The host xanthenol compound forms a 1:1 clathrate with dioxane, namely 9-(1-naphthyl)-9H-xanthen-9-ol–1,4-dioxane, C23H16O2·C4H8O2. The structure of this clathrate is reported, along with a study of the kinetics of desolvation and the determination of an activation energy. The guest mol­ecules are stabilized by Ohost—H⋯Oguest hydrogen bonds [O—H = 0.968 (2) Å, O⋯O = 2.7532 (13) Å and O—H⋯O = 151.9 (4)°]

Jacobs, Ayesha

Nassimbeni, Luigi R

Taljaard, Benjamin

Acta Crystallographica

English

Cape Town University OpenUCT

Desorption kinetics of a xanthenol±dioxane clathrateAyesha Jacobs,a* Luigi R. Nassimbenia and BenjaminTaljaardbaFaculty of Applied Sciences, Cape Technikon, PO Box 652, Cape Town 8000, SouthAfrica, and bDepartment of Chemistry, University of Port Elizabeth, Port Elizabeth6000, South AfricaCorrespondence e-mail: jacobsa@ctech.ac.zaReceived 5 May 2004Accepted 20 July 2004Online 11 August 2004The host xanthenol compound forms a 1:1 clathrate withdioxane, namely 9-(1-naphthyl)-9H-xanthen-9-ol±1,4-dioxane,C23H16O2C4H8O2. The structure of this clathrate is reported,along with a study of the kinetics of desolvation and thedetermination of an activation energy. The guest moleculesare stabilized by OhostÐH  Oguest hydrogen bonds [OÐH =0.968 (2) AÊ , O  O = 2.7532 (13) AÊ and OÐH  O =151.9 (4)].CommentThe conformations of the two components of 9-(1-naphthyl)-9H-xanthen-9-ol±dioxane, (I), are shown in Fig. 1. A search ofthe Cambridge Structural Database (CSD, Version 5.25; Allen,2002) revealed that no structures of this host molecule havebeen published to date. We present here the crystal structureof the title clathrate, (I).Bond lengths and angles for the host and guest in (I)generally fall in the expected ranges. The xanthene ring of thehost is slightly non-planar, with the dihedral angle between theleast-squares planes of the two phenyl rings being 5.17 (4).The host naphthalene moiety and the xanthene ring are nearlyorthogonal, the dihedral angle between their least-squaresplanes being 88.21 (2). This is comparable with the confor-mation found in similar structures, such as bis(9-phenyl-9-hydroxy)xanthene tris(dioxane) clathrate (CsoÈ regh et al.,1993). In other structures, such as 9-(cyclohepta-2,4,6-trien-1-yl)xanthen-9-ol (Badejo et al., 1991), the dihedral angle issubstantially different, at 21.9 (2). The 1,4-dioxane guestmolecule is in the expected chair conformation (Fig. 1).Dioxane is an interesting guest molecule, since it has two Oatoms which are capable of being hydrogen-bond acceptors. Aseries of similar hosts have been observed to include dioxane,with host±guest stoichiometries varying from 2:1 to 2:3(CsoÈ regh et al., 1993), with the guests situated in channels orcages. In this study, each host molecule is hydrogen bonded viaorganic compoundso668 # 2004 International Union of Crystallography DOI: 10.1107/S0108270104017792 Acta Cryst. (2004). C60, o668±o670Acta Crystallographica Section CCrystal StructureCommunicationsISSN 0108-2701Figure 3TGA and DSC curves for (I).Figure 1A view of the two components of (I), showing the atom-numberingscheme. Displacement ellipsoids are drawn at the 50% probability leveland H atoms are shown as small spheres of arbitrary radii.Figure 2The structure of (I), viewed down [100]. The hydrogen bond is shown as adashed line.its hydroxyl moiety to one dioxane molecule (Table 1). This isconsistent with CsoÈ regh's study, which suggested that the morebulky the substituent attached to the xanthene ring, thegreater the tendency for a single host±guest interaction.In the crystal structure of (I), the host molecules pack inzigzag layers parallel to [100] and the dioxane guests lie incages created by the host framework (Fig. 2). The hydrogen-bonded host±guest units form spirals which extend along[010]. The spiral shape is largely due to the torsion anglebetween the xanthenol and naphthalene moieties of the host[C8ÐC7ÐC14ÐC15 = 61.56 (14)]. We used the programSECTION(Barbour,1999a) to map the cavities and found thatthe approximate size of these cages is 7.6  6.5  7.4 AÊ . Thiscompares favourably with other structures, such as the 9-[4-(tert-butyl)phenyl]¯uoren-9-ol±dioxane clathrate (CsoÈ regh etal., 1993), where the cages have approximate dimensions 5.77.1  9.7 AÊ .Thermogravimetric analysis (TGA) of (I) shows a singlemass-loss step (calculated mass loss = 21.4% and observedmass loss = 21.3%), which is consistent with a host±guest ratioof 1:1. Two endotherms were observed in the differentialscanning calorimetry (DSC) pro®le. The ®rst of these (Ton =380.4 K) corresponds to the loss of guest and the second (Ton =468.0 K) represents the host melt. Both TGA and DSC curvesare shown in Fig. 3.The kinetics of