1. Characterization of Structural Motifs for CO 2 Accommodation in Two Model Ionic Liquid Systems Using Cryogenic Ion Vibrational Predissociation Spectroscopy Joseph A. Fournier, Conrad T. Wolke, Christopher J. Johnson, and Mark A. Johnson Sterling Chemistry Laboratory, Yale University June 20, 2013

2. CO 2 Capture and Activation Masel, Science, 2011, 334, 643. CO 2 ↔ CO + ½O 2 V eq = 1.3 V In water: 2.1 V required to produce CO → 0.8 V overpotential In [emim]BF 4 : 1.5 V required to produce CO → 0.2 V overpotential

3. Ionic Liquids Liquid at or near room temperature Nonvolatile: “Green” solvents High CO 2 solubility Anion dependence: Ac – > Tf 2 N – > TFA > PF 6 – > BF 4 – J.F. Brennecke, E.J. Maginn. JACS, 2004, 124, 5300.

4. The Instrument ESI Needle Temperature Controlled Ion Trap Mounted to He Cryostat Ion Optics 2m Flight Tube Wiley- McLaren TOF Reflectron-1 Coaxial TOF Reflectron-2 DC-Turning Quad Pulsed Valve Electron Gun MCP Detector MCP Detector Nd:YAG OPO/OPA Tunable IR 600-4500 cm -1 Ion Optics Differential Aperture Skimmers Heated Capillary RF-Ion Guides Nd:YAG OPO/OPA Tunable IR 600-4500 cm -1 + e ‒ ∙ +

5. Predissociation Yield 1200140016001800200022002400 Photon Energy / cm -1 Ac ‒ ∙Ar Ac ‒ ∙CO 2 Ac ‒ ∙2CO 2 Ac ‒ ∙4CO 2 Ac ‒ asym. OCOAc ‒ sym. OCO ν 3 CO 2 * Ac – (CO 2 ) m

6. Pred. Yield 1200140016001800200022002400 Calculated Intensity Photon Energy / cm -1 Ac – (CO 2 ) 1 Pred. Yield 1200140016001800200022002400 Calculated Intensity Photon Energy / cm -1 Ac – (CO 2 ) 2 MP2/6-311+G(d,p)

7. Pred. Yield Calculated Intensity 16001800200022002400 Photon Energy / cm -1 Ac – (CO 2 ) 4

8. How About a Real Ionic Liquid? [(emim) 2 BF 4 ] + +N 2 +2N 2 +3N 2 300320340360380400 m/z 334336338340 m/z 10 B 11 B 13 C 1 2 3 4 5

9. The IL “Building Block” 60080010001200140016002800300032003400 Calculated Intensity Photon Energy / cm -1 Pred. Yield Why the complexity? B3LYP/6-31+G(d,p) Ring CH str. Me/Et CH str. Ring Str. Me/Et CH bends CH ip bend Mixed BF 4 /Ring Modes CH oop bends Conrad Wolke

10. 80010001200140016002800300032003400 Photon Energy / cm -1 N 2 Predissociation Yield [(emim) 2 BF 4 ] + [(emim) 3 (BF 4 ) 2 ] + Ring CH str. Me/Et CH str. Ring Str. Me/Et CH bends CH ip bend Mixed BF 4 /Ring Modes C 2 -H oop bend Absorption (%) Bulk Are the Gas-Phase Clusters Related to the Bulk??

11. Isomers? Pred. Yield Ion Dip Signal 280029003000310032003300 Photon Energy / cm -1 NO! Single Isomer! 80010001200

12. Identifying the CH’s Photodissociation Yield 80010001200140016002800300032003400 Photon Energy / cm -1 X X X

13. Identifying the CH’s The Evidence: 1.Red-shifting of the ring CH’s (10-15 cm -1 ) from (2,1) to (3,2) cluster. 2.Double resonance reveals a single isomer. 3.Loss of specific bands upon methyl substitution at the C 2 position. 60080010001200140016002800300032003400 Photon Energy / cm -1 C 2 -H C 4 -H/C 5 -H C 2 -H ip bend C 4 -H/C 5 -H oop bend C 2 -H oop bend

14. 300320340360380400420 m/z CO 2 Condensation in the Ion Trap +CO 2 +2CO 2 Optimal conditions: 5% CO 2 buffer gas, 90 K 340360380400420440460 m/z [(emim) 2 BF 4 ] + [(bmim) 2 BF 4 ] + +CO 2 +2CO 2 WOW!!!

15. CO 2 Condensation in the Ion Trap: emim Pred. Yield 8001000120014001600240026002800300032003400 Photon Energy / cm -1 5 5 6 9 4 3.3Å 5.3Å 3.1Å 2.8Å 3.5Å 2.7Å

16. Outlook Electrospray acetate-based ionic liquid Condense CO 2 onto the cluster in the trap Transfer intact, dissolved CO 2 -acetate complex from solution Determine structure of other ionic liquids (PF 6 -, TFA, Tf 2 N - ) and tag with CO 2 Next-generation instrumental improvements (trap-to-trap, reaction of ESI ions with CO 2 ‒ cluster beam, etc.)

17. Acknowledgments Prof. Mark Johnson Prof. Gary Weddle Chris Johnson Chris Leavitt Andrew DeBlase Arron Wolk Conrad Wolke Olga Garlova

18. Im(CO 2 ) m – CO 2 Predissociation Yield 800120016002000240028003200 Photon Energy / cm -1 x3 Im(CO 2 ) 2 – Im(CO 2 ) 3 – Im(CO 2 ) 6 – IHB ν 3 CO 2 – ν 1 CO 2 –

19. Pred. Yield 800120016002000240028003200 Calculated Intensity Photon Energy / cm -1 Im(CO 2 ) 2 – Pred. Yield 800120016002000240028003200 Calculated Intensity Photon Energy / cm -1 Im(CO 2 ) 3 –

20. Predissociation Yield 1200140016001800200022002400260028003000 Photon Energy / cm -1 (CO 2 ) 7 ‾ Im(CO 2 ) 2 vs Py(CO 2 ) 2 – –