Polyaza receptors

In Other examples anion binding can cause quenching of the Ru (bpy)3 MLCT emission. In aqueous solution polyaza receptors 80-82 bind phosphate and ATP anions, producing up to a 15% reduction in the emission intensity of max at 605 nm [16]. Similarly, 76 shows up to a 40% reduction in the intensity of the luminescent emission at 630 nm in the presence of dihydrogenphosphate in DMSO solution. 

Costa. J. Delgado, R. Drew. M.G.B. Felix, V. Saint-Maurice, A. A new redox-responsive 14-membered tetraazamacrocycle with ferrocenylmethyl arms as receptor for sensing transition-metal ions. J. Chem. Soc., Dalton Trans. 2000. 1907-1916 and references therein. Lloris. J.M. Martinez-Miner. R. Soto, J. Pardo, T.J. An electrochemical study in acetonitrile of macrocyclic or open-chain ferrocene-containing oxa-aza or polyaza receptors in the presence of protons, metal cations and anions. J. Organomet. Chem. 2001. 637-639. 151-158 and references therein. 

Indeed, although this receptor exhibits a weaker interaction with ATP, Mc4N6 induces a larger rate acceleration for the ATP desphorilation with respect to the dimensionally analogous [ISJaneN. These data strongly confirm that nucleophilicity plays a basic role in determining the catalytic ability of polyaza receptors. 

Crescent-shaped polyaza clefts are commonly used in recognition ensembles. " Anslyn et al. reported the synthesis of several polyazaclefts characterized by a tricyclic core with appendant guanidiunium groups (28 and 29). P-NMR titrations in DMSO/HiO mixtures indicated that 29 bound dibenzyl phosphate with both 1 1 and 2 1 stoichiometries, with affinity constants on the order of 10 Receptor 29 bound dibenzylphos-... 

Polyammonium macrocycles are successful mimics of a variety of phosphoryl transfer enzymes. These simple compounds are noted for their capability to bind to a number of anions, including the simple phosphate and polyphosphates as well as more complex nucleotides. "Large" polyazacycloalkanes in their protonated forms have been found to exhibit ATP binding as well as ATPase activity. A general accepted mechanism for ATP hydrolysis catalyzed by polyaza macrocycles involve the formation of a ATP-receptor complex, held by electrostatic interaction and hydrogen bonds, followed by the formation of a covalent intermediate macrocyclic-phosphoramidate species, which is subsequently hydrolyzed (see Figure 2)P... 

Although a great variety of oxa-azamacrocyclic receptors has been examined in the search for synthetical host molecules, only few attempts have been devoted to the synthesis of macrocyclic structures containing both polyoxa and polyaza subunits as potentially hard and soft binding sites. To this purpose we have synthesized some new compartmental oxa-aza macrocyclic receptors, as reported in Figure 4, which display two different binding sites (one N5 and one O2 or O3 subunits), located at opposite side of the same macrocycle. 

Polyaza-oxa macrocycles can also be attached to cobaltocenium moieties, and function as both cation and anion receptors [123, 124]. 

Three polyaza cleft molecules (non-carbohydrate) have been investigated as binding receptors fi>r various tri-deoxycyclitols. ... 

Here we concentrate on the receptors containing a crown-ether fragment, to which an additional functional moiety, connected through the appropriate spacer, has been specifically added for the interaction with the anionic part of the zwitterions. Podands and aza or polyaza crown ethers have also been used and should be considered here, when appropriate. In particular, the use of aza or polyaza crown ethers is very common as the presence of the nitrogen atoms greatly facilitates the synthetic effort for the introduction of the spacer or the complementary functionality. 

Huang, C. Y., Cabell, L. A., and Anslyn, E. V. "Molecular Recognition of Cyditols by Neutral Polyaza-Hydrogen Bonding Receptors The Strength and Influence of Intramolecular Hydrogen Bonds Between Vidnal AIco ... 

The blank flux of urea can not be neglected (Jbiank == 4.4 x 10 mol m s, and the assisted flux was obtained by substraction of the blank flux from the measured flux. The model has been applied for the transport of urea using two types of carriers, e,g. lipophilic metallomacrocycles 15 and 16 69), and polyaza (cleft-type) receptors 17, 18, and 19 71), The transport data are presented in Table 9. Transport experiments were carried out by varying the urea concentration to obtain and In Figure 18, the assisted flux is plotted vs. the initial urea concentration for carrier 15. Diffusion constants and extraction constants for macrocycles 15 and 16 are also given in Table 9. 

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