Systematic Conversion of Photoinduced Intramolecular Electron Transfer in Trinuclear M-Ir-M (M = Re, Ir) Complexes to Intersystem Charge Transfer by Coupling to Gold Nanoclusters

Twotrinuclear cyclometalated iridium(III)-based complexes of M-Ir-M(M = Re, Ir) type were strategically designed with characteristicallydifferent electron distributions based on the electronegativitiesof Re and Ir. Photoinduced intramolecular electron transfer (PIIET)is readily observed in these complexes with different lifetimes ofthe radicals. The free amine ends of these symmetric complexes actas the electron donor for PIIET. These ends, on the other hand, canalso act as centers for reducing gold (Au) salt (HAuCl4 & BULL;3H(2)O) to generate Au atomistic nanoclusters (AuNCs)protected and templated by the trinuclear complexes. Formation ofthe AuNCs completely stops the PIIET and induces excited state intersystemcharge transfer (ESICT) from the surrounding complexes to the AuNCcore on exciting the system with radiation of the same wavelength.The trinuclear cyclometalated complexes were synthesized by chelationof the transition metal units, such as Re(CO)(3)Cl and Ir(ppy)(2), to thiosemicarbazone (TSC) appended with cyclometalatedligands of the precursor Ir(III) complex. Such a phenomenon of conversionof PIIET in a trinuclear cyclometalated coordination complex completelyto ESICT on coupling to a noble metal nanocluster is unique and promisingfor applications in energy devices.

Automated summary

Twotrinuclear cyclometalated iridium(III)-based complexes of M-Ir-M (M = Re, Ir) type were designed to exhibit different electron distributions and demonstrate photoinduced intramolecular electron transfer (PIIET) with various lifetime of radicals. The amine ends of these complexes can also reduce gold salt to generate Au atomistic nanoclusters (AuNCs) and induce excited state intersystem charge transfer (ESICT) when excited with radiation. This phenomenon of converting PIIET to ESICT in a coordination complex coupled with a noble metal nanocluster is unique and shows potential for energy device applications.