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, [Mn2(tea)Mo(CN)7]-H20, 1, and [Mn2(tea)Mo(CN)7], 2 (tea stands fortriethanolamine), formed with the 4d ion building block, [Mo(CN)7^~, Mn" 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 Tc = 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" site found to be square-pyramidal for 1 and tetrahedral for 2.