Towards ionic channels with crown ethers and calix[n]arenes (with n=6,8)

This thesis reports the new crystal structures of crown ethers and calixarenes as well as the ionic conduction properties of crown ether channels. Chapter I gives general knowledge about ion channels. It deals also with the state of the art on crown ethers and calix[n]arenes. Chapter II present the different compounds obtained with crown ethers and calixarenes. In a first part, it shows a study of ionic conduction through crown ether channel structures 1 and 2. It describes as well all the attempts done to obtain the isostructural structure of 1 with tribromide ions. It presents a pH-dependency of the DB18C6 to form crystals. Finally this chapter ends on calix[n]arene channel structures (with n=6 and 8) and a comparison between 4-tert-butylcalix[8]arene structures which evolve from a single molecule to a dimer and finally channel compounds thanks to water aggregates. Those aggregates are dependent of the alkali metal present. Potassium ions are related on water cubes and caesium ions influence on the octahedral organization of the water molecules. Rubidium ions tolerate both: On average, the structure with rubidium ions is an alternation of cubes and octahedron separated by a heterooctahedron of water molecules and rubidium ions. Chapter III summarizes related work and describes a possible developments of this project: the possible applications of crown ethers, and the derivatisation of the upper rim of calixarenes

Transport properties of solid state crown ether channel systems

Single crystals of [(H₂O)⊂(DB18C6)(μ₂-H₂O)2/2][(H₃O)⊂(DB18C6)(μ₂-H₂O)2/2]I₃ 1 were shown to possess ideally stacked crown ether molecules which form channels running in one direction through the solid state structure. By immersion of single crystals of 1 into NaOH, ion exchange takes place to yield the compound [(Na)⊂(DB18C6)(μ₂-H₂O)2/2][(Na)⊂(DB18C6)(μ₂-OH)2/2]I₃ 2, with slightly but significantly different cell parameters. Both compounds were tested for transport properties through these channels by using two different devices, one for water transport, the other for NaOH transport, through single crystals of 1 and 2, respectively. The results indicate that transport can take place via a hopping mechanism

From simple rings to one-dimensional channels with calix[8]arenes, water clusters, and alkali metal ions

The macrocycle 4-tert-butylcalix[8]arene (L) was reacted with alkali metal carbonates (Li₂CO₃, Na₂CO₃, K₂CO₃, Rb₂CO₃, and Cs₂CO₃) at the interface of a biphasic THF/water system. Needle-like crystals with a general formula [Ax(4-tert-butylcalix[8]arene-xH)(THF)y(H₂O)z] (with A=Li, Na, K, Rb, Cs, x=1, 2, y=4, 5, 8, and z=6, 7) were thereby obtained. The solid state structures were investigated by X-ray diffraction of single crystals and by TGA measurements. They do not appear to be maintained in solution

Water trapped in dibenzo-18-crown-6: theoretical and spectroscopic (IR, Raman) studies

Experimental (IR and Raman) and theoretical (Kohn-Sham calculations) methods are used in a combined analysis aimed at refining the available structural data concerning the molecular guests in channels formed by stacked dibenzo-18-crown-6 (DB18C6) crown ether. The calculations are performed for a simplified model comprising isolated DB18C6 unit and its complexes with either H2O or H3O+ guests, which are the simplest model ingredients of a one-dimensional diluted acid chain, to get structural and energetic data concerning the formation of the complex and to assign the characteristic spectroscopic bands. The oxygen centers in the previously reported crystallographic structure are assigned to either H2O or protonated species