Tuning the nuclearity of [Mo₂O₂S₂]²⁺-based assemblies by playing with the degree of flexibility of bis-thiosemicarbazone ligands

[Mo^V₂O₂S₂]²⁺-based thiosemicarbazone complexes appear as very promising molecules for biological applications due to the intrinsic properties of their components. This paper deals with the synthesis and characterization of six coordination complexes obtained by the reaction of [Mo^V₂O₂S₂]²⁺ clusters with bis-thiosemicarbazone ligands that contain flexible or rigid spacers between the two thiosemicarbazone units. Interestingly, structural characterization by single-crystal X-ray diffraction, MALDI-TOF MS technique and NMR spectroscopy revealed that the nuclearity of the complex is controlled by the nature of the spacer between the thiosemicarbazone units. Binuclear complexes, namely [Mo^V₂O₂S₂(L^1-3)], are isolated with flexible spacers while tetranuclear complexes [(Mo^V₂O₂S₂)₂(L^4-6)₂] are formed when the bis-thiosemicarbazone ligands are built on rigid spacers.