Xuzhen199

Graphene Oxide Liquid Crystals as a Versatile and Tunable Alignment Medium for the Measurement of Residual Dipolar Couplings in Organic Solvents.

J Am Chem Soc. 2014 Jul 30;

Authors: Lei X, Xu Z, Sun H, Wang S, Griesinger C, Peng L, Gao C, Tan RX

Abstract
Residual dipolar couplings (RDCs) have proven to be an invaluable anisotropic NMR parameter for the structural elucidation of complex biopolymers and organic molecules. However, a remaining bottleneck limiting its wider use by organic and natural product chemists is the lack of a range of easily applicable aligning media for diverse organic solvents. In this study, graphene oxide (GO) liquid crystals (LCs) were developed to induce partial orientation of organic molecules allowing RDC measurements. These LCs were determined to be maintainable at very low concentrations (as low as 1 mg/mL, corresponding to a quadrupolar 2H splitting ranging from 2.8 Hz to 30 Hz and 13C-1H dipolar couplings of a maximum of 20 Hz for camphor in CH3COCH3/water system) and to be remarkably stable and broadly compatible with aqueous and organic solvents such as DMSO, CH3COCH3 and CH3CN. Moreover, compared to other alignment media, very clean and high-quality NMR spectra were acquired with the GO molecules in solution because of their rigidity and large molecular weight. The developed medium offers a versatile and robust method for RDC measurements that may routinize the RDC-based structure determination of organic molecules.

PMID: 25075756 [PubMed - as supplied by publisher]