The simultaneous action of the tridentate ligand (C(2)H(5))(2)NCH(2)CH(2)N(CH(2)CH(2)SH)(2) and the monodentate coligand HSC(6)H(4)OCH(3) on a suitable ReO(3+) precursor results in a mixture of syn- and anti-oxorhenium complexes, ReO[(C(2)H(5))(2)NCH(2)CH(2)N(CH(2)CH(2)S)(2)] [SC(6)H(4)OCH(3)], in a ratio of 25/1. The complexes are prepared by a ligand exchange reaction using ReO(eg)(2) (eg = ethylene glycol), ReOCl(3)(PPh(3))(2), or Re(V)-citrate as precursor. Both complexes have been characterized by elemental analysis, FT-IR, UV-vis, X-ray crystallography, and NMR spectroscopy. The syn isomer C(17)H(29)N(2)O(2)S(3)Re crystallizes in the monoclinic space group P2(1)/n, a = 14.109(4) Å, b = 7.518(2) Å, c = 20.900(5) Å, beta = 103.07(1) degrees, V = 2159.4(9) Å(3), Z = 4. The anti isomer C(17)H(29)N(2)O(2)S(3)Re crystallizes in P2(1)/n, a = 9.3850(7) Å, b = 27.979(2) Å, c = 8.3648(6) Å, beta = 99.86(1) degrees, V = 2163.9(3) Å(3), Z = 4. Complete NMR studies show that the orientation of the N substituent chain with respect to the Re=O core greatly influences the observed chemical shifts. Complexes were also prepared at the tracer ((186)Re) level by using (186)Re-citrate as precursor. Corroboration of the structure at tracer level was achieved by comparative HPLC studies.

In developing 99mTc complexes as potential brain-imaging agents, we investigated the coordination chemistry of ligands containing sulfur and nitrogen donor atoms with the general formula R-CH2CH2N(CH2CH2SH)2 (R = C2H5S, (C2H5)2N). These ligands act as tridentate SNS chelates to the TcO3+ core, leaving open one coordination site cis to the oxo group. In reactions with the highly reactive [99TcOCl4]- precursor, this vacancy was occupied by a chlorine atom. When the ligands reacted in the presence of 4-methoxythiophenol, using 99Tc(V)-gluconate as precursor, the vacancy was filled with 4-methoxythiophenol, which acted as coligand. Thus neutral mixed ligand complexes of the general formula [TcO((SCH2CH2)2NCH2CH2R)X], where X = Cl or 4-methoxythiophenol, were synthesized. The complexes were characterized by UV-vis, IR, 1H NMR, crystallographic, and elemental analyses. The crystal structures of 3a (R = C2H5S, X = Cl) and 4b (R = (C2H5)2N, X = 4-methoxythiophenol) demonstrated that the coordination geometry is trigonal bipyramidal with the N1 and Cl or S3 occupying the apical positions and the basal plane defined by the S1 and S2 of the tridentate ligand and the oxo group. The complexes 4a(99mTc) (R = C2H5S, X = 4-methoxythiophenol) and 4b(99mTc) were prepared using 99mTc-glucoheptonate as precursor and were purified by HPLC. Biodistribution in mice showed high initial brain uptake (3.68% and 3.56% dose/organ for 4a(99mTc) and 4b(99m-Tc), respectively). Complex 4b(99mTc) displayed significantly higher brain/blood values and prolonged retention in brain as well. The results suggest that structural modifications based on configurations 4a,b may provide novel 99mTc brain-imaging agents with improved biological characteristics.

When aqueous solutions of sodium 10-undecenoate at concentrations above the cmc of the surfactant (8.24 g/dm3; 0.04 M) are irradiated by y rays the low molecular weight polysoap poly (sodium 10-undecenoate) is formed which has a degree of polymerization equal to ten and exhibits micellar behavior by solubilizing hydrophobic molecules. The cmc of the polymeric micelle is equal to zero, each micelle being built of a single poly(sodium 10-undecenoate) molecule. These micelles, called "intramolecular" micelles, are known to have equal hydrated size with the corresponding monomeric micelles of sodium 10-undecenoate. Fluorescence studies with the micropolarity probe pyrene show that the fluorophore penetrates the intramolecular polymeric micelle less than the monomeric one. This is understood in terms of the more compact structure of the polymeric micelle due to the presence of polymerization-induced covalent bonds among the terminal methylene groups of the undecenoate chains. When the concentration of poly(sodium 10-undecenoate) in water exceeds 2.06 g/dm3 hydrophobic aggregation of intramolecular micelles occurs which leads to the formation of large "intermolecular" micelles having an intrinsic viscosity of 0.079 100 mL/g compared to 0.048 100 mL/g for the intramolecular and monomeric micelles.

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