Determination of relative intramolecular configuration by nuclear quadrupole double resonance

Abstract

The influence of a nuclear quadrupole spin system B on the spin echo of a nuclear quadrupole system A is governed by a 1/r⁶ law. This relation was used to determine relative intramolecular arrangements within molecules and complex ions in solids. By heteronuclear double resonance ⁸¹Br [graphic omitted] ²⁷Al in KAl₂Br₇ the bridging bromine has been determined and also the Br frequencies have been assigned to certain Br—Al bonds. Homonuclear double resonance ³⁵Cl [graphic omitted] ³⁵Cl was applied to molecular compounds of Cl₃CCO₂H and the close-lying frequencies of two molecules in the asymmetric unit were split-up into the appropriate groups. Finally, from isotopic ⁸¹Br [graphic omitted] ⁷⁹Br double resonance in 3,5-dichlorophenoxy aluminiumdibromide and 4-chlorophenoxy aluminiumdibromide a structure is proposed for these molecules. The aluminium atoms in these dimeric compounds are connected by bridging oxygen atoms, whereas the bromine atoms are in terminal positions.