Structures of 4,4′-Bis(diphenylhydroxymethyl)diphenyl with Picolines: Selectivity and Phase Transformation Luigi R.
Nassimbeni,*,†
Hong
Su,†
Edwin
Weber,‡
and Konstantinos
Skobridis#
Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa, and Institut fu¨ r Organische Chemie, Technische Universita¨ t Bergakademie Freiberg, Leipziger Strasse 29, D-09596 Freiberg/Sachs., Germany, and Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece
CRYSTAL GROWTH & DESIGN 2004 VOL. 4, NO. 1 85-88
Received August 6, 2003
ABSTRACT: The crystal structures of the inclusion compounds of 4,4′-bis(diphenylhydroxymethyl)diphenyl with 3- and 4-picolines were elucidated. The selectivity of enclathration is concentration dependent. The 4-picoline inclusion compound undergoes a phase transition between 235 and 240 K. The transition is second order with no change in volume and is accompanied by a small change in the host conformation. Introduction The compound 4,4′-bis(diphenylhydroxymethyl)diphenyl, H, is a host compound that conforms to Weber’s rules for host design,1 in that it is bulky, rigid, and has hydroxyl moieties that act as hydrogen-bonding donors, thus facilitating the formation of coordinato-clathrates. The synthesis of the family of compounds corresponding to the general formula
where Ar, Ar′, Ar′′ are aromatic moieties and X ) H or OH, has been described, a number of such compounds have been characterized,2 and the crystal structures of two polymorphs of the title compound have been elucidated.2 The inclusion properties of these host compounds have been studied,2 and the structures and thermal stability of the title host with acetone, acetophenone, 1,4-dioxane, and p-xylene have been determined.3 We have employed wheel-and-axle type host compounds to effect the separation of isomers by enclathration. Thus, the host 1,4-bis(9-hydroxy-9-fluorenyl)benzene has been used to separate lutidine regioisomers,4 while the host 1,1,6,6-tetraphenylhexa-2,4-diyne-1,6-diol has been extensively exploited for the selective enclathration of lutidines,5 picolines,6 and aminobenzonitriles.7 Remarkably, in the latter separation, we demonstrated that the same selectivity results were obtained by solidsolid reactions as in solution. As part of a systematic study of the inclusion properties of these compounds with substituted pyridines, we elucidated the structures of the title host compound with * To whom correspondence should be addressed. Prof. Luigi R. Nassimbeni, Department of Chemistry, University of Cape Town, PrivateBag,Rondebosch7701,SouthAfrica.E-mail:
[email protected]. Tel +27 21 6502569. Fax +27 21 6854580. † University of Cape Town. ‡ Technische Universita ¨ t Bergakademie Freiberg. # University of Ioannina.
3-picoline and 4-picoline and noted that the latter inclusion compound underwent a temperature-dependent phase transition. We now report on the structural features of these compounds and on the results of the selectivity experiments. Experimental Section The inclusion compounds of the host, H, with 3-picoline, H‚ 3PIC, and of the host with 4-picoline, H‚4PIC, were grown by evaporation of the solutions of the host dissolved in the appropriate picoline guests, respectively. The host/guest ratio of 1:2 was checked by thermal gravimetry, which showed that the picoline guests were lost in multiple steps over a temperature range of 60-200 °C (Mettler Toledo TGA/SDTA 851, experimental mass loss 25.9-26.7%, calculated mass loss 26.4%). X-ray intensity data were collected on a Nonius Kappa-CCD diffractometer using graphite monochromated MoKR radiation. Temperature was controlled by an Oxford Cryostream cooling system (Oxford Cryostat). The strategy for the data collections was evaluated using the COLLECT software, scaled, and reduced with DENZO-SMN software.8 All structures were solved by direct methods using SHELX-869 and refined employing full-matrix least-squares with the program SHELX97 refining on F2.10 All non-hydrogen atoms were treated anisotropically. All hydrogen atoms appeared in a difference electron density map, and the H atoms bound to carbon were refined with appropriate geometric constraints. The hydroxyl hydrogens of the host were refined independently without constraints. Packing diagrams were produced using the program PovRay included in the graphic interface X-seed.11 The inclusion compound with 4-picoline as guest undergoes a temperature-dependent phase transition and the structures of its inclusion compound were determined both at room temperature, 298 K, H‚4PIC(RT) and at low temperature, 198 K, H‚4PIC(LT). Competition experiments were carried out by dissolving the host in mixtures of the two picoline guests, varying their mole fractions systematically from 0 to 1. The total guests/host ratio was kept at a molar ratio of 20:1. The inclusion compounds were allowed to crystallize, and the relative amounts of 3-picoline versus 4-picoline guest enclathrated by the host were analyzed by gas chromatography.12
Results and Discussion The crystal and experimental data for the three structures: H‚3PIC, H‚4PIC(RT), and H‚4PIC(LT) are given in Table 1.
