Impact of Intermolecular Non-Covalent Interactions in a Cu I 8 Pd II 1 Discrete Assembly: Conformers' Geometries and Stimuli-Sensitive Luminescence Properties

A new highly solid-state luminescent phase of a previously reported weakly luminescent Cu Pd dicationic assembly is reported revealing the high geometrical versatility of this moiety that importantly alters its luminescent properties. This very minor new species B is based on a different conformer scaffold than the one encountered in the previously reported B form and, essentially differs from B by displaying shorter Cu -Cu intermetallic distances. DFT calculations allow concluding that the predominance in the solid-state of the weakly luminescent and less stable B phase is due to the extra stability induced by a larger number of intermolecular non-covalent π-CH interactions in its crystalline packing and not by the intrinsic stability of the Cu Pd dicationic moiety. Calculations also revealed that a more stable conformation B is expected in vacuum, which bears a different distribution of Cu -Cu intermetallic distances than the dications in B and B phases. Taking into account that the geometrical alterations are associated to drastic changes of luminescence properties, this confer to the Cu Pd assembly high potentiality as stimuli-sensitive luminescent materials. Indeed, by applying mechanical or thermal stress to samples of B phase, new phases B and B , respectively, were obtained. Alterations of the solid-state photophysical properties of these new species compared to those recorded for B are reported together with a combined experimental and computed study of the structures/properties relationships observed in these phases.