Solution and solid-state electrochemiluminescence of a fac-tris(2-phenylpyridyl)iridium(III)-cored dendrimer

The solution phase and solid-state electrochemistry and electrochemiluminescence (ECL) of an iridium(III) complex-cored dendrimeric analogue of Ir(ppy)3, (G1pIr), are reported. The solid-state electrochemistry and solid-state ECL of Ir(ppy)3 itself is also described for the first time. In solution phase, the dendrimer displays greater immunity to oxygen quenching in photoluminescence (PL) experiments and exhibits greater ECL efficiency compared to the parent Ir(ppy)3 core under the same conditions, despite a lower photoluminescence quantum yield. It is proposed that the dendrons which effectively shield the core from PL quenching interactions in the solid-state counteract the effects of parasitic side-reactions during the solution ECL experiments. Electroactive and ECL-active solid-state films of both Ir(ppy)3 and G1pIr were produced by drop-coating on boron doped diamond electrodes. Films of Ir(ppy)3 produced stable co-reactant ECL. However, films of G1pIr produced lower than expected ECL intensity. This was attributed to poorer charge transport and the lipophilicity of the film limiting the rate of interaction with the co-reactant required for formation of the excited state.

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