Bathophenanthroline Disulfonate Ligand-Induced Self-Assembly ofIr(III) Complexes in Water: An Intriguing Class of PhotoluminescentSoft Materials

摘要

Strong evidence of concentration-induced and dissolved electrolyteinduced chromophore aggregation has been universally observed in numerous watersoluble bis-cyclometalated Ir(III) photosensitizers bearing the sulfonated diimine ligandsbathophenanthroline disulfonate and bathocuproine disulfonate. This new class ofaqueous-based soft materials was highly photoluminescent in their aggregated state wheredetailed spectroscopic investigations of this phenomenon revealed significant blue shifts oftheir respective photoluminescence emission spectra with concomitant increases inexcited-state lifetimes and quantum yields initiating even at micromolar chromophoreconcentrations in water or upon the addition of a strong electrolyte. A combination ofnanoscale particle characterization techniques, static and dynamic photoluminescencespectroscopic studies, along with atomistic molecular dynamics (MD) simulations ofthese soft materials suggests the formation of small, heterogeneous nanoaggregatestructures, wherein the sulfonated diimine ancillary ligand serves as a pro-aggregatingsubunit in all instances. Importantly, the experimental and MD findings suggest the likelihood of discovering similar aqueousaggregation phenomena occurring in all transition-metal complexes bearing these water-solubilizing diimine ligands.