Crystal Structure, Thermal Decomposition Behavior, and Order-Disorder Transition of the Guest Component of Concomitant Pseudodimorphic Clathrates between 2,2′-Bis(9-hydroxy-9-fluorenyl)biphenyl Host and Chloroform Guest
CRYSTAL GROWTH & DESIGN 2003 VOL. 3, NO. 4 541-546
Omay Sumarna,† Ju¨rgen Seidel,*,† Edwin Weber,‡ Wilhelm Seichter,‡ Bakhtiyar T. Ibragimov,§ and Kayrat M. Beketov| Institut fu¨ r Physikalische Chemie der Technischen Universita¨ t Bergakademie Freiberg, Leipziger Strasse 29, D-09596, Freiberg/Sachsen, Germany, Institut fu¨ r Organische Chemie der Technischen Universita¨ t Bergakademie Freiberg, Leipziger Strasse 29, D-09596 Freiberg/Sachsen, Germany, Institute of Bioorganic Chemistry, Uzbekistan Academy of Sciences, H. Abdullaev Street 83, Tashkent, 700143, Uzbekistan, and Institute of Chemical Sciences, Kazakh Academy of Sciences, Ualikhanov Street 106, Almaty, 480100, Kazakhstan Received January 29, 2003;
Revised Manuscript Received March 26, 2003
ABSTRACT: Two clathrates between the 2,2′-bis(9-hydroxy-9-fluorenyl)biphenyl host and chloroform guest, having 1:2 (R-phase) and 1:1 (β-phase) stoichiometries, have been obtained in the same vial by fast evaporation of a supersaturated solution in chloroform. The structures of the pseudodimorphs were determined by single-crystal X-ray diffraction. Their thermal properties were studied by using combined thermogravimetry-differential scanning calorimetry (TG-DSC), variable temperature X-ray powder diffraction in the temperature interval 20-250 °C, and DSC in the low-temperature interval from -140 to 20 °C. The thermal decomposition behavior of the R- and β-phase pseudodimorphs, a difference in the desolvation onset temperatures, as well as an occurrence of endothermic peaks in the low-temperature DSC curves (order-disorder transition of the guest component) have been explained on the basis of the structural data. Introduction Crystalline inclusion compounds (clathrates, hostguest complexes)1 are of increasing importance in supramolecular chemistry2 because of their significant potential in addressing a variety of fundamental and practical items such as molecular recognition,3 crystal engineering,4 chemical sensing,5 or the design of new solid materials with tailored physical and chemical properties.6 The frequent occurrence of polymorphism and pseudopolymorphism7,8 coupled with the current lack of understanding and control of these phenomena are major obstacles toward these objectives.9,10 However, polymorphic or pseudopolymorphic behavior of inclusion compounds may also open up new possibilities for tailoring or adapting their properties.11 In view of this potentiality, several polymorphism and pseudopolymorphism of crystalline inclusions have previously been studied by the authors using different versatile host compounds.12,13 It could be shown that the crystallization conditions, especially temperature and supersaturation (low supersaturation at slow crystallization rates near equilibrium and higher supersaturation at fast crystallization far from equilibrium), control the resulting clathrate phases. These results en* Corresponding author. Phone: +49-3731-39 2368. Fax: +49-373139 3588. E-mail:
[email protected]. † Institut fu ¨ r Physikalische Chemie der Technischen Universita¨t Bergakademie Freiberg. ‡ Institut fu ¨ r Organische Chemie der Technischen Universita¨t Bergakademie Freiberg. § Uzbekistan Academy of Sciences. | Kazakh Academy of Sciences.
couraged us to investigate in more detail the formation and properties of pseudopolymorphic clathrate phases of 2,2′-bis(9-hydroxy-9-fluorenyl)biphenyl (BHFB),14 which is a classic example of the diol host compounds.15 Recently, we reported on the pseudopolymorphism of acetone coordinato-clathrates of this host, determined their structures, and discussed the thermal degradation behavior.16 In the present paper we extend the investigations to a study of the formation, structure, and thermal behavior of the pseudopolymorphic clathrates of the same host (BHFB) with chloroform as a guest molecule. The choice of chloroform as a guest molecule was stimulated by the fact that this molecule usually behaves inertly not showing specific host-guest interactions,15 which is in contrast to acetone,5,16 thus making a more systematic study and understanding of the polymorphism/pseudopolymorphism of clathrates possible. Experimental Section Synthesis. The synthesis of the BHFB host compound (Scheme 1) is described elsewhere.14 Crystals of the pseudopolymorphic clathrates were obtained by fast evaporation of chloroform from saturated solutions in an open 50 mL beaker at temperatures between 20 and 45 °C (see also Results and Discussion). TG-DSC Investigations. The desolvation behavior of the samples has been studied by means of a simultaneous TGDSC 111 system (Setaram, France) using open aluminum crucibles, sample weights of approximately 4 mg, a linear heating rate of 5 K min-1, and argon at 1 dm3 h-1 as purge gas for all measurements. Crystals were taken from the mother liquor, blotted dry on filter paper, and transferred into the crucibles for weighing and measuring.
10.1021/cg034013a CCC: $25.00 © 2003 American Chemical Society Published on Web 04/12/2003
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Crystal Growth & Design, Vol. 3, No. 4, 2003 Scheme 1.
Sumarna et al.
Formula Structure of BHFB
Table 1. Crystal Data and Some Selected Experimental Details for the Crystal Structures of the r- and β-Phases of the Chloroform Inclusion Compounds of BHFB empirical formula formula weight crystal system space group T (K) a (Å) b (Å) c (Å) R (deg) β (deg) γ (deg) V (Å3) Z Dcalc ( g cm-3 ) radiation F(000) absorption coefficient (mm-1) crystal size (mm) θ-ranges (deg) index range reflections collected independent reflections observed reflections data/restraints/parameters goodness-of-fit on F2 R, wR [I > 2σ(I)] largest diff. peak and hole (e- Å-3)
β-phase
R-phase
C39H27Cl3O2 633.96 monoclinic C2/c 183 29.977(7) 10.782(1) 19.184(3) 90 92.81(2) 90 6193(2) 8 1.360 Cu-KR 2624 2.952 0.4 × 0.35 × 0.25 2.95-64.95 0
