title: Bond characterization of a unique thiathiophthene derivative: combined charge density study and X-ray absorption spectroscopy.
abstract: Thiathiophthene (TTP), a planar molecule with two fused heterocyclic five-membered rings and an essentially linear S-S-S bond, is a molecule of great interest due to its unique chemical bondings. To elucidate the remarkable bonding nature, a combined experimental and theoretical study on the electron density distribution of 2,5-dimethyl-3,4-trimethylene-6a-TTP (1) is investigated based on a multipole model through high-resolution X-ray diffraction data experimentally and on the density functional calculations (DFT) theoretically. In addition, S K-edge X-ray absorption spectroscopy (XAS) is measured to verify the chemical bonding concerning the sulfur atoms. The molecule can be firmly described as 10π electron with aromatic character among the eight atoms, S3C5, of the two fused five-membered rings plus three-center four-electron σ character along the S-S-S bond. Such bonding description is verified with the calculated XAS spectrum, where the pre-edge absorption for transitions from S 1s to π* and σ* are located. The three-center four-electron S-S-S σ bond makes the terminal S atoms richer in electron density than the central one.
authors.affiliation: Department of Chemistry, National Taiwan University , Taipei 10617, Taiwan.
authors.forename: Yu-Chun
authors.initials: YC
authors.lastname: Chuang
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Li
authors.forename: I-Jui
authors.initials: IJ
authors.lastname: Hsu
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
mesh_terms: D006576:Heterocyclic Compounds, 4 or More Rings / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory; D013440:Sulfides / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D006576:Heterocyclic Compounds, 4 or More Rings; D013440:Sulfides; D013455:Sulfur