DOI: 10.1021/cg9009288
Large Single Crystals of Isomorphous Hexaaquametal(II) D-Camphor10-sulfonates
2010, Vol. 10 559–563
)
Dejan A. Jeremic,*,†,X Goran N. Kalu{erovic,*,‡ Santiago G omez-Ruiz,§ Ilija Brceski,† Becko Kasalica, and Vukadin M. Leovac^ †
Faculty of Chemistry, University of Belgrade, Studentski trg 16, P.O. Box 158, 11000 Belgrade, Serbia, Department of Chemistry, Institute of Chemistry, Technology and Metallurgy, University of Belgrade, anica y Analitica, ESCET, Studentski trg 14, 11000 Belgrade, Serbia, §Departamento de Quı´mica Inorg Universidad Rey Juan Carlos, 28933 M ostoles, Madrid, Spain, Faculty of Physics, University of ^ Belgrade, Studentski trg 12, Serbia, and Department of Chemistry, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovi ca 3, 21000 Novi Sad, Serbia )
‡
Received August 6, 2009; Revised Manuscript Received November 16, 2009
ABSTRACT: Novel hexaaquametal(II) bis(D-camphor-10-sulfonates) with Mn(II), Fe(II), and Co(II) ions were synthesized as large single crystals. During the crystallization process, suitable metal wires were used to induce crystallization. Crystals were analyzed by means of X-ray analysis, IR spectrophotometry, and solid state UV-vis spectroscopy. The obtained substances are stable in air, and their UV-vis spectra imply their potential use as optical filters and optical materials.
Introduction Nature is unique in designing the most beautiful, as well the largest, crystals. However, the formation of natural big crystals takes a very long time, usually more than a hundred thousand years. The largest natural crystals, found in Mexico in “Cueva de los Cristales”, are of up to 11 m in length and are formed of gypsum.1 With the aim of accelerating the process of crystal growth, a search for a simple model system in which this phenomenon could be followed directly has been commenced. The simple salts of camphorsulfonic anion with transition metal ions have been poorly investigated, particularly their hexaaqua complexes. In addition, it is well-known that the ion of camphorsulfonic acid is neutral from a physiological point of view.2,3 This suggests that stoichiometrically defined compounds of D-camphor-10-sulfonic acid may be used in human and veterinary medicine4 as a source of the corresponding metal ions, as well in agriculture as microfertilizers. Sometimes for a facile crystallization of compounds, it is necessary to start the synthetic reaction with larger counteranions. In this sense, the anion of camphorsulfonic acid is more beneficial from the commercial point of view than PF6h, BF4h, or (C6H5)4Bh. In late 1930s, the camphorsulfonate of calcium was obtained in solution and its potential application in human and veterinary medicine was implied.4 Later, camphorsulfonates of complex compounds, which were used for the separation of racemic mixtures, were greatly described in the literature; however, in that period, literature data concerning simple salts of camphorsulfonic acid could not be evidenced. In the late 1970s, the first crystal structure of the simple 7 D-camphor-10-sulfonate of copper was established. In addition, to the best of our knowledge, only the crystal structures of Cu(II), Ni(II), Cd(II), Zn(II), Mg(II), and Ca(II) camphorsulfonates have hitherto been determined.5-10 However, data concerning the crystal size and other physical properties, *To whom correspondence should be addressed. X E-mail:
[email protected]. r 2009 American Chemical Society
