Luminescence from open-shell, first-row transition metal dipyrrin complexes†
Several first-row transition metal complexes of the 1,9-bis(2′,4′,6′-triphenylphenyl)-5-mesityl dipyrrinato ligand and its tetrahalogenated analogues have been synthesized and their luminescence spectra obtained. The protonated ligands, as well as the Li(I), Mn(II), Cu(I), Cu(II), and Zn(II) chelates show appreciable luminescence, despite the paramagnetism of the Mn(II) and Cu(II) ions. Fluorescence quantum yields (ΦF) as high as 0.67 were observed for the zinc complex. Luminescence was partially quenched by the introduction of heavy halogens to the backbone of the ligand, as well as by the introduction of paramagnetic metal ions. Room-temperature, solution state phosphorescence was observed from the halogenated dipyrrinato lithium salts, as well as from the non-halogenated Mn(II) complex.