Synthesis and structural characterization of new oxorhenium and oxotechnetium complexes with XN2S-tetradentate semi-rigid ligands (X = O, S, N)

Abstract

Twelve novel oxo-technetium and oxo-rhenium complexes based on N2S2-, N2SO- or N3S-tetradentate semi-rigid ligands have been synthesised and studied herein. By reacting the ligands with a slight excess of suitable [MO]3+ precursor (ReOCl3(PPh3)2 or [NBu4][99gTcOCl4]), the monoanionic complexes of general formula [MO(Ph-XN2S)]- could be easily produced in high yield. The complexes have been characterized by means of IR, electrospray mass spectrometry, elemental analysis, NMR and conductimetry. The crystal structures of [PPh4][ReO(Ph-ON2S)] 1b and [NBu4][99gTcO(Ph-ON2S)] 1c have been established. The [MO]3+ moiety was coordinated via the two deprotonated amide nitrogens, the oxygen and the terminal sulfur atoms in 1b and 1c. In both compounds, the ON2S coordination set is in the equatorial plane, and the complexes adopted a distorted square-pyramidal geometry with an axial oxo-group. The chemical and structural identity of the different prototypic complexes (rhenium, 99gTc complexes and their corresponding 99mTc radiocomplexes) have been also established by a comparative HPLC study.

Synthesis and β-amyloid binding properties of rhenium 2-phenylbenzothiazoles

“…The semi-rigid XH-diamine-thiol (X = O in 5 and X = S in 6 ) chelators used for our studies were modified from the XH-diamide-thiol chelators reported by Le Gal and coworkers 24. The complexation of [Re(V)O] 3+ with Le Gal’s XH-diamide-thiol chelators led to Re complexes with one negative charge due to the loss of four protons.…”

Rhenium and Technetium-oxo Complexes with Thioamide Derivatives of Pyridylhydrazine Bifunctional Chelators Conjugated to the Tumour Targeting Peptides Octreotate and Cyclic-RGDfK

“…2.15–2.18 Å) suggesting some degree of multiple bond character. 51 , 56 The Re–N1–N2 and Re–N5–N6 bond angles average 124°, suggesting an approximately sp 2 hybridized nitrogen. The Re–S bond distances average 2.29 Å and are similar to the Re–S bond distances in rhenium(V) complexes with amino thiolate ligands and Re–S bond distances in rhenium complexes with thiosemicarbazonato ligands.…”

Synthesis of Oxorhenium(V) and Oxotechnetium(V) Complexes That Bind to Amyloid-β Plaques

“…A further complication is that thiol-containing ligands are often air-sensitive and prone to oxidation, and this makes their incorporation into premade radiopharmaceutical kits challenging. The use of semirigid tetradentate ligands, lacking tertiary amines, for complexation with [TcO] 3+ has the advantage of precluding the formation of syn and anti diastereomers. , …”

“…Both complexes crystallize in centrosymmetric space groups, with both SP-5-13-C and SP-5-13-A enantiomers present in the unit cell . In [ReO L 1 ], the Re–N1 bond length [1.908(2) Å] is shorter than the Re–N2 bond [1.978(3) Å], but both bonds are shorter than typical Re–N single bonds (approximately 2.13 Å), suggesting some degree of multiple-bond character consistent with deprotonation of the amine and amide, respectively, and consistent with other complexes that feature a Re–N amide bond. , The Re–N pyridine bond in [ReO L 2 ] [2.086(2) Å] is marginally shorter than the Re–N pyridine bond in [ReO L 1 ] [2.130(2) Å], but both are similar to the Re–N pyridine bond length found in [ReO 2 (pyridine) 4 ] + . The Re–O phenolate bond distance is 1.968(2) Å in [ReO L 1 ] and 1.969(2) Å in [ReO L 2 ].…”