1. PFI-ZEKE Spectroscopy of Aluminum-Imidazole and -Pyrimidine Complexes JUNG SUP LEE, XU WANG, SERGIY KRASNOKUTSKI, and DONG-SHENG YANG University of Kentucky Lexington, KY 40506

2. Motivations  Determine how Al binds to imidazole & pyrimidine

3. 1 3 Ligands 5 2 Non-equivalent nitrogen atoms ImidazolePyrimidine Formula1,3-C 3 H 4 N 2 1,3-C 4 H 4 N 2 Dipole moment 3.96 Debye2.33 Debye Equivalent nitrogen atoms 1 3

4. Al Binding Sites 1 3 2 5  -bonding  -bonding

5. Motivations  Determine how Al binds to imidazole & pyrimidine  Binding energies of these metal ion complexes have been measured with collision-induced dissociation. - N.S.Rannulu, R. Amunugama, Zhibo Yang, and M.T.Rodgers, J. phys. Chem. A 2004, 108, 6385-6396. -R.Amunugama and M.T.Rodgers. J. phys. Chem. A 2001, 105, 9883-9892.

6. Motivations  Determine how Al binds to imidazole & pyrimidine  Binding energies of these metal ion complexes have been measured with collision-induced dissociation.  No information on the binding energy of these neutral complexes - N.S.Rannulu, R. Amunugama, Zhibo Yang, and M.T.Rodgers, J. phys. Chem. A 2004, 108, 6385-6396. -R.Amunugama and M.T.Rodgers. J. phys. Chem. A 2001, 105, 9883-9892.

7. Relationship of Ionization & Dissociation Energies Al + -L IP (Al-L) D 0 + (Al + -L) Energy IP (Al) Al-L D 0 (Al-L) 0 0 + = + IP (Al-L) IP (Al)D 0 + (Al + -L)D 0 (Al-L) ZEKE

8. Experimental and Computational  Experimental methods:  Laser ablation and molecular beams  Photoionization TOF mass spectrometry  Photoionization efficiency spectroscopy  Pulsed-field ionization ZEKE spectroscopy  Computational methods:  Density functional theory calculations - structures & frequencies, B3LYP/6-311+G(d,p)  Multidimensional Franck-Condon factor calculations  Simulations

9. Experimental Apparatus

10. Wavenumber (cm -1 ) 35344(5) 308 125 IP= 35344(5) Ar Al-imidazole

11. Calculated Structure of Al-Imidazole Planar structure Point group Cs R(Al -N3) = 2.232 Å 4 5 1 2 3 HOMO of 2 A’ (top view)

12. ΔE (cm -1 ) 1A’1A’ 2 A’’ 2A’2A’ 0 535 35528 1 A’ 2 A’ Ion Neutral 1 A’ 2 A’’ Electronic Transitions of Al-Imidazole HOMO of 2 A’’ (top view)  E ( 2 A’’- 2 A’) = 535 cm -1

13. Z Y X Orbital Interactions XY-plane

14. Z Y X Orbital Interactions Strong electron repulsion High energy

15. Z Y X Orbital Interactions HOMO of 2 A’’ (side view)

16. Z Y X Orbital Interactions HOMO of 2 A’ (top view)

17. Wavenumber (cm -1 ) 1 A’ 2 A’’ 1 A’ 2 A’ experiment Experimental and Simulated Spectra

18. 0-0 IP= 35344(5) Wavenumber (cm -1 ) 308 125 experiment 1 A’ 2 A’ Al-imidazole

19. Observed Vibrations of Al- Imidazole Metal-ligand stretch (     ) 308 cm -1 Metal-ligand In-plane bending (   ) 125 cm -1

20. Calculated structure of Al-Pyrimidine Planar structure Point group Cs R(Al –N1) = 1.923 Å 5 4 3 2 1 6 HOMO of 2 A’’ (top view)

21. ΔE (cm -1 ) 1A’1A’ 2 A’’ 0 43941 Ion Neutral 1 A’ 2 A’’ Electronic transition of Al-Pyrimidine HOMO of 2 A’’ (side view)

22. Ar Wavenumber (cm -1 ) 44182(6) 261 115 IP= 44182(6) Al-Pyrimidine He

23. experiment Wavenumber (cm -1 ) 0-0 IP= 44182(6) 261 115 1 A’ 2 A’’ Al-Pyrimidine

24. Observed Vibrations of Al- Pyrimidine Metal-ligand stretch ( 26 + ) 262 cm -1 Metal-ligand In-plane bending (   ) 115 cm -1

25. Summary

26. 1 3 Ligands 5 2 ImidazolePyrimidine Formula 1,3-C 3 H 4 N 2 1,3-C 4 H 4 N 2 Dipole moment 3.96 Debye2.33 Debye

27. Summary

29. Conclusions  σ-bonding structures of Al-imidazole and –pyrimidine  Ground electronic states of these neutral ( 2 A’ for imidazole and 2 A’’ for pyrimidine) and ionized ( 1 A’) complexes  Adiabatic ionization and metal-ligand dissociation energies of these neutral states ( 2 A’ and 2 A’’)

30. THANK YOU !