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

Half-lantern Pt(II) dinuclear complexes [{Pt((CNpz)-N-boolean AND)(mu-(SN)-N-boolean AND (R))}(2)] ((HCNpz)-N-boolean AND = 1-naphthalen-2-yl-1H-pyrazole; R = H, (HSN)-N-boolean AND: 2-mercaptopyrimidine 1; R = CF3, (HSNF)-N-boolean AND: 4-(trifluoromethyl)-2-mercaptopyrimidine 2) were selectively obtained as single isomers with the (CN)-N-boolean AND groups in an anti-arrangement and rather short metallophilic interactions (d(Pt-Pt) = 2.8684(2) & Aring; for 2). They reacted with haloforms in the air and sunlight to obtain the corresponding oxidized diplatinum(III) derivatives [{Pt((CNpz)-N-boolean AND)(mu-(SN)-N-boolean AND (R))X}(2)] (X = Cl (1-Cl), Br (1-Br), I (1-I, 2-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 1 and 2 with CHI3 in the dark afforded mixtures of [IPt((CNpz)-N-boolean AND)(mu-(SN)-N-boolean AND)(2)Pt((CNpz)-N-boolean AND)CHI2] and 1-I or 2-I, with the former being the major species under an Ar atmosphere, while the reactions of 1 with CHBr3 and CHCl3 need light to occur. These Pt-2(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.