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Abstract: In an attempt to understand the aqueous interactions of Cr(III) with the low molecular mass physiological ligand citric acid, the pH-specific synthesis in the binary Cr(III)–citrate system was pursued, leading to the new complexes Na3[Cr(C6H5O7)2]·8.5H2O (1) and (Hdmphen)6[Cr(C6H5O7)2]·(NO3)3·14H2O (2). Complexes 1 and 2 were characterized by elemental analysis, spectroscopic, structural, thermal, and magnetic susceptibility studies. The structures of 1 and 2 reveal a mononuclear octahedral complex of Cr(III) with two citrate ligands bound to it. Albeit of the same deprotonation state, the disposition of the two citrate ligands with respect to Cr(III) differs between 1 and 2 in the solid state, thus reflecting the presence of pH-structural variants in the requisite binary system. This conformational difference is lifted in aqueous solution, thus providing (a) comparative information on the distribution and diversity of species in the binary Cr(III)–citrate system, and (b) insight into the nature of interactions developing in the binary Cr(III)–hydroxycarboxylate systems in abiotic and biological applications. [Copyright &y& Elsevier]

Abstract: Two rhenium(I) tricarbonyl complexes with the tridentate monoanionic NSO ligands, 4-(benzimidazol-2-yl)-3-thiabutanoic acid (complex 3) and [1-(11-carboxyundecanyl)-4-(benzimidazol-2-yl)]-3-thiabutanoic acid (complex 4) were synthesized and characterized by spectroscopic methods and elemental analysis. X-ray crystallographic analysis of complex 3 revealed a distorted octahedral geometry around rhenium defined by the three facially bound CO groups and the NSO donor atom set of the tridentate ligand. The analogous technetium-99m complexes (complexes 5 and 6) were also prepared quantitatively by reaction of the NSO ligands with the fac-[99mTc(H2O)3(CO)3]+ synthon and their identity was established by chromatographic comparison to their rhenium congeners. Biodistribution in mice of complex 6 bearing the fatty acid chain showed significant heart uptake (6.26±0.79% ID/g p.i.) at 1min accompanied, however, with a heart:blood ratio below 1. [Copyright &y& Elsevier]

Abstract: The reaction of [NEt4]2[Re(CO)3Br3] with equimolar amount of a tridentate NSO ligand in methanol leads to the formation of neutral tricarbonyl rhenium(I) complexes of the general formula Re(CO)3(NSO), where the NSO ligand is o-C5H4N-CH2CH2-S-CH2CH(NHCOCH3)COOH (L1H), complex 1 or o-C5H4N-CH2CH2-S-C(CH3)2CH(NHCOCH3)COOH (L2H), complex 2. Both complexes have been characterized by elemental analysis and spectroscopic methods, while complex 2 has also been characterized by X-rays analysis. At technetium-99m level, the corresponding fac-[99mTc(CO)3(NSO)] complexes 3 and 4, were obtained in high yield by reacting ligands L1H or L2H with the fac-[99mTc(CO)3(H2O)3]+ precursor in water. Their structure was established by chromatographic comparison to the prototype rhenium complex using high-performance liquid chromatographic techniques. [Copyright &y& Elsevier]

Abstract: Two rhenium(I) tricarbonyl complexes, with the monoanionic tridentate NSO type ligand, 4-(imidazolin-2-yl)-3-thiabutanoic acid and 4-(N-ethylimidazolin-2-yl)-3-thiabutanoic acid were synthesized and isolated in pure form. Both complexes were characterized by spectroscopic methods and elemental analysis. The solid-state structure of 4-(imidazolin-2-yl)-3-thiabutanoic acid and of both complexes was established by X-ray crystallography. The geometry about the rhenium is octahedral. The analogous technetium-99m complexes were also prepared quantitatively by the reaction of both ligands with the fac-[99mTc(CO)3(H2O)3]+ synthon and their identity was established by chromatographic comparison to their rhenium congeners. [Copyright &y& Elsevier]

A novel mixed ligand hexacoordinated rhenium(III) complex of the general formula ReIII[P][NN][S][SO] has been synthesized by reacting ReVOCl3(PPh3)2 with 2,2′-bipyridine (NN), p-thiocresol (S) and N-acetyl-l-cysteine (SO) in a 1:1:1:1 ratio in methanol. During the reaction, the central rhenium atom undergoes reduction from Re(V) to Re(III). The complex was isolated as red crystals and characterized by elemental analysis, IR and NMR spectroscopies. X-ray crystallographic studies showed that the coordination geometry around rhenium is distorted octahedral. The equatorial plane is defined by the two nitrogen atoms of 2,2′-bipyridine, the sulfur of N-acetyl-l-cysteine and the sulfur of the aromatic thiol, while the phosphorous and the carboxylate oxygen of N-acetyl-l-cysteine occupy the apical positions. [Copyright &y& Elsevier]

Presents a synthesis and characterization of mixed-ligand oxerhenium complexes with the SNN type ligand. Synthesis; X-ray studies of compounds; NMR studies of complexes.