Ensembles of cationic conjugated polymer and anionic platinum(ii) complexes: from FRET properties to application studies in E. coli imaging and singlet oxygen generation

Abstract

A series of anionic alkynylplatinum(II) complexes with terpyridine (tpy) or 2,6-bis(benzimidazol-2′-yl)pyridine (bzimpy) as the tridentate N-donor pincer ligand has been synthesized and characterized. These complexes are found to form ensembles with a cationic poly(fluorene-co-phenylene) derivative (PFP-NMe₃⁺) through electrostatic, Pt(II)⋯Pt(II) and π–π stacking interactions. Förster resonance energy transfer (FRET) has been found to take place, consequently gave rise to fluorescence quenching of the polymer donor and the emergence of low-energy emission from the platinum(II) complex assemblies. The spectroscopic and FRET properties of the two-component systems have been investigated by UV-vis absorption, emission and Stern–Volmer quenching studies. Pathogen imaging and photodynamic therapy (PDT) studies using the polymer–platinum(II) complex ensembles have demonstrated better performance compared to that using PFP-NMe₃⁺ only, which highlights the potential of this class of ensembles for various biological applications.