Synthesis of a symmetrical tris-tetrazole as isostere of a tricarboxylic acid: behind new tridentate ligands for MOFs

The synthesis and characterization of three tridentate ligands for new MOFs is described. A triple aminolysis of the 1,3,5-tribenzoyl chloride with p-aminobenzoic acid gave the tricarboxylic acid 1 in 90% yield. Moreover, the same reaction, also from the 1,3,5-tribenzoyl chloride, but using p-aminobenzonitrile gave the new tris-benzonitrile 2 in 85% yield. Finally, this later one was treated with sodium azide and a Lewis acid to synthesize the also new tris-tetrazole-based ligand 3 in 72% yield through a [3+2] azide-nitrile cycloaddition. It is noteworthy that the isosterism between carboxylic acids and tetrazoles may be considered to design and fabricate new MOFs with expected similar properties.