This disclosure relates to compositions comprising substituted iminodiacetic acid ligands and metal tricarbonyl complexes containing the ligands and derivatives thereof. In certain embodiments, the metal tricarbonyl complexes are used as radioisotope tracers such as renal tracers. In certain embodiments, the metal complexes comprise 99mTc or Re. In certain embodiments, the ligands are substituted with a fluorine, a fluorine-18(F18) radioisotope, or other radionuclide.