Synthesis of Cationic Iridium Cyclometalated Heteroleptic Complexes for Conversion of Sun Light into Solar Fuels

Research in the field of artificial photosynthesis applies the fundamental scientific principles of the natural process, in order to develop new processes for an efficient conversion of solar energy. [1] In the last decade, photocatalytic systems for hydrogen production from water have been widely investigated. In water-splitting reactions the [Ru(bpy)3]+-type complexes have been historically the most common photo-sensitizer choice, but Ir(III) derivatives are nowadays under investigation as potential alternatives, [2] thanks also their tunable photophysical and electrochemical properties, and to their ability to generate long-lived excited states after irradiation. [3] A common approach consists into study separately the two halves of the water-splitting reaction. This is done by employing a proper sacrificial reagent that allows to investigate water reduction induced by a light harvesting complex coupled with an homogeneous water reducing catalyst. [4] We herein report preliminar results towards the synthesis of novel monocationic iridium(III) photosensitizers (Ir-PSs) with the general formula [IrIII(C^N)2(N^N)]+ (C^N = cyclometalating benzilpyridine ligand, N^N = 4,4’-substituted bipyridine) as potential candidates for water splitting applications