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

Abstract

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 A′1/2A′ for Ga+/Ga–NH(CH3)2 and A11/2A″ 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.