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

Motivations  Determine how Al binds to imidazole & pyrimidine

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

Al Binding Sites  -bonding  -bonding

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, R.Amunugama and M.T.Rodgers. J. phys. Chem. A 2001, 105,

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, R.Amunugama and M.T.Rodgers. J. phys. Chem. A 2001, 105,

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

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

Experimental Apparatus

Wavenumber (cm -1 ) 35344(5) IP= 35344(5) Ar Al-imidazole

Calculated Structure of Al-Imidazole Planar structure Point group Cs R(Al -N3) = Å HOMO of 2 A’ (top view)

ΔE (cm -1 ) 1A’1A’ 2 A’’ 2A’2A’ 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

Z Y X Orbital Interactions XY-plane

Z Y X Orbital Interactions Strong electron repulsion High energy

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

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

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

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

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

Calculated structure of Al-Pyrimidine Planar structure Point group Cs R(Al –N1) = Å HOMO of 2 A’’ (top view)

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

Ar Wavenumber (cm -1 ) 44182(6) IP= 44182(6) Al-Pyrimidine He

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

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

Summary

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

Summary

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’’)

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