Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle...

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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.

Transcript of Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle...

Page 1: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

Infrared Spectroscopy of Alanine in Solid

Parahydrogen

Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose

Department of ChemistryUniversity of British ColumbiaVancouver, BC, Canada.

Page 2: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

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).

Page 3: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

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

Page 4: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

Using solid pH2 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 pH2 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)

Page 5: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

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

Page 6: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

Method

D 2 la

mp

• 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 D2 lamp (λ = 180 – 270 cm-1)

Page 7: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

Method

Computational

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

Page 8: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

Results and Discussions

0.05

0.04

0.03

0.02

0.01

0.00Abs

orba

nce,

relat

ive un

it

18001780176017401720Wavenumber, cm

-1

0.25

0.20

0.15

0.10

0.05

0.00

IV

I

III

I

IV

Para-H2Ar

II

III not observed in

Ar

0.10

0.08

0.06

0.04

0.02

0.00Abso

rban

ce, r

elativ

e unit

830820810800790780Wavenumber, cm

-1

III

VII IV

II

I

ν (C=O) regionω(NH2) region

Conformational Composition

Page 9: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

Results and Discussions

11601150114011301120111011001090

Wavenumber, cm-1

Para-H2Ar

Para-H2Ar

III

II & I

IV

VIIVII

II

I

IV

Deposition Spectra

UV-Irradiation Difference Spectra

Ab

sorb

an

ce, re

lativ

e u

nit

ν (C-O) region

UV PhotochemistryConformer I II III IV VIIPopulation before UV 1.00 0.63 0.19 0.36 0.11Population after UV 0.73 0.46 0.25 0.49 0.03Change 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.

Page 10: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

Results and Discussions

Temperature dependence of conformational population

40

30

20

10

Exp

erim

enta

l pop

ulat

ion

ratio

, %

390388386384382380

Sublimation temperature, K

Conformer I Conformer II Conformer III Conformer IV Conformer VII

Conformer I II III IV VIIΔEZPE, kJ/mol 0.0 2.0 7.4 3.9 5.4

Boltzmann distribution at 390 K, % 46.4 25.4 4.7 14.1 9.0Boltzmann distribution at 380K, % 47.5 25.4 4.5 13.8 8.7

Page 11: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

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

Page 12: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

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 pH2 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 pH2 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

Page 13: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

UV Photolysis on β-alanine

Current Work

Aside from conformational changes, β-alanine also seems to photodissociate into CO2 molecule and other fragments. We are now performing computation calculations on some possible candidates in hope to assign these β-alanineUV photolysis products.

Ab

sorb

an

ce,

rela

tive

inte

nsi

ty

24002350230022502200 Wavenumber, cm

-1

CO2

At Deposition

After 4hrs UV Irradiation

185018481846184418421840

New product peakfrom UV photolysis

Page 14: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

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

Page 15: Infrared Spectroscopy of Alanine in Solid Parahydrogen Shin Yi Toh, Ying-Tung Angel Wong, Pavle Djuricanin, and Takamasa Momose Department of Chemistry.

Acknowledgement

Supervisor: Takamasa Momose

Collaborator: Ying-Tung Angel Wong

Technician: Pavle Djuricanin