desolvation for (I) were determined byperforming a series of isothermal TG experiments between328 and 348 K. The resultant mass±time curves were sigmoidaland ®tted the Avrami±Erofeev rate law (A4), [ÿln(1 ÿ )]1/4 =kt, where  is the extent of the reaction and k is the rateconstant (Brown, 1988). The corresponding Arrhenius plot isshown in Fig. 4. An activation energy of 111 (2) kJ molÿ1 wasobtained.ExperimentalThe host compound was synthesized using the method of Dilthey etal. (1939). IR spectra of the host alone showed max values (CHCl3) of3584.1 (s, free OH) and 3370.1 cmÿ1 (br, bonded OH). IR spectrawere recorded on a Perkin±Elmer 1600 Series FT spectrometer.Suitable crystals of (I) were obtained by slow evaporation of dilutesolutions of the host in liquid dioxane at room temperature. Thecrystals were crushed for thermal analysis. TGA was performed on aMettler±Toledo Stare system and DSC was carried out on a Perkin±Elmer PC7 Series system.Crystal dataC23H16O2C4H8O2Mr = 412.46Orthorhombic, Pna21a = 13.597 (3) AÊb = 10.404 (2) AÊc = 14.735 (3) AÊV = 2084.5 (7) AÊ 3Z = 4Dx = 1.314 Mg mÿ3Mo K radiationCell parameters from 14 703re¯ections = 4.5±26.6 = 0.09 mmÿ1T = 173 (2) KRectangular, colourless0.36  0.30  0.27 mmData collectionNonius KappaCCD area-detectordiffractometer1 ’ scans and ! scans14 703 measured re¯ections2202 independent re¯ections2095 re¯ections with I > 2(I)Rint = 0.027max = 26.6h = ÿ15! 16k = ÿ13! 13l = ÿ18! 18Re®nementRe®nement on F 2R[F 2 > 2(F 2)] = 0.030wR(F 2) = 0.076S = 1.072202 re¯ections284 parametersH atoms treated by a mixture ofindependent and constrainedre®nementw = 1/[2(Fo2) + (0.0476P)2+ 0.3201P]where P = (Fo2 + 2Fc2)/3(/)max = 0.004max = 0.27 e AÊÿ3min = ÿ0.27 e AÊ ÿ3The aromatic H atoms of the host and the CH2 H atoms of thedioxane guest were located in difference electron-density maps, butthey were geometrically constrained with CÐH distances ®xed at0.95 and 0.99 AÊ , respectively. The hydroxyl H atom was located in adifference electron-density map, and was initially re®ned isotropi-cally. Thereafter, it was placed in a geometrically calculated positionbased on the relationship between OÐH and O  O distances(Olovsson & JoÈ nsson, 1975), and its position was re®ned underdistance restraints, starting with O2ÐH1 = 0.919 (15) AÊ andH1  O2G = 1.837 (1) AÊ . Friedel pairs were merged for the ®nalre®nement.Data collection: COLLECT (Nonius, 2000); cell re®nement:DENZO±SMN (Otwinowski & Minor, 1997); data reduction:DENZO±SMN; program(s) used to solve structure: SHELXS97(Sheldrick, 1997); program(s) used to re®ne structure: SHELXL97(Sheldrick, 1997); molecular graphics: X-SEED (Barbour, 1999b);software used to prepare material for publication: SHELXL97 andPLATON (Spek, 2003).The authors thank the National Research Foundation(Pretoria) for Research Grants.organic compoundsActa Cryst. (2004). C60, o668±o670 Ayesha A. Jacobs et al.  C23H16O2C4H8O2 o669Figure 4Arrhenius plot for the desolvation of (I).Table 1Hydrogen-bonding geometry (AÊ , ).DÐH  A DÐH H  A D  A DÐH  AO2ÐH1  O2Gi 0.968 (3) 1.861 (2) 2.7532 (13) 151.9 (4)Symmetry code: (i) xÿ 12; 32ÿ y; z.Supplementary data for this paper are available from the IUCr electronicarchives (Reference: TA1455). Services for accessing these data aredescribed at the back of the journal.ReferencesAllen, F. H. (2002). Acta Cryst. B58, 380±388.Badejo, I. T., Fry, J. L., Karaman, R., Nadkarni, D. & Pinkerton, A. A. (1991).Acta Cryst. C47, 1895±1898.Barbour, L. J. (1999a). J. Appl. Cryst. 32, 353.Barbour, L. J. (1999b). X-SEED. University of Missouri, Columbia, Missouri,USA.Brown, M. E. (1988). Introduction to Thermal Analysis, ch. 13. New York:Chapman and Hall.CsoÈ regh, I., Weber, E., Nassimbeni, L. R., Gallardo, O., Dorpinghaus, N., Ertan,A. & Bourne, S. A. (1993). J. Chem. Soc. Perkin Trans. 2, pp. 1775±1782.Dilthey, W., Quint, F. & Heinen, J. (1939). J. Prakt. Chem. 152, 49±98.Nonius (2000). COLLECT. Nonius BV, Delft, The Netherlands.Olovsson, I. & JoÈ nsson, P. (1975). The Hydrogen Bond ± Structure andSpectroscopy, edited by P. Schuster, G. Zundel & C. Sardefy. New York:North-Holland Publishing Company.Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276,Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M.Sweet, pp. 307±326. New York: Academic Press.Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University ofGoÈ ttingen, Germany.Spek, A. L. (2003). J. Appl. Cryst. 36, 7±13.organic compoundso670 Ayesha A. Jacobs et al.  C23H16O2C4H8O2 Acta Cryst. (2004). C60, o668±o670

Desorption kinetics of a xanthenol-dioxane clathrate

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Desorption kinetics of a xanthenol-dioxane clathrate

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