Kenneth Hoi-Yiu Chan

Single-stranded nucleic acid-induced helical self-assembly of alkynylplatinum(II) terpyridyl complexes

Single-stranded nucleic acids, which carry multiple negative charges in an aqueous medium at near neutral pH, are found to induce the aggregation and self-assembly of the positively charged alkynylplatinum(II) terpyridyl complexes via electrostatic binding of the platinum complexes to the single-stranded nucleic acids, as revealed by the appearance of new UV-vis absorption and emission bands upon addition of single-stranded nucleic acids to a buffer solution of the complex. Changes in the intensity and pattern of circular dichroism (CD) spectroscopy are also observed, many of which are consistent with the assembly of the platinum complexes into helical structures, via metal⋯metal and π⋯π stacking interactions. The induced spectroscopic property changes are found to depend on the structural properties of the nucleic acids.

Polyelectrolyte-Induced Self-Assembly of Positively Charged Alkynylplatinum(II)–Terpyridyl Complexes in Aqueous Media

Polyelectrolytes carrying multiple negative charges were found to induce the aggregation and self-assembly of the positively charged platinum(II)-terpyridyl complexes in aqueous media. The aggregation and self-assembly of the complexes were driven by electrostatic interactions between the polymer and the complex, and by terpyridine ligand pi-pi stacking and platinum-platinum (metal-metal) interactions. As a result, remarkable UV/Vis and emission spectral changes were observed. The spectroscopic property changes were related to the structural properties of the metal complexes as well as the polyelectrolytes. The induced self-assembly of the platinum complexes was also strongly affected by the solution properties of the aqueous media, for example, the solution pH, ionic strength, and the percentage of organic solvent added.

Towards thermochromic and thermoresponsive near-infrared (NIR) luminescent molecular materials through the modulation of inter- and/or intramolecular Pt⋯Pt and π–π interactions

A series of mononuclear and dinuclear alkynylplatinum(II) terpyridyl complexes has been found to show inter- and/or intramolecular aggregation in fluid solution state at low temperature or even at room temperature. Drastic colour changes and near infra-red (NIR) emission enhancement as well as broad and poorly resolved resonance signals in the 1H NMR spectra were observed. Such aggregation processes have been probed by 1H NMR, electronic absorption and emission spectroscopy.

Proof-of-principle concept for label-free detection of glucose and α-glucosidase activity through the electrostatic assembly of alkynylplatinum(II) terpyridyl complexes.

A two-component platinum(II) complex-polymer ensemble has been demonstrated for label-free spectroscopic detection of glucose and α-glucosidase activity, based on the electrostatic assembly of cationic platinum(II) complex molecules onto a glucose-bound anionic polymer.

Chiral Poly(4-ethynylbenzoyl-L-valine)-Induced Helical Self-Assembly of Alkynylplatinum(II) Terpyridyl Complexes with Tunable Electronic Absorption, Emission, and Circular Dichroism Changes

A chiral amino acid-containing polyacetylene, poly(4-ethynylbenzoyl-L-valine), was found to induce the aggregation and self-assembly of square-planar alkynylplatinum(II) terpyridyl complexes by electrostatic binding of the positively charged metal complexes to the anionic sites of the polyacetylene, as revealed by the appearance of new UV/Vis absorption and emission bands upon mixing under basic conditions. The induced complex self-assembly was found to be influenced by the polyacetylene and/or base concentration, and the effect of pH on the reversibility of the aggregate/monomer interconversion was also studied. The conformational changes of the polyacetylene were probed by circular dichroism (CD) spectroscopy, in which the chirality signal of the corresponding chain helicity in the presence of the base was enhanced and stabilized upon addition of the platinum(II) complexes. The induced complex aggregation was dependent on the structural properties of the polyacetylene, while the chirality of the polyacetylene was strongly influenced by the introduction of the complex.

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

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 PtPt and/or π-π interactions at high temperature, which have not been reported so far, as revealed by UV/Vis absorption, emission and (1)H 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.