Zwitterionic Aromaticity on Azulene Extrapolated to carbo-Azulene
Corresponding Author
Dr. Jordi Poater
Departament de Química Inorgànica i Orgànica & IQTCUB, Universitat de Barcelona, 08028 Barcelona, Spain
ICREA, 08010 Barcelona, Spain
Search for more papers by this authorJuliane Heitkämper
Universität Stuttgart, Institut für Theoretische Chemie, Pfaffenwaldring 55, 70569 Stuttgart, Germany
Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, c/ Mª Aurèlia Capmany 69, 17003 Girona, Catalonia, Spain
Search for more papers by this authorCorresponding Author
Dr. Albert Poater
Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, c/ Mª Aurèlia Capmany 69, 17003 Girona, Catalonia, Spain
Search for more papers by this authorDr. Valérie Maraval
LCC-CNRS, University of Toulouse, 205 route de Narbonne, 31077 Toulouse, France
Search for more papers by this authorCorresponding Author
Prof. Dr. Remi Chauvin
LCC-CNRS, University of Toulouse, 205 route de Narbonne, 31077 Toulouse, France
Search for more papers by this authorCorresponding Author
Dr. Jordi Poater
Departament de Química Inorgànica i Orgànica & IQTCUB, Universitat de Barcelona, 08028 Barcelona, Spain
ICREA, 08010 Barcelona, Spain
Search for more papers by this authorJuliane Heitkämper
Universität Stuttgart, Institut für Theoretische Chemie, Pfaffenwaldring 55, 70569 Stuttgart, Germany
Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, c/ Mª Aurèlia Capmany 69, 17003 Girona, Catalonia, Spain
Search for more papers by this authorCorresponding Author
Dr. Albert Poater
Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, c/ Mª Aurèlia Capmany 69, 17003 Girona, Catalonia, Spain
Search for more papers by this authorDr. Valérie Maraval
LCC-CNRS, University of Toulouse, 205 route de Narbonne, 31077 Toulouse, France
Search for more papers by this authorCorresponding Author
Prof. Dr. Remi Chauvin
LCC-CNRS, University of Toulouse, 205 route de Narbonne, 31077 Toulouse, France
Search for more papers by this authorIn memory of Klaus Hafner
Graphical Abstract
DFT unveils inverse orientations of the dipole moments of azulene and carbo-azulene and their “zwitterionic aromatic” character, following the Hückel rule for monocycles within the bicycles. Local aromaticity indices for the two rings, with 5 and 7 C−C bonds in azulene or C−C2−C edges in carbo-azulene show the independence of size on qualitative π-electronic properties.
Abstract
Azulene is stabilized by “zwitterionic aromaticity”, what about its ring carbo-mer? The greater dipole moment of the latter is oriented in the opposite direction, while providing an enhanced zwitterionic aromatic character. Comparison of local aromaticity indices for the two rings, with 5 and 7 C−C bonds in azulene or C−C2−C edges in carbo-azulene, allows analysis of the quasi-independent influence of size on the π-electronic properties of these aromatic bicyclic molecules exhibiting quasi-identical shapes and π-resonance schemes between their common set of sp2C−H vertices. The electrostatic features of such dipolar hydrocarbons are also analyzed by comparison with their respective radical cation and anion, and with their apolar bicyclic isomer, naphthalene and carbo-naphthalene.
Conflict of interest
The authors declare no conflict of interest.
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