18-crown dynamic simulations

Thuery, P., Nierlich, M., Bryan, J.C. et al. 1997. Crown ether conformations in 1,3-calix[4]arene bis(crown ether) Crystal structures of a cesium complex and solvent adducts and molecular dynamics simulations. J. Chem. Soc. Dalton Trans. 1997 (22) 4191 4202. 

Lamare, V., Dozol, J-F., Allain, F., Virelizier, H., Moulin, C., Jankowski, C-K., Tabet, J-C. 2000. Behavior of calix[4]arene-bis-crown-6 under irradiation Electrospray-mass spectrometry investigations and molecular dynamics simulation on Cs+ and Na+ complexes of a degradation compound, in ACS Symposium Series 757, Calixarenes Molecules for Separations-, Lumetta G., Rogers R.D., Gopalan A.S. Eds. American Chemical Society Washington, DC, 56-70. 

Crown ethers continue to be one of the most useful parts of supramolecular chemistry/91 From the beginning computations of metal ions complexes with synthetic ionophores/101 which have been aptly reviewed/111 emphasized the importance of including explicitly solvation in free energy calculations, also with ab initio calculations on calixarene complexes/121 Molecular dynamics simulations of 18-crown-6 ether complexes in aqueous solutions predict too low affinities, but at least correctly reproduce the sequence trend K+ > Rb+ > Cs+ > Na+. However, only the selection of K+ over Rb+ and Cs+ is ascribed to the cation size relative to that of the crown cavity, whereas K+ appears in these calculations to be selected over Na+ as consequence of the greater free energy penalty involved in displacing water molecules ftomNa/1131... 

Straatsma, T. P., McCammon, J. A. (1989), Treatment of Rotational Isomers in Free Energy Calculations. II. Molecular Dynamics Simulation of 18-Crown-6 in Aqueous Solution as an Example of Systems with Large Numbers of Rotational Isomeric States, J. Chem. Phys. 91, 3631-3637. 

L. Troxler and G. Wipff,/. Am. Chem. Soc., 116,1468 (1994). Conformation and Dynamics of 18-Crown-6, Cryptand 222 and Their Complexes in Acetonitrile Studied by Molecular Dynamics Simulations. 

Experimental work on new partitioning techniques is performed in the fiiamework of two projects. The first one has the objective to develop processes for the separation of minor actinides from very acidic aqueous solutions containing high level waste without the generation of secondary solid waste. In the second one, extractants selective to strontium, actinides -I- lanthanides, and actinides only such as calixarene and crown ether derivatives will be synthesised. The extracting properties of these compounds will be determined experimentally and modelled with molecular mechanics and molecular dynamics simulations. 

Sieffert, N. Wipff, G. (2006a). Alkali cation extraction by calix[4]crown-6 to room-temperature ionic liquids. The effect of solvent anion and humidity investigated by molecular dynamics simulations. /. Phys. Chem. A, 110,1106-1117. 

Interestingly, the energy difference is smallest for S7O which as a heterocycle forms a crown-shaped eight-membered ring similar to and isoelec-tronic with the well known 8 structure of 04a symmetry. The transformation of the heterocycle S7O into the homocyclic isomer 7=0 was studied by the molecular dynamics/density functional method but the unrealistically high barrier of 5 eV calculated for this transformation indicates that the system was far from equilibrium during most of the simulation [66]. 

SIMULATIONS OF THE DYNAMICS OF 18-CROWN-6 AND ITS COMPLEXES FROM THE GAS PHASE TO AQUEOUS INTERFACES WITH SC-C02 AND A ROOM-TEMPERATURE IONIC LIQUID... 

The simulations in the dry and in the humid RTIL started with 12 crowns (Q form) "diluted" in the solvent box. The crowns rapidly underwent a conformational change to D3d, showing that this structure is more stable in the two forms of the RTIL. Typical snapshots at the end of the dynamics (1.5 ns) and radial distribution functions (see Figure 10) reveal the importance of solvent cations. 

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