Abstract
Various [3.3.3]metacyclophane derivatives were synthesized from 6,15,24-tri-tert-butyl-9,18,27-trimethoxy [3.3.3] metacyclophane-2,11,20-trione 1 using simple chemical reactions. The conformations of the synthesized compounds were studied using mainly solution Proton Nuclear Magnetic Resonance (1H NMR) spectroscopic methods. Two of the synthesized compounds 5, 6, were found to have a partial cone conformation with the third, 4, having the cone conformation. Detailed variable temperature Proton Nuclear Magnetic Resonance studies further confirmed the partialcone conformation for the two products, 5, 6. During the variable temperature nuclear magnetic resonance spectroscopic studies, 6,15,24-tri-tert-butyl-9,18,27-trimethoxy[3.3.3]metacyclophane-2,11,20-triol was found to have a coalescence temperature of about 0?C.
Highlights
The development of ammonium ion recognition systems has been of great concern over the years because of the important roles that ammonium ions play in both chemistry and biology [1,2,3]
The calixarenes which are a special type of metacyclophanes formed by a condensation reaction involving a phenol and formaldehyde show properties similar to those of the crown ethers
It has been reported that calix[n]arene derivatives with C3 and C6 symmetry can selectively bind ammonium ions [4,5,6,7,8,9]
Summary
The development of ammonium ion recognition systems has been of great concern over the years because of the important roles that ammonium ions play in both chemistry and biology [1,2,3]. Lehn and his coworkers reported that C3 symmetry crown ethers bearing ester groups form very stable complexes with primary ammonium ions [2,3]. The calixarenes which are a special type of metacyclophanes formed by a condensation reaction involving a phenol and formaldehyde show properties similar to those of the crown ethers They have a chalice—like shape with defined upper and lower rims, and a central annulus (Figure 1). It has been reported that calix[n]arene (where n stands for the number of aromatic rings) derivatives with C3 and C6 symmetry can selectively bind ammonium ions [4,5,6,7,8,9]. The wellknown calixarene molecules include calix[4]arene, calix [6]arene and calix[8]arene [10,11,12,13,14]
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