Jason F. Fuller

Pulsed-field ionization electron spectroscopy and binding energies of alkali metal-dimethyl ether and -dimethoxyethane complexes

Lithium and sodium complexes of dimethyl ether (DME) and dimethoxyethane (DXE) were produced by reactions of laser-vaporized metal atoms with organic vapors in a pulsed nozzle cluster source. The mono-ligand complexes were studied by photoionization and pulsed field ionization zero electron kinetic energy (ZEKE) spectroscopy. Vibrationally resolved ZEKE spectra were obtained for Li(DME), Na(DME) and Li(DXE) and a photoionization efficiency spectrum for Na(DXE). The ZEKE spectra were analyzed by comparing with the spectra of other metal-ether complexes and with electronic structure calculations and spectral simulations. Major vibrations measured for the M(DME) (M=Li,Na) ions were M-O and C-O stretches and M-O-C and C-O-C bends. These vibrations and additional O-Li-O and O-C-C-O bends were observed for the Li(DXE) ion. The M(DME) complexes were in C2v symmetry with the metal atom binding to oxygen, whereas Li(DXE) was in a C2 ring configuration with the Li atom attaching to both oxygen atoms. Moreover, the ionization energies of these complexes were measured from the ZEKE or photoionization spectra and bond dissociation energies were derived from a thermodynamic cycle.

A photoionization and photoelectron study of vibrational and electronic cooling in metal molecular beams

Abstract Threshold photoionization and pulsed-field-ionization zero-electron-kinetic-energy photoelectron spectra have been used to study the vibrational cooling of Cu–N(CH 3 ) 3 and the electronic cooling of Al–NH 3 in helium and argon supersonic jets. The vibrational temperatures of Cu–N(CH 3 ) 3 are estimated to be ∼40 K in argon and ∼120 K in helium, whereas the electronic temperatures of Al–NH 3 are about 20 and 80 K, respectively. Argon more efficiently cools the internal degrees of freedom of the metal systems, but helium provides additional spectroscopic information about the neutral molecules. The differences in the observed spectra have greatly facilitated spectral assignments for these complexes.

Pulsed-field ionization zero electron kinetic energy spectroscopy and theoretical calculations of copper complexes: Cu–X(CH3)3 (X=N,P,As)

The copper complexes were produced in pulsed laser vaporization molecular beams and investigated by pulsed-field ionization zero electron kinetic energy (ZEKE) spectroscopy and second-order Moller–Plesset (MP2) perturbation and hybrid B3LYP density functional theory calculations. The ground electronic states of Cu–X(CH3)3 and Cu+–X(CH3)3 (X=N,P,As) are 2A1 and 1A1, respectively, both with C3v symmetry. From the ZEKE spectra, the adiabatic ionization potentials of the neutral molecules are determined to be 44 730, 41 508, and 42 324 cm−1, and the Cu+/Cu–X stretching frequencies are 268/199, 214/187, and 188/155 cm−1 for X=N, P, and As, respectively. The degenerate Cu+/Cu–P–C and Cu+/Cu–As–C bending frequencies are measured to be 146/83 and 118/52 cm−1, while the Cu+/Cu–N–C mode was not observed. In addition, the CH3 wag, X–C stretching, and XC3 umbrella modes are also measured for the phosphine and arsine complexes. From the MP2 theory, the dissociation energies of the Cu+ and Cu complexes are estimated to...

Photoelectron and photoionization spectroscopy of weakly bound aluminum–methylamine complexes

Aluminum–methylamine complexes are produced in pulsed molecular beams. Their electronic spectra are obtained using threshold photoionization and zero-electron-kinetic-energy photoelectron spectroscopies and interpreted using density functional and ab initio calculations. The photoelectron spectra reveal ground electronic states and intermolecular and ligand-based vibrations of Al–NHn(CH3)3−n and Al+–NHn(CH3)3−n (n=0–2), adiabatic ionization energies of Al–NHn(CH3)3−n, and a low-lying excited electronic state of Al–NH2CH3. In addition, the spectroscopic measurements and theoretical calculations show strong methyl substitution effects on the ionization energies and metal–ligand binding. Striking spectral differences are discovered between these aluminum complexes and previously studied gallium and indium analogues.

Zero electron kinetic energy photoelectron spectroscopy and density functional theory calculations of gallium-methylamine complexes

Gallium–dimethylamine and –trimethylamine were produced in pulsed laser vaporization molecular beams and studied by threshold photoionization and pulsed-field ionization zero electron kinetic energy (ZEKE) photoelectron spectroscopies and density functional theory calculations. Analyses of the ZEKE spectra yield molecular adiabatic ionization potentials and metal–ligand and ligand-based vibrational frequencies. Comparisons of the experimental and theoretical results establish the ground electronic states of the neutral and ionic complexes. The ionization potentials, Ga+/Ga–N stretching, and Ga+/Ga–N–C bending frequencies are 38 790, 206/177, and 132/128 cm−1 for the dimethylamine complex and 38 081 cm−1, 188/133, and 111/92 cm−1 for the trimethylamine species. The electronic ground states are 1A′/2A′ for Ga+/Ga–NH(CH3)2 and 1A1/2A″ for Ga+/Ga–N(CH3)3. The calculated metal–ligand binding energies of Ga+/Ga–NH(CH2)2 and –N(CH3)3 are 36.2/9.7 and 37.1/8.5 kcal mol−1, respectively.

Photoelectron spectroscopy and density functional theory of puckered ring structures of Group 13 metal-ethylenediamine.

The ethylenediamine (en) complexes of Al, Ga, and In atoms were prepared in laser-vaporization supersonic molecular beams and studied with pulsed field ionization zero electron kinetic energy photoelectron spectroscopy and density functional theory. Several conformers of each metal complex are obtained by B3LYP calculations, and a five-membered cyclic structure is identified by combining the experimental measurements and theoretical calculations. Adiabatic ionization potentials, vibrational frequencies, and bond dissociation energies are determined for the ring structure. The ionization potentials of the Al, Ga, and In species are measured to be 32 784 (5), 33 324 (5), and 33 637 (7) cm(-1), respectively, and metal-ligand dissociation energies of the ionic and neutral complexes are calculated to be 60.2/16.2 (Al(+)/Al), 55.5/13.0 (Ga(+)/Ga), and 50.0/11.4 (In(+)/In) kcal mol(-1). Metal-ligand stretch and bend as well as a number of ligand-based vibrations are measured. Harmonic frequencies and anharmonicities of the M(+)-N (M=Al,Ga,In) stretch are determined for all three M(+)-en ions and the C-C-N bend of Ga(+)-en and In(+)-en. In comparison to monodentate methylamine, the bidentate binding of ethylenediamine leads to a significantly lower ionization potential and higher metal-ligand bond strength of the metal complexes.