried gel and 9 ml of water were placed in a Teflon-lined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with water/ethanol (1/1 v/v) mixture and dried in air at room temperature (relative humidity RH¼33%). The yield was 88%. The P/Ti atomic ratio was 2, according to the energy-dispersive X-ray microanalysis (EDX). Anal. Calcd. for C12H10TiO6P2 (360.04): 40.03% C, 2.80% H; found 39.87% C, 2.31% H. 2.2. Preparation of Ti(HOOCC6H4PO3)2 0.5H2O (TiCPhP) A solution of 0.54 g of 4-carboxyphenylphosphonic acid monohydrate in 50 ml of hot water was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. A white gel was immediately formed, which was separated by centrifugation and dried at room temperature. This dried gel and 9 ml of water were placed in a Teflon-lined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with water/ethanol (1/1 v/v) mixture and dried in air at room temperature (RH¼33%). The yield was 67%. The P/Ti atomic ratio was 2, according to EDX. The water content was determined by thermogravimetry (see
´nova ´ et al. / Journal of Physics and Chemistry of Solids 73 (2012) 1452–1455 K. Mela
Table 1 Basal spacings of the compounds prepared and their weight losses during their thermal decomposition. Compound
TiPhP TiCPhP TiNSPhP TiSPhP TiSPhP–PhP TiPPhP
Weight loss (%) found (calc.)
Basal spacing
First step
Total
˚ (A)
o1.0(0) 2.0(2.0) 2.0(1.7) 6.5(6.5) 11.0(11.1) 5.9(6.0)
40.0(38.4) 50.5(51.5) 59.1(57.9) 58.3(60.1) 52.2(54.4) 27.0(26.0)
15.02 18.52 19.72 20.15 19.85 9.50
Table 1). Anal. Calcd. for C14H10TiO10P2 0.5H2O (457.06): 36.79% C, 2.43% H; found 36.15% C, 2.38% H.
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2.6. Preparation of Ti(HO3SC6H4PO3)0.9(C6H5PO3)1.1 3H2O (TiSPhP– PhP) A mixture of 0.2 g of phenylphosphonic acid and 5.46 ml of 0.225 M solution of 4-sulfophenylphosphonic acid in 40 ml of isopropanol was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. A white gel was immediately formed, which was separated by centrifugation and dried at room temperature. This dried gel and 9 ml of 1-hexanol were placed in a Teflon-lined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with isopropanol and dried in air at room temperature (RH¼33%). The yield was 80%. The P/Ti atomic ratio was 2.02, P/S ratio was 2.22, according to EDX. The water content was determined by thermogravimetry (see Table 1). Anal. Calcd. for C12H10O8.7S0.9P2Ti 3H2O (486.14) 29.65% C, 3.32% H, 5.94% S; found 30.21% C, 3.58% H, 6.07% S.
2.3. Preparation of Ti(NH2SO2C6H4PO3)2 0.5H2O (TiNSPhP) A solution of 0.64 g of 4-sulfamoylphenylphosphonic acid in 10 ml water and 40 ml of isopropanol was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. A colorless gel was slowly formed, which was separated by centrifugation and dried at room temperature. To obtain crystalline product, this dried gel and 9 ml of water were placed in a Teflon-lined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with water/ethanol (1/1 v/v) mixture and dried in air at room temperature (RH¼33%). The yield was 86%. The P/Ti atomic ratio was 2.1, P/S ratio was 0.97, according to EDX. The water content was determined by thermogravimetry (see Table 1). Anal. Calcd. for C12H12N2O10S2P2Ti 0.5H2O (527.20): 27.34% C, 2.49% H 5.31% N, 12.17% S; found 28.06% C, 2.81% H, 5.52% N, 12.06% S. 2.4. Preparation of Ti(O3PC6H4PO3) H2O (TiPPhP). A solution of 0.293 g of 1,4-benzenediphosphonic acid in 5 ml of water and 40 ml of isopropanol was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. The colloidal solution formed was evaporated in a rotary evaporator to dryness and together with 9 ml of water were placed in a Teflonlined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with water/ethanol (1/1 v/v) mixture and dried in air at room temperature (RH¼33%). The yield was 75%. The P/Ti atomic ratio was 2.03, according to EDX. The water content was determined by thermogravimetry (see Table 1). Anal. Calcd. for C6H4TiO6P2 H2O (299.94) 24.03% C, 2.02% H; found 23.32% C, 1.96% H. 2.5. Preparation of Ti(HO3SC6H4PO3)2 2H2O (TiSPhP) 10.92 ml of 0.225 M solution of 4-sulfophenylphosphonic acid and 40 ml of isopropanol was added to 10 ml of 0.123 M solution of titanium tetraisopropoxide in isopropanol. No gel was formed. The solution was evaporated in a rotary evaporator to dryness and together with 9 ml of 1-hexanol was placed in a Teflon-lined 23 ml Parr acid digestion bomb and heated under autogenous pressure at 180 1C for 20 h. After cooling, the product was separated by filtration, washed with isopropanol and dried in air at room temperature (RH¼33%). The yield was 67%. The P/Ti atomic ratio was 1.95, P/S ratio was 1.0, according to EDX. The water content was determined by thermogravimetry (see Table 1). Anal. Calcd. for C12H10O12S2P2Ti 2H2O (556.19) 25.91% C, 2.54% H, 11.53% S; found 25.36% C, 2.67% H, 11.27% S.
