Dual pH- and Temperature-Responsive Metallosupramolecular Block Copolymers with Tunable Critical Micelle Temperature by Modulation of the Self-Assembly of NIR-Emissive Alkynylplatinum(II) Complexes Induced by Changes in Hydrophilicity and Electrostatic Effects

Terpyridylplatinum(II)-based metallosupramolecular triblock copolymers with hydrophilic alkynyl ligands have been synthesised and characterised. As a result of the intrinsic properties of Pluronics, reversible temperature-induced micellisation occurred at high temperature leading to aggregation of the platinum(II) complex moieties through PtPt and - interactions, resulting in significant UV/Vis absorption and near-infrared (NIR) emission spectral changes. The critical micelle temperatures of the complexes were found to vary from 21 to 30 degrees C due to differences in the hydrophilicity of the alkynyl ligands and the electrostatic repulsions between the positively charged platinum(II) complex moieties. One of the complexes with pH-responsive CH2NMe2 groups on the alkynyl ligand was found to show NIR emission that is sensitive to both pH and temperature. Such dual-responsive behaviour has been ascribed to the modulation of the self-assembly of the complex moieties by temperature-induced micellisation and the changes in the hydrophilicity as well as electrostatic interactions upon protonation/deprotonation of the CH2NMe2 groups on the alkynyl ligand.