Synthesis and Study of Luminescent Properties of a new Family of Cyclometalated PtIV Compounds with N,N’-Donot Ligands

Resumen

Numerous studies have been carried out on cyclometalated complexes of d6 (RuII, OsII or IrIII) and d8(PtII and AuIII) metal ions due to their potential applications in fields such as photocatalysis, biologicalsensing, photosensitizers and optoelectronic devices. By contrast, related luminescent PtIVderivativeshave received less attention1.Our group has recently published two series of neutral bis(cyclometalated)pentafluorophenyl PtIVcomplexes with Cl- or CN- as auxiliary ligands2. Given the broad applicability of benzothiazole inmedicinal chemistry and as a continuation in our ongoing interest on biological activity ofcycloplatinated complexes based on 2-arylbenzothiazoles3, we have designed two new series ofdicationic bis-cyclometalated PtIV compounds based on 2-phenylbenzothiazole cyclometalated (pbt)groups. In detail, we present the synthesis of dicationic compunds [Pt(pbt)2(N^N)]X2 (X = PF6, CF3CO2)(N^N = phen 4, 4'; pyraphen 5, 5'; NH2-phen 6, 6'), using compounds [Pt(pbt)2Cl2] (2) and[Pt(pbt)2(OCOCF3)2] (3) as precursors. All new complexes have been fully characterized byspectroscopic techniques, and the molecular structure of 3 has been confirmed X-ray diffraction. Acomparative study of their optoelectronic properties in different media (solid state, solution andpolymeric film for emission) has been carry out. 2 and 3 exhibit emission based on pbt (3IL), whereasthe excited states of phenantroline-based ligands are of mixed 3LL’CT/3IL/3IL’ configuration withremarkable 3IL’ (phen-NH2) ligand contribution. To insight into the nature of the optical properties,theoretical analysis has been carried out at DFT/TD-DFT level for selected complexes (2, 3, 42+ and62+).