2.7. Reactions of TiCPhP, TiSPhP and TiSPhP–PhP with sodium hydroxide The reactions were carried out at room temperature using a computer-controlled Schott Titronic 97 piston burette. Using the burette, 0.096 M aqueous NaOH was added to a host suspended in water–ethanol mixture. The pH of the solution during the reaction was measured with a glass pH electrode. 2.8. Reactions of TiCPhP, TiSPhP and TiSPhP–PhP with hexylamine The reactions were done under the same experimental arrangement but using a 0.0503 M hexylamine solution in ethanol. 2.9. Instrumentation The titanium, phosphorus and sulfur contents were determined by an electron scanning microscope JEOL JSM-5500LV and energy-dispersive X-ray microanalyser IXRF Systems (detector GRESHAM Sirius 10). The accelerating voltage of the primary electron beam was 20 kV. The thermogravimetric measurements were carried out in air between 30 and 960 1C at a heating rate of 5 1C min 1. Powder X-ray diffraction data were obtained with a D8-Advance diffractometer (Bruker AXS, Germany) with Bragg– Brentano y–y geometry (40 kV, 30 mA) using CuKa radiation with secondary graphite monochromator. The diffraction angles were measured at room temperature from 21 to 501 (2y) in 0.0251 steps with a counting time of 4 s per step.
3. Results and discussion White or colorless gels are formed by the reaction of titanium tetraisopropoxide with phenylphosphonic, 4-carboxyphenylphosphonic, 4-sulfamoylphenylphosphonic and 1,4-benzenediphosphonic acids. Hydrothermal treatment is necessary to obtain crystalline solids. In the case of 4-sulphophenylphosphonic acid, no gel was formed and the crystalline product was obtained by solvothermal treatment in 1-hexanol. Diffractograms of the phenylphosphonates prepared contain series of basal reflections from which the basal spacings given in Table 1 were calculated. Except titanium phenylphosphonate, all substituted phenylphosphonates contain interlayer water molecules. They lose weight in two steps on heating. In the first step from 50 to 230 1C, the interlayer water is released. In the second one, a decomposition of the phenylphosphonate anion occurs. The end product of the thermal decomposition is titanium diphosphate TiP2O7 (JCPDS No. 04-012-4504) [14]. The found and calculated weight losses
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are given in Table 1. The amount of interlayer water for substituted titanium phenylphosphonates depends on the relative humidity of the atmosphere. As an example, the dependences of the basal spacing and water content x for TiSPhP and TiSPhP–PhP on the relative humidity are shown in Fig. 1. Samples were stored over solutions with defined RH for one week before the TG and XRD measurements and were covered with a protecting foil during the XRD measurement to avoid spontaneous dehydration. The basal spacing of TiSPhP changes only little from 20.15 at 11% RH to 21 A˚ at 98% RH whereas the water content increases from two to nearly four at 98% RH. On the other hand, TiSPhP–PhP is able to uptake about 8.5 water molecules per formula unit at 98% RH, which is accompanied with a large increase of the basal spacing from 19.8 A˚ ˚ to 25.5 A. The ability of the compounds containing acidic groups (TiCPhP, TiSPhP, TiSPhP–PhP) to interact with basic compounds was tested by their titration with sodium hydroxide and hexylamine solutions. The titration curves are shown in Figs. 2 and 3. In the case of TiSPhP–PhP, all sulfonic groups are neutralized either with sodium hydroxide (with the Na/S ratio of 0.9, as found by EDX) or with hexylamine. On the other hand, only a part of the sulfonic groups is neutralized when TiSPhP is titrated with sodium hydroxide and hexylamine solutions