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SUMMARY:Analysis of bonding patterns and reactivity in molecular systems e
 xhibiting partial biradical character - Dr. Sotiris Xantheas\, Pacific Nor
 thwest National Laboratory
DTSTART:20160219T120000Z
DTEND:20160219T124000Z
UID:TALK63968@talks.cam.ac.uk
CONTACT:Lisa Masters
DESCRIPTION:A quantitative scale of the biradical charater (0 ≤ β ≤ 1
 ) of a molecular system based on a Multi-Reference Configuration Interacti
 on (MRCI) wavefunction is introduced and used to analyze its underlying el
 ectronic structure and bonding pattern. Triatomic ions in the FX2+ series\
 , where X = O\, S\, Se\, Te and Po are the terminal atoms\, were found to 
 exhibit unusually high biradical characters (0.76 < β < 0.92)\, the large
 st among the homologous\, 18 valence electron molecules CX22-\, NX2−\, X
 3 and OX2 (X = O\, S\, Se\, Te and Po). The concept of biradical character
  was further used to investigate the bonding mechanism in ozone (O3) and i
 ts sulfur-substituted analogues\, SO2\, OS2\, and S3. We demonstrate that 
 the bonding in these molecules can be described by a mixture between a clo
 sed shell structure with one and a half bond between the central and termi
 nal atoms and an open-shell structure with a single bond and two lone elec
 trons on each terminal atom. Our analysis further offers an explanation fo
 r the different O-O\, S-O and S-S bond lengths and singlet-triplet splitti
 ngs of these species\, the stabilization of OSO and SSO over the SOO and S
 OS isomers as well as the (X-YZ) relative binding energies (X=S\, O)\, all
  based on their different biradical character. These concepts are finally 
 used to analyze the biradical character of the Criegee Intermediate (CI) a
 nd address the apparent contradiction between its small biradical characte
 r and its rich reactivity with regards to atmospheric particle formation.\
 n\nE. Miliordos\, K. Ruedenberg and S. S. Xantheas\, Ang. Chem. Int. Ed. 5
 2\, 5736 (2013)\nE. Miliordos and S. S. Xantheas\, J. Amer. Chem. Soc. 136
 \, 2808 (2014)\nE. Miliordos and S. S. Xantheas\, Ang. Chem. Int. Ed. 55\,
  1015 (2016)\n
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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