Ultrafast Photoinduced Electron Transfer from Cyclometalated Rhodium and Iridium Complexes to Cyan Emitting Copper Nanoclusters: Footsteps toward Light Harvesting

Abstract

AbstractIn recent times, copper nanocluster (Cu NC) has become a promising candidate as an interesting nanomaterial for its potential applications in optoelectronics, sensing, catalysis and bioimaging. Herein, we have synthesized L–Cysteine protected Cu NC in 1:1 water:acetonitrile (ACN) solvent possessing bright cyan emission (λem=495 nm) with 10.4% quantum yield. Furthermore, the cyclometalated complexes of Ir(III) and Rh(III) are light harvesters, which are applied in photoinduced electron and energy transfer and photocatalysis. Three such cyclometalated complexes of Rh and Ir have been employed herein, which on electrostatic interaction with Cu NCs in 1:1 water:ACN medium, quench the fluorescence from Cu NC dramatically. This quenching could be suitably attributed to photoinduced electron transfer (PET) where Cu NC acts as an electron acceptor. PET has been confirmed by steady state and time resolved fluorescence spectroscopy as well as by ultrafast femtosecond upconversion and transient absorption spectroscopy.