Capture of the [Mo3S4]4+ Cluster within a {Mo18} Macrocycle Yielding a Supramolecular Assembly Stabilized by a Dynamic H-Bond Network

The use of the [Mo3S4(Hnta)(3)](2-) Complex (nta(3-) = nitrilotriacetate) as structuring agent toward the self-condensation process of the [Mo2O2S2(OH2)(6)](2+) cation leads to the largest oxothiomolybdenum ring In the solid state, X-ray diffraction analysis reveals the presence of the targeted molecular compound (noted 1a), which consists of the {Mo18O18S18(OH)(18)} host templated by the [Mo3S4(Hnta)(3)](2-) guest Nevertheless, the structure shows an additional molecular moiety corresponding to a dinuclear unit {Mo2O2S2} coordinated to two nta(3-) ligands, mutually arranged in a cis fashion (1b) In the solid state, both entities interact through two short hydrogen bonds to give a striking supramolecular adduct, noted {1a-1b} Synthetic procedures to prepare the individual species as pure compounds were reported la was obtained as a pure mixed Cs+/NMe4+ salt while the dinuclear unit [Mo2O2S2(Hnta)(2)](2-) was obtained as mixed K+/Na+ crystals. X-ray diffraction study of the latter reveals a trans isomer (noted 1b'), characterized by the specific coordination of both nta3- ligands All the compounds were characterized in solution (D2O or DMSO) by multiexperiment H-1 NMR (1D, COSY, NOESY, and DOSY) The overall results were consistent with the retention of the adduct {1a-1b} which exhibits a supramolecular reactivity The dinuclear individual species in solution gave rise to cis-trans equilibrium, while in the presence of the oxothiomolybdenum ring 1 a, the dinuclear unit is maintained as a frozen cis complex. DOSY NMR provides a definitive argument for the integrity of the supramolecular assembly In addition, preliminary electrochemical study of la is also reported