Spectroscopy With Polarized Light Polarized Matrix Infrared Spectra

Spectroscopy With Polarized Light: Polarized Matrix Infrared Spectra of Cyclopentadieneone THOMAS K. ORMOND, ADAM M. SCHEER, G. BARNEY ELLISON, Department of Chemistry and Biochemistry, University of Colorado, Boulder; MARK R. NIMLOS, Center for Renewable Chemical, Technologies & Materials, NREL, Golden, CO; JOHN W. DAILY, Department of Mechanical Engineering, University of Colorado, Boulder; and JOHN F. STANTON, Institute for Theoretical Chemistry, Department of Chemistry, University of Texas, Austin OSU MOLECULAR SPECTROSCOPY SYMPOSIUM JUNE, 2012 Thomas K. Ormond G. Barney Ellison Group Department of Chemistry and Biochemistry University of Colorado, Boulder

Cyclopentadieneone (C 5 H 4=O) Intermediate in thermal decomposition pathways of lignin model monomers leading to formation of acetylenes and substituted acetylenes – known precursors to PAHs and soot Partial anti aromatic character and rapid dimerization - cannot be isolated Depuy & Lyons, J. Am. Chem. Soc. 1960, 82, 631 -633.

Scheer, Mukarakate, Robichaud, Nimlos, & Ellison, Thermal Decomposition Mechanisms of the Methoxyphenols, J. Phys. Chem. A 2011, 115, 13381 -13389.

Cyclopentadieneone (C 5 H 4=O) Need a clean source of C 5 H 4=O and deuterated species: C 5 D 4=O and C 5 H 2 D 2=O - Synthesis of o-phenylene sulfite De. Jongh, D. C. ; Van Fossen, R. Y. ; Bourgeois, C. F. Tetrahedron Lett. , 1967, 271.

C 5 H 4=O molecular beam diagnostics Molecular diagnostics: C 5 H 4=O+ VUV-TOF-PIMS detection and matrix isolation FTIR phenylene sulfite entrained in He/Ar carrier gas. Temperature monitor Optical Pyrometer 64 cm Wiley-Mc. Laren TOF spectrometer m/ m 2100 pulsed valve 1 msec open @ 10 Hz 1 mm Si. C tube @ 300– 1700 K (tubular reactor) 50 µsec Supersonic Jet of Radicals/He into 10 -8 Torr IE(C 5 H 4=O ) = 9. 49 e. V 118. 2 nm VUV Laser (10. 487 e. V) h VUV + C 54=O C 5 H 4=O+ + e– Supersonic Jet of Radicals/Ar into 10 -6 Torr onto Cs. I window @ 10 K

C 5 H 4=O molecular beam diagnostics: 118. 2 nm (10. 487 e. V) photoionization mass spectrometry

C 5 D 4=O molecular beam diagnostics: 118. 2 nm (10. 487 e. V) photoionization mass spectrometry – fully deuterated isotopomer

C 5 H 4=O and C 5 D 4=O matrix infrared absorption spectroscopy

C 5 H 4=O molecular beam diagnostics: matrix infrared absorption spectroscopy

C 5 H 4=O molecular beam diagnostics: matrix infrared absorption spectroscopy

Linear dichroism IR spectroscopy: Carbonyl dissociative transition – formaldehyde test case z z y x y-polarized UV radiation photo orients sample via electronic transition y x y-polarized IR radiation excites b 2 vibrational transitions [Abs(Y)], zpolarized IR excites a 1 vibrations [Abs(Z)] In this way, we can selectively excite vibrations of a particular symmetry

Linear dichroism IR spectroscopy: Carbonyl dissociative transition – formaldehyde test case

Linear dichroism IR spectroscopy: Cyclopentadieneone

Linear dichroism IR spectroscopy: d 4 -Cyclopentadieneone

Linear dichroism IR spectroscopy: d 4 -Cyclopentadieneone

Thanks to: • This work is funded by the NSF and DOE • Ellison (CU Boulder) and Nimlos (NREL) group members • Don David and Ken Smith (CIRES machine shop) • Chuck Depuy (CU Boulder) • Hans-Heinrich Carstensen (Colorado School of Mines)