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

摘要

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 Pt×××Pt and π-π 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 °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 CH_2NMe_2 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 CH_2NMe_2 groups on the alkynyl ligand. NIR-emitting dual sensor: Terpyridylplatinum(II)-based metallosupramolecular triblock copolymers with functionalised alkynyl ligands show tunable critical micelle temperatures and dual-responsive behaviour (see figure).