NIR-II Emission from Cyclometalated Dinuclear Pt(III) Complexes.

Half-lantern Pt(II) dinuclear complexes [{Pt(CN)(μ-SN)}] (HCN = 1-naphthalen-2-yl-1-pyrazole; R = H, HSN: 2-mercaptopyrimidine ; R = CF, HSN: 4-(trifluoromethyl)-2-mercaptopyrimidine ) were selectively obtained as single isomers with the CN groups in an -arrangement and rather short metallophilic interactions ( = 2.8684(2) Å for ). They reacted with haloforms in the air and sunlight to obtain the corresponding oxidized diplatinum(III) derivatives [{Pt(CN)(μ-SN)X}] (X = Cl (), Br (), I (, )). The single-crystal X-ray structures exhibit Pt-Pt distances typical for the existence of a metal-metal bond, which evidence fairly well the influence of the axial ligand (X). The reactions of and with CHI in the dark afforded mixtures of [IPt(CN)(μ-SN)Pt(CN)CHI] and or , with the former being the major species under an Ar atmosphere, while the reactions of with CHBr and CHCl need light to occur. These Pt(III,III) complexes display low-energy absorptions and emissions that strongly depend on the axial ligand. In the solid state, they show a broad NIR emission ranging from 985 to 1070 nm at RT that suffers a hypsochromic shift when cooling down to 77 K. The photoemissive behavior of the dinuclear Pt(II) and Pt(III) systems is disclosed with the aid of density functional theory calculations.