1. Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry University of British Columbia Vancouver, BC, Canada.

2. Introduction Motive – To study amino acids in relation to interstellar chemistry Start with simple amino acid  β-alanine β-alanine in Astrochemistry: Found in various classes of carbonaceous meteorites. Most abundant type of amino acid in CI chondrites (class of carbonaceous meteorites). Formed preferentially over α-alanine in ion-molecule reactions with smaller molecules found in interstellar medium. [1] J.G. Lawless, Geochim. Cosmochim. Ac., 37, 2207 (1978). [2] O. Botta, Z. Martins, and P. Ehrenfreund, Meteorit. Planet. Sci., 42, 81 (2007). [3] V. Blagojevic, S. Petrie, and D.K. Bohme, Mon. Not. R. Astron. Soc., 339, L7 (2003).

3. Computation: First began with Ramek (1990) M. Ramek, J. Mol. Struct. (Theochem), 208, 301 (1990) Derived 20 stable conformers of β-alanine at HF/4-31G level of theory. Gas Phase Spectroscopy: McGlone and Godfrey (1995) S.J. McGlone and P.D. Godfrey, J. Am. Chem. Soc., 117, 1043 (1995) Free-expansion jet spectrometry; observed conformers I, V. Sanz et al. (2006) M.E. Sanz, A. Lesarri, M.I. Peña, and V. Vaquero, J. Am. Chem. Soc., 128, 3812 (2006) Fourier transform microwave spectroscopy; found conformers II and III, in addition to I, V. Matrix-isolation spectroscopy: Dobrowolski et al. (2008) J.C. Dobrowolski, M.H. Jamróz, R. Kolos, J.E. Rode, and J. Sadlej, Chem. Phs. Chem., 9, 2042 (2008) Matrix-isolation IR spectroscopy (argon matrices); detected at least 3 conformers: I, II, IV. Stepanian et al. (2012) S. G. Stepanian, A. Y. Ivanov, D. A. Smyrnova, and L. Adamowiez, J. Mol. Struct., 1025, 6 (2012) Matrix-isolation FT-IR spectroscopy (argon matrices) + irradiation + matrix annealing + deuteration; detected the presence of at least 5 conformers: I, II, IV, V, VII. Previous studies on β-alanine

4. Using solid pH 2 matrix-isolation FT-IR spectroscopy, we aim to: determine the gas-phase conformational composition of β-alanine, and compare to that in argon matrix. investigate the outcomes of UV photochemistry on gas-phase β-alanine. Objective In on this study Parahydrogen as matrix host The soft and more inert property of pH 2 allow for the trapping of highly energetic states  possibility of more conformers detection. Matrix isolation spectroscopy of amino acids: Identify vibrational frequency of different conformers Identify stable conformer under various condition (low temperature, UV irradiation, etc)

5. Method Experimental 18mm 1.6mm Cartridge Heater NTC Thermistor Ortho-Para Converter: Operates at 14K – triple point of hydrogen Magnetic catalyst: (FeOH)O Yields parahydrogen gas of 99.95% purity Knudsen Cell: Β-alanine sublimation temperatures - 390±1K or 380±1K

6. Method D 2 lamp FT-IR spectrometer: KBr beamsplitter, MIR glowbar light source, liquid cooled MCT detector. 0.2 cm -1 resolution, 1000 scans, approx. 5000-700 cm -1 range UV-irradiation with D 2 lamp (λ = 180 – 270 cm -1 )

7. Method Computational Theoretical frequencies and intensities calculated for the 11 lowest energy β-alanine conformers at the B3LYP/aug-cc-pVTZ level of theory.

8. Results and Discussions III not observed in Ar ν (C=O) regionω(NH 2 ) region Conformational Composition

9. Results and Discussions ν (C-O) region UV Photochemistry ConformerIIIIIIIVVII Population before UV1.000.630.190.360.11 Population after UV0.730.460.250.490.03 Change in population- 0.27-0.17+0.06+0.13-0.08  All population numbers are normalized to the population of conformer I at deposition.

10. Results and Discussions Temperature dependence of conformational population ConformerIIIIIIIVVII ΔE ZPE, kJ/mol0.02.07.43.95.4 Boltzmann distribution at 390 K, %46.425.44.714.19.0 Boltzmann distribution at 380K, %47.525.44.513.88.7

11. Conformational Studies: Five conformers of β-alanine were identified: I, II, IV, III, and VII. Conformer III was found for the first time under matrix isolation technique. Conformer V: possibility of inconclusive assignment by previous research. UV Photochemistry: Conformational change: I & II  IV VII  III Sublimation Temperature: Trend follows Boltzmann distribution. With increasing temperature: Lowest energy conformer (conformer I) decrease. Higher energy conformers (conformer II, IV, III, and VII) increase. Useful technique for conformational studies of other similar molecules: Aid in identifying the most stable conformer. Conclusions

12. Advantages: Conserves the room temperature conformations of the gas-phase sample. Lighter collision of the host molecule to the gaseous sample preserve the highly energized states of the target molecule. More profound isomerization of amino acids under UV irradiation in pH 2 matrix compare to in Ar matrix. Comparable spectra line-width of the sample with that performed in Ar matrix. Expectation: narrower line-width. Disadvantage: No matrix annealing experiment. The range of temperature change without distorting the pH 2 crystal is very narrow (4-7K) as compared to solid Ar (4-40K).  Alternative technique – sublimation temperature experiment Preservation of amino acids’ conformational population at sublimation temperature due to the softer collision effect on the sample. Summary of Parahydrogen as matrix host for studies of amino acids

13. UV Photolysis on β-alanine Current Work Aside from conformational changes, β-alanine also seems to photodissociate into CO 2 molecule and other fragments. We are now performing computation calculations on some possible candidates in hope to assign these β-alanine UV photolysis products.

14. Using similar experimental settings and concepts as the ones employed for gas phase β-alanine, we aim to further expand the present spectroscopic knowledge on amino acids by conducting solid parahydogen matrix- isolation FTIR spectroscopy on other simple amino acids. We also aim to study the zwitterion form of the molecules in study. Currently under investigation: α-alanine β-alanine zwitterion Future Work

15. Acknowledgement Supervisor: Takamasa Momose Collaborator: Ying-Tung Angel Wong Technician: Pavle Djuricanin