10.1021/cg030030o CCC: $27.50 © 2004 American Chemical Society Published on Web 12/06/2003
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Table 1. Crystal Data and Structure Refinements empirical formula formula weight data collection temperature crystal system, space group a (Å) b (Å) c (Å) R (°) β (°) γ (°) volume (Å3) Z, calculated density (Mg m-3) absorption coefficient µ (mm-1) F(000) Theta range for data collection limiting indices h, k, l reflections collected/unique data/restraints/parameters goodness-of-fit on F 2 final R indices [I > 2σ(I)] R indices (all data) largest diff peak and hole (e Å-3)
H‚3PIC C38H30O2‚2C6H7N 704.87 203(2) K monoclinic, C2/c 25.6563(3) 9.9269(2) 18.2908(2) 90 121.244(1) 90 3982.8(1) 4, 1.176 0.071 1496 3.25-28.28 deg -33,34; (13; (24 9487/4920 [Rint ) 0.028] 4920/0/244 1.043 R1 ) 0.0531 wR2 ) 0.1243 R1 ) 0.0924 wR2 ) 0.1425 0.472 and -0.506
Figure 1. Projection viewed along [010] of structure H‚3PIC. All H atoms except the hydroxyl hydrogens are omitted.
The H‚3PIC compound crystallizes in the space group C2/c with Z ) 4; the host molecules were therefore located on a diad at Wyckoff position e, while the 3-picoline guest lies at a general position. The packing of the structure is shown in Figure 1 as a projection viewed along [010]. The conformation of the host molecule is such that the two central phenyl moieties are tilted to each other with the torsion angle about the central bond, C(16)-C(11)-C(11)′-C(16)′ ) 41.1(3)° and the hydroxyl moieties are in the gauche conformation, with the torsion angle O(1)-C(1)-C(1)′-O(1)′ ) 120.5(2)°. The 3-methylpyridine guests are hydrogen bonded via (host)O-H‚‚‚N(guest) interactions with a O‚‚‚N distance of 2.831(2) Å. The metrics of the hydrogen bonds for all the structures are given in Table 2. The 3-methylpyridine guests lie in undulating channels along [010], which are shown in Figure 2, where the host atoms are represented with van der Waals radii and the guest is shown as sticks. The room temperature structure H‚4PIC(RT), carried out at 298 K, is triclinic, space group P1 h , with Z ) 1. The host is located in a center of inversion at Wyckoff position b. Symmetry requires the hydroxyl moieties to be in the trans-conformation, and the structure is stabilized by a (host)O-H‚‚‚N(guest) hydrogen bond with a O‚‚‚N distance of 2.839(2) Å (Table 2). The 4-picoline guests are located between layers of host molecules perpendicular to [001].
H‚4PIC(RT) C38H30O2‚2C6H7N 704.87 298(2) K triclinic, P1 h 8.5482(1) 9.0927(2) 14.6664(3) 94.233(1) 100.182(1) 114.718(1) 1005.20(3) 1, 1.164 0.071 374 3.20-27.50 deg -9,11; -11,10; -18,19 7028/4549 [Rint ) 0.0137] 4549/0/249 1.048 R1 ) 0.0537 wR2 ) 0.1476 R1 ) 0.0868 wR2 ) 0.1704 0.225 and -0.231
H‚4PIC(LT) C38H30O2‚2C6H7N 704.87 198(2) K triclinic, P1 h 8.5513(2) 19.9897(4) 23.7128(6) 97.586(1) 98.264(1) 94.898(1) 3953.6(2) 4, 1.184 0.071 1496 1.25-27.90 deg (11; -25,26; (31 32097/18504 [Rint ) 0.0451] 18504/0/994 1.016 R1 ) 0.0645 wR2 ) 0.1506 R1 ) 0.1744 wR2 ) 0.1970 0.211 and -0.168
Figure 2. van der Waals representation of structure H‚3PIC, showing the guest molecules (sticks) are located in channels running along [010]. Table 2. Hydrogen Bonding Details Donor-H‚‚‚ Acceptor H‚3PIC O(1)-H(1)‚‚‚ N(1G) H‚4PIC O(1)-H(1)‚‚‚ (RT) N(1G) H‚4PIC O(1X)-H(1X)‚‚‚ (LT) N(1C) O(2X)-H(2X)‚‚‚ N(1D) O(1Y)-H(1Y)‚‚‚ N(1A) O(2Y)-H(2Y)‚‚‚ N(1B)
d(D-H) d(H‚‚‚A) d(D‚‚‚A)
