Multinuclear NMR studies of lead(II) soaps II.13C and1H studies of solid and liquid-crystalline phases

Abstract

Abstract The solid and liquid-crystalline phases of two long chain lead(II) carboxylates have been studied by 13C and 1H NMR spectroscopy. High resolution 13C NMR spectra of the solid phase of lead(II) decanoate and octadecanoate, reveal splittings of the peaks attributed to the carboxylate and adjacent methylene groups. This may result from two different environments for the carboxylate chains coordinated to the same Pb(II) ion. On going from the solid to liquid-crystalline or liquid phases, this splitting is lost, and small changes in chemical shift of the bands due to the methyl and methylene groups are observed. These are attributed to the onset of conformational disordering, and analysis of the data gives a gauche population in good agreement with that from Raman spectra and theoretical calculations. Longitudinal 13C relaxation times are reported. From these, and from spectral data, the -CH3 group is seen to have different dynamics from the rest of the chain, and to retain high mobility even in the s...