Starting from the potent inhibitory effect of the previously described 2-methyl-6-(2-thienyl) imidazo [2, 1-b] thiazole on mitochondrial complex I, we prepared a series of derivatives in order to study the effect of a different substitution at the positions 2, 5 and 6. The replacement of the thienyl group at position 6 with a phenyl group does not modify the biological behaviour of the lead compound, whereas the shift of the methyl group from ...