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

Titan’s 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, , Landera, A.; Mebel, A. M. Journal of the American Chemical Society 2013, 135, 7251.

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, Sebree, J.; et al., Journal of the American Chemical Society 2012, 134, Selby, T. M.; et al., The Journal of Physical Chemistry A 2005, 109, 4484 Cis-o-CyanostyreneIsoquinoline ?

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

Experimental Methods (LIF/DF) S0S0 SnSn Fluorescence Dispersed

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

Para-Cyanostyrene (p-CNs:Excitation) S1S1 ModeExperimentalCalculated * ν ν 24 (6a/X) ν 27 (6b) ν 29 (6a/X) ν ν ν ν (6a/X) A-axis cm (6a/X) *B3LYP/6-31G+(d)

Para-Cyanostyrene (p-CNs: DF) S0S0 ModeExpt.Calc. ν ν 24 (6a/X)827 ν ν 27 (6b) ν 29 (6a/X)383 ν ν ν

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

Meta-Cyanostyrene (m-CNs: UV Depleton)

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.: cm -1 Meta-Cyanostyrene (m-CNs) : Cis vs Trans 13.9 cm cm -1 Trans Cis 1. Selby, T. M.; et al., The Journal of Physical Chemistry A 2005, 109, 4484 Graphic not to scale

(6b) B-axis Meta-Cyanostyrene (m- CNs: Conformer A: cis) S1S1 S0S0 ModeExpt.Calc.Expt.Calc. ν ν 23 (12) ν 25 (6b) ν ν 28 (6a/X) ν 29 (6a/X) ν ν ν 39 ν ν (6a/X) A-axis (6a/X) (12)

Meta-Cyanostyrene(m- CNs: Conformer B: trans) S0S0 ModeExpt.Calc. ν ν 23 (12) ν 25 (6b) ν 27 (6a/X) ν 28 (6a/X) ν ν ν

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

Cis 456 cm -1 over trans – E a =981 cm -1 trans-o- ethynylstyrene – k isom >k collision – Isomerization Barrier: 710 cm -1 – cm -1 to cis Ortho-Cyanostyrene (o-CNs) : Cis preferred S1S1 S0S0 ModeExperimentalCalculatedExperimentalCalculated ν 19 (13) ν 25 (1) ν ν 28 (6a/X) ν 29 (6a/X) ν ν ν ν ν ν cm cm -1 Trans Cis 1. Selby, T. M.; et al., The Journal of Physical Chemistry A 2005, 109, 4484

Ortho-Cyanostyrene (o-CNs) : DF Origin

Ortho-Cyanostyrene (o-CNs) : DF Mixed

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

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

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

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