Use of subspectra of 77Se in the 1H nuclear magnetic resonance spectroscopy of molecules partially oriented in a nematic mesophase. Analysis of selenophen-2-carbaldehyde

Abstract

The 100 MHz ¹H n.m.r. spectrum of selenophen-2-carbaldehyde dissolved in a nematic mesophase was recorded and analysed. The ⁷⁷Se subspectrum was also used to obtain a set of ⁷⁷Se–¹H anisotropic coupling constants. A theoretical force field was derived in order to take the vibrational averaging effects in the D_ij direct coupling calculations into account. The contribution of ⁷⁷Se–¹H anisotropic indirect couplings appears to be negligible. The existence of a single Se–O cis-conformer was confirmed and some evidence was found for the presence of a small percentage of Se–O trans-conformer.