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Spectroscopic Investigation of o-, m-, and p-Cyanostyrenes International Symposium for Molecular Spectroscopy FE-12 Joseph A. Korn , Stephanie N. Knezz , Robert J. McMahon , and Timothy S. Zwier Department of Chemistry, Purdue Univesity, West Lafayette, IN, USA Dept. of Chemistry,University of Wisconsin, Madison, WI, USA The Zwier Lab

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Titans Atmosphere Hydrocarbons and Nitrogenated hydrocarbons Cassini-Huygens mission Pathways to Tholins Subsituted Aromatics C 2 H 2 /C 3 HN addition Ring-closing mechanisms Photochemical/Discharge driven pathways Introduction 1.Waite Jr., J.H.; et al.,Science, 2007. 316, 870-875 2.Landera, A.; Mebel, A. M. Journal of the American Chemical Society 2013, 135, 7251.

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Isomers of Quinoline (C 9 H 7 N, 129 amu) Isoquinoline (E)/(Z)-Cinnamonitrile o-,m-,p-Cyanostyrene Analogous Studies Naphthalene photochem o,-m-,p-Ethynylstyrene Isomer specific pathways to larger polyaromatic nitrogenated heterocycles (PANHs) Introduction 1.Landera, A.; Mebel, A. M. Journal of the American Chemical Society 2013, 135, 7251. 2. Sebree, J.; et al., Journal of the American Chemical Society 2012, 134, 1153. 3. Selby, T. M.; et al., The Journal of Physical Chemistry A 2005, 109, 4484 Cis-o-CyanostyreneIsoquinoline ?

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Experimental Methods (R2PI) Ionization Continuum S0S0 SnSn Tuned Laser Ionization Laser (193 nm) Laser Port TOF MS Einzel Lens 2-Stage Ion Acceleration Jordan Valve Boltzmann distribution of vibrational population prior to expansion Collisional cooling to zero-point vibrational level A A B B UV High pressure helium A A B B C C C C C A A A A A A A B B B B B B B C C C C C Supersonic Expansion

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Experimental Methods (LIF/DF) S0S0 SnSn Fluorescence Dispersed

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10 Hz scanned holeburn laser 20 Hz fixed probe t~200 ns Active baseline subtraction Conformation specific UV spectrum Experimental Methods (UV-Depletion)

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Para-Cyanostyrene (p-CNs:Excitation) S1S1 ModeExperimentalCalculated * 20 11751187 24 (6a/X)760787 27 (6b)512549 29 (6a/X)332369 30 239240 31 102139 44 143145 45 5157 29 1 0 (6a/X) A-axis 33923 cm -1 24 0 1 (6a/X) *B3LYP/6-31G+(d)

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Para-Cyanostyrene (p-CNs: DF) S0S0 ModeExpt.Calc. 20 12141208 24 (6a/X)827 25 678686 27 (6b)550562 29 (6a/X)383 30 234245 31 134139 45 3745

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Para-Cyanostyrene (p-CNs: DF: Fermi Resonace)

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Meta-Cyanostyrene (m-CNs: UV Depleton)

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B3LYP/6-31+G(d) m-ethynylstyrene Trans Calc.: -29 cm -1 Expt.: +75 to -81 cm -1 Barrier to Isomerization Calc.: 1237 cm -1 Expt.: 990-1070 cm -1 Meta-Cyanostyrene (m-CNs) : Cis vs Trans 13.9 cm -1 1326 cm -1 Trans Cis 1. Selby, T. M.; et al., The Journal of Physical Chemistry A 2005, 109, 4484 Graphic not to scale

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25 1 0 (6b) B-axis Meta-Cyanostyrene (m- CNs: Conformer A: cis) S1S1 S0S0 ModeExpt.Calc.Expt.Calc. 18 1238125612481262 23 (12)-98310081012 25 (6b)667693714721 26 -578570580 28 (6a/X)443432466468 29 (6a/X)-417434445 30 299252-246 38 625.9616-- 39 40 974976-- 45 -934043 28 1 0 (6a/X) A-axis 29 1 0 (6a/X) 23 1 0 (12)

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Meta-Cyanostyrene(m- CNs: Conformer B: trans) S0S0 ModeExpt.Calc. 18 12511266 23 (12)10081012 25 (6b)717723 27 (6a/X)535549 28 (6a/X)466470 29 414419 43 229210 45 3853

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Ortho-Cyanostyrene (o-CNs) : R2PI S 1 S 0 33074 cm -1

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Cis 456 cm -1 over trans E a =981 cm -1 trans-o- ethynylstyrene k isom >k collision Isomerization Barrier: 710 cm -1 -696.4 cm -1 to cis Ortho-Cyanostyrene (o-CNs) : Cis preferred S1S1 S0S0 ModeExperimentalCalculatedExperimentalCalculated 19 (13)1205119812211214 25 (1)682705727736 26 596598-- 28 (6a/X)421426460456 29 (6a/X)298402405426 30 244243254249 31 136139132145 42 292287416393 43 149187205210 44 109101124125 45 78653045 456 cm -1 981 cm -1 Trans Cis 1. Selby, T. M.; et al., The Journal of Physical Chemistry A 2005, 109, 4484

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Ortho-Cyanostyrene (o-CNs) : DF Origin

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Ortho-Cyanostyrene (o-CNs) : DF Mixed

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Ortho-Cyanostyrene (o- CNs) : DF Fundamentals False Origin

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Spectra of Cyanostyrenes are identified Cis/trans observed in m-CNs only 6a-type modes coupled to styrene/nitrile vibrations Duschinsky mixing is prevalent in S 1 Conclusions

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Photoisomerization of cis-trans m-CNs Photochemistry of o-CNs to Isoquinoline Chirped Pulse Microwave study of o-CNs Cis dipole moment: 4.4052 Debye Trans dipole moment: 4.6386 Debye Future Work

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Dr. Timothy S. Zwier Dr. Robert McMahon Zwier Lab McMahon Lab (Stephanie N. Knezz) Acknowledgements Funding: