A comparative study of cryptand-based (triple-head and triple-tail) amphiphiles at the air-water interface

Abstract

Two cryptands have been derivatized by reacting with acid chlorides of different alkyl chain lengths (between C₄ and C₁₈) to get a set of cryptand-based (triple-head and triple-tail) neutral amphiphiles. The cavity of either cryptand headgroup can accommodate a first-row transition metal ion forming stable cryptates. The free as well as the Cu(II)-complexed amphiphiles are studied at the air-water interface in a Langmuir-Blodgett trough. They form stable monolayers at the air-water interface, which can be transferred onto different substrates (viz., glass, fluorite, and quartz). They form Y-type Langmuir-Blodgett films. The amphiphile L₅ crystallizes in the monoclinic space group P2₁/c with a = 10.091(3) Å, b = 29.994(8) Å, c = 18.174(5) Å, Z = 4, R_f = 0.1048, R_wf = 0.2660, and GOF = 0.925. The amphiphile L₆ crystallizes in the trigonal space group P31c with a = 15.118(2) Å, b = 15.118(2) Å, c = 11.734(2) Å, Z = 2, R_f = 0.033, R_wf = 0.062, and GOF = 0.813. The solid-state structures of both the amphiphiles show a 3-fold symmetry about a point in the center of the cryptand headgroup. The hydrophobic tails of the cryptands are packed in the lattice both in interdigitizing and in noninterdigitizing manners.