Phosphorescent 2-phenylbenzothiazole PtIV bis-cyclometalated complexes with phenanthroline-based ligands

We describe a family of dicationic heteroleptic complexes of the type [Pt( pbt)2(N<^>N)]Q2, bearing two cyclometalating 2-phenylbenzothiazole ( pbt) groups and a N<^>N phenanthroline-based ligand [N<^>N = 1,10-phenanthroline ( phen) 4, pyrazino[2,3-f][1,10]-phenanthroline ( pyraphen) 5, 5-amine-1,10-phenanthroline (NH2-phen) 6], with two different counteranions (Q = CF3CO2 and PF6). Complexes 4-6-PF6 and 4-6-CF3CO2 were obtained through ligand substitution from cis-[Pt(pbt)(2)Cl-2] 2 and cis-[Pt ( pbt)(2)(OCOF3)(2)] 3, respectively. The molecular structures of 2, 3 and 4-PF6 and the photophysical and electrochemical properties of all complexes were studied in detail. The precursors 2 and 3 exhibit highenergy emissions from 3IL excited states centered on the cyclometalated pbt, with lower efficiency in 2 in relation to 3 by the presence of closer thermally accessible deactivating (LMCT)-L-3 excited states in 2. The PtIV complexes 4-5-CF3CO2/PF6 display orange emission in CH2Cl2 solution, solid state (298, 77 K) or PS films, arising from a 3IL( pbt) emissive state. The NH2-phen derivatives 6-CF3CO2/PF6 show dual emission associated to two close different emissive states, (IL)-I-3 ' CT (L ' = NH2-phen) and 3IL( pbt), depending on the medium and the excitation wavelength. DFT and time-dependent TD-DFT calculations support these assignments and allow explain the luminescence of these tris-chelate PtIV complexes.