Dinuclear coumarin-containing alkynylplatinum(ii) terpyridine complexes with supramolecular assembly-assisted photodimerization

Abstract

A series of dinuclear coumarin-containing alkynylplatinum(II) terpyridine complexes were shown to feature solvent-induced self-assembly behaviors via Pt⋯Pt, π–π stacking, and hydrophobic interactions, displaying drastic color changes from yellow to orange, then to red in solution with the new appearance of a metal–metal-to-ligand charge transfer (MMLCT) absorption band upon increasing the water content in their dimethyl sulfoxide (DMSO) solutions. Photodimerization of the coumarin moieties was found to occur only in the aggregated states with the presence of non-covalent interactions, assisted by the directional Pt⋯Pt interaction, which preorganized the CC bond of the photo-responsive coumarin moieties in close proximity to each other, enabling topochemical photodimerization upon UV excitation. The aggregation-assisted photodimerization of this series of alkynylplatinum(II) terpyridine complexes have been probed by UV-vis absorption spectral changes, ¹H NMR spectroscopy, high-resolution electrospray ionization (ESI)-mass spectrometry and transmission electron microscopy (TEM), demonstrating the role played by supramolecular assembly of the Pt(II) complexes in switching on the photodimerization reaction.