A series of new luminescent iridium(III) terpyridine complexes functionalised with an isothiocyanate group, [Ir(tpy-R)(tpy-C6H4-NCS-p)](PF6)3 [R = H (1), C6H5 (2), C6H4-CH3-p (3), C6H4-Cl-p (4)] has been synthesised, characterised and their photophysical properties studied; the X-ray crystal structure of one of the intermediate complexes, [Ir(tpy-C6H4-Cl-p)(CF3SO3)3] (4b), has also been determined; complex 1 has been used as a luminescent label for proteins.