The 1,3,4-thiadiazole annelation based on the reaction of acyl chlorid
es with methyl 2-methyldithiocarbazate followed by cyclization with pe
rchloric acid and further reaction with primary amines, allows the pre
paration of a novel kind of ligands bearing two or three 1,3,4-thiadia
zole rings connected either by an aliphatic, aromatic or heteroaromati
c bridge.