Molecular and Vibrational Structure of 1,6,6aλ⁴-Trithiapentalene. Infrared Linear Dichroism Spectroscopy and ab Initio Normal-Mode Analyses

Abstract

The vibrational structure of the title compound (TTP) was studied by experimental and theoretical methods. IR absorption spectra were recorded in argon matrix and in stretched polyethylene at 12 K. The linear dichroism (LD) observed in the latter solvent provided experimental symmetry assignments of the observed vibrational states. Molecular geometries and harmonic force fields were calculated ab initio with the 6-311G** basis set using three different procedures: restricted Hartree−Fock theory (HF), second-order Møller−Plesset perturbation theory (MP2), and density functional theory (DFT). In the latter, Becke's gradient-corrected exchange functional was combined with Perdew and Wang's correlation functional (BPW91), leading to excellent agreement with observed IR transitions. The combined experimental and theoretical evidence enabled an essentially complete assignment of the fundamental vibrations. Of particular importance is the assignment for the first time of the long-sought “bell-clapper” mode associated with the unique S−S−S structural element of TTP, giving rise to an intense, long-axis polarized transition in the far-IR (153 cm-1).

On the molecular and vibrational structure of 1,6,6aλ4-trithiapentalenes. Analysis of the “bell-clapper’' asymmetrical S–S–S stretching mode

“…The corresponding band in the spectrum of parent TTP was observed at 153 cm~1 with a somewhat similar, relatively broad, shape (stretched PE, 12 K). 22 The shape of these bands suggests the possible signiÐcance of anharmonic e †ects, and in the following section we present the results of an anharmonic analysis of this mode.…”

“…This is l8 \ 158.6 also the theoretical wavenumber in closest agreement with the observed value, cm~1 (ref. 22). The B3LYP results are l8 \ 153 analyzed in more detail in Fig.…”

Organohypervalent heterocycles

“…205,206 However, a more precise illustration of these compounds involves 'nonhypervalent betaine structures' with eight electrons on the sulfur atom. These compounds are associated with extensive theoretical and synthetic interest [207][208][209] and a discussion on heterocyclic mesomeric betaines including sulfur or other elements has been well-reviewed. 210,211 Thianthrenium salts represent a typical class of organosulfur compounds with exceptional potential applications in organic synthesis.…”

Electrochemical Behaviors of Hexathiadipentalene Ring, Dithiol Ring, and Methyl Sulfide Groups on Anthracene Derivatives Confined on Electrode

“…That is, the center S atom probably moves toward one or the other of the two neighboring S atoms. 14 The electrochemical oxidation of thioketone and ANT in aprotic solvents usually used does not occur until the applied potential of +5.00 V, where the decomposition reaction of solvent begins. Consequently, we can conclude that two reversible redox waves observed in the potential range between +3.15 and +4.20 V in Fig.…”