The ultraviolet spectroscopy of phenylcyclopentene and phenylcyclopentadiene. Josh J. Newby, Ching-Ping Liu, Christian Müller and Timothy S. Zwier FD02 Department of Chemistry, Purdue University West Lafayette, IN 47907

2 stage ion acceleration pulsed valve laser port diffusion pump cryocooler Einzel lens mass gate pulser ground plate MCP Origins of Phenylcyclopentenes Electrodes Reaction channel Insulator II C6C6 C7C7 C8C8 C9C9 C 10 C 11 C 12 WI06 Butadiene Discharge

What is m/z 142? Benzene discharge Vinylacetylene discharge Personal Communication T. Schmidt 2006 Butadiene discharge II C6C6 C7C7 C8C8 C9C9 C 10 C 11 C 12 UVMPI

 -methylstyrene and beyond ~72 cm -1 ? ?

Cools gas phase molecules to effective temperatures of a few degrees Kelvin Jet-cooled UV spectrum Boltzmann distribution of the vibrational population prior to expansion Collisional cooling to zero-point vibrational level B* C E C C B A D A C A A B C C A A E B B B B B D UV C UV-chromophore A Jet-Cooled Spectroscopy

Resonant 2 Photon Ionization (R2PI): MS to UV Spectrum R2PI S1S1 S0S0 Ion

Synthesis of phenylcyclopentadiene 1 7 Bernard-Henriet, C. and Chanon M. Tetrahedron letters 37(14) PCP4D PCP3D

Cyclopentadiene dimer Δ 170 

Identification of Phenylcyclopentadiene (PCPD) Synthetic Discharge or

Identification of phenylcyclopentene (PCP) a) b) Commercial Discharge

UVHB S1S1 S0S0 Hole-burn Probe B* C E C C B A D A C A A B C C A A E B B B B B D Probe C A Hole-burn nsec UV Hole-burn UV probe Isomer and Conformation Selectivity UV Holeburning Spectroscopy UV Hole-burn laser fixed: Provides  selectivity UV probe laser tuned Records the UV spectrum of a single conformation free from interference from others present in the expansion

R2PI A B UVHB of PCPD and PCP * R2PI * *

Phenylcyclopentadienes (PCPD)

Phenylcyclopentenes Twisted  ~19  Heavy atom planar  ~ 0   Twisted  ~29    One Conformation Gaussian 03 B3LYP G (d,p) PCP3DPCP4DPCP One Conformation Gaussian 03 B3LYP G (d,p) One Conformation Gaussian 03 B3LYP G (d,p)

Progression of phenylcyclopentene 6a 6b 12

PCP Excited State Torsion Gaussian 03 CIS 6-31+G (d,p)

UV laser tuned A (S 0,v=0) A * (S 1 ) Detect total fluorescence UV laser Fixed Total fluorescence CCD Laser Induced Fluorescence (LIF) Single Vibronic Level Fluorescence (SVLF) Fluorescence Techniques PMT

SVLF of PCP 6a6b18

PCP Ground State Torsion Gaussian 03 B3LYP G (d,p)

PCP3D Ground State Torsion

Origin SVLF of PCP3D

Laser Induced Fluorescence Chamber To Roots pump PMT Carrier gas UV beam y x z Lens Mirror Pulsed valve Expansion

Origin Dispersed Fluorescence

Dispersed Fluorescence PCP

LIF of PCPD X/D ~10 R2PI

Dispersed Fluorescence of PCPD

Dispersed Fluorescence Cont.

LIF PCPD X/D~5 71

Conclusions 1 Conformation of each species –PCP, PCP3D, PCP4D Torsional Motions of PCP –Harmonic excited –Anharmoic, distorted ground All three seem to play a role in PAH formation

Dispersed Fluorescence of +71

Acknowledgements Professor Timothy S. Zwier U.S. Department of Energy National Aeronautics and Space Administration The Zwier Group Esteban BaqueroTG11 V. Alvin ShubertTG08, RA07, FD07 Tracy LeGreveTF13 Nathan Pillsbury William JamesTG12 Chirantha RodrigoRA09 Josh Sebree Dr. Jaime Stearns Dr. Talitha Selby Dr. Jasper Clarkson Dr. Ching-Ping Liu*FD01 Dr. Christian MüllerRA10

Pressure Study

The Zwier Group

Acknowledgements Professor Timothy S. Zwier The Zwier Group Esteban Baquero V. Alvin Shubert Tracy LeGreve Nathan Pillsbury William James Chirantha Rodrigo Josh Sebree Dr. Jaime Stearns* Dr. Talitha Selby Dr. Jasper Clarkson Dr. Ching-Ping Liu* Dr. Christian Müller U.S. Department of Energy National Aeronautics and Space Administration

Interesting Spectra m/z 142 m/z 144

Finding 142 and 144 m/z 142m/z 144

Discharge C4H6C4H6 Reaction Quenched by Expansion C6H6C6H6 C 12 H 10 C9H8C9H8 C4H6C4H6 C4H6C4H6

Phenylcyclopentadienes Top: Synthetic Right: Discharge

Phenylcyclopentadi-1,4-ene

Conformation by IR ss ring as ring as CH ss CH2 Gaussian 03 B3LYP G (d,p)

S1S1 S0S0 IR Probe B* C E C C B A D A C A A B C C A A E B B B B B D Probe C A IR nsec IRUV probe RIDIRS Resonant Ion Dip IR Spectroscopy IR tuned UV probe laser fixed Records the IR spectrum of a single conformation free from interference from others present in the expansion Ion

RIDIRS

Progression of phenylcyclopentene ~72 cm -1 

Synthesis of Phenylcyclopentadiene Bernard-Henriet, C. and Chanon M. Tertahedron letters 37(14)