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

The interest for heterometallic lanthanide-d or-p 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)(3)Al(L)(3)], Ln= Eu(3+) and Tb(3+). Using different L ligands, we investigated the effect of the steric and electronic properties of the Al(L)(3) fragment, highlighting the general validity of the employed synthetic route. A marked difference in the light emission of [Eu(hfac)(3)Al(L)(3)] and [Tb(hfac)(3)Al(L)(3)] complexes has been observed. Thanks to photoluminescence experiments and Density Functional Theory calculations, Ln(3+) emissions are explained with a model involving two non-interacting excitation paths through hfac or Al(L)(3) ligands.