New ditopic and tripodal 1,2,4-triazole- and tetrazole-based ligands for coordination chemistry

The practical synthesis of two new classes of polytopic azole-based ligands is reported. The synthesis of the precursor amines was achieved by substitution of a leaving group by an azide followed by reduction with triphenylphosphine and water. Another efficient method employs a Mitsunobu coupling with phthalimide allowing the conversion of a primary alcohol into a primary amine. The triazole and tetrazole were obtained by cyclization of these amine precursors. The first family consisted of ditopic ligands containing both 1-R-tetrazole and 4-R-1,2,4-triazole moieties linked by an alkyl spacer, white the second consists of branched ligands with three azole cycles linked to a benzene core through ether bonds. Both classes are suitable for building multidimensional polynuclear coordination assemblies and for the observation of thermal spin state crossover behavior with iron(II) ions.