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Combined Computational and Experimental NMR Study of Calix[4]arene Derivatives
journal contribution
posted on 2012-11-08, 00:00 authored by Vincenzo Verdolino, Laura Baldini, Ferruccio Palazzesi, Federico Giberti, Michele ParrinelloA combined computational and experimental study of a
complex supramolecular
system constituted by calix[4]arene derivatives that dimerize upon
CO2 binding is presented. The theoretical investigation
includes ab initio density functional theory, molecular dynamics,
and metadynamics analysis of both monomers and dimers. The ab initio
calculation of the dimerization energy demonstrates the exergonic
character of the process, due to the formation of a strong hydrogen
bond network between ammonium and carbamate groups. The dimerization
is driven by −31.1 kcal/mol in the case of the fully outward
orientation of the carbamic hydrogens, while it results in a weaker
process when different carbamic orientations are considered. The molecular
dynamics simulations show the critical conformational degrees of freedom
driving monomers and dimers toward common structures. These conformations
show tilted orientations of the carbamic groups highlighting the fundamental
role of dynamics in evaluating the most stable configurations. Metadynamics
simulations describe, in agreement with the other computational tools,
the conformational free energy surface of these calix[4]arenes defining
three stable conformational families. ROESY and variable temperature 1H NMR experiments are in agreement with our simulations. The
presented approach aims to be the reference for investigating complex
supramolecular systems.
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supramolecular systemmonomercarbamate groupshydrogen bond networkdimersMetadynamics simulationsenergy surfacecarbamic hydrogensexergonic characterdynamics simulations showcalixcarbamic groupsdimerization energyab initio densityab initio calculationCO 2 bindingtemperature 1 H NMR experimentsmetadynamics analysisExperimental NMR StudyROESYconformations showsupramolecular systemscarbamic orientations
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