For example, compounds containing a ???L1 H, ???L2H, or ???L3H group (where L1, L2 and L 3 is each a linker atom or group) may be treated with an alkylating agent: [0183] ,(R7) uL3Alk3 tX2 or R7aX2 respectively in which X2 is a leaving atom or group such as a halogen atom, e.g. a fluorine, bromine, iodine or chlorine atom or a sulphonyloxy group such as an alkylsulphonyloxy, e.g. trifluoromethylsu