Vibrational spectra, conformational properties and argon matrix photochemistry of diacetyl diselenide, CH3C(O)Se2C(O)CH31. (31st May 2016)

• Record Type: Journal Article
• Authors: Gómez Castaño, Jovanny A.; Romano, Rosana M.; Salamanca, Ana R.; Amésquita, Germán; Beckers, Helmut; Willner, Helge; Della Védova, Carlos O.
• Other Names: Buján Elba I. guestEditor.
• Is Part Of: Journal of physical organic chemistry. Volume 29:Number 11(2016)
• Page Start: 636
• Page End: 644
• Publication Date: 2016-05-31
• Subjects: diselenide -- hyperconjugation -- matrix photochemistry -- NBO -- photodecomposition; Chemistry, Physical organic -- Periodicals; 547.1
• DOI: 10.1002/poc.3587
• Languages: English
• ISSNs: 0894-3230

Abstract

Abstract : By oxidation of selenoacetic acid, CH3 C(O)SeH, we have prepared the hitherto unknown diacetyl diselenide, [CH3 C(O)Se]2 . Its vibrational properties were studied experimentally, both in neat liquid (Fourier transforminfrared spectroscopy and Raman) with the molecule isolated in argon matrix at low temperatures and theoretically using MP2 and B3LYP methods in combination with 6‐31+G(d), 6‐311++G(3df, 3dp) or aug‐cc‐pvDZ basis sets. Analysis of Ar matrix spectra reveals a conformational equilibrium in gas phase at room temperature, which was interpreted by considering only two of the three stable rotamers predicted by our three‐dimensional potential energy surface scans. Energetic properties of three minima found theoretically were further studied in terms of donor–acceptor interactions by using natural bond orbital calculations at the same levels of theory. From this, it was possible to rationalize the conformational stability order and molecular structures by means of vicinal hyperconjugative delocalizations involving lone pairs on selenium or oxygen atoms and C=O, C–C or Se–C antibonding orbitals. The photochemistry of the compound in the argon matrix in the range between 200 and 800 nm was also investigated, revealing only onephotochemical path to produce ketene, H2 C=C=O, methylselane, CH3 SeH, and carbonyl selenide, OCSe. Copyright © 2016 John Wiley & Sons, Ltd. Abstract : Bis(acetyl)diselenide ▪ CH3 C(O)Se▪2 was prepared for the first time. Molecular characterization was performed by GC‐MS, FTIR, FTRaman and Ar‐matrix isolation‐photochemistry experiments, in conjunction with DFT and ab‐initio calculations. Gas phase composition at 298K was presented as a conformational equilibrium between two structures: a(C2) and b(C1). Major stability of conformer C2 was rationalized by means of hyperconjugative interactions involving nO, nSe, ▪ CO, ▪ *C‐C, and ▪ *SeC orbitals. UV‐vis photolysis of molecule trapped in solid argon brings about H2 CCO, OCSe and CH3 SeH.