Search

The reaction of [[N[Et.sub.4]].sub.2][Re[Br.sub.3][(CO).sub.3]] with 2,4-pentanedione (acac) has produced a complex of the type fac-Re(acac)([O[H.sub.2])[(CO).sub.3] under aqueous conditions. Acac is used as a bidentate ligand system in a '2+1' approach, which has the potential for linking to targeting molecules for generating in situ tridentate complexes for nuclear medicine applications.

The Re(V) and Re(III) Schiff base phosphine complexes synthesized were fully characterized, including single-crystal X-ray diffraction and cyclic voltammetric analysis. The Re(III) complexes would not be accessible to in vivo reduction, on the basis of their III/II redox potentials and the strong sigma-donating and pi-back-bonding properties of the phosphines should stabilize Re(III) to oxidation.

Several rhenium (V) oxo complexes with tetradenate N(sub 2)O(sub 2) Schiff base ligands were synthesized and characterized. The crystallographic data for the structures is reported.

In the last two decades, a number of chelate strategies have been proposed for the fac-[MI(CO)3]+ (M = Re, 99mTc) core in radiopharmaceutical applications. However, the development of new ligands/complexes with improved function and in vivo performance has been limited in recent years. Expanding on our previous studies using the 2 + 1 labeling strategy, a series of bidentate ligands (neutral vs. anionic) containing an aromatic amine in combination with monodentate pyridine analogs or imidazole were explored to determine the influence of the bidentate and monodentate ligands on the formation and stability of the respective complexes. The 2 + 1 complexes with Re and 99mTc were synthesized in two steps and characterized by standard radio/chemical methods. X-ray characterization and density functional theory analysis of the Re 2 + 1 complexes with the complete bidentate series with 4-dimethylaminopyridine were conducted, indicating enhanced ligand binding energies of the neutral over anionic ligands. In the 99mTc studies, anionic bidentate ligands had significantly higher formation yields of the 2 + 1 product, but neutral ligands appear to have increased stability in an amino acid challenge assay. Both bidentate series exhibited improved stability by increasing the basicity of the pyridine ligands. [ABSTRACT FROM AUTHOR]

In the last two decades, thefac-[MI(OH2)3(CO)3]+(M = Re,99mTc) core has been an important synthon in the development of new radiopharmaceuticals and methodologies. A bidentate N,N-diethylbenzoylthiourea (HEt2btu,H1) ligand was reacted withfac-[MI(OH2)3(CO)3]+as part of a 2+1 strategy consisting of a bidentate and a monodentate ligands to saturate the coordination sphere. When excessH1was used in the reaction, an unusual 2+1 complex offac-[ReI(CO)3(1)(H1)],2, was isolated that contained twoH1ligands, OS bidentate and S monodentate in different protonation states. Equimolar concentrations of HEt2btu andfac-[ReI(CO)3]+generated the single addition of the ligand; however, isolation of the solid revealed a μ-sulfur-bridged dimer offac-[ReI(CO)31)]2,3. Reaction ofH1withfac-[MI(OH2)3(CO)3]+followed by the addition of a monodentate ligand (i.e. pyridine, methyl imidazole, cyclohexyl isocyanide, triphenylphosphine) yielded the corresponding 2+1fac-[MI(CO)3(1)(L)] complexes. Single-crystal X-ray structural analysis of the Re complexes revealed conformational differences of the ligand on the metal depending on the protonation state of the central amine in the protonatedH1versus1ligand. Comparison of these complexes with previous complexes and freeH1revealed significant shifts in the bond angles, bond lengths, and ligand planarity that are discussed further. The corresponding 2+1fac-[99mTcI(CO)3(1)(L)] complexes were also prepared in moderate to good yields and their stability examined by amino acid challenge studies. [ABSTRACT FROM AUTHOR]

