either R4 is H or a lower alkyl radical and R5 is a lower alkyl radical, or R4 and R5 are joined together with the adjacent nitrogen atom to form a heterocyclic radical; R6 is H or a lower alkyl radical; R7 is H, halo, OH, a lower alkyl radical, or is a buta-1,3-dienyl radical which together with the adjacent benzene ring forms a naphthyl radical; R8 is H or OH; and n is 2;