Quenching of the phosphorescence of thermally reversible photochromic naphthopyran Re(i) complexes initiated by either visible or ultraviolet radiation.

Re(i) complexes bearing thermally reversible photochromic naphthopyran axial ligands undergo highly efficient, reversible phosphorescence quenching actuated by either visible or UV irradiation. The photoinduced quenching of the triplet metal-to-ligand charge-transfer (3MLCT) emission is interpreted based on changes in the relative energies of the excited states.