Several rhenium(V) oxo complexes with tetradentate N[sub 2]O[sub 2] Schiff base ligands were synthesized and characterized. The general synthetic procedure involved reaction of [NBu[sub 4]][ReOCl[sub 4]] with a tetradentate Schiff base ligand (L[sub 1] = N,N'-ethylenebis(acetylacetoneimine), (acac[sub 2]en) or L[sub 2] = N,N'-propylenebis(acetylacetoneimine) (acac[sub 2]pn))in ethanol solution to generate complexes of the form trans-ReOX(L) where X = CI[sup -], MeO[sup -], ReO[sub 4, sup -], or H[sub 2]O. The product isolated from the reaction was found to be dependent on the reaction conditions, in particular the presence or absence of water and/or base. The μ-oxo-Re[sub 2]O[sub 3](L)[sub 2] dimers were synthesized and characterized for chemical and structural comparison to the related monomers. Conversion of the monomer to its dimer analogue was followed qualitatively by spectrophotometry. The complexes were characterized by ¹H and [sup 13]C NMR, UV-vis, and IR spectroscopy, elemental analysis, and single crystal X-ray diffraction. The crystallographic data reported for the structures are as follows: trans-[ReO(OH[sub 2])(acac[sub 2]en)]Cl (H[sub 20]C[sub 12]CIN[sub 2]O[sub 4]Re) 1, triclinic (P&1macr;), a = 7.2888(6) Å, b = 9.8299(8) Å, c = 10.8195(9) Å, α = 81.7670(10)°, β = 77.1510(10)°, γ= 87.6200(10)°, V= 747.96(11), ˚³, Z = 2; trans-[ReO(OReO[sub 3])(acac[sub 2]en)] (H[sub 18]C[sub 12]N[sub 2]O[sub 7]Re[sub 2]) 2, monoclinic (P2[sub 1]/c), a = 7.5547(4) Å, b = 8.7409(5) ,Å, c = 25.7794(13) Å, β = 92.7780(10)°, V = 1700.34(16) ų, Z = 4; trans-[ReOCl(acac[sub 2]pn)] (H[sub 20]C[sub 13]N[sub 2]O[sub 3]CIRe) 3, monoclinic (P2[sub 1]/c), a = 8.1628(5) Å, b = 13.0699(8) Å, c = 28.3902(17) Å, β = 97.5630(10)°, V=3002.5(3) ų, Z=8; trans-[ReO(OMe)(acac[sub 2]pn)] (H[sub 23]C[sub 14]N[sub 2]O[sub 4]Re) 4, monoclinic (P2[sub 1]/c), a = 6.7104(8) Å,, b = 27.844(3) Å, c = 8.2292(9) Å, β = 92.197(2)°, V = 1536.4(3) ų, Z = 4; trans-[μ-oxo-Re[sub 2]O[sub 3](acac[sub 2]en)[sub 2]] (H[sub 36]C[sub 24]N[sub 4]0[sub 7]Re[sub 2]) 5, monoclinic (P2[sub 1]/n), a = 9.0064(5) Å, b = 12.2612(7) Å, c = 12.3695(7) Å, β = 90.2853(10)°, V = 1365.94(13) ų, Z=2; and trans-[μ-oxo Re[sub 2]O[sub 3](acac[sub 2]pn)[sub 2]] (H[sub 40]C[sub 26]N[sub 4]O[sub 7]Re[sub 2]) 6, monoclinic (P2[sub 1]/n), a = 9.1190(5) Å,, b = 12.2452- (7) Å, c = 12.8863(8) Å, β = 92.0510(10)°, V=1438.01(14) ų, Z= 2. [ABSTRACT FROM AUTHOR]

A fluorescent tridentate phosphine, BodP3 (2), forms rhenium complexes which effectively image cancer cells. Related technetium analogues are also readily prepared and have potential as dual SPECT/fluorescent biological probes. [ABSTRACT FROM AUTHOR]

Reaction of [NEt4]2[ReBr3(CO)3] with 24-pentanedione (acac) yields a complex of the type fac-Re(acac)(0H2)(CO)3 (1) under aqueous conditions. 1 was further reacted with a monodentate ligand (pyridine) to yield a fac-Re(acac)(pyridine)(CO)3 complex (2). Complex 1 was found to react with primary amines to generate a Schiff base (imine) in aqueous solutions. When a mixed-nitrogen donor bidentate ligand, 2-(2-aminoethyl)pyridine, that has different coordination affinities for fac-Re(acac)(0H2)(CO)3 was utilized, a unique tridentate ligand was formed in situ utilizing a metal-assisted Schiff base formation to yield a complex fac-Re(CO)3(3[(2- phenylethyl)imino]-2-pentanone) (3). Tridentate ligand formation was found to occur only with the Re-coordinated acac ligand. Reactions of acac with fac-Re(CO)3Br(2-(2-aminoethyl)pyridine) (4) or a mixture of [NEt4]2[ReBr3(CO)3], acac, and 2-(2-aminoethyl)pyridine did not yield the formation of complex 3 in water; [ABSTRACT FROM AUTHOR]