title: 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.
abstract: 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 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.
authors.affiliation: Institute of Molecular Functional Materials (Areas of Excellence, Scheme, University Grants Committee, Hong Kong) and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong (P. R. China), Fax: (+852) 2857-1586.
authors.forename: Clive Yik-Sham
authors.initials: CY
authors.lastname: Chung
authors.forename: Vivian Wing-Wah
authors.initials: VW
authors.lastname: Yam
keywords: hydrophilicity; luminescence; platinum; sensors; supramolecular chemistry