Department of Chemistry University of Kentucky CHASING NONEXISTENT COMPOUNDS WITH LASERS: Electronic Spectroscopy of Main Group Transient Molecules, Free Radicals, and Ions Dennis J. Clouthier Department of Chemistry University of Kentucky Lexington, KY 40506-0055

(Reactive Intermediates) Nonexistent Compounds? (Reactive Intermediates)

Pulsed Discharge Jet Schematic

Pulsed Discharge Jet Apparatus Digital Delay DC Power Supply Discharge Circuit

Pulsed Discharge Jet Assembly Reheat Tube Discharge head Pulsed valve

Pulsed Discharge Jet Exploded View Pulsed valve Ground electrode Spacer Positive Electrode Reheat Tube

Synchronous-Scan LIF Technique Tunable Dye laser Pump Laser Laser: 21000 22000 23000 24000 20000 19000 16000 15000 17000 18000 cm-1 Offset: 450 cm-1 PMT

Main Group Nonexistent Compounds

Boron Containing Free Radicals BS2 BC BF2 BCl2 HBF HBCl HBBr http://www.buzzle.com/img/articleImages/276159-50511-8.jpg

Industrial Significance of Boron Radicals BF3 and BCl3, often with H2, are used extensively in semiconductor doping and etching processes. The triatomic BF2, BCl2, HBF and HBCl radicals are likely products of such industrial processes. There have been no previous detailed studies of the absorption, LIF or emission spectra of these important free radicals.

Walsh Diagrams for 17 e- Radicals B F   F B    

BF2 Theory & Experiment BF3 BF2 + F Dr. Riccardo Tarroni

BF2 Emission Spectra Dr. Jie Yang

Isotope Shifts and Assignments

BF2 High Resolution Spectrum 13213 Σ band

BF2 Ground State Structure 1.310(1) Å 119.7(6) º

Aluminum Reactive Intermediates AlC2 AlCCH http://theodoregray.com/PeriodicTable/Tiles/013/s7.JPG

Motivations Organoaluminum molecules important in organometallic synthesis, catalysis, CVD …. Interstellar aluminum molecules: AlO, AlF, AlCl, AlOH & AlNC have been identified. Organoaluminum species (AlC, AlC2, AlCCH etc.) could result from reactions of Al atoms with hydrocarbon radicals. AlCCH is a tetra-atomic Renner-Teller molecule in the 1Π excited state. C. Apetrei, H. Ding and J. P. Maier, PCCP 9, 3897 (2007). http://daffy.as.arizona.edu/overview/

The Tetra-atomic Renner-Teller Effect υ4 MRCI/cc-pV(Q+d)Z ε4 (HCC bend) = +0.51 ε5 (AlCC bend) = -0.38 υ5

Calculated AlCCH 1Π State Energy Levels B3LYP/aug-cc-pV5Z frequencies

AlCCH A1Π- X 1Σ+ Sync-Scan LIF Spectra ~ ~ Mohammed Gharaibeh AlCCH A1Π- X 1Σ+ Sync-Scan LIF Spectra (CH3)3Al  AlCCH + ?? Relative Wavenumber (cm-1)

AlCCD 0-0 Band Emission Spectrum υ3 = AlC str. υ4 = DCC bend

High Resolution 0-0 Band of AlCCH MH06 (2010) FOURIER TRANSFORM MICROWAVE SPECTRUM OF AlCCH (X1Σ+) AND ITS 13C/D ISOTOPOLOGUES. M. SUN, D. J. CLOUTHIER, AND L. M. ZIURYS

Arsenic Species AsC CCAs HAsO AsH2 H2AsO WG05: ROBERT A. GRIMMINGER http://periodictable.com/Samples/033.7/s12s.JPG

Arsenic Carbide MO’s and Electronic States

As12C B 2Σ+ -X 2Σ+ LIF Bands AsH3 + 12CO2 As12C Dr. Jie Yang

As12C Emission Spectrum from B 2Σ+ v = 0

High Resolution B - X 0-0 Band of As12C

SEP B 2Σ+ - A 2Π 0-0 Band of As12C DUMP PUMP 2Π1/2 826.3 cm-1 2Π3/2

Molecular Geometries ...π4 σ1 ...π3 σ2 ...σ*1π4 σ2 ...σ*2π3 σ1 π*1 X 2Σ+ 1.1718 Å 1.5620 Å 1.6802 Å A 2Π 1.2333 Å 1.6544 Å 1.775 Å B 2Σ+ 1.1511 Å 1.6894 Å 1.9225 Å ...π4 σ1 ...π3 σ2 ...σ*1π4 σ2 ...σ*2π3 σ1 π*1

Heavy Atom Nitroxyl Radicals P N Phosphoryl radicals: nonplanar, reactive, polymer chemistry Nitroxyl radicals: planar, spin trap, R2NO stable As Arsenyl radicals: nonplanar, reactive?

