A targeting radioactive immunoreagent comprises a metal radionuclide ion, a complexing agent, and an immunoreactive group covalently bonded to said complexing agent, the complexing agent having the structure (AI), wherein R represents hydrogen, alkyl, alkoxy, alkylthio, alkylamino, alkylformamido, aryl, aryloxy, heterocyclyl or a protein reactive group; R1 represents hydrogen, alkyl, alkoxy, alkylthio, alkylamino, alkylformamido, aryl, aryloxy, heterocyclyl or a protein reactive group; R2 represents hydroxy, carboxy, hydroxyalkyl, thioalkyl, formyl, carbonyliminodiacetic acid, methyleneiminodiacetic acid, methylenethioethyleneiminodiacetic acid, carboxyalkylthioalkyl, hydrazinylidenediacetic acid, or a salt of such acids, or two R2 groups, taken together, represent the atoms necessary to complete a macrocyclic ring structure containing at least one heteroatom coordinating site and at least one, preferably two alkylene groups forming part of the ring structure; R3 represents hydrogen, alkyl, alkoxy, alkylthio, alkylamino, alkylformamido, aryl, aryloxy, heterocyclyl or a protein reactive group; R4 represents hydrogen or a protein reactive group; n is 0 to 4; o is 0 or 1; m is 0 or 1; provided that at least one of n and m is 0 and at least one of R, R?1, R3 and R4¿ is a protein reactive group. In another aspect, this invention provides novel terpyridines, quaterpyridines, quinqepyridines, sexipyridines and phenanthrolines having the structure (AI). Preferred terpyridines have the structure (AI) above wherein n=1, o=1, m=0, and R is a protein reactive group or a phenyl substituted with a protein reactive group. Optionally, the phenyl may also contain one or more substituents selected from alkyl and alkoxy. Preferred phenanthrolines have the structure (AI) above wherein n=0, o=1, m=1 and at least one R4 is a protein reactive group. The targeting radioactive immunoreagents are particularly useful in therapeutic and diagnostic imaging compositions and methods.