title: Synthesis and characterization of novel 99gTc(V) and Re(V) complexes with water-soluble tetraaza diamido dipyridino ligands: single-crystal X-ray structural investigations of mono- and dinuclear complexes.
abstract: 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-C(5)H(4)NCH(2)NHCO)(2)CH(2), 1 (L(1)H2), (2-C(5)H(4)NNHNHCO)(2)CH(2), 2, and [2-C(5)H(4)N(+)(O)(-)CH(2)NHCO](2)CH(2), 3, were synthesized. Reaction of L(1)H2 with ReOCl(3)(PPh(3))(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-Bu(4)N][ReOCl(4)] resulted in the neutral complex 6, trans-[ReO(L(1))]Cl. Similarly, when ligand 1 was reacted with [n-Bu(4)N][(99g)TcOCl(4)], the neutral trans-[(99)TcO(L(1))]Cl complex 7 was formed, which upon dissolution transformed into a cationic complex 8, trans-[(99)TcO(L(1))(OH(2))](+)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.
authors.affiliation: Chemistry Department, University of Missouri, Columbia, MO 65211, USA.
authors.forename: Laszlo
authors.initials: L
authors.lastname: Kurti
authors.forename: Dioni
authors.initials: D
authors.lastname: Papagiannopoulou
authors.forename: Minas
authors.initials: M
authors.lastname: Papadopoulos
authors.forename: Ioannis
authors.initials: I
authors.lastname: Pirmettis
authors.forename: Catherine P
authors.initials: CP
authors.lastname: Raptopoulou
authors.forename: Aris
authors.initials: A
authors.lastname: Terzis
authors.forename: Efstratios
authors.initials: E
authors.lastname: Chiotellis
authors.forename: Michael
authors.initials: M
authors.lastname: Harmata
authors.forename: Robert R
authors.initials: RR
authors.lastname: Kuntz
authors.forename: Raghoottama S
authors.initials: RS
authors.lastname: Pandurangi
mesh_terms: D000588:Amines / Q000737:chemistry; D001372:Aza Compounds / Q000737:chemistry; D018360:Crystallography, X-Ray; D007202:Indicators and Reagents; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000737:chemistry; D012211:Rhenium / Q000737:chemistry*; D013237:Stereoisomerism; D013667:Technetium / Q000737:chemistry*; D014867:Water
chemical_list: D000588:Amines; D001372:Aza Compounds; D007202:Indicators and Reagents; D009942:Organometallic Compounds; D011725:Pyridines; D019275:Radiopharmaceuticals; D014867:Water; D012211:Rhenium; D013667:Technetium