Abstract A novel series of melatonin analogues based on the benzothiophene nucleus is described. In these compounds the methoxy group was replaced by electron-attracting groups such halogens (Br and Cl) with the aim of supplementing structure-affinity relationships on melatoninergic ligands. Target derivatives were prepared from the corresponding 4-halo-thiophenol. Some of these derivatives had high affinity for mt 1 and ...