The present invention provides tetra-amine chelator conjugates with biological targeting moieties, linked via a linker group and technetium complexes thereof as radiopharmaceuticals. The linker group is such that the chelator is mono-functionalized at the bridgehead position and provides both flexibility and a lack or aryl groups, to minimize lipophilicity and steric hulk. Protected versions of the chelators are provided which permit conjugation with a wide range of targeting molecules without interfering reactions with the amine nitrogens of the tetra-amine chelator. Syntheses of the functionalised chelators are described, together with bifunctional chelate precursors. Radiopharmaceutical compositions comprising the technetium metal complexes of the invention are described, together with non-radioactive kits for the preparation of such radiopharmaceuticals.
