{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,15]],"date-time":"2026-09-15T08:24:24Z","timestamp":1789460664438,"version":"build-2803163510"},"reference-count":56,"publisher":"American Chemical Society (ACS)","issue":"41","license":[{"start":{"date-parts":[[2015,9,24]],"date-time":"2015-09-24T00:00:00Z","timestamp":1443052800000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-029"},{"start":{"date-parts":[[2015,9,24]],"date-time":"2015-09-24T00:00:00Z","timestamp":1443052800000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-037"},{"start":{"date-parts":[[2015,9,24]],"date-time":"2015-09-24T00:00:00Z","timestamp":1443052800000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-045"}],"funder":[{"name":"University of Alaska Foundation"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2015,10,15]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Sulfur dioxide\u2013pyridine complex formation was reinvestigated using Fourier transform infrared (FTIR) spectroscopy and computational methods. The SO2\u2013pyridine dimer has been proposed to have a v-shaped, Cs-symmetric structure based on the microwave spectrum; however, recent research showing the occurrence of X\u00b7\u00b7\u00b7H\u2013C hydrogen bonds in noncovalent complexes suggested that the structure of the complex should be re-examined. The FTIR spectrum of the dimer was obtained by numerical analysis of the spectra of pyridine\u2013SO2 mixtures in CCl4. The spectrum showed ortho C\u2013H stretching modes consistent with a C1-symmetric structure containing a S\u2013O bond oriented approximately coplanar with the pyridine ring and adjacent to an ortho C\u2013H moiety. The C1 structure, which was identified as the global minimum by various density functional theory and correlated ab initio calculations, is also consistent with the out-of-plane second moment (Pbb) value previously determined by microwave spectroscopy. The complex is converted to its mirror image via three possible Cs-symmetric transition states: v-shaped, bisected, and flat. At the M06\u20132X\/6\u2013311++G\u00ad(2d,p) level of theory, the rotational barriers (\u0394Go\u2021) are 1.40, 1.87, and 3.63 kcal mol\u20131, respectively. Natural bond order analysis indicated the asymmetric complex is stabilized both by N\u2192S donation and back-donation from O to antibonding orbitals on pyridine. Atoms in molecules calculations identified a bond critical point within the O\u00b7\u00b7\u00b7H\u2212C gap consistent with a normal, albeit weak, hydrogen bond. Theoretical studies also identified a high-energy sandwich-type dimer with Cs symmetry, and a C2-symmetric SO2\u2013pyridine2 trimer.<\/jats:p>","DOI":"10.1021\/acs.jpca.5b06122","type":"journal-article","created":{"date-parts":[[2015,9,24]],"date-time":"2015-09-24T17:09:19Z","timestamp":1443114559000},"page":"10390-10398","source":"Crossref","is-referenced-by-count":30,"title":["Sulfur Dioxide\u2013Pyridine Dimer. FTIR and Theoretical\nEvidence for a Low-Symmetry Structure"],"prefix":"10.1021","volume":"119","author":[{"given":"John W.","family":"Keller","sequence":"first","affiliation":[{"name":"University of Alaska Fairbanks , , Fairbanks , Alaska 99775-6160 ,","place":["United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2015,9,24]]},"reference":[{"key":"2026081807110480600_cit1","doi-asserted-by":"publisher","first-page":"25251","DOI":"10.1029\/98JD02091","article-title":"A Time-Averaged\nInventory of Subaerial Volcanic Sulfur\nEmissions","volume":"103","author":"Andres","year":"1998","journal-title":"J. Geophys. Res."},{"key":"2026081807110480600_cit2","doi-asserted-by":"publisher","first-page":"11399","DOI":"10.1002\/jgrd.50826","article-title":"Application of OMI, SCIAMACHY, and GOME-2 Satellite\nSO2 Retrievals for Detection of Large Emission Sources","volume":"118","author":"Fioletov","year":"2013","journal-title":"J. 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