Substantial increase of the ordering temperature for {MnII/MoIII(CN)7}-based magnets as a function of the 3d ion site geometry:: Example of two supramolecular materials with Tc=75 and 106 K

Two molecule-based magnets, [Mn-2(tea)Mo(CN)(7)](H2O)-H-., 1, and [Mn-2(tea)Mo(CN)(7)], 2 (tea stands for triethanolamine), formed with the 4d ion building block, [Mo(CN)(7)](4-), Mn-II ions, and an additional ligand, tea, have been prepared and structurally characterized by single-crystal X-ray analyses. Whereas 1 is obtained by a self-assembling process in solution, compound 2 is quantitatively formed through a smooth thermal treatment of 1. Their magnetic properties revealed that these compounds exhibit magnetic ordering at T-c = 75 and 106 K respectively for compounds 1 and 2. The difference for their critical temperature is attributed to the geometry of the coordination sphere of a Mn-II site found to be square-pyramidal for 1 and tetrahedral for 2.