which could imply their potential usage, are scanty in the literature, except in the cases of magnesium and calcium.5,6 There is a lot of published scientific work on growing and creating large crystals, some of them very inspiring11-13 with the beauty and possible use of the compounds. The aim of this work was to obtain a cheap source of transition metal ions of high solubility in organic solvents with a relatively large and poorly reactive anion. As the D-camphor-10-sulfonic acid satisfies all the mentioned parameters, a series of its crystalline salts were prepared. In general, transition metal compounds exhibit characteristic optical spectra that reflect their specific electron configuration and coordination environment. Since the single crystals of the investigated compounds grew to a size that could be expressed in centimeters, they qualify as potential optical materials. The “new” facile synthetic method applied in this study enabled hexaaquametal(II) camphorsulfonates of high purity to be obtained. Results and Discussion Currently, we are investigating the design of crystals composed of substances that contain interchangeable bivalent cations, M(II) ions, with the aim of developing crystals of quality and size large enough to be useful as optical materials. The crystals that were used for UV-vis spectral investigation in this study were crystallized by placing a metal wire into the solution (Figure 1). Namely, the wire was placed so that one-third of its length was above the solution to allow for heat transfer, thus causing a slight temperature difference between the solution and the site of crystallization, “zone cooling”. The application of other crystallization techniques did not result in sufficiently big crystals. The other methods of crystallization afforded small crystals which were randomly distributed. The employment of a glass vessel yielded crystals of better optical quality than those obtained using a Teflon vessel. The crystals collected in the first “harvest” were the largest, the most beautiful, and the optically purest. This indicates that the Published on Web 12/22/2009
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Figure 1. Some of the crystals of the Mn, Fe, and Co complexes (from left to right) used in the UV-vis spectral study. Figure 3. UV-vis spectra of D-camphor-10-sulfonic-acid (HCSA), and the Fe, Co, and Mn metal complexes.
Figure 2. IR spectra of D-camphor-10-sulfonic acid (HCSA) and the Fe complex.
concentration of impurities in the solution was greater after removal of the first-obtained crystals. An interesting and also important observation is that the “shelf-life” of the newly synthesized hexaaquairon(II) bis(D-camphor-10-sulfonate) complex was longer than those of other commercial organosoluble and water-soluble sources of iron(II). Thus, the very good solubility of the Mn(II), Fe(II), and Co(II) salts in water, as well as in polar organic solvents (methanol, acetone, and acetonitrile), suggests the potential use of these compounds in synthetic reactions. IR Spectroscopy. The IR spectra of all the synthesized compounds were almost identical, without visible differences, and as an example, the spectrum of Fe is given in the upper diagram of Figure 2. The IR spectra of the metal complexes show a strong band belonging to coordinated water molecules (3416 cm-1 vs). This band does not exist in the IR spectrum of the pure acid (lower diagram of Figure 2). The SO3- group by the presence of two bands in the IR spectrum (1168 cm-1 vs; 1045 cm-1 vs) was confirmed as the SO3H group and gives only one band (1039 cm-1 vs). No significant changes were found in the band positions of the aliphatic alkyl groups (CH-, CH2-, CH3-, 2958 cm-1 w) and of the CdO (1734 cm-1 m) groups. UV-vis Spectra. Comparing the absorption spectra of the Mn, Fe, and Co crystals, characteristic bands can be seen. The splitting of the 3d levels in the crystal field of the coordination compound, which are degenerate in free transition metals ions, results in electronic transitions between these levels. The energy of these transitions lies in the UV-vis range of the electromagnetic spectra, giving characteristic bands in the absorption spectra. For a detailed interpretation of absorption spectra, it is necessary to use the method of K€ onig-Kremer diagrams, which is described elsewhere.14
Figure 4. Crystal structure of the Mn complex. Hydrogen atoms are not labeled for clarity. Ellipsoids are set at the 50% probability level.
