We report the results of a pulsed jet Fourier transform microwave investigation of the molecular complex tert-butanol center dot center dot center dot 1,4-dioxane and of its isotopologue tert-butanol(OD)center dot center dot center dot 1,4-dioxane. The rotational spectra have been observed only for one conformer in which tert-butanol acts as a proton donor to one of the axial lone pairs of one ring oxygen. The D quadrupole coupling constants have been determined for the OD isotopologue, and a 0.006 angstrom shrinking of the O center dot center dot center dot O distance upon deuteration of the hydroxyl group (Ubbelohde effect) has been observed. (C) 2011 Elsevier B.V. All rights reserved.