ELECTRON SPIN STATES AND STRUCTURES OF LANTHANIDE Ce

ELECTRON SPIN STATES AND STRUCTURES OF LANTHANIDE (Ce, Pr, AND Nd) COMPLEXES OF CYCLOOCTATETRAENE Ce [Xe]4 f 5 d 6 s 2 Pr [Xe]4 f 36 s 2 Nd [Xe]4 f 46 s 2 SUDESH KUMARI, YANG LIU, MOURAD ROUDJANE, DILRUKSHI HEWAGE, and DONG-SHENG YANG University of Kentucky Lexington, KY 40506 -0055

BACKGROUND Ø Photoionization and anion photoelectron spectroscopy of [Lnn(COT)m] Ø Mass selected photodissociation spectroscopy of lanthanide complexes Ø Magnetic moments of lanthanide complexes Ø Time-of-flight spectrometry of Ln+ with cyclic hydrocarbons Ø Computational studies on Ln(COT)2 • • • Nakajima, A. ; Kaya, K. J. J. Phys. Chem. A 1999, 104, 176. Scott, A. C. ; Foster, N. R. ; Grieves, G. A; Duncan, M. A. Int. J. Mass Spectrom. 2007, 263, 171. Miyajima, K. ; Knickelbein, M. B. ; Nakajima, A. Polyhedron 2005, 24, 2341 -2345. Gibson, J. K. J. Phys. Chem. 1996, 100, 15688. Liu, W. ; Dolg, M. ; Flude, P. J. Phys. Chem. 1997, 107, 3584.

MOTIVATIONS Ø Role of f electrons of lanthanides Ø Metal-ligand binding mode Ø Conformational change in ligand Ø Symmetry and electronic states of the complexes Ø Zero electron kinetic energy spectroscopy of Gd(COT) complex 4 f 75 d 6 s 2 + Gd →→ • Roudjane, M. ; Kumari , S. ; Yang, D. -S. J. Phys. Chem. A 2011, 116, 839 -845.

EXPERIMENTAL SETUP MCP TOF Extraction Can Pulsed Valve and Metal rod -Metal Shielding GV HV Carrier Gas Mixture Diffusion Pump Turbo pump

PIE SPECTRA OF Ce, Pr, AND Nd(COT) 38200 (200) Pr(COT) 37700 (200) 36750 (150) Ce(COT)

ZEKE SPECTRA OF Ce, Pr, AND Nd(COT) 0 -0 Ce(COT) 0 -0 Pr(COT) 0 -0 Nd(COT)

ZEKE SPECTRA OF Ce AND La(COT) 0 -0 Ce(COT) • [Xe]5 d 4 f 6 s 2 • IE = 36773 cm-1 • Ce+-L(stretch. ) = 278 cm-1 Ce(COT) La(COT) • [Xe]5 d 6 s 2 • IE = 36641 cm-1 • La+-L(stretch. ) = 278 cm-1

ZEKE SPECTRA OF Ce AND La(COT) 0 -0, 36905 278 0 -0, 36773 Four band systems 278 • Different isomers • Different electronic transitions 0 -0, 37684 272 0 -0, 38234 278

COMPUTATIONAL METHODS Ø Geometries and vibrational frequencies • B 3 LYP, MP 2 • 6 -311+G(d, p) {C, H} • SDD {Ce, Pr, and Nd} Ø Single point energies • CCSD(T)//B 3 LYP and CCSD(T)//MP 2 Ø SA-CASSCF Ø Spectral simulations

RELATIVE ENERGIES (Erel, cm-1), ELECTRON CONFIGURATION OF NEUTRAL AND ION OF Ce(COT) FROM CCSD(T)//MP 2 Electronic state Electron configuration 3 A 4 f 06 s 1 3 E 4 f± 16 s 1 3 E 4 f± 26 s 2 3 E 4 f± 36 s 3 2 A 4 f 0 1 15 d 16 s 2 2 E Ce 4 f 4 f± 1 1 2 E 4 f± 2 2 2 E 4 f± 3 3 Ø CASSCF calculations supports ground state determination Erel 0 260 410 897 36176 36395 37132 37596

ELECTRONIC TRANSITIONS, ELECTRON CONFIGURATION, RELATIVE ADIABATIC IONIZATION ENERGIES (AIErel, cm-1), OF Ce(COT) Transition Electron AIErel (MP 2) AIErel (Exp) configuration Transitions from lowest energy neutral 2 A 3 A 4 f 06 s 0 0 1 1 2 E 3 A 4 f± 1 4 f 06 s 195 132 1 1 2 E 3 A 4 f± 2 4 f 06 s 997 911 2 1 2 E 3 A 4 f± 3 4 f 06 s 1427 1461 3 1