The absorption spectra of the Co and Mn complexes show an intensive band in the UV range at 228 nm, but this band does not appear in the spectrum of the Fe complex (Figure 3). It is well-known that the electronic transition in this wavelength region does not arise from d-d transitions but from charge-transfer transitions from the ligand to metal and vice versa. A possible explanation for the absence of a maximum at 228 nm in the Fe complex could be found in spectrochemical series of transition metals which represent the relative splitting caused by the various metals (Mn2þ < Co2þ ≈ Ni2þ < Fe2þ < Cr2þ < V2þ ≈ Cu2þ). As can be seen in the UV-vis spectra, a transparency range is well defined for specific wavelengths and sharply separated from the nontransparent ranges. The UV-vis transparent range starts from 317 nm, and the maximum transparency is at 340 nm. Thus, it may be possible that the title compounds could be employed as optical-filter materials, considering their good spectral characteristics, since the crystals are obtainable in dimensions of up to a few centimeters. Crystal Structure Description of the Hexaaquametal(II) D-Camphor-10-sulfonate Complexes. The hexaaquametal(II)
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Table 1. Selected Bond Lengths (A˚) and Bond Angles (deg) in the Fe, Co, and Mn Complexes
Table 2. Hydrogen Bonds in the Mn Complex
Fe M-O9 M-O10 M-O11 M-O12 M-O13 M-O14 S1-O1/S2-O5 S1-O2/S2-O6 S1-O3/S2-O7 S1-C10/S2-C20 O4-C3/O8-C13 O9-M-O10 O11-M-O12 O13-M-O14 O9-M-O11 O10-M-O13 O10-M-O14 O1-S1-O2/ O5-S2-O6 O1-S1-O3/ O5-S2-O7 O2-S1-O3/ O6-S2-O7
2.118(2) 2.135(2) 2.124(2) 2.129(2) 2.092(1) 2.081(1) 1.456(2)/ 1.458(2) 1.455(2)/ 1.450(2) 1.457(2)/ 1.461(2) 1.774(2)/ 1.768(2) 1.202(3)/ 1.195(3) 178.67(9) 179.3(1) 178.42(6) 96.60(6) 93.04(8) 87.78(8) 112.4(1)/ 113.0(1) 112.2(9)/ 112.5(1) 113.0(1)/ 111.91(8)
Co 2.271(3) 2.226(3) 1.969(1) 1.956(1) 2.000(2) 2.011(3) 1.457(2)/ 1.450(2) 1.461(2)/ 1.461(2) 1.458(2)/ 1.462(2) 1.768(2)/ 1.778(2) 1.196(4)/ 1.211(3) 178.3(1) 179.3(1) 179.9(1) 90.3(1) 90.5(1) 82.7(1) 112.5(1)/ 112.8(1) 111.8(1)/ 112.2(1) 112.9(1)/ 112.4(1)
Mn 2.171(2) 2.161(2) 2.160(2) 2.173(2) 2.141(1) 2.125(1) 1.456(2)/1.456(2) 1.454(2)/1.457(1) 1.458(1)/1.457(2) 1.771(2)/1.771(2) 1.201(2)/1.208(2) 178.18(7) 178.95(7) 177.43(6) 85.43(8) 89.47(7) 89.02(7) 111.90(7)/ 112.92(9) 112.64(9)/ 112.33(8) 112.74(9)/ 112.44(9)
