Solvation and temperature-modulated supramolecular assembly of amphiphilic water-soluble Schiff base-containing platinum(ii) complexes†‡

A new class of water-soluble amphiphilic Schiff base-containing platinum(ii) complexes with dendritic triethylene glycol units has been investigated to show self-assembly properties by the balance of multiple noncovalent interactions including hydrophobic, intermolecular Pt⋯Pt and π–π stacking interactions in water or DMSO–water solutions, accompanied by drastic spectroscopic changes. The UV–vis spectra have been recorded, and the electronic structures and intermolecular Pt⋯Pt interactions have been confirmed by computational studies and non-covalent interaction (NCI) analysis of the dimer of the complex. These complexes have been found to exhibit a cooperative self-assembly mechanism, in which the molecules were stacked in a head-to-tail arrangement in a slightly staggered fashion. Additionally, the length of the alkoxy chains has been found to show a significant effect on the extent of Pt⋯Pt and π–π stacking interactions and the stability of their self-assembled aggregates. Under the influence of temperature, this class of Schiff base-containing platinum(ii) complexes has been shown to exhibit an unexpected hysteresis effect and unusual thermo-responsive behavior accompanied by morphological transformation. This work represents a rare example of a systematic study on the self-assembly properties of water-soluble platinum(ii) Schiff base complexes induced by molecular hydrophobicity, solvation and temperature. It provides an in-depth insight into the rational molecular design for the construction of supramolecular architectures and potential advances in stimuli-responsive probes.