. . . "Thus, Z may be, for example, a halogen atom, for example a chlorine, bromine or iodine atom or a group selected from --SH, --NH2, hydrazine (--NHNH2) or a derivative thereof, [for example --N(CH3)NH2, --NHCONHNH2, --NHCSNHNH2, or phenyl hydrazine], --NCO, --NCS, --COR10, [where R10 is a halogen atom such as a chlorine or bromine atom, or a N3, C1-6 alkoxy, e.g. methoxy, C6-12 aryloxy (e.g. nitroph" . .