Chirality and Achirality in Crystal Structures

1. Chirality and Achirality in Crystal Structures H. D. Flack and G. Bernardinelli University of Geneva, Switzerland www.flack.ch/howard/cristallo/publcns.html

2. L- and D- quartz

3. Chirality in Chemistry

4. Hans Erni’s drawing

5. Kelvin’s definition of chirality

6. Lord Kelvin

7. Modern definitions of Chirality • IUPAC: The geometric property of a rigid object (or spatial arrangement of point or atoms) of being non-superposable by pure rotation and translation on its image formed by inversion through a point; the symmetry group of such an object contains no symmetry operations of the second kind ( 1, m, 3, 4, 6). When the object is superposable by pure rotation and translation on its inverted image, the object is described as being achiral; the symmetry group of such an object contains symmetry operations of the second kind. • Barron: True chirality is exhibited by systems that exist in two distinct enantiomorphic states that are interconverted by space inversion by not by time reversal combined with any proper spatial rotation.

8. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) 1 2 4 3 6 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 4 42m 6 6m2 43m

9. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) 1 2 4 3 6 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 4 42m 6 6m2 43m

10. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) 1 2 4 3 6 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 4 42m 6 6m2 43m

11. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) 1 2 4 3 6 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 4 42m 6 6m2 43m

12. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) 1 2 4 3 6 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 4 42m 6 6m2 43m

13. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) 1 2 4 3 6 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 4 42m 6 6m2 43m

14. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) NC 1 2 4 3 6 CA 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 NA 4 42m 6 6m2 43m

15. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) 1 2 4 3 6 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 4 42m 6 6m2 43m

16. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) 1 2 4 3 6 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 4 42m 6 6m2 43m

17. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) 1 2 4 3 6 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 4 42m 6 6m2 43m

18. Optical activity in crystals and molecules

19. Useful terms • Enantiomorph: One of a pair of chiral objects or models of opposite chirality sense. • Enantiomer: One of a pair of chiral molecular entities of opposite chirality sense. • Racemate: An equimolar mixture of a pair of enantiomers. • IUPAC Basic Terminology of Stereochemistry http://www.chem.qmul.ac.uk/iupac/stereo/

20. Crystal structures formed from chiral and achiral molecules

21. Crystal structures formed from chiral and achiral molecules

22. Crystal structures formed from chiral and achiral molecules

23. Crystal structures formed from chiral and achiral molecules

24. Crystal structures formed from chiral and achiral molecules

25. Crystal structures formed from chiral and achiral molecules

26. Crystal structures formed from chiral and achiral molecules

27. () o-tyrosine

28. Crystal structures formed from chiral and achiral molecules

29. Idealized binary phase diagrams for enantiomeric mixtures

30. Conglomerate - phase diagram

31. Racemic structure formation – phase diagram

32. -(1-naphthoxy) propionic acid & -(1-naphthyl) propionic acid

33. m-fluoromandelic acid & m-chlorophenyl hydracylic acid

34. Free energy vs temperature

35. Solid solution formation

36. Methyprylon

37. Methyprylon 3D

38. Crossing isodimorphism with two minima

39. Melting point diagram of methyprylon

40. Methyprylon cell dimensions and optical activity Einem glücklichen Zufall ist zu verdanken, dass in der Fraktion A beide Modifikationen entdeckt wurden.

41. Solid solution formation

42. Frederic Stanley Kipping 1863 - 1949

43. Prelog’s L- and D- quartz

44. Brazil twin of quartz

45. Hexahelicene From racemic solution From enantiopure solution

46. Characterisation of enantiomers for absolute configuration determination • Optical activity • CD spectrum (circular dichroism) • Enantioselective (chiral) chromatography

47. E. P. Kündig, M. Kondratenko, F. Robvieux, G. Bernardinelli, (2003). Organometallics, 22, - • Space group P212121; crystals grown from racemate; refinements using the above configuration: • Crystal 1: Flack parameter x = 0.36(4); ee = 28(8)% • Crystal 2: Flack parameter x = 0.90(3); ee = -80(6)% • CD spectra, from crystal 1 and crystal 2 in solution, normalised to allow for the volume of the crystal.

48. E. P. Kündig, M. Kondratenko, F. Robvieux, G. Bernardinelli, (2003). Organometallics, 22, - ee(x-ray) / ee(x-ray) = -0.35(10); CD(350) / CD(350) = -0.42

49. P. Müller, D. Riegert, G. Bernardinelli, (2003). Helv. Chim. Acta86, - • Space group P21; Flack parameter x = -0.03(12) • CD spectrum flat; []D = 0.7 • Substance ee = 43%, semi-preparative separation by HPLC • Enantiomer composing the single crystal used for X-ray diffraction was unequivocally identified by HPLC.

50. 32 geometric crystal classes 222 422 32 622 23 432 1 2/mmmm 4/mmm3m 6/mmm (m3m) 1 2 4 3 6 4/m3 6/m (m 3) 4mm 3m 6mm m mm2 4 42m 6 6m2 43m