SECONDARY INTERACTIONS IN WEAKLY-BOUND COMPLEXES - A HIGHLY NONLINEARHYDROGEN-BOND IN THIIRANE...HCN ESTABLISHED BY ROTATIONAL SPECTROSCOPY

The ground-state rotational spectra of two isotopomers, (CH2)(2)S-32.. .(HCN)-N-14 and (CH2)(2)S-32...(HCN)-N-15, Of a complex formed by thii rane with hydrogen cyanide were analysed to give rotational constants, centrifugal distortion constants and N-14-nuclear quadrupole coupling constants. The spectroscopic constants were interpreted in terms of a geometry of the complex characterised by the angle phi=89.2(9)degrees made by the S...H internuclear axis with the thiirane heavy atom plan e at S and a nonlinearity theta approximate to 43 degrees of the S H-C hydrogen bond. This large nonlinearity is contrasted with that in (CH 2)(2)O...HCN and the difference discussed in terms of a simple model o f the hydrogen bond.