ZEKE SPECTRA OF Ce(COT) 254 0 -0 (36773) ~16 0 -0 (36905) 278 252 0 -0 (37684) 252 272 0 -0 (38234) 278 (a) Expt, He (c)+(d)+(e)+(f) (c) 2 A 1 3 A 1 (d) 2 E 1 3 A 1 (e) 2 E 2 3 A 1 (f) 2 E 3 3 A 1

Ce(COT) STRETCHING FREQUENCIES (cm-1) AND AIEs (cm-1) OF Ce(COT) COMPLEXES State 3 A 1 2 E 2 2 E 3 Frequency ZEKE 254 276 Calc. 260 281 278 272 278 281 278 Transitions AIE 2 A 3 A 1 1 2 E 3 A 1 1 ZEKE 36773 36905 Calc. 36094 36289 3 A 2 1 2 E 3 A 3 1 37684 38234 37091 37521 2 E

CONCLUSIONS Øf electrons • do not change binding mode • responsible for low-lying electronic states Ø Half sandwich complex 8 binding mode Ø Planar COT in the complex Ø Neutral electronic states • Ce(COT) 3 A 1 4 X Pr(COT) • 5 X Nd(COT) •

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Ø Photoionization and anion photoelectron spectroscopy of lanthanide complexes Ø Mass selected photodissociation spectroscopy of lanthanide complexes Ø Anion photoelectron study of Fe and Co complexes Ø Computational studies on half-sandwich complexes of alkaline earth metals Ø ZEKE spectroscopy of group III metal complexes • • • Nakajima, A. ; Kaya, K. J. J. Phys. Chem 2000, 104, 176. Scott, A. C. ; Foster, N. R. ; Grieves, G. A; Duncan, M. A. Int. J. Mass Spectrom. 2007, 263, 171. Gong, Z; Shen, H. ; Zhu, W. ; luo, X. ; Chen, K. ; Jiang, H. Chem. Phys. Lett. 2006, 423, 339. Li, X. ; Eustis, S. N. ; Bowen, K. H. ; Kandalam, A. J. Chem. Phys. 2008, 129, 124312. Lee, J. S. ; Lei, Y. ; Kumari, S. ; Ynag, D. -S. J. Chem. Phys. 2009, 131, 104304.

State 3 A Ce-C 2. 599 2. 561 2. 560 2. 562 2. 556 C-C 1. 421 1. 420 1. 472, 1. 351 1 2 A 1 2 E 2 2 E 3 COT 1. 443, 1. 385 C-H 1. 089 1. 088 COT 21. 421

Electronic transitions, electron configuration, relative adiabatic ionization energies (AIErel, cm-1), of Ce(COT) complexes from ZEKE spectroscopy and MP 2 calculations. Transition 2 A 2 E 2 E 2 E 1 1 2 3 3 A 1 3 E 2 3 E 3 3 1 A 1 2 E 3 A 1 1 2 E 3 A 2 1 2 E 3 A 3 1 2 A Electron AIErel (MP 2) AIErel (Exp) configuration Transition according to electron configuration 4 f 06 s 0 0 4 f± 16 s -101 132 4 f± 26 s -41 911 4 f± 36 s 927 1461 Transition from lowest energy neutral 4 f 06 s 0 0 4 f± 1 4 f 06 s 195 132 4 f± 2 4 f 06 s 997 911 4 f± 3 4 f 06 s 1427 1461

Electron configuration, point groups, relative energies (Erel, cm-1), metal -ligand stretching frequencies (cm-1) and AIEs (cm-1) of 3 A 1, 2 E 2, and 2 E 3 electronic states of Ce(COT) complexes from DFT/MP 2. State 3 A 1 Electron configuration 4 f 06 s 2 A 1 4 f 0 C 8 v 35895 276 a 281 2 E 1 3 A 1 2 E 1 4 f± 1 C 8 v 36092 278 a 281 2 E 2 3 A 1 2 E 2 4 f± 2 C 8 v 36931 272 a 281 2 E 3 3 A 1 2 E 3 4 f± 3 C 8 v 37363 278 a 278 a From ZEKE measurements Point group C 8 v Erel Frequency Transitions 0 254 a 260 2 A 1 3 A 1 AIE 36773 a 36094 36905 a 36289 37684 a 37091 38234 a 37521

ZEKE SPECTRA OF Pr(COT) 254 0 -0, 37585 20 274 0 -0, 37749 0 -0, 37839 (a) Expt. , He (b) Combined simulation for three transitions 3 X← 4 X

ZEKE SPECTRA OF Nd(COT) 0 -0, 38185 260 272 0 -0, 38285 0 -0, 38202 0 -0, 38398 (a) Expt. , He (b) Combined simulation for three transitions 4 X← 5 X