Anion Binding and Recognition by Inorganic Based Receptors

p-tert-Butylthiacalix[4]arenes functionalized by N-(4'-nitrophenyl)acetamide and N,N-diethylacetamide fragments: synthesis and binding of anionic guests

New p-tert-butylthiacalix[4]arenes, which are mono-, 1,2-di- and tetrasubstituted at the lower rim containing N-(4'-nitrophenyl)acetamide and N,N-diethylacetamide groups in cone and partial cone conformations have been synthesized. Their complexation ability towards a number of tetrabutylammonium salts n-Bu₄NX (X = F^-, Cl^-, Br^-, I^-, CH₃CO₂^-, H₂PO₄^-, NO₃^-) was studied by UV spectroscopy. The effective receptor for the anions studied as well as selective receptors for F^-, CH₃CO₂^- and H₂PO₄^- ions, which based on the synthesized thiacalix[4]arenes, have been obtained. It was shown that p-tert-butylthiacalix[4]arene tetrasubstituted at the lower rim by N-(4'-nitrophenyl)acetamide moieties bonded to the anions studied with association constants within the range of 3.55 × 10³-7.94 × 10⁵ M^-1. Besides, the binding selectivity for F^-, Cl^-, CH₃CO₂^-, and H₂PO₄^- anions against other anions was in the range of 4.1-223.9. Substituting one or two fragments in the macrocycle with N,N-diethylacetamide groups significantly reduces the complexation ability of the receptor. In contrast to the 1,3-disubstituted macrocycle containing two N-(4'-nitrophenyl)acetamide moieties, the 1,2-disubstituted thiacalix[4]arene, which contains only one such fragment and a N,N-diethylacetamide moiety, selectively binds F^- anions.

Synthesis and study of a calixpyrrole-texaphyrin chimera: A new oligopyrrolic chloride anion receptor

Reported here is the synthesis and characterization of a new class of macrocycle that represents a hybrid between texaphyrin and calixpyrrole. These polypyrrolic macrocycles were prepared in one step by the acid-catalyzed condensation between diformyl dipyrromethanes and o-phenylenediamines in high yields. The X-ray crystal structure of one of these new “chimeras” was solved. It reveals that the diprotonated Schiff-base macrocycle has a V-shape in which one chloride anion is bound. Isothermal titration calorimetry (ITC) studies served to confirm the ability of the hybrid macrocycles to bind chloride anion in acetonitrile solution. These compounds may be useful as easy-to-make anion receptors.

Synthesis, structure and properties of ferrocene functionalized porphyrins

A series of free-base and metallated mixed ferrocenamido- and pivalamidophenylporphy-rins have been prepared from the α,α′,α″,α‴ isomer of 5,10,15,20-tetra(o-aminophenyl)porphyrin. The X-ray crystal structure of the iron(III) α,α′,α″,α‴-5,10,15,20-tetrakis(o-ferrocenamidophenyl)-porphyrin bromide has been determined and compared with related structures of cobalt(III) α,α′,α″,α‴-5,10,15,20-tetrakis(o-pivalamidophenyl)porphyrin bromide pyridine and the free base α,α′,α″,α‴-5,10,15,20-tetrakis(o-pivalamidophenyl)porphyrin. In both metalloporphyrins the coordinated axial bromides are contained in the cavity formed by the appended pickets with all the amide N - H bonds directed toward the anion.