Generally, the luminescence emission of CuIXL (X=halide, L=N-donor ligand) complexes can be assigned to ligand-centered (LC), metal-to-ligand charge transfer (MLCT), ligand-to-metal charge transfer (LMCT), halide-to-ligand charge transfer (XLCT), and metal centered (d10-d9π1*) transfer (MCT). The emission spectra of copper(I)halide complexes of pyridine and pyridine derivatives have been extensively studied and found to show high-energy and low-energy bands.