| Autor: |
Mauro Formica, Vieri Fusi, Eleonora Macedi, Paola Paoli, Giovanni Piersanti, Patrizia Rossi, Giovanni Zappia, Pierfrancesco Orlando |
| Předmět: |
|
| Zdroj: |
New Journal of Chemistry; Jul2008, Vol. 32 Issue 7, p1204-1214, 11p |
| Abstrakt: |
The synthesis and characterization of the two new hosting molecules for anions 4(N),10(N)-bis-[2-(4-nitrophenylureido)acetamido]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (L1) and 1-((diethylcarbamoyl)methyl)-3-(4-nitrophenyl)urea (L2) are reported. L1 is a branched tetraazamacrocycle bearing two p-nitrophenylureido groups as side-arms, whereas L2 has the same linear chain and binding moiety of L1 side-arm. The best synthetic routes for use in obtaining L1 were explored, affording the synthesis of the new intermediate 4, a versatile building block for further functionalized branched macrocyclic hosts. The binding properties of both ligands towards the halides series and acetate anions (G) were investigated by NMR and UV-Vis spectroscopy in a dimethyl sulfoxideâ0.5% water solution. Both ligands interact with Fâ, Clâ and AcOâ while Brâ and Iâ did not. The NMR experiments proved that the binding occurs via H-bond to the ureido fragments. Fluoride anion is basic enough to deprotonate the ureido group of both ligands, thus preventing the determination of the addition constants to both ligands; this was instead possible for Clâ and AcOâ. L1 forms GâL species of 1 : 1 ([GL1]) and 2 : 1 ([G2L1]) stoichiometry while L2 forms only the 1 : 1 [GL2] species. The higher value of the formation constant of the [AcOL1]âvs. the [AcOL2]â species (log K = 5.5 vs. 2.8 for the reaction AcOâ L = AcOLâ) suggested that both side-arms of L1 cooperate in binding acetate; this does not occur with Clâ. The results confirmed that this tetraaza-macrocyclic base acts as a preorganizing scaffold for side-arms when they are linked to it via an amide function. The crystal structure of L2·H2O is also reported. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
