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

Abstract

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.

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

“…The emission band also diminished when acid was added into the complex mixture. On the basis of our previous work and other related studies, [10][11][12][13][14][25][26][27][28] the newly formed UV/Vis shoulders of complexes 1 and 2 at longer wavelengths are assigned as MMLCT transitions, as a result of the aggregation of the complexes induced by the polyelectrolyte through metal···metal and p···p interactions. Consequently, the NIR emission bands are attributed to triplet MMLCT phosphorescence.…”

“…Poly(4-ethynylbenzoyl-l-valine), [34] [PtA C H T U N G T R E N N U N G (tpy)(CCÀC CCH 2 OH)]OTf (1), [27,28] [13,14] and [Pt- [26] were synthesized according to the methods previously described by us.…”

“…[25] Recent work also demonstrated the possibility of utilizing synthetic polyelectrolytes or multiple negatively charged biopolymers such as single-stranded nucleic acids and poly-(amino acids) in inducing the aggregation of the complexes. [26][27][28] Remarkable color changes and emission enhancement were observed due to such polyanion-induced self-assembly via metal-metal and p-p stacking interactions in solution.…”

Supramolecular Assembly of Metal‐Ligand Chromophores for Sensing and Phosphorescent OLED Applications

“…In this case, switching on and off of the Pt···Pt and π–π stacking interactions could be achieved upon variation of the pH value of the polyelectrolytes. Extension of the effort has been made to study the related polyelectrolyte‐induced self‐assembly of water‐soluble alkynylplatinum(II) terpyridine complexes, [Pt(terpy)(C≡C‐C≡C‐CH 2 ‐OH)]OTf, [Pt(terpy){C≡C‐C≡C‐CH 2 ‐N(CH 3 ) 3 }](OTf) 2 , Pt(terpy){C≡C‐C 6 H 4 ‐CH 2 N(CH 3 ) 3 }](OTf) 2 , and [Pt(terpy){C≡C‐CH 2 ‐N(CH 3 ) 3 }](OTf) 2 , with various anionic polyelectrolytes including polyacrylate, poly(vinyl sulfonate), and poly(4‐styrene sulfonate) . Similar emergence of new UV‐vis absorption bands and luminescence at lower‐energy region with drastic electronic absorption and luminescence spectral changes have been observed in an aqueous buffer solution upon mixing of various polyelectrolytes with the platinum(II) complexes of different cationic charges and hydrophobicity on the ligands.…”

Supramolecular Assembly of Phosphole Oxide Based Alkynylplatinum(II) 2,6‐Bis(N‐alkylbenzimidazol‐2’‐yl)pyridine Complexes—An Interplay of Hydrophobicity and Aromatic π‐Surfaces

“…In recent decades, luminescent platinum(II) polypyridine complexes have attracted much attention because of their unique spectroscopic and luminescence properties, and their ability to exhibit Pt⋅⋅⋅Pt and π–π stacking interactions . This class of complexes has shown interesting self‐assembly properties with notable color changes, together with luminescence enhancement in response to external stimuli, such as solvent composition changes, or addition of polymers, nucleic acids, or electrolytes . In addition to the terpyridine system, the tridentate N‐donor ligand 2,6‐bis(N‐alkylbenzimidazol‐2’‐yl)pyridine (bzimpy) exhibits interesting self‐assembly through Pt⋅⋅⋅Pt and π–π stacking interactions ,.…”