1. Investigation of the Amide I Band of N-Methylacetamide in Solid Parahydrogen using FTIR Spectroscopy Leif O. Paulson and David T. Anderson Department of Chemistry University of Wyoming, Laramie, WY 82071 Monday, June 22, 2009

2. Overview N-Methylacetamide Experimental setup Examination and discussion of the Amide I feature Summary

3. N-Methylacetamide (NMA) H H H H trans-N-Methylacetamide

4. NMA IR Transition 1 FWHM = 4.5 cm -1 1. L. O. Paulson and D. T. Anderson. 61 st Ohio State University International Symposium on Molecular Spectroscopy, talk R008 (2006)

5. Why NMA? Amide I Vibrational Mode Simple model of peptide bond Well studied specimen Amide I mode is extremely sensitive to its environment 2 Large molecule to study Rationale and Challenges 2. K. E. Amunson and J. Kubelka. J. Phys. Chem. B. 111, 9993 (2007)

6. Producing Variable Amounts of Orthohydrogen and Parahydrogen 3,4 nH 2 pH 2 3. S. Tam and M. E. Fajardo. Rev. Sci. Instrum. 70, 1926 (1999 ) 4. Yoshioka, K., Raston, P. L., and D. T. Anderson. Int. Rev. Phys. Chem. 25, 469 (2006) Cryostat cold tip Fe(OH) 3 catalyst T=14-80K Obtain variable amounts of parahydrogen (pH 2 ) and orthohydrogen (oH 2 )

7. FTIR Beam nH 2 Bruker IFS 120 HR FTIR FTIR Beam MCT Detector BaF 2 substrate o/p converter Chemical dopant Synthesis of NMA-doped pH 2 Crystals 5 5. M. E. Fajardo and S. Tam. J. Chem. Phys. 108, 4237 (1998)

8. Experimental Setup pH 2 NMA FTIR

9. NMA Compared with Formic Acid 6 6. L. O. Paulson and D. T. Anderson. J. Phys. Chem. A. 113, 1770 (2009) NMA 0.005% oH 2 NMA 51% oH 2 Formic Acid 0.005% oH 2 Formic Acid 51% oH 2

10. Matrix Shift as a Function of oH 2 Concentration 7. J. Kubelka and T. A. Kiederling. J. Phys. Chem. A. 105, 10922 (2001) Gas phase NMA Amide I gas phase frequency 7 is 1731 cm -1 0.005% oH 2 51% oH 2 Δν matrix =ν para -ν gas (cm -1 ) 51% ortho0.005% ortho -27.6 (1.59%)-23.5 (1.36%)

11. Intermolecular Interactions in the Matrix J=0 pH 2 J=1 oH 2

12. Matrix Shift Effect pH 2 oH 2 NMA ν=1 ν=0 Gas phase In pH 2 In pH 2 with trace oH 2 In pH 2 /oH 2 mixture 1731 cm -1 1710.0 cm -1 1707.5 cm -1 1703.4 cm -1

13. Frequency Shift due to Orthohydrogen Amount 0.005% oH 2 51% oH 2 27.6 cm -1 23.4 cm -1

14. The Environment of the Matrix NMA Temp. increases Increased diffusion 8 allows for oH 2 molecules to move about in the matrix at 4.3K There is a greater electrostatic interaction between the oH 2 quadrupole and NMA dipole moments, causing the oH 2 molecules to agglomerate around the NMA dopant 9 8. J. van Kranendonk. Solid Hydrogen (Plenum, New York, 1983) 9. K. Yoshioka and D. T. Anderson. J. Chem. Phys. 119, 4731 (2003) 1.8K4.3K

15. Temperature Effects 51% oH 2 0.005% oH 2 1.99K 4.36K 1.92K 1.83K 4.34K 1.65K

16. NMA Widths with Variable oH 2 Concentrations 0.005% oH 2 FWHM=4.5 cm -1 51% oH 2 FWHM=1.8 cm -1

17. NMA Matrix Environment at High Orthohydrogen Concentrations oH 2 pH 2 NMA NMA is surrounded by oH 2 molecules Results in a primarily homogeneous environment

18. Linewidths due to the Matrix Environment 0.005% oH 2 FWHM=4.5 cm -1 51% oH 2 FWHM=1.8 cm -1 Inhomogeneous Homogeneous Broad Asymmetric Narrow Symmetric

19. Summary NMA Amide I mode is extremely sensitive to its environment NMA Amide I mode remains broad in solid pH 2 due to residual oH 2 -27.6 cm -1 -23.5 cm -1 -8.2 cm -1 -11.4 cm -1 Δν p-o =ν ortho -ν para (cm -1 ) Formic AcidNMA -3.2-4.1 NMA Formic Acid Red=0.005% oH 2 Blue=51% oH 2

20. Acknowledgments Dr. David T. Anderson Ms. Sharon C. Kettwich Ms. Elsbeth Klotz NSF for the funding Thank you for listening!! See S.C.K.’s talk on Wednesday