OSU International Symposium on Molecular Spectroscopy meeting June

OSU International Symposium on Molecular Spectroscopy meeting, June 19 -23, in Columbus, Ohio, USA Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex Juan-Ramon Aviles-Moreno, Jean Demaison and Thérèse R. Huet Laboratoire de Physique des Lasers, Atomes et Molécules UMR 8523 CNRS – Université Lille 1, 59655 Villeneuve d’Ascq Cedex, France 0+ 0 - CC-W-1 CC-W-2 CC-W-1

Glycolaldehyde: the simplest sugar Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet n structural formula : CH 2 OHCHO A=18. 474 GHz B=6. 548 GHz C=4. 984 GHz μa=0. 4 D μb=2. 3 D μc=0. 0 D Glycolaldehyde 1 CC (C 2 v) (E = 0. 0 k. J/mol) 2 TT E = 14. 63 k. J/mol 3 TG E = 15. 39 k. J/mol 4 CT E = 21. 72 k. J/mol Experimental : micro-wave and millimeter-wave datas • Marstokk, K. -M. ; Møllendal, H. J. Mol. Struct. 1970, 5, 205 -213. • Butler, R. A. H. ; De Lucia, F. C. ; Petkie, D. T. ; Møllendal, H. ; Horn, A. ; Herbst, E. Ap. J. Supp. Ser. 2001, 134, 319 -321. • Weaver, S. L. W. ; Butler, R. A. H. ; Drouin, B. J. ; Petkie, D. T. ; Dyl, K. A. ; De Lucia, F. C. ; Blake G. A. Ap. J. Supp. Ser. 2005, 158, 188 -192. Ab initio calculations : structure + energy of 4 conformers (MP 2/aug-cc-p. VTZ and MP 4/cc-p. VQZ) • Ratajczyk, T. ; Pecul, M. ; Sadlej, J. ; Helgaker, T. J. Phys. Chem. A 2004, 108, 2758 -2769. • Senent, M. L. J. Phys. Chem. A 2004, 108, 6286 -6293.

Hydrated glycolaldehyde (GA-W) Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet n Structures optimized at the B 3 LYP/6 -311++G(2 df, p) level of theory n Energies: the Gaussian-3 (G 3) compound method was used in its G 3 MP 2 B 3 version as implemented in Gaussian 03 n The two lowest experimentally accessible energy structures were also optimized using the B 3 LYP/aug-cc-p. VTZ level of theory. 209. 6 194. 4 186. 0 197. 5 197. 4 CC-W-3 (4. 03 k. J/mol) 214. 2 200. 0 CC-W-1 (0 k. J/mol) CC-W-2 (2. 12 k. J/mol) CC-W-4 (5. 83 k. J/mol)

Conformers CC-W-1 and CC-W-2 Principal Bond Lengths, Bond Angles, and Dihedral Angles (B 3 LYP/aug-cc-p. VTZ ) Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet CC-W-1 CC-W-2 GA skeleton: 186. 4 197. 5 186. 0 4 O-7 H/pm 97. 6 97. 5 3 C-4 O-7 H/deg 110. 88 111. 49 1 O-2 C-3 C-4 O/deg - 10. 5 10. 8 7 H-4 O-3 C-2 C/deg 46. 9 44. 1 9 H-10 O/pm 97. 2 97. 1 11 H-10 O/pm 96. 2 96. 1 9 H-10 O-11 H/deg 106. 42 106. 57 7 H-10 O/pm 186. 5 186. 6 9 H-1 O/pm 195. 4 195. 2 10 O-9 H-3 C-2 C/deg 161. 1 169. 6 11 H-10 O-1 O-2 C/deg 135. 5 255. 5 197. 4 Water skeleton: CC-W-1 (0 k. J/mol) GA-W: CC-W-2 (2. 12 k. J/mol)

The experimental setup Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet n Microwave Fourier transform spectrometer (6 -20 GHz) coupled to a supersonic molecular jet Carrier gas P= 3 bars (Ne) Heated nozzle T= 363 K Glycolaldehyde * Mirror Carrier gas + H 2 O H 2 O * GA dimer: crystalline mixture of stereoisomers (Sigma Aldrich, purity 98%) Inside the cavity… cavity

