With the aim of developing the concept of pretargeted click chemistry for the diagnosis of Alzheimer's disease two antibodies specific for amyloid-β were modified to incorporate trans-cyclooctene functional groups. Two bis(thiosemicarbazone) compounds with pendant 1,2,4,5-tetrazine functional groups were prepared and radiolabelled with positron emitting copper-64. The new copper-64 complexes rapidly react with the trans-cyclooctene functionalized antibodies in a bioorthogonal click reaction and cross the blood-brain barrier in mice.