The present invention relates to compounds and related technetium and rhenium complexes thereof which are suitable for imaging or therapeutic treatment of tissues, organs, or tumors. In another embodiment, the invention relates the methods of imaging tissues, organs or tumors using radiolabeled metal complexes, particularly tissues, organs, or tumors which express certain receptors to which the compounds or complexes of the invention have an affinity. The present invention also relates to methods of treating cancer, particularly those cancer lines which express certain receptors to which the compounds or complexes of the invention have an affinity. In yet another embodiment, the present invention provides methods of imaging and/or inhibiting receptors or neuroreceptors using compounds or complexes of the invention which have an affinity for the receptor or neuroreceptor to be imaged and/or inhibited.