The AsH2 Free Radical and More…

As O H H H2AsO: A New Free Radical AsH3 + CO2 H2AsO 1.672(1) Å Dr. Sheng-Gui He 1.672(1) Å As O 1.513(4) Å 101.8(4) ° As O H H H H Out-of-plane angle = 63.1°

Electronic States of the Arsenyl Free Radical X 2A' ~ A2A" B2A' T0 = 0.0 cm-1 T0 = 5400 cm-1 T0 = 19616 cm-1 (Ab initio) …(π)2 (n)1 (π*)2 …(π)1 (n)2 (π*)2 …(π)2 (n)2 (π*)1

H2AsO Walsh Diagram   As H O

Cation Radical Anion  π*  π* π*   n n  n   π π π oop =48° 1.463 Å +0.052 Å +0.044 Å O P O P O 122° oop =48° oop =65° 1.601 Å +0.065 Å +0.035 Å As As O O As O 118° oop =59° oop =69°  n π π*  π*  π*  n  n  π  π

Ground State 1st Excited State 2nd Excited State    π* π* π*    1.507 Å -0.024 Å P O P O P O +0.171 Å oop =67° oop =84° oop =48° 102.7° As 1.666 Å +0.148 Å -0.040 Å O As O As O oop =59° oop =70° oop =86°    π* π* π*     n n n     π π π

A Family of Heavy Atom Nitroxyl Radicals P O P S H F H F As O H H P S P S H H Cl Cl

+ 1.555(1) Å Ions HCP+ CO2+ CS2+ Cl2+ N2O+

2Πu - 2Πg UV-visible spectrum of Cl2+ known since 1928. Upper state vibrational levels severely perturbed although rotational structure is regular. Despite many studies, the upper state vibrational numbering, bond length, and the mechanism of the perturbations are still uncertain.

Mohammed Gharaibeh LIF Spectrum of Cl2+

New Bands of Cl2+ in the Red

High Resolution 1 – 0 Band of 35Cl2+

Pieces of the Cl2+ Puzzle Matrix elements ~ 120 cm-1 re = 2.2287(7)Å re = 1.8917(1) Å Cl + R. P. Tuckett and S. D. Peyerimhoff, Chem. Phys. 83, 203 (1984)

Phosphorus Transient Species HPO HPS HPCl HPBr PCN CCP H2PO H2PS Cl2PS F2PS http://www.sciencephoto.com/images/showFullWatermarked.html/A150324-Phosphorus-L.jpg?id=651500324

Diversity of Main Group Dicarbide Geometries Linear: C2H, C2N, C3, C2O, C2S, Cyclic: BC2 Bent: C2Cl T-Shaped: SiC2, AlC2 C2P, C2As http://www.takdangaralin.com/wp-content/uploads/2009/02/priodictable1.jpg

The Previously Unknown CCP Free Radical 12CH4 + PCl3 C P 47

Rotational Analysis Dr. Fumie Sunahori 48

Interstellar Molecule? Phosphorus compounds of interest in astrobiology. PO, PN, CP and HCP known interstellar molecules. Cannot account for all the interstellar phosphorus. CCP dipole moment ~ 3.4 D. 49

University of Arizona, Steward Observatory

Mm-wave Spectrometer in Ziurys Lab Dr. DeWayne Halfen

Phosphorus Source

New Microwave Spectra C=C=P• • •P−C≡ N P=S H

12m Radiotelescope, Kitt Peak, AZ

CW Leonis (IRC+10216) 650 light years from earth, brightest IR object in sky after then sun, is a red giant that is dying, spewing out enormous quantities of materials into circumstellar atmosphere. It’s diameter is about 5 times the distance of earth to sun. Radius is 500 times that of our sun.

CCP Exists in Space! 28.2 MHz 45.1MHz

In Conclusion…. The pulsed discharge technique has proven to be a powerful method for studying transient molecules, free radicals and ions. A plethora of novel small molecules remain to be discovered and characterized in terrestrial and extraterrestrial environments. Many nonexistent compounds do exist!

Acknowledgements Fumie Sunahori Lucy Ziurys Mohammed Gharabeih Bob Grimminger Sheng-Gui He Jie Wei Jie Yang Lucy Ziurys DeWayne Halfen Ming Sun Jie Min Funding: NSF KSEF Richard Judge Riccardo Tarroni