Reversible thermo-responsive luminescent metallo-supramolecular triblock copolymers based on platinum(ii) terpyridyl chromophores with unusual aggregation behaviour and red-near-infrared (NIR) emission upon heating

Abstract

Two platinum(II) terpyridyl-based metallo-supramolecular triblock copolymers, [ClPt(tpy)PEO-PPO-PEO(tpy)PtCl](OTf)₂ (1) and [(Ph–C≡C)Pt(tpy)PEO-PPO-PEO(tpy)Pt(C≡C–Ph)](OTf)₂ (2), have been synthesized and characterized. The two complexes were found to aggregate with Pt⋯Pt and/or π–π interactions at high temperature, which have not been reported so far, as revealed by UV/Vis absorption, emission and ¹H NMR study. This is due to the formation of spherical micelles driven by the PEO-PPO-PEO copolymers at temperatures above the critical micelle temperature, which was confirmed by TEM and DLS. The red-near-infrared (NIR) emission of the complexes can be switched on and off by at least ten cycles of heating and cooling, suggesting that the micellization was highly reversible.