Facile Approaches to Phosphorescent Bis(cyclometalated) Pentafluorophenyl Pt^IV Complexes: Photophysics and Computational Studies

Abstract

A convenient and general strategy for the synthesis of stable bis(cyclometalated) pentafluorophenyl Pt^IV complexes fac-[Pt(C^N)₂ (C₆ F₅ )Cl] (3 a-f) and mer-[Pt(C^N)₂ (C₆ F₅ )(CN)] (4 c,d) has been developed. Complexes 3 were selectively generated by low-temperature oxidation of the cyclometalated Pt^II complexes [Pt(C^N)(HC^N)(C₆ F₅ )] 2 [prepared from cis-[Pt(C₆ F₅ )₂ (HC^N)₂ ] (1) intermediates] with PhICl₂ and subsequent metalation of the pendant HC^N ligand. Complexes 3 a,b were also alternatively generated by irradiation (Hg lamp, 400 W) of complexes 2 a,b, respectively, in CH₂ Cl₂ . This latter reaction proceeds via the hydride Pt^IV species cis-[Pt(C^N)₂ (C₆ F₅ )H], detected as the only intermediate species. The molecular structures of 1 a,d, 2 a, and 3 a,b,d,e were confirmed by X-ray diffraction. The substitution of Cl^- by CN^- in fac-[Pt(C^N)₂ (C₆ F₅ )Cl] [C^N=2-phenylbenzothiazole (3 c), 2-(4-bromophenyl)benzothiazole (3 d)] evolved with isomerization to give rise to the isomers (OC-6-42)-[Pt(C^N)₂ (C₆ F₅ )(CN)] (4 c, 4 d) having a mer disposition of the cyclometalated and C₆ F₅ groups (X-ray, 4 c). All the complexes are luminescent and their electronic spectra have been compared and interpreted with the aid of time-dependent DFT calculations.