Synthesis and Study of Photophysical Properties of Mono and Binuclear Cycloplatinated Compounds with Pyrazole and Pyrazolate Ligands

Resumen

In the last two decades, the design and study cycloplatinated(II) complexes has undergone a notabledevelopment due to their use as triplet emitting materials. In these complexes, the combination ofheteroaromatic cyclometalated goups and auxiliary ligands allows the fine-tuning of various mixed (π-π*)LC/MLCT excited states1. In this framework, pyrazole (RpzH)-ligands provide an interesting entry tothe design of homo and polymetallic systems with interesting structures and intriguing luminescentproperties. Indeed, a great variety of luminescent homo and heteropolynuclear pyrazolate complexes[Pt2M2] (M = Ag, Cu)2 and pyrazolate-briged dinuclear PtII complexes have been recently reported3. Inthe latter, the Pt···Pt distance strongly depends on the steric hindrance of the pyrazolate substituentsand modifies the nature of the low-lying emissive state switching from a 3LC/3MLCT to a 3MMLCTnature. Furthermore, oxidation processes of pyrazolate-bridged PtIIPtII are an ease entry to unusualPtIII-PtIII complexes3.In this work, we present the synthesis, characterization and photophysical properties of a series ofmononuclear bis-pyrazole complexes [Pt(pbt)(RpzH)2]PF6 (RpzH = pz 1, 3,5-Me2pzH 2, 3,5-iPr2pzH 3)and their deprotonation to form butterfly-like bis-pyrazolate bridged diplatinum complexes{[Pt(pbt)(μ-Rpz)]2} (4-6). Finally, oxidation of {[Pt(pbt)(μ-pz)]2} 4 afforded the symmetrical PtIII-PtIIIcomplex {[Pt(pbt)(μ-pz)Cl]2} 7, which is emissive in rigid media.