Deep-red to near-infrared emission of binuclear platinum(ii) complexes by breaking hydrogen bonds

Abstract

Three binuclear platinum(II) complexes, named [Pt₂(amt)₄]·2DMF (1), [Pt₂(mmt)₄] (2) and [Pt₂(mmtt)₄] (3), have been synthesized by the use of three thiadiazole ligands with different substituents. The structures of complexes 1–3 are comprised of similar turbine-like binuclear platinum(II) structures with metallic Pt⋯Pt distances of 2.7594(4) Å, 2.7621(8) Å and 2.7713(4) Å, respectively. Two types of hydrogen bonds are found to form in complex 1. The photoluminescence peaks of the binuclear Pt(II) complexes vary from 737 to 789 nm, showing deep-red to near-infrared emissions. The relationship between structure and luminescence has been investigated and the result shows that electron-donating substituents of the ligands and the intramolecular hydrogen bonding interactions play important roles in the regulation of the emission. Subsequently, 1 was immersed into 1,4-dioxane to break hydrogen bonds, and then, as expected, the emission wavelength was redshifted and finally extended to the near-infrared region (770 nm).