Descending Group 2, we also observed the appearance of two new absorption bands, which are clearest in the case of 1-Ca (341 nm, ϵ = 2460 M -1 cm -1 and 425 nm, ϵ = 650 M -1 cm -1 ). These are substantially weaker than the absorption at 283 nm, and likely correspond to ligand-tometal charge transfer (LMCT) transitions in the M-C and M-N bonds. This is due to the greater ionicity of these bonds, thereby lowering the energy of the transition into the visible region.