Ground and excited state aromaticity and antiaromaticity: magnetic criteria and the valence-bond picture

DSpace/Manakin Repository

Show simple item record

dc.contributor.author Karadakov, Peter
dc.date.issued 2010-07-06
dc.identifier.citation Karadakov, P. (2010). Ground and excited state aromaticity and antiaromaticity: magnetic criteria and the valence-bond picture. A 'IX Girona Seminar'. Girona: Universitat. [Consulta 6 setembre 2010]. Disponible a: http://hdl.handle.net/10256.1/1708
dc.identifier.uri http://hdl.handle.net/10256.1/1708
dc.description.abstract The idea that the concepts of aromaticity and antiaromaticity apply to molecules in other than their electronic ground states can be traced back to Baird who argued that the well-known 4n+2 and 4n rules for ground-state aromaticity in cyclic conjugated hydrocarbons are reversed in their lowest triplet states: rings with 4n π electrons become aromatic while 4n+2 systems should be regarded as antiaromatic. We show that Baird’s ‘triplet’ aromaticity and antiaromaticity represent particular cases of broader concepts of excited state aromaticity and antiaromaticity. Magnetic criteria including nucleus-independent chemical shifts (NICS), proton shieldings and magnetic susceptibilities calculated using complete-active-space selfconsistent field (CASSCF) wavefunctions constructed from gauge-including atomic orbitals (GIAOs) strongly suggest that, in contrast to the well-known aromaticity of the S0 state of benzene, the T1 and S1 states of this molecule are antiaromatic, whereas in the two most popular examples of antiaromatic cycles, square cyclobutadiene and D8h cyclooctatetraene, the T1 and S1 states are aromatic.These findings can be rationalized using valence-bond models in which aromaticity and antiaromaticity are associated with resonance and antiresonance
dc.format.mimetype video/H263
dc.format.mimetype audio/mpeg
dc.language.iso eng
dc.publisher Universitat de Girona. Departament de Química
dc.publisher Universitat de Girona. Institut de Química Computacional
dc.relation.ispartofseries IX Girona Seminar
dc.rights Aquest document està subjecte a una llicència Creative Commons: Reconeixement - No comercial - Compartir igual (by-nc-sa)
dc.rights.uri http://creativecommons.org/licenses/by-nc-sa/3.0/es/deed.ca
dc.subject Química quàntica -- Congressos
dc.subject Quantum chemistry -- Congresses
dc.title Ground and excited state aromaticity and antiaromaticity: magnetic criteria and the valence-bond picture
dc.type info:eu-repo/semantics/lecture


Files in this item

The following license files are associated with this item:

Show simple item record

Related Items

Search DUGiMedia


Browse

My Account

Statistics

You can copy this text:

This file is restricted

The file you are attempting to access is a restricted file and requires credentials to view. Please login below to access the file.

  1. We will contact you via the email address you have provided us.