Phosphorescent molecular tweezers based on alkynylplatinum(ii) terpyridine system: turning on of NIR emission via heterologous Pt⋯M interactions (M = PtII, PdII, AuIII and AuI)

Abstract

A novel molecular tweezers-type complex 1, based on a phosphorescent cationic alkynylplatinum(II) terpyridine building block, has been synthesized and characterized by NMR, mass spectroscopy, elemental analysis and X-ray diffraction study. Host–guest chemistry of the host complex 1 and various guest metal complexes with different ligands, charges and/or metal centres has been investigated. Various metal complexes including the negatively charged platinum complexes can interact with 1 in a 1 : 1 manner, which is in contrast to the commonly observed formation of insoluble platinum(II) double salts in a one-dimensional infinite chain such as the Magnus's green salt. Upon addition of guest molecules to 1 in CH2Cl2 solution, spectroscopic changes with new absorptions and emissions in the lower-energy region were observed as a result of significant metal–metal, π–π, and electrostatic interactions. 1H NMR titration and 2D NMR studies suggest that the host–guest interaction is predominantly in the sandwiched association mode of the molecular tweezers.