| Autor: |
Shegani A, Triantis C, Nock BA, Maina T, Kiritsis C, Psycharis V, Raptopoulou C, Pirmettis I, Tisato F; Istituto di Chimica della Materia Condensata e di Tecnologie per l'Energia, Consiglio Nazionale delle Ricerche , 35127 Padova, Italy., Papadopoulos MS |
| Abstrakt: |
In the present work, we investigated potential means to obtain neutral tricarbonyl mixed-ligand fac-[M(CO) 3 L 1 L 2 ] complexes (M = Re, 99m Tc) containing the (2-hydroxyphenyl)diphenylphosphine (POH) bidentate ligand (L 1 H) and a series of monodentate ligands (L 2 ). First, fac-[Re(CO) 3 (PO)(H 2 O)], 1, was synthesized by reaction of POH and [Et 4 N] 2 [Re(CO) 3 Br 3 ] in equimolar amounts in MeOH at room temperature. Interestingly, with excess of POH this reaction afforded fac-[Re(CO) 3 (PO)(POH)], 2, with POH operating both as a bidentate and as a monodentate ligand. Owing to the presence of the labile aqua ligand, which can be readily replaced by various monodentate ligands, 1 was further used as a precursor to generate a small library of the desired fac-[M(CO) 3 L 1 L 2 ] complexes. Specifically, by reaction of triphenylphosphine (PPh 3 ), imidazole (im), pyridine (py), cyclohexyl isocyanide (cisc), and tert-butyl isocyanide (tbi), the following products were readily obtained in excellent yields (92%-95%): fac-[Re(CO) 3 (PO)(PPh 3 )], 3, fac-[Re(CO) 3 (PO)(im)], 4, fac-[Re(CO) 3 (PO)(py)], 5, fac-[Re(CO) 3 (PO)(cisc)], 6, and fac-[Re(CO) 3 (PO)(tbi)], 7. All compounds were fully characterized by elemental analysis, IR and NMR spectroscopies, and electrospray ionization(+) mass spectrometry. Their solid-state structure was elucidated by X-ray crystallography. Of considerable interest is the fact that the corresponding 2'-7' were easily accessible at the 99m Tc-tracer level in quantitative yields after reaction of POH and the respective monodentate ligand L 2 with fac-[ 99m Tc(CO) 3 (H 2 O) 3 ] + in aqueous MeOH, as verified by comparative chromatographic methods adopting dual photo- and radiometric detection modes. The high stability displayed by all 99m Tc complexes during histidine and cysteine challenge assays underscored the suitability of the fac-[M(CO) 3 (PO)L 2 ] system for radiopharmaceutical development purposes. |
