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Department of Chemistry University of Kentucky

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1 Department of Chemistry University of Kentucky
Mass-Analyzed Threshold Ionization Spectroscopy of Cyclic La(C5H6) Formed By La Atom Activation of Pentyne and Pentadiene Wenjin Cao, Yuchen Zhang, Dong-Sheng Yang Department of Chemistry University of Kentucky

2 Background and Motivations
Metal activation of hydrocarbons plays an important role in organic synthesis and catalysis. Extensive studies on metal atoms reactions with hydrocarbons. Flow reactor kinetic studies Crossed molecular beam studies Few spectroscopic studies, little information about the structures and electronic states of the intermediates and products. Carrol, J.J.; et al. J., Am. Chem. Soc. 1993, 115, 6962. Hinrichs, R.Z.; et al., J. Phys. Chem. A. 2008, 112, 3010.

3 Our Project Mass-analyzed threshold ionization (MATI) spectroscopy of La reactions with small hydrocarbons La + alkanes → not reactive enough La + alkenes/alkynes → various products

4 Experimental Setup Detector TOF Tube Extraction Can HC PV GV HV UV He
320 V/cm 532 nm Diffusion Pump Turbo pump Reaction Chamber Spectroscopy Chamber

5 MATI 320 V/cm Ion Neutral Rydberg states Extraction Can 1 ~ 5-20V DC +

6 TOF-MS Spectra La + 1-pentyne La(C3H4) La(C5H6) La + 1,4-pentadiene
La + isoprene LaO La(C5H8)

7 PIE Curves of La(C5H6) La + 1-pentyne La + 1,4-pentadiene 37900 cm-1

8 MATI Spectra of La(C5H6) La + 1-pentyne La + 1,4-pentadiene

9 MATI Spectra of La(C5H6) (La + 1,4-pentadiene reaction)
39741 cm-1 a + b a + c b + c b 2a + b 416 a 318 c 545 864 735 632 960 1041 -276 -367

10 Possible Structures Geometric optimization and frequency calculations:
1,4-elimination 1,3-elimination 7343 cm-1 1,5-elimination 2,3-elimination 10826 cm-1 6756 cm-1 Geometric optimization and frequency calculations: B3LYP/6-311+g(d,p) for C, H and SDD for La

11 1,3-Elimination 37941/38383 Experimental 1A ← 200 K

12 1,5-Elimination 37941/39943 Experimental 1A' ← 200 K

13 1,4-Elimination 37941/40221 Experimental 1A ← 200 K

14 2,3-Elimination 37941/41363 Experimental 1A' ← 200 K

15 Experimental and Simulated Spectra
37941/38383 276/282 (a) 316/313 (a) 367/376 (b) 416/407 (b) 545/553 (c) Experimental 1A ← 200K

16 Summary 2A 1A Freq (cm-1) Animation (a) 313 (b) 407 (c) 553 2.58 La C5
2.75 2.33 1.41 2.70 2.75 C4 C1 C3 1.40 C2 1.37 1.47 2A 2.48 La C5 2.70 2.28 1.41 2.65 2.70 C1 C4 C3 C2 1.37 1.40 1.47 1A

17 Future Work Reaction mechanism?

18 Future Work La + 1-pentyne La + 1,4-pentadiene La(C3H4) La(C5H6) LaO


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