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. (C) 2003 American Institute of Physics.