Five Tb3+/Eu3+ mixed nonanuclear clusters with the general formula [Eu9–xTbx(acac)16(µ3‐OH)8(µ4‐O)(µ4‐OH)] ([Eu9–xTbx], x = 0.9–8.1, acac = acetylacetonate) were synthesized. Characterization by powder X‐ray diffraction (PXRD), energy‐dispersive X‐ray spectroscopy (EDS) and inductively coupled plasma optical emission spectroscopy (ICP‐OES) highlight a near‐perfect match between the amounts of Tb3+ and Eu3+ ions input in the reaction mixture and the amounts in the clusters. The luminescence properties of these [Eu9–xTbx] clusters were investigated thoroughly in the solid state, and a strong energy transfer from the Tb3+ to Eu3+ emitters was evidenced. Thus, these nano‐nonanuclear 4f clusters, which can be viewed as square pyramids that share one top, exhibit dual luminescence that can be adjusted by controlling the ratio of the lanthanide ions within the crystal architecture.

A copper iodide complex coordinated by three phosphine ligands with the formula [Cu2I2(Ph2PC2(C6H4)C2PPh2)3] exhibits solvatochromic and vapochromic luminescence properties. A mechanism based on solvent‐dependent molecular motion appears to occur. The highly contrasted response observed upon THF solvent exposure makes this complex an appealing candidate for chemical sensor applications.