Quantitative Treatment of the Rotational Dynamics of Flexible-Chain Molecules. 13C NMR Relaxation Study of Hydrocarbon Chains Attached to the Fluorene Anchor

Article abstract of DOI:10.1002/mrc.1260320503

13C spin-lattice relaxation times (T1) and nuclear Overhauser enhancements (NOEs) were measured for individual carbons in flexible-chain molecules consisting of a hydrocarbon chain attached to fluorene moiety at position 3 through an ester bond.Quantitative treatment of the relaxation data of the ring carbons revealed an anisotropic motion for all the molecules studied.The relaxation times of the chain carbons were analysed in terms of a correlation function describing multiple internal rotations about successive C-C bonds.The results (rotational diffusion constants) were used to discuss features of the chain mobility as a function of chain length and chain unsaturation.The assumptions involved in the quantitative treatment were examined and the values were compared with those of n-alkanes and lipid bilayers. - Keywords: 13C NMR spin-lattice relaxation times Rotational diffusion constants Rotational dynamics Overall and internal motions Hydrocarbon-chain esters of fluorene-3-carboxylic acid