Stimuli-Responsive Solvatochromic Au(I)-Ag(I) Clusters: Reactivity and Photophysical Properties Induced by the Nature of the Solvent.

Reaction of the heterometallic polymer [Au2Ag2(C6Cl5)4(OEt2)2] n with 4 equiv of pyridazine leads to the new discrete complex [Au2Ag2(C6Cl5)4(μ2-C4H4N2)2(C4H4N2)2] (1). Complex 1 is solvoluminescent, leading to drastic structural changes, depending on the coordination ability of the chosen solvent. Thus, the reaction of complex 1 with acetonitrile leads to a new Au(I)-Ag(I) complex of stoichiometry [Au2Ag2(C6Cl5)4(μ2-C4H4N2)2(NCMe)2] n·2CH3CN(2), while if the reaction is carried out with a noncoordinating solvent such as dichloromethane, complex [Au2Ag2(C6Cl5)4(C4H4N2)2] n·CH2Cl2 (3) is obtained. Furthermore, when complexes 1, 2, and 3 are exposed to tetrahydrofuran, different results are obtained. In the case of complex 1, the metallic core disposition remains and THF is incorporated as a crystallization solvent in [Au2Ag2(C6Cl5)4(μ2-C4H4N2)2(C4H4N2)2]·2THF (1·THF). On the other hand, reaction of complexes 2 or 3 with THF gives rise to a mixture of the corresponding polymeric complex [Au2Ag2(C6Cl5)4(THF)2] n, in which pyridazine ligands are displaced, together with a polymorph of complex 1·THF. All these complexes are luminescent in solid state displaying different emission energies depending on their structural disposition as well as on the presence of the metallophilic interactions. These subtle changes in the cluster structures, only based on the solvent used, lead to spectacular reversible changes in the emissive behavior of the complexes, allowing the tuning of the luminescent emissions in a wide range. DFT and TD-DFT calculations support the experimental photophysical studies.