salts of D-camphor-10-sulfonic acid are isomorphous. As these structures crystallized in the chiral space group P21, determination of their absolute structure was successfully realized, as was demonstrated by the low values of the Flack parameter15,16 for all the structures, which were -0.005(14), -0.070(14), and -0.002(12) for the Fe, Co, and Mn complexes, respectively. The metal complexes had unit cells with dimensions and volumes that differed at most by 46 A˚3 (3%). The Fe, Co, and Mn complexes had a similar crystal packing in addition to molecular structure. The lattice of the title compounds consists of [M(H2O)6]2þ cations [M = Fe(II), Co(II), and Mn(II)] and two crystallographically independent D-camphor-sulfonate anions (Figure 4). The cations were essentially octahedral, with M;O distances ranging from 2.081(1) to 2.135(2) A˚ (Fe), 1.95(1) to 2.271(3) (Co), and 2.125(1) to 2.173(2) (Mn), and O;M;O angles between 82.7(1) and 96.63(6) (Fe), 82.7(1) and 97.33(7) (Co), and 83.10(8) and 95.89(6) (Mn) (Table 1). The two independent D-camphor-10 sulfonate anions showed only small differences in bond parameters. No coordination of either the sulfonate or the ketone O atoms of the anions was observed. The five-membered rings were found to be in an envelope conformation (on C1/C11 atoms) and the sixmembered ring was found to be very similar to a boat conformation in both D-camphor-10 sulfonate anions.17 The packing in these solids was dominated by hydrogen bonding between the D-camphor-10-sulfonate anions and water molecules coordinated to the metal(II) ions, resulting in sheet formation (Table 2). The sheets, with an ABA sequence (A = D-camphor-10 sulfonate anion; B = hexaaquametal(II) ion), were joined to each other by weak C-H 3 3 3 O hydrogen bonds in between the anions.18,19 As in the lattices of the related Mg(II), Ni(II), Cu(II), Zn(II), and Cd(II) compounds,5-9 the water sphere and the O atoms of the sulfonate groups were involved in a complex hydrogen-bonding network (Table 2, Figure 5). In contrast to the structure of the Zn(II) complex,10 in which it was found that
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D-H (A˚) H 3 3 3 A (A˚) D 3 3 3 A (A˚) D-H 3 3 3 A (deg) 0.88(2) 1.96(2) 2.820(3) 166(2) O9-H91 3 3 3 O3 2.824(3) 173(2) O9-H92 3 3 3 O5iv 0.86(2) 1.97(2) O10-H101 3 3 3 O1 0.84(2) 1.92(2) 2.749(3) 169(3) O10-H102 3 3 3 O6 0.84(2) 1.95(2) 2.788(3) 171(2) O11-H111 3 3 3 O2 0.84(2) 1.95(2) 2.786(3) 174(2) ii 2.787(3) 166(2) O11-H112 3 3 3 O6 0.90(2) 1.91(2) iii 2.779(3) 164(2) O12-H121 3 3 3 O7 0.85(2) 1.96(2) 2.824(3) 169(2) O12-H122 3 3 3 O3v 0.83(2) 2.00(2) O13-H131 3 3 3 O5 0.84(2) 1.97(2) 2.743(3) 153(2) ii 2.720(3) 166(2) O13-H132 3 3 3 O7 0.85(2) 1.89(2) 2.712(3) 164(2) O14-H141 3 3 3 O1iii 0.85(2) 1.89(2) 2.698(3) 152(2) O14-H142 3 3 3 O2v 0.86(2) 1.92(2) C10-H10B 3 3 3 O4 0.99 2.33 2.845(3) 111 i 2.56 3.542(3) 170 C16-H16A 3 3 3 O8 0.99 C17-H17B 3 3 3 O5 0.99 2.52 3.218(3) 128 C19-H19A 3 3 3 O7 0.98 2.51 3.254(3) 133 parametera
iii
a i = 1 - x, -1/2 þ y, 2 - z; ii = x, -1 þ y, z; iii = -x, -1/2 þ y, 1 - z; iv = 1 - x, -1/2 þ y, 1 - z; v = -x, 1/2 þ y, 1 - z.
