Rhenium and technetium are known for their useful applications in nuclear medicine with similar properties. In this study, new diamido dipyridino (N-4) water-soluble ligands (2-C5H4NCH2NHCO)(2)CH2, 1 (L(1)H2), (2-C5H4NNHNHCO)(2)CH2, 2, and [2-C5H4N+(O)-CH2NHCO](2)CH2, 3, were synthesized. Reaction of L(1)H2 with ReOCl3(PPh3)(2) resulted in the novel six-coordinated rhenium(V) complex, trans-ReO(L-1)(OEt), 4. The complex was characterized by spectroscopic methods, and its X-ray crystallographic analysis revealed that rhenium is coordinated to four nitrogen atoms of the ligand and to two oxygen atoms from the deprotonated ethanol and the oxo group respectively in a distorted octahedral geometry. In solution, complex 4 was transformed to a new complex 5, which was proved to be the dinuclear complex mu-oxo [ReO(L-1)](2)O. Reaction of 1 with [n-Bu4N][ReOCl4] resulted in the neutral complex 6, trans-[ReO(L-1)]Cl. Similarly, when ligand 1 was reacted with [n-Bu4N][(TcOCl4)-Tc-99g], the neutral trans-[(TcO)-Tc-99(L-1)]Cl complex 7 was formed, which upon dissolution transformed into a cationic complex 8, trans-[(TcO)-Tc-99(L-1)(OH2)]Cl-+(-). The single-crystal X-ray structure of 8 reveals that the coordination sphere about technetium is a distorted octahedron with four nitrogen atoms in the equitorial plane, while doubly bonded oxygen and coordinated water occupy the apical positions. Further dissolution of 8 resulted in the formation of dinuclear mu-oxo [TcO(L-1)](2)O, 9. This study shows that Tc and Re have similar metal core structures in solution for diamido dipyridino systems, besides similarity in geometrical structure, proved by the X-ray structures on the same ligands.