1. 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

2. (Reactive Intermediates)
Nonexistent Compounds?
(Reactive Intermediates)

3. Pulsed Discharge Jet Schematic

4. Pulsed Discharge Jet Apparatus
Digital Delay
DC Power Supply
Discharge Circuit

5. Pulsed Discharge Jet Assembly
Reheat Tube
Discharge head
Pulsed valve

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

7. 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

8. Main Group Nonexistent Compounds

9. Boron Containing Free Radicals
BS2 BC
BF2
BCl2
HBF
HBCl
HBBr

10. 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.

11. Walsh Diagrams for 17 e- RadicalsB F   F B
 
 

12. BF2 Theory & Experiment
BF BF2 + F
Dr. Riccardo Tarroni

13. BF2 Emission Spectra
Dr. Jie Yang

14. Isotope Shifts and Assignments

15. BF2 High Resolution Spectrum
13213 Σ band

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

17. Aluminum Reactive Intermediates
AlC2
AlCCH

18. 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).

19. The Tetra-atomic Renner-Teller Effectυ4
MRCI/cc-pV(Q+d)Z
ε4 (HCC bend) = +0.51
ε5 (AlCC bend) = υ5

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

21. 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)

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

23. 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

24. Arsenic Species AsC CCAs HAsO AsH2 H2AsO WG05: ROBERT A. GRIMMINGER

25. Arsenic Carbide MO’s and Electronic States

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

27. As12C Emission Spectrum from B 2Σ+ v = 0

28. High Resolution B - X 0-0 Band of As12C

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

30. Molecular Geometries ...π4 σ1 ...π3 σ2 ...σ*1π4 σ2 ...σ*2π3 σ1 π*1
X 2Σ+ Å Å Å
A 2Π Å Å
1.775 Å
B 2Σ+ Å Å Å
...π4 σ1 ...π3 σ2
...σ*1π4 σ2
...σ*2π3 σ1 π*1

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

32. The AsH2 Free Radical and More…

33. 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°

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

35. H2AsO Walsh Diagram   As H O

36. Cation Radical Anion  π*  π* π*   n n  n   π π π oop =48°
1.463 Å Å Å O P O P O
122°
oop =48°
oop =65°
1.601 Å Å Å As As O O As O
118°
oop =59°
oop =69°  n π π*  π*  π*  n  n  π  π

37. Ground State 1st Excited State 2nd Excited State    π* π* π*   
1.507 Å Å P O P O P O Å
oop =67°
oop =84°
oop =48°
102.7° As
1.666 Å Å Å O As O As O
oop =59°
oop =70°
oop =86°    π* π* π*     n n n     π π π

38. A Family of Heavy Atom Nitroxyl RadicalsP O P S H F H F As O H H P S P S H H Cl Cl

39. +
1.555(1) Å
Ions
HCP+
CO2+
CS2+
Cl2+
N2O+

40. 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.

41. Mohammed Gharaibeh
LIF Spectrum of Cl2+

42. New Bands of Cl2+ in the Red

43. High Resolution 1 – 0 Band of 35Cl2+

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

45. Phosphorus Transient Species
HPO HPS
HPCl HPBr
PCN
CCP
H2PO H2PS
Cl2PS F2PS

46. Diversity of Main Group Dicarbide Geometries
Linear: C2H, C2N, C3, C2O, C2S,
Cyclic: BC2
Bent: C2Cl
T-Shaped: SiC2, AlC2
C2P, C2As

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

48. Rotational Analysis
Dr. Fumie Sunahori 48

49. 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

50. University of Arizona, Steward Observatory

51. Mm-wave Spectrometer in Ziurys Lab
Dr. DeWayne Halfen

52. Phosphorus Source

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

54. 12m Radiotelescope, Kitt Peak, AZ

55. 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.

56. CCP Exists in Space!
28.2 MHz
45.1MHz

57. 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!

58. 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