Induced Self-Assembly and Disassembly of Alkynylplatinum(II) 2,6-Bis(benzimidazol-2' -yl)pyridine Complexes with Charge Reversal Properties: Proof-of-Principle Demonstration of Ratiometric Fo?rster Resonance Energy Transfer Sensing of pH

A series of pH-responsive alkynylplatinum(II) 2,6-bis(benzimidazol-2 & PRIME;-yl)pyridine (bzimpy) complexes with charge-reversal properties was synthesized, and the supramolecular assemblies between conjugated polyelectrolyte, PFP-OSO3 (-), and [Pt{bzimpy(TEG)2}{C equivalent to C-C6H3-(COOH)(2)-3,5}]Cl (1) have been studied using UV-vis absorption, emission, and resonance light scattering (RLS) spectroscopy. An efficient Fo''rster resonance energy transfer (FRET) from PFP-OSO3- donor to the aggregated 1 as acceptor with the aid of Pt(II)...Pt(II) interactions has been presented, which leads to a growth of triplet metal-metal-to-ligand charge transfer (3MMLCT) emission in the low-energy red region. The two-component PFP-OSO3--1 ensemble was then exploited as a proof-of-principle concept strategy for pH sensing by tracking the ratiometric emission changes. With the aid of judicious molecular design on the pH-driven charge-reversal property, the polyelectrolyte-induced self-assembly and the FRET from PFP-OSO3- to the platinum(II) aggregates have been modulated. Together with its excellent reversibility and photostability, the extra stability provided by the Pt(II)...Pt(II) and pi-pi stacking interactions on top of the electrostatic and hydrophobic interactions existing in polyelectrolye-complex assemblies has led to a selective and sensitive pH sensing assay.

Automated summary

A series of pH-responsive alkynylplatinum(II) complexes were synthesized and their supramolecular assemblies with a conjugated polyelectrolyte were studied. Efficient energy transfer was observed from the polyelectrolyte to the platinum aggregates, resulting in emission in the low-energy red region. By utilizing the pH-responsive property and controlling the self-assembly and energy transfer, selective and sensitive pH sensing was achieved.