Multifrequency ESEEM (electron spin echo envelope modulation) and EPR spectroscopies are employed to elucidate the electronic structure of the monoradical anion of tris(1,3-diphenyltriazenido)aluminum, [Al(dpt)(3)](-), which is obtained by the chemical reduction of Al(dpt)(3). Analysis of the EPR and ESEEM spectra obtained for various isotope-labeling combinations, including N-15 isotope labeling of either the 1,3 (flanking) or 2 (central) positions of the diphenyltriazenide ligands, allows for the detailed study of the electronic structure of the radical anion. EPR spectra of the N-15-labeled derivatives clearly indicate that the radical anion complex is ligand-centered with strong hyperfine couplings to the nitrogen nuclei of a single triazenide ligand observed. However, detailed analysis of the strong hyperfine couplings exhibited in the EPR spectra is prevented by the lack of resolution, A multifrequency ESEEM spectroscopy study was undertaken in order to resolve the weakly coupled nuclei obscured in the EPR spectra by the inhomogeneous line broadening. A very weak coupling to the aluminum center is manifested in the ESEEM spectra, further supportive of the ligand-centered nature of the radical anion complex. Also evident from the ESEEM spectra are three distinguishable types of nitrogen nuclei : weak, anisotropically coupled central and flanking nitrogens and weak, isotropically coupled (ca. 1 Gauss) flanking nitrogens. Ab initio calculations were performed in order to aid in the assignment of the nuclear hyperfine couplings observed in the ESEEM and EPR spectra to specific nitrogen positions on the triazenide rings. Together, the EPR, ESEEM, and nb initio calculations give a coherent picture of the electron spin density distribution and bonding in the radical anion [Al(dpt)(3)](-). Reduction of the aluminum complex results in localization of the electron onto the p-pi* molecular orbitals of one of the three diphenyltriazenide ligands.