two water H atoms do not form hydrogen bonds, in the structures described here and in related M(II) complexes, all the water H atoms participate in hydrogen bonds. Conclusions The synthesized and characterized compounds of D-camphor-10-sulfonic acid represent the expected aqua-complexes of the metal ions in which the camphor-sulfonate anion was found to be in the outer sphere. These complexes crystallize as large monoclinic plates. The characterization was based on X-ray diffraction analysis. It was shown that IR spectroscopy was not reliable, due to the very similar spectra of these compounds. The solid state UV-vis spectra of some of the investigated compounds gave very sharp and characteristic shoulders and peaks, which could lead to potential practical use of these compounds because they were stable under ambient conditions. As a final conclusion, “Beauty of Simplicity” in the developed method and designed crystals is emphasized. Experimental Section Synthesis of Hexaaquairon(II) Bis(D-camphor-10-sulfonate), FeComplex. D-Camphor-10-sulfonic acid monohydrate (70 g, 0.30 mol) was dissolved in approximately 150 mL of deionized water. Iron chips (20 g, 0.36 mol) were added, and the solution was refluxed for 48 h. The solution was filtered off, and a new iron rod (3 mm diameter, 100 mm long) was added as a crystallization center. The solution was allowed to cool down in a refrigerator over 2 weeks. The obtained monoclinic crystals, up to 2 cm in dimensions, were pale bluish-green (usual iron(II) color), transparent in visible light, and suitable for X-ray analysis. The UV-vis transparent range starts from 317 nm and was very sharp (the maximum transparency was at 340 nm). Synthesis of Hexaaquacobalt(II) Bis(D-camphor-10-sulfonate), Co-Complex. D-Camphor-10-sulfonic acid monohydrate (25.00 g, 0.11 mol) was dissolved in 80 mL of deionized water. Basic cobaltous carbonate (2 g) was added, and the solution was stirred at room temperature until almost all the cobaltous salt had dissolved. The solution was filtered off on a B€ uchner funnel. The clear solution was heated in a water bath, and a bent cobalt wire (4 mm diameter, 100 mm long) was added as a crystallization center. The solution was allowed to cool very slowly in a large water bath for about 3 days in a steady place. The obtained orange monocrystals were up to 3 cm in length and were transparent in visible light. Crystals of a suitable size for X-ray analysis were also present. UV-vis maximums: 229, 363, 717 nm.
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Figure 5. View of the crystal packing (normal to the [010] plane) and the hydrogen bonding for the Mn complex. Synthesis of Hexaaquamanganese(II) Bis(D-camphor-10-sulfonate), Mn-Complex. D-Camphor-10-sulfonic acid monohydrate (25 g, 0.11 mol) was dissolved in 80 mL of deionized water. Freshly prepared manganese carbonate (2 g) was added, and the solution was stirred at room temperature until almost all the manganese salt had dissolved. The solution was filtered off on a B€ uchner funnel. The clear solution was heated in a water bath, and a titanium or platinum wire (both metals showed the same properties as crystallization surfaces) (0.5 mm diameter, 80 mm long) was added as a crystallization center. The solution was allowed to cool slowly in a large water bath for about 3 days in a steady place. The obtained pale-pink monocrystals were up to 3.5 cm in length and were transparent in visible light. Crystals of a suitable size and quality for X-ray analysis were also present. UV-vis max: 226 nm. Physical Measurements. UV-vis spectra of solid samples were recorded on a double beam Specord M40 instrument (Carl Zeis, Jena), in the range 200-900 nm. Digitalization was performed using a Graph digitizer 2.0. The IR spectra were recorded on a Nicolet 6700 FT-IR instrument (Thermo Scientific) using the KBr technique, in the range 4000-480 cm-1. X-ray Crystallography of the Fe, Co, and Mn Complexes. The data of Fe, Co, and Mn complexes were collected with a CCD Oxford Xcalibur S (λ(Mo KR) = 0.71073 A˚) using the multiscan mode. Semiempirical absorption corrections from equivalents were carried
Table 3. Crystallographic Data and Refinement Information for Fe, Co, and Mn Metal Complexes formula formula weight crystal system space group crystal color a (A˚) b (A˚) c (A˚) β (deg) V (A˚3) Z Dcalc (g/cm3) no. of reflns μ (mm-1) R wR2 Flack parameter
Fe
Co
Mn
C20H42FeO14S2 626.51 monoclinic P21 pale bluish-green 11.6413(3) 7.1057(2) 17.1401(4) 94.084(2) 1414.22(6) 2 1.471 33485 0.71073 0.0329 0.0729 -0.005(14)
C20H42CoO14S2 629.59 monoclinic P21 orange 11.6550(3) 7.0138(3) 17.0735(7) 94.122(3) 1392.08(9) 2 1.502 13923 0.71073 0.035 0.0764 -0.070(14)
C20H42MnO14S2 625.6 monoclinic P21 very pale pink 11.733(5) 7.104(5) 17.281(5) 93.315(5) 1438.0(13) 2 1.445 36860 0.71073 0.0264 0.0645 -0.002(12)
out with SCALE3 ABSPACK.20 The structure was solved with direct methods.21 Structure refinement was performed with SHELXL-97.22 All non-hydrogen atoms were refined anisotropically. Table 3 lists the
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crystallographic details. The hydrogen atoms were refined isotropically. They were placed in calculated positions with fixed displacement parameters (Riding model), except for the hydrogen atoms attached to oxygen atoms, which were found in the electron density map and refined freely. The ORTEP-3 program was used for the presentation of the structure.23 Crystallographic data for the structural analyses of the Co, Fe, and Mn complexes are deposited with the Cambridge Crystallographic Data Centre, CCDC-743184, CCDC-743185, and CCDC743186. Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (Fax: þ44-1223-336033. E-mail:
[email protected] or http//www.ccdc.cam.ac.uk).
