Engineering Nanorafts of Calixarene Polyphosphonates

Abstract

The water-soluble calix[4]arene bearing p-substituted phosphonic acid groups is accessible in five steps in overall 62 % yield, with the hydrogen-bonding prowess of the acidic groups dominating its self-assembly processes. These include the formation of 3.0(3) nm and 20(2) nm nanorafts of the calixarene in water using spinning disc processing, stabilized by acetonitrile, and nanorafts in the gas phase (<or=20 molecules). The 20(2) nm particles transform into 3.0(3) nm particles prior to crystallization into a compact bilayer, whereas crystallization in the presence of large organic molecules gives an expanded bilayer interposed by layers of water molecules.

Organization of Lower RimO-Alkylatedp-Phosphonic Acid Calix[4]arenes

“…Previously p -phosphonic acid calix[n]arenes (n = 4, 5, 6 and 8) have been shown to form stable nano-arrays (nano-particles) or nano-rafts (n = 4) in the gas phase using MALDI-TOF-MS with around 20 calixarene units (18-30 kDa) per nano-array 10. As for the p -phosphonic acid calixarenes, nano-arrays are also observed in the gas phase for the alkylated p -phosphonic acid calix[4]arenes with successive peaks out to 15, 33 and 16 calixarene units for the methyl, butyl and octadecyl derivatives, 12-14 , respectively (Figure 5).…”

“…Recently we reported a series of new water-soluble calixarenes, which incorporate phosphonic acid groups on the upper rim with the lower rim devoid of substitution,10 with a similar synthesis of the p -phosphonic acid calix[4]arene, and some lower rim alkyl substituted analogues (including methyl and n-propyl), being simultaneously reported by Dziemidowicz et al 11. These p -phosphonic acid calix[n]arenes (n = 4, 5, 6 and 8) form supramolecular arrays both in solution and the gas phase which relates in part to the H-bonding capability of the phosphonic acid group,10 In the present paper we report the synthesis of p -phosphonic acid calix[4]arene substituted with a variety of alkyl group substitutions on the lower rim, namely methyl, n -butyl and n -octadecyl, in an attempt to decouple the effect of the H-bonding of the phosphonic acid groups with that of the lower rim OH groups, although they tend to favour cyclic intramolecular H-bonding.…”

“…These p -phosphonic acid calix[n]arenes (n = 4, 5, 6 and 8) form supramolecular arrays both in solution and the gas phase which relates in part to the H-bonding capability of the phosphonic acid group,10 In the present paper we report the synthesis of p -phosphonic acid calix[4]arene substituted with a variety of alkyl group substitutions on the lower rim, namely methyl, n -butyl and n -octadecyl, in an attempt to decouple the effect of the H-bonding of the phosphonic acid groups with that of the lower rim OH groups, although they tend to favour cyclic intramolecular H-bonding. To this end we report their properties in solution and the gas phase along with their packing in the solid state.…”

Layered Calcium Structures ofp-Phosphonic AcidO-Methyl-Calix[6]arene

“…Previously we have reported that a series of p -phosphonic acid calix[n]arenes (n = 4, 5, 6 and 8) form stable nano-arrays (nano-particles) or nano-rafts (n = 4) in the gas phase using MALDI-TOF-MS with around 20 calixarene units (18-30kDa) per nano-array 8. This has been extended to alkylated p -phosphonic acid calix[4]arenes with successive peaks out to 15, 33 and 16 calixarene units for the methyl, butyl and octadecyl derivatives respectively 9.…”

“…These calixarenes are water soluble, and form bi-layers in the solid state, held together by strong hydrogen bonding between the diprotic phosphonic acid groups, and in solution and the gas phase they can form nano-rafts 8. O-alkylation at the lower rim while maintaining the integrity of the phosphonic acid/phosphate groups has also been reported, for methyl, n -butyl and n -octadecyl chains 9.…”