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

Half-lantern Pt(II) dinuclear complexes [{Pt(C ∧ N pz )(μ-S ∧ N R )} 2 ] (HC ∧ N pz = 1-naphthalen-2-yl-1 H -pyrazole; R = H, HS ∧ N: 2-mercaptopyrimidine 1 ; R = CF 3 , HS ∧ N F : 4-(trifluoromethyl)-2-mercaptopyrimidine 2 ) were selectively obtained as single isomers with the C ∧ N groups in an anti -arrangement and rather short metallophilic interactions ( d Pt-Pt = 2.8684(2) Å for 2 ). They reacted with haloforms in the air and sunlight to obtain the corresponding oxidized diplatinum(III) derivatives [{Pt(C ∧ N pz )(μ-S ∧ N 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 CHI 3 in the dark afforded mixtures of [IPt(C ∧ N pz )(μ-S ∧ N) 2 Pt(C ∧ N pz )CHI 2 ] and 1-I or 2-I , with the former being the major species under an Ar atmosphere, while the reactions of 1 with CHBr 3 and CHCl 3 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.