Acknowledgment. The authors are grateful to the Ministry of Science and Technological Development of the Republic of Serbia for financial support (Project No. 142062). Note Added after ASAP Publication. This paper was published on the Web on December 22, 2009 with an error to Figure 3’s caption. The corrected version was reposted on December 28, 2009.
References (1) Garcı´ a-Ruiz, J. M.; Villasuso, R.; Ayora, C.; Canals, A.; Otalora, F. Geology 2007, 35, 327–330. (2) Baldacci, U. Arch. Farmacol. Sper. Sci. Affin. 1938, 65, 102–4. (3) Sinha, H. K. Indian J. Pharm. 1940, 2, 114–6. (4) Fantoni, C. R. Ateneo Parmense 1940, 12, 40–2. (5) Jeremic, D.; Kalu{erovic, G. N.; Brceski, I.; G omez-Ruiz, S.; Andelkovic, K. K. Acta Crystallogr. 2008, E64, m952.
563
(6) Jeremic, D.; Kalu{erovic, G. N.; Brceski, I.; G omez-Ruiz, S.; Andelkovic, K. K. Acta Crystallogr.,C 2009, 65, m143–5. (7) Couldwell, C.; Prout, K.; Robey, D.; Taylor, R. Acta Crystallogr., B 1978, 34, 1491–9. (8) Henderson, W.; Nicholson, B. K. Acta Crystallogr., C 1995, 51, 37– 40. (9) Zhou, J.-S.; Cai, J.-W.; Ng, S. W. Acta Crystallogr., E 2003, 59, o1185–6. (10) Schepke, M.; Edelmann, F. T.; Blaurock, S. Acta Crystallogr., E 2007, 63, m2071. (11) Zhang, G.; Qin, J.; Liu, T.; Zhu, T.; Fu, P.; Wu, Y.; Chen, C. Cryst. Growth Des. 2008, 8, 2946–9. (12) Kishore Kumar, T.; Janarthanan, S.; Pandi, S.; Selvakumar, S.; Prem Anand, D. Cryst. Growth Des. 2009, 9, 2061–4. (13) Hulliger, J. Angew. Chem., Int. Ed. Engl. 1994, 33, 143–162. (14) K€ onig, E.; Kremer, S. Ligand Field Energy Diagrams; Plenum Press: New York, 1977; pp 1-67, 353-401. (15) Flack, H. D. Acta Crystallogr., A 1983, 39, 876–881. (16) Bernardinelli, G.; Flack, H. D. Acta Crystallogr., A 1985, 41, 500– 511. (17) Evans, G. G.; Boeyens, J. A. Acta Crystallogr., B 1989, 45, 581–590. (18) Steiner, T. Angew. Chem., Int. Ed. Engl. 2002, 41, 48–76. (19) Desiraju, G. R.; Steiner, T. The weak hydrogen bonds. IUCr Monographs on Crystallography; Oxford University Press: Oxford, 1999. (20) SCALE3 ABSPACK: Empirical absorption correction, CrysAlis Software package; Oxford Diffraction Ltd.: 2006. (21) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure Solution; G€ottingen, 1997. (22) Sheldrick, G. M. SHELXL-97, Program for the Refinement of Crystal Structures; G€ottingen, 1997. (23) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565.
