On the Vibrational Interlacing Rule in Deuterated Thiophene: I. Out-of-plane Vibrations

According to the interlacing rule, if A and B^sub τ^ are two molecules which differ by a single isotopic substitution at atomic site τ, vibrational frequencies of a molecule A are interlaced with the vibrational frequencies of molecule B^sub τ^. This rule is valid within the harmonic approximation, and in the case of planar molecules one has two interlacing rules, one for in-plane and another for out-of-plane frequencies. The validity of this rule is verified for theoretical and experimental out-of-plane frequencies of thiophene and deuterated thiophene molecules. This rule can help to analyze vibrational spectra, especially in assignments of experimental frequencies to various vibrational types. [PUBLICATION ABSTRACT]