title: Rhenium(V) oxocomplexes with novel pyrazolyl-based N4- and N3S-donor chelators.
abstract: The novel pyrazolyl-based ligands 3,5-Me2pz(CH2)2NH(CH2)2NH(CH2)2NH2 and pz*(CH2)2NH-Gly-CH2STrit (pz*=pz, 3,5-Me2pz, 4-(EtOOC)CH(2)-3,5-Me2pz) were synthesized, and their suitability to stabilize Re(V) oxocomplexes was evaluated using different starting materials, namely (NBu4)[ReOCl4], [ReOCl3(PPh3)2] and trans-[ReO2(py)4]Cl. Compound reacts with trans-[ReO2(py)4]Cl yielding the cationic compound [ReO(OMe){3,5-Me2pz(CH2)2N(CH2)2NH(CH2)2NH2}](BPh4) in a low isolated yield. In contrast, the neutral complexes [ReO{pz*(CH2)2NH-Gly-CH2S}] (pz*=pz, 3,5-Me2pz, 4-(EtOOCCH2)-3,5-Me2pz) were synthesized almost quantitatively by reacting [ReOCl3(PPh3)2] or (NBu4)[ReOCl4] with the trityl-protected chelators. The X-ray diffraction analysis of and confirmed the tetradentate coordination mode of the respective ancillary ligands. In the monoanionic chelator coordinates to the metal through four nitrogen atoms, while in the chelator is trianionic, coordinating to the metal through three nitrogens and one sulfur atom. Solution NMR studies of , including two-dimensional NMR techniques (1H COSY and 1H/13C HSQC), confirmed that the N3S coordination mode of the chelators is retained in solution. Unlike , complexes may be considered relevant in the development of radiopharmaceuticals, as further corroborated by the synthesis of the congener [99mTcO{pz(CH2)2-NH-Gly-CH2S}]. This radioactive compound was obtained from 99mTcO4- in aqueous medium, in almost quantitative yield and with high specific activity and radiochemical purity.
authors.affiliation: Departamento de Química, ITN, Estrada Nacional 10, 2686-953, Sacavém Codex, Portugal.
authors.forename: Carolina
authors.initials: C
authors.lastname: Moura
authors.forename: Rute F
authors.initials: RF
authors.lastname: Vítor
authors.forename: Leonor
authors.initials: L
authors.lastname: Maria
authors.forename: António
authors.initials: A
authors.lastname: Paulo
authors.forename: Isabel C
authors.initials: IC
authors.lastname: Santos
authors.forename: Isabel
authors.initials: I
authors.lastname: Santos
mesh_terms: D002614:Chelating Agents / Q000737:chemistry*; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011720:Pyrazoles / Q000737:chemistry*; D011868:Radioisotopes; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000737:chemistry; D012211:Rhenium / Q000737:chemistry*
chemical_list: D002614:Chelating Agents; D009942:Organometallic Compounds; D011720:Pyrazoles; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D012211:Rhenium; D009584:Nitrogen