The microwave spectrum of GA-W Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet n Signals: GA (red dots), water dimer (blue circles), GA-W (assigned lines) GA-W: (JKa. Kc)’-(JKa. Kc)’’ § Decomposition products: Acetic acid, formic acid and formaldehyde (high T). Methyl formate was not detected

GA-W: the molecular parameters Semirigid rotor: Ir representation, A reduction. k = -0. 28. Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet n The Doppler components are splitted (30 k. Hz): Large amplitude motion associated with two equivalent structures ? 0+ Constants 0 - A/MHz 5616. 5972(13) 5616. 6051(13) B/MHz 3483. 4258(14) 3483. 4321(14) C/MHz 2285. 7921(8) 2285. 7929(8) DJ/k. Hz 6. 45(4) 6. 47(4) DJK/k. Hz -14. 24(14) -14. 50(14) DK/k. Hz 21. 94(11) 21. 31(11) d. J/k. Hz 1. 958(20) 1. 934(20) d. K/k. Hz 5. 16(25) 6. 00(25) Std/k. Hz 4. 1 4. 3 D/amu. Å2 -13. 9648(2) -13. 9645(2)

Conformational assignment The identity of the experimentally detected conformer is CC-W-1 Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet Exp. CC-W-1 CC-W-2 CC-W-3 CC-W-4 VTZ (2 df, p) A/MHz 5616. 6 5551. 8 5545. 0. 5577. 8 5559. 2 9883. 4 17731. 3 B/MHz 3483. 4 3595. 6 3592. 4 3553. 6 3562. 5 1887. 4 1675. 5 C/MHz 2285. 8 2309. 4 2309. 1 2277. 1 2283. 4 1877. 9 1545. 3 D/amu. Å2 -13. 96 -12. 75 -12. 96 -10. 88 -11. 44 -49. 78 -3. 09 ma/D strong -1. 2 -1. 1 -1. 6 -1. 5 -0. 5 0. 1 mb/D medium 0. 6 0. 7 1. 2 1. 3 mc/D - 0. 2 2. 4 2. 5 186. 4 1. 5 0. 6 1. 4 0. 0 197. 5 CC-W-1 (0 k. J/mol)

Tunneling effect Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet n Simple model: « Mirror » CC-W-1 Structure of the transition state TS 1 (17. 72 k. J/mol): CC-W-1 TS 1 n The conformational flexibility was investigated through a two dimensional potential energy surface calculated along the hydroxyl group (i. e. the 7 H 4 O-3 C-2 C dihedral angle) and the free OH water group (i. e. the 11 H-10 O 1 O-2 C dihedral angle) coordinates, and associated with the two most stable conformers (CC-W-1 and CC-W-2).

Conformational flexibility Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet n The grid was built by steps of 5 degrees, as a function of the energy by optimizing the structure of the 1440 grid points at the B 3 LYP/6 -31 G* level of theory. The structure of all the maxima and minima was also optimized at the B 3 LYP/6 -311++G(2 df, p) level. Finally the energy of the maxima and minima was calculated at the MP 2/cc-p. VQZ level of theory. § Results: TS 1: 17. 72 k. J/mol TS 1 TS 2: 4. 36 k. J/mol TS 2 TS 3 CC-W-2 TS 3: 4. 98 k. J/mol CC-W-1: 0 k. J/mol CC-W-2: 2. 36 k. J/mol CC-W-1

Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet Conformational flexibility TS 1 CC-W-1 TS 3 CC-W-2 n The splitting of the lines TS 3 CC-W-2 TS 2 CC-W-1 is due to a tunneling effect between two equivalent structures of the CC-W-1 conformers. TS 2 TS 1 n The energetically CC-W-1 favourable path involves TS 2, CC-W-2, and TS 3.

Acknowledgment Conformational Flexibility in Hydrated Sugars: The Glycolaldehyde-Water Complex J. -R. Aviles-Moreno, J Demaison and T. R. Huet n The Institut du Développement des Ressources en Informatique Scientifique (contract IDRIS 51715, France) n The Programme National de Physico-Chimie du Milieu Interstellaire (PCMI, France) Manuscript submitted to the J. Am. Chem. Soc. 0+ 0 - CC-W-1 CC-W-2 CC-W-1