Phosphorescent 2-phenylbenzothiazole Pt IV bis-cyclometalated complexes with phenanthroline-based ligands

• Published in: Dalton transactions : an international journal of inorganic chemistry 2023-05, Vol.52 (19), p.6543-6550
• Main Authors: Corral-Zorzano, Andrea, Gómez de Segura, David, Lalinde, Elena, Moreno, M Teresa
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/D3DT00801K

We describe a family of dicationic heteroleptic complexes of the type [Pt(pbt) (N^N)]Q , bearing two cyclometalating 2-phenylbenzothiazole (pbt) groups and a N^N phenanthroline-based ligand [N^N = 1,10-phenanthroline (phen) 4, pyrazino[2,3- ][1,10]-phenanthroline (pyraphen) 5, 5-amine-1,10-phenanthroline (NH -phen) 6], with two different counteranions (Q = CF CO and PF ). Complexes 4-6-PF6 and 4-6-CF3CO2 were obtained through ligand substitution from -[Pt(pbt) Cl ] 2 and -[Pt(pbt) (OCOF ) ] 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 high-energy emissions from IL 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 excited states in 2. The Pt complexes 4-5-CF3CO2/PF6 display orange emission in CH Cl solution, solid state (298, 77 K) or PS films, arising from a IL(pbt) emissive state. The NH -phen derivatives 6-CF3CO2/PF6 show dual emission associated to two close different emissive states, IL'CT (L' = NH -phen) and IL(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 Pt complexes.