Conformational changes in molecules due to confinement are present throughout nature and serve a variety of roles in biological functions. Although many NMR experiments and computational studies have been performed on the confinement of guests in capsules such as cavtiands, none have made a direct comparison of the guest's chemical shifts and calculated shielding constants from the simulation. In this study molecular dynamics simulations were performed on alkane guests of increasing length in an octa-acid cavitand dimer. Using dihedral principal component analysis, representative structures for each simulation were found, with a trend of conformational motifs similar to that of a recent experimental study. By using those representative structures from the simulations with Gauge Invariant Atomic Orbital calculations, NMR isotropic shielding constants were calculated. A linear regression was performed on the experimental chemical shifts and the shielding constants, showing a linear relationship between the two. This is the first time that NMR spectra has been directly related to simulation results in this way for encapsulated guests in a dimeric cavitand system. By combining experiment and simulation we are able to gain further insight into the length-dependent conformational motifs present in the encapsulated alkane guests.

Molecular dynamics study of the confinement of alkane guests in an octa-acid dimer

249th National Meeting (2015)

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