title: Conjugated Polyelectrolyte-Induced Self-Assembly of Alkynylplatinum(II) 2,6-Bis(benzimidazol-2'-yl)pyridine Complexes.
abstract: Water-soluble cationic alkynylplatinum(II) 2,6-bis(benzimidazol-2'-yl)pyridine (bzimpy) complexes have been demonstrated to undergo supramolecular assembly with anionic polyelectrolytes in aqueous buffer solution. Metal-metal-to-ligand charge transfer (MMLCT) absorptions and triplet MMLCT ((3) MMLCT) emissions have been found in UV/Vis absorption and emission spectra of the electrostatic assembly of the complexes with non-conjugated polyelectrolytes, driven by Pt⋅⋅⋅Pt and π-π interactions among the complex molecules. Interestingly, the two-component ensemble formed by [Pt(bzimpy-Et){CCC6 H4 (CH2 NMe3 -4)}]Cl2 (1) with para-linked conjugated polyelectrolyte (CPE), PPE-SO3 (-) , shows significantly different photophysical properties from that of the ensemble formed by 1 with meta-linked CPE, mPPE-Ala. The helical conformation of mPPE-Ala allows the formation of strong mPPE-Ala-1 aggregates with Pt⋅⋅⋅Pt, electrostatic, and π-π interactions, as revealed by the large Stern-Volmer constant at low concentrations of 1. Together with the reasonably large Förster radius, large HOMO-LUMO gap and high triplet state energy of mPPE-Ala to minimize both photo-induced charge transfer (PCT) and Dexter triplet energy back-transfer (TEBT) quenching of the emission of 1, efficient Förster resonance energy transfer (FRET) from mPPE-Ala to aggregated 1 molecules and strong (3) MMLCT emission have been found, while the less strong PPE-SO3 (-) -1 aggregates and probably more efficient PCT and Dexter TEBT quenching would account for the lack of (3) MMLCT emission in the PPE-SO3 (-) -1 ensemble.
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).
authors.forename: Kevin
authors.initials: K
authors.lastname: Chan
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).
authors.forename: Clive Yik-Sham
authors.initials: CY
authors.lastname: Chung
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). wwyam@hku.hk.
authors.forename: Vivian Wing-Wah
authors.initials: VW
authors.lastname: Yam
keywords: conjugated polyelectrolytes; energy transfer; metal-metal interactions; platinum; supramolecular chemistry