Efficient analysis of highly complex nuclear magnetic resonance spectra of flexible solutes in ordered liquids by using molecular dynamics

Abstract

The NMR spectra of n-pentane as solute in the liquid crystal 5CB are measured at several temperatures in the nematic phase. Atomistic molecular dynamics simulations of this system are carried out to predict the dipolar couplings of the orientationally ordered pentane, and the spectra predicted from these simulations are compared with the NMR experimental ones. The simulation predictions provide an excellent starting point for analysis of the experimental NMR spectra using the covariance matrix adaptation evolutionary strategy. This shows both the power of atomistic simulations for aiding spectral analysis and the success of atomistic molecular dynamics in modeling these anisotropic systems.

Dyes as guests in ordered systems: current understanding and future directions

“…[84,85] There are now multiple reports of simulations of guest molecules within liquid crystal hosts, providing favourable comparisons with results of electron paramagnetic resonance [86][87][88] and nuclear magnetic resonance [89,90] experiments, as well as providing assessments of the validity of mean field models of molecular alignment. [91] The increase in computational resources has also made electronic structure calculations more accessible with time.…”

A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

“…We also include in the analysis six sets of dipolar couplings measured for n-pentane in the nematic liquid crystal 5CB at temperatures between 273.5 and 298.5 K. 20 Unfortunately, as indicated earlier, only the product S n × p n in Eq. (2) can be obtained from the dipolar couplings.…”

“…We also include in the analysis spectral parameters obtained previously 20 from six spectra of n-pentane as solute in the nematic phase of 5CB. The spectra were taken in 5 • steps from 273.5 to 298.5 K. In addition, we make extensive use of the results of Ref.…”

Order and Conformation of Biphenyl in Cyanobiphenyl Liquid Crystals: A Combined Atomistic Molecular Dynamics and 1H NMR Study

“…[1][2][3][4][5][6][7][8][9][10][11] Of course, the success of this effort is strictly connected to the quality of the force field (FF), the set of intra and intermolecular interactions employed, which must inevitably be tested, and/or the use of parameterised versus experimental observations. [1][2][3][4][5][6][7][8][9][10][11] Of course, the success of this effort is strictly connected to the quality of the force field (FF), the set of intra and intermolecular interactions employed, which must inevitably be tested, and/or the use of parameterised versus experimental observations.…”

“…For this type of analysis, atomistic simulations in conjunction with efficient algorithms for fitting the LXNMR spectra, such as that based on evolutionary optimisation methods recently proposed by Meerts et al, [14] promise to significantly increase the range of molecules that can be studied. [6,7,22] Beyond this important but technical aspect of helping the spectral analysis and line assignment, an even more exciting possibility is the combination of MD simulations and NMR spectroscopy to extend the range of properties that can be reliably investigated. A realistic simulation of the dipolar couplings can also provide insights into fundamental mechanisms of the studied systems (e.g.…”