Self-assembled heterometallic complexes showing enhanced two-photon absorption and their distribution in living cells

Heterometallic binuclear Ru-Pt and trinuclear Zn-Pt complexes were prepared via self-assembly by attaching Pt-II-tpy (tpy = 2,2 ':6 ',2 ''-terpyridine) onto the Ru-II-tpy and Zn-II-bis(tpy) moiety. The visible absorption bands for Ru-Pt complexes are primarily due to Ru-II -> tpy MLCT transitions with some overlap from Pt-II -> tpy MLCT, while no MLCT transition is observed for the Zn-Pt complex. The emission intensity of the Ru-Pt complexes was improved relative to the mononuclear Ru-II precursor; however, the emission of Zn-Pt was decreased when compared with strongly emissive Zn-II-bis(tpy). Z-scan results revealed relatively high two-photon absorption (TPA) cross sections sigma(2), with maximal values of 962 GM for Ru-Pt and 200 GM for Zn-Pt. All the heterometallic complexes were proved to localize preferably into lysosomes by confocal fluorescence imaging results, which also showed improved cell-free O-1(2) quantum yield compared to their mononuclear precursor.

Automated summary

Heterometallic Ru-Pt and Zn-Pt complexes were prepared by self-assembly, exhibiting different absorption and emission characteristics. Ru-Pt complexes showed enhanced emission intensity while Zn-Pt complexes had decreased emission compared to their mononuclear precursors. Additionally, both Ru-Pt and Zn-Pt complexes demonstrated high two-photon absorption cross sections.