“…The low-energy broad bands at 369, 359, 356, and 359 nm for 1-4, respectively, are assigned to a metal-to-ligand charge-transfer transition (MLCT) (dπ(Re)-π*(pyrimidine-NHC)), similar to those of the analogous Re(I) carbonyl12 complexes of the reported complexes, such as [Re(CO) 3 (bipy)Cl][48] (λ max 371 nm), and [Re(CO) 3 (py-NHC)Cl][35] (λ max 355 nm).As shown inFig. 3, the excitation at the MLCT absorption region (~420 nm) of complexes 1-4 in the deaerated CH 2 Cl 2 solution leads to broad emissions centered at 555-570 nm, respectively, the characteristic MLCT emissions of Re I complexes[49].In the solid state, the emission spectra of 1-4 centered at 515-532 nm, blue shifted by about 50 nm in comparison to those of the solution samples.…”