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The complexation of a tweezers ligand with zinc perchlorate in the absence and presence of amines in methanol solution was explored. L2Zn2(ClO4)4was a thermodynamic product of the reaction in the absence of an amine. The complex was shown to interact with aliphatic amines resulting in the formation of a Zn–N(amine) bond. If metal–ligand complexation was carried out in the presence of an amine the formation of a trinuclear zinc complex L3Zn36+was observed. Moreover the transformation of complex L2Zn24+to L3Zn36+occurred, when the former was subjected to an amine in the amount, which is sufficient to coordinate more than one amino group on each zinc atom. Complexes ligand-zinc-amine were shown to be kinetically stable, and the method of their preparation was crucial to the purity of the final complexes. L3Zn36+was favored under kinetic control: reagent concentration 10−5M, slow addition of zinc perchlorate to the mixture of an amine and the ligand. Under thermodynamic control (fast mixing of reagents, concentration 10−2–10−3M) formation of a mixture of complexes was observed. All pure complexes and their mixtures were characterized using UV-Vis, ROESY, PFGSE NMR and ESI-MS techniques. On the basis of DFT calculations the mechanism of influence of an amine on self-assembly was suggested. [ABSTRACT FROM AUTHOR]

The synthesis and anion binding properties of a neutral macrocyclic receptor bearing H-bond donor coordination sites are described. The anion binding studies by use of UV-vis and 99Tc NMR methods revealed that the receptor can coordinate perrhenate and pertechnetate in dimethylsulfoxide and chloroform solutions with the relatively high binding constants, viz. log Ka > 4. The coordination mode of the perrhenate to the receptor was determined by a single-crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

The synthesis, characterization, and anion-binding properties of a series of 2,6-diamidopyridine dipyrromethane hybrid macrocycles is presented. As part of this work, a new method for effecting the oxidation of dipyrromethane-based macrocycles in organic solvents has been developed. The macrocyclic frameworks presented here stand out because of their ease of synthesis and tunable anion-binding properties. Evidence for anion binding was obtained from UV-vis spectroscopic titrations carried out in acetonitrile. The results clearly indicate that by changing the flexibility, cavity size, and directionality of anion-binding moieties in the macrocyclic framework the anion selectivity may be changed dramatically. These results are in accord with density functional theory molecular modeling calculations performed on one member of the series. [ABSTRACT FROM AUTHOR]

Abstract: Formation of associates of phosphate receptor 1 in the concentration range 10−13–10−5 M was investigated in individual and mixed solutions with lipidomimetic 2. The receptor 1 forms associates of different nature depending on the concentration of solution. Threshold concentration is 10−7 M. Mixed systems 1+2 with normal (C 1 =10−5 M) and low (C 2 =10−9 M) concentration of the receptor 1 considerably differ not only in the size of mixed micelles but also in the catalytic activity. The concentration dependences of the catalytic activity of mixed systems and the size of mixed micelles are related and have an U-shape. [Copyright &y& Elsevier]