The present technology provides compounds as well as compositions including such compounds useful in targeted radiotherapy of cancer and/or mammalian tissue overexpressing prostate specific membrane antigen (“PSMA”) where the compounds are represented by the following: or a pharmaceutically acceptable salt thereof, or a pharmaceutically acceptable salt thereof, or a pharmaceutically acceptable salt thereof, wherein M1 is independently at each occurrence an alpha-emitting radionuclide. Equivalents of such compounds are also disclosed.