Competing excitation paths in luminescent heterobimetallic Ln-Al complexes: Unraveling interactions via experimental and theoretical investigations.

The interest for heterometallic lanthanide- or- metal (Ln-M) complexes is growing because of a potential cooperative or synergistic effect related to the proximity of two different metals in the same molecular architecture affording special tunable physical properties. To exploit the potentiality of Ln-M complexes, suitable synthetic approaches, and the in-depth understanding of the effect of each building block on their properties are mandatory. Here, we report the study on a family of heterometallic luminescent complexes [Ln(hfac)Al(L)], Ln= Eu and Tb. Using different L ligands, we investigated the effect of the steric and electronic properties of the Al(L) fragment, highlighting the general validity of the employed synthetic route. A marked difference in the light emission of [Eu(hfac)Al(L)] and [Tb(hfac)Al(L)] complexes has been observed. Thanks to photoluminescence experiments and Density Functional Theory calculations, Ln emissions are explained with a model involving two non-interacting excitation paths through hfac or Al(L) ligands.