Complexation of Pu(IV) with the actinide extractant CyMe₄-BTPhen (2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-1,10-phenanthroline) was followed by vis-NIR spectroscopy in acetonitrile solution. The solid-state structure of the crystallized product suggests that Pu(IV) is reduced to Pu(III) upon complexation. Analysis by DFT modeling is consistent with metal-based rather than ligand-based reduction.