Tunneling Effects and Conformation Determination of The Polar Forms of 1,3,5 Trisilapentane Frank E. Marshalla, William Raymond Neal Tonksb , David Joseph Gillcrista, Charles J. Wurreyc, Gamil A. Guirgisb, G. S. Grubbs IIa aMissouri University of Science and Technology bCollege of Charleston CUniversity of Missouri, Kansas City

Motivation Contacted by Gamil Guirgis from the College of Charleston, South Carolina 1,3,5 Trisilapentane had never been studied in the Microwave regime Interest in conformation orderings Interest in silyl rotors

Energy Difference (cm-1) Theoretical Data Theoretical information was provided Utilizes MP2(Full)/6-311+G(2d,2p) methods 4 Different conformations predicted C2 should not be detectable due to minimal dipole Cs has sizable dipole, however the energy barrier is large Conformation Dipole X Y Z C2 0.00 0.0625 C1 -0.6819 1.007 0.8197 C2V 4.8834 Cs 0.623 0.8458 Conformation Energy Difference (cm-1) C2 C1 145 C2v 196 Cs 667

C1 conformation Conformation: C1 X -0.6819 Y 1.007 Z 0.8197

C2V Conformation Conformation: C2V X 0.00 Y Z 4.8834

Missouri S&T CP-FTMW 6-18 GHz linear frequency sweep (“chirp”) Expandable to 2-18 GHz with a specific amplifier 4us, 6GHz chirps Low noise, High fidelity instrument Minimal number of parts AWG and Oscilloscope eliminate multiple circuit components 23GHz, 100GS/s oscilloscope 40W Solid state power amplifier 50GS/s digitization rate, 20GHz bandwidth AWG Insert ArHCl spectra.

Data Analysis Initial Fits done via Pickett in tandem with the AABS1 package C1 fits Approximately 80 lines A and E states have been fit 1)Z. Kisiel, PROSPE – Programs for Rotational SPEctroscopy, URL: http://info.ifpan.edu.pl/ kisiel/prospe.htm A states E states

Data Analysis C2V Fits Only 18 Lines Only some of the E states have currently been identified

Silyl Rotor Analysis Fits in XIAM have so far proven unsuccessful Only C1 has been analyzed thus far C2V is still ongoing Letting the structure vary has yielded unreasonable structures Letting barrier heights vary has yielded unreasonable results Letting f vary yields unreasonable results To our knowledge, no program can fit a C1 molecule with 2 tops. Any suggestions on how to attempt this problem would be appreciated!

Acknowledgements Dr. Garry Grubbs Dr. Gamil Guirgis Lab Members University of Missouri Research Board Grant Pictures of Galen, Brooks, Corey Evans