Conformational and Orientational Determination from Dipolar Couplings in a Weakly Ordering Organic-Based Lyotropic and a Strongly Ordering Thermotropic Liquid Crystal

Abstract

A weakly ordering organic-based lyotropic phase and a strongly ordering nematic liquid crystal have been used as NMR media for a parallel study of the conformation and orientational order of the same solute, trans-stilbene. A careful comparison allows to figure out some interesting conclusions on accessibility and precision of the experimental data and reliability and accuracy of the conformational descriptions into these two kinds of mesophases.

Exploring the impact of alignment media on RDC analysis of phosphorus-containing compounds: a molecular docking approach

“…Furthermore, for highly flexible molecules such as 3 , the conventional approach for the experimental determination of RDCs may fail. 12,24,32,48,49 Typically, the J -couplings extracted from experiment in the isotropic environment ( i.e. , isotropic J -couplings) are subtracted from the total T -couplings measured in the anisotropic environment to yield RDCs (eqn (1) in Experimental Section).…”

“…Furthermore, for highly flexible molecules such as 3, the conventional approach for the experimental determination of RDCs may fail. 12,24,32,48,49 Typically, the J-couplings extracted from experiment in the isotropic environment (i.e., isotropic Jcouplings) are subtracted from the total T-couplings measured in the anisotropic environment to yield RDCs (eqn (1) in Experimental Section). However, the isotropic J-couplings may significantly differ from the real anisotropic J-couplings in the alignment medium, as indicated by the different conformer populations in isotropic and in anisotropic environments.…”

Molecular Dynamics with Orientational Tensorial Constraints: A New Approach to Probe the Torsional Angle Distributions of Small Rotationally Flexible Molecules

“…A different way to address inherent flexibility is via theoretically robust mean-field approaches based on analytical models with continuous bond rotation. , Initially developed for solutes in highly oriented liquid-crystalline media, the additive potential (AP) and the AP-direct probability description (AP-DPD) models, , the maximum entropy (ME) approach, − and a combination of the two, the APME method, , have also found application in low-order liquid crystalline systems. − However, these methods present severe shortcomings, as they are computationally demanding or give very flat distributions for low-oriented solutes, and in general fail for real systems with several degrees of freedom.…”