giving products with formulas Ti(C6H4PO3SO3)2H0.6Na1.4 xH2O (based on the Na/S ratio equal to 0.7 found by EDX) and Ti(C6H4PO3SO3H)2 0.86 (C6H13NH2) xH2O, respectively. This phenomenon, that is the lower amounts of the intercalated species than those corresponding to the theoretical amounts in the case of TiSPhP, was also observed on titration of g-Ti(HPO4)2 2H2O with amines [15]. It was explained by steric hindrances in the interlayer space, in which the acidic groups are too close to each other to allow neutralization of all of them. In our case this explanation is supported by the fact that in the case of TiSPhP–PhP the acidic groups are not so closely packed and all of them are neutralized. It is questionable whether this explanation can be applied also for the titration of TiSPhP with NaOH. During this titration the basal spacing decreases from 20.15 A˚ found for TiSPhP to 19.4 A˚ for Ti(C6H4PO3SO3)2H0.6Na1.4. Perhaps this decrease of the basal spacing prevents the movement of the sodium atoms in the interlayer space and thus stops further neutralization of the sulfonic groups. The intercalates of hexylamine have the basal spacings of 31.4 and 32.6 A˚ for TiSPhP–PhP and TiSPhP, respectively. As the basal
Fig. 2. Titration of 4-substituted phenylphosphonates with NaOH.
Fig. 3. Titration of 4-substituted phenylphosphonates with hexylamine.
Fig. 1. Dependence of the basal spacing and water content x on the relative humidity of the atmosphere (RH) for TiSPhP (squares) and TiSPhP–PhP (circles).
spacings of the hexylamine intercalates are about 12 A˚ higher than those of the pure hosts and the length of the hexylamine ˚ we suppose that the hexylamine molemolecule is about 9.2 A, cules are arranged in a bilayer way. In the case of TiCPhP, only a quarter of the carboxy groups was neutralized by sodium hydroxide (confirmed by Na/P ratio of 0.4 found by EDX) and no reaction was observed in the case of the hexylamine solution. Intercalations of butylamine and 1,12-diaminododecane were done by shaking the solid TiSPhP–PhP and TiSPhP with an eightfold excess of the guest in an ethanol solution at room temperature. The TiSPhP intercalates are stable at ambient condition. The butylamine intercalate has the basal spacing of 28.95 A˚ and contains about 0.6 butylamine per formula unit as follows from thermogravimetry (see Fig. 4). The 1,12-diaminododecane intercalate has the basal spacing of 32.4 A˚ and contains about 0.4 diamine per formula unit. In contrast to the TiSPhP intercalates, the TiSPhP–PhP intercalates are not stable (see Fig. 4); during washing and drying their basal spacings decrease (from 28.5 to 19.9 A˚ and from 32.08 to 24.95 A˚ for the butylamine and diaminododecane intercalates, respectively) probably due to a loss of the intercalated
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Acknowledgment This work was supported by the Czech Science Foundation (Grant no. 203/08/0208). J. Klevcov participated in the work in the frame of the ’’Open Science II’’ project.
Appendix A. Supplementary Information Supplementary data associated with this article can be found in the online version at doi:10.1016/j.jpcs.2011.11.016.
References
Fig. 4. Diffractograms of the TiSPhP intercalate with butylamine and the TiSPhP– PhP intercalate with 1,12-diaminododecane: (a) as prepared with excess of the guest and (b) washed and dried.
guest and/or water. Similar instability of the amine intercalates was observed for the intercalates of mixed zirconium sulfophenyl– phenylphosphonate [16]. Other amines and diamines can be also intercalated into both TiSPhP and TiSPhP–PhP. A more thorough study of these intercalations is now under way.
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