. . . . "Particularly useful optional substituents include halogen atoms, especially fluorine, chlorine or bromine atoms, or C1-6 alkyl groups, especially C1-3 alkyl groups, most especially a methyl group, or haloC1-6alkyl groups, especially fluoroC1-6alkyl groups, most especially a ???CF3 group, or C1-6 alkoxy groups, especially a methoxy, ethoxy, propoxy or isopropoxy group, or haloC1-6alkoxy groups, esp" . .