Order parameters and carbon shielding tensors of bis-MSB from 13C NMR measurements in a nematic liquid crystal

Order parameters of α,ω-diphenylpolyenes in a nematic liquid crystal from an integrated computational and C13 NMR spectroscopic approach

“…This assumption was implicitly taken in all our previous works, [26][27][28] and some recent studies 20,58 have confirmed its applicability. This is in general quite a strong assumption, but in the present case it can be safely invoked since the rotational isomerism around bonds does not radically change the elongated rodlike shape of the molecules.…”

“…In a previous study, 20 we have tested the use of computed chemical shieldings as input data for the determination of the orientational behavior of some rigid organic molecule dissolved in a thermotropic liquid crystal, whose order parameters are known from 2 D-NMR results. [26][27][28] Moreover, an analysis of the dependence on the magnetic properties from the molecular structure has been performed. We focus our attention to an homologous series of ␣, -diphenylpolyenes dissolved in the thermotropic liquid crystal ZLI-1167.…”

A Combined Theoretical and Experimental Approach to Determining Order Parameters of Solutes in Liquid Crystals from 13C NMR Data

“…A method has been proposed some years ago to compute the solute order parameters from a sufficient number of independent shielding tensor anisotropies: the method is briefly summarized in the following and is exhaustively described in refs −17. This approach avoids many of the limitations of other NMR-based determinations of ordering properties: it has been successfully applied to find the ordering matrix of fused aromatic rings (e.g., naphthalene, pyrene, anthracene, and derivatives) , and of conjugated systems like p -bis( o -methylstyryl)benzene in the nematic phase of the aliphatic liquid crystalline mixture ZLI-1167. The main obstacle to the extension of the method is that the 13 C chemical shielding tensors are known only for a few systems: the experimental technique illustrated in ref can provide both the σ anisotropy and the order parameters, but it needs a sensible “starting point”, i.e., a rather accurate estimate of the shielding tensor for at least two chemically different carbon atoms of the solute.…”