As the electronic absorption features of Ln(II) complexes are sensitive to both the identity of the Ln(II) ion and the coordination environment, 1 the electronic transitions of 2 mM toluene solutions of 1-Ln, 3-Ln and 4-Ln were studied by UV/Vis/NIR absorption spectroscopy (see Figure for compiled spectra; individual spectra are available in the SI Figures ). Within the visible region for Ln(II) complexes, strong broad absorptions are observed as a result of the formal spin-and Laporte-allowed f-d transitions from the stabilization of 5d-orbitals (c.f. Ln(III) complexes). The intraconfigurational f-f transitions, which are typically Laporte-forbidden are often not observed for Ln(II) complexes due to the intense, broad f-d features. It is known that the Sm(II) ion gives rise to complexes which exhibit intense colors as a result of the multiple spin-and orbital-allowed f-d transitions within the visible region. Toluene solutions of dinuclear 1-Sm are dark green and display a broad and intense absorption feature containing multiple shoulders which spans across the visible region (Figure ), with λmax = 22,730 cm -1 (440 nm, ε = 1575 M -1 cm -1 ). This complex has the highest absorption coefficient amongst the family of complexes reported herein, likely as a result of the presence of two Sm(II) centers.