The Conformational Landscape, Internal Rotation, and Structure of 1,3,5-Trisilapentane using Broadband Rotational Spectroscopy and Quantum Chemical Calculations


The rotational spectrum of 1,3,5-trisilapentane was observed on a chirped-pulse Fourier transform microwave spectrometer and is reported. During assignment, multiple conformations of the molecule were identified in the molecular beam. Prior quantum-chemical calculations performed on the molecule show that the identified spectra correspond to the lowest three calculated energetic structures. These structures are of C2 (Conf.1), C (Conf.2), and C1 (Conf.3) symmetry, with relative energy ordering of Conf.1 < Conf.3 < Conf.2, which is in stark contrast to n-pentane and all known silicon-substituted n-pentane derivatives. This is found to most likely arise from the elongation of the Si-C bond and the size of the silicon atoms providing for the C2 and C1 structures relieving steric hindrance in comparison to that of the C. In the C and C1 conformers, splitting in the spectra due to internal rotation of the -SiH3 end groups of 1,3,5-trisilapentane was observed and determined. The C equivalent V3 values are 368.46(33) cm-1, and the C1V3 values are 347.78(21) and 360.18(88) cm-1, respectively. These barriers are compared to similar species in order to help verify their veracity and are determined to be accurate based on similar molecular silyl rotors.



International Standard Serial Number (ISSN)

1089-5639; 1520-5215

Document Type

Article - Journal

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© 2020 NLM (Medline), All rights reserved.

Publication Date

14 May 2020

PubMed ID