TY - JOUR
T1 - Proaromaticity
T2 - Organic charge-transfer chromophores with small HOMO-LUMO gaps
AU - Wu, Yi Lin
AU - Bureš, Filip
AU - Jarowski, Peter D.
AU - Schweizer, W. Bernd
AU - Boudon, Corinne
AU - Gisselbrecht, Jean Paul
AU - Diederich, François
PY - 2010/8/16
Y1 - 2010/8/16
N2 - Novel donor- and/or acceptor- substituted cross-conjugated carbocycles based on quinoids or expanded quinoids, with radiaannulene perimeters, were prepared and investigated to validate proaromaticity as a concept for reducing HOMO-LUMO gaps in push-pull chromophores. Analyses of IR, 1H NMR, and UV/Vis/NIR spectra in conjunction with molecular structures determined by X-ray diffraction show that these push-pull quinoids have significant charge-separated ground states. This feature results in small optical gaps (near IR region) and diatropic magnetic environments inside the carbocycles, as suggested by nucleus- independent chemical shift (NICS) calculations. The NICS results, together with the bond-length analysis of the quinoid spacers, provide strong support that proaromaticity, that is, aromatized zwitterionic mesomeric contributions in the ground state, is effective. A push-pull tetrakis(ethynediyl)- expanded quinoid chromophore represents the first proaromatic radiaannulene.
AB - Novel donor- and/or acceptor- substituted cross-conjugated carbocycles based on quinoids or expanded quinoids, with radiaannulene perimeters, were prepared and investigated to validate proaromaticity as a concept for reducing HOMO-LUMO gaps in push-pull chromophores. Analyses of IR, 1H NMR, and UV/Vis/NIR spectra in conjunction with molecular structures determined by X-ray diffraction show that these push-pull quinoids have significant charge-separated ground states. This feature results in small optical gaps (near IR region) and diatropic magnetic environments inside the carbocycles, as suggested by nucleus- independent chemical shift (NICS) calculations. The NICS results, together with the bond-length analysis of the quinoid spacers, provide strong support that proaromaticity, that is, aromatized zwitterionic mesomeric contributions in the ground state, is effective. A push-pull tetrakis(ethynediyl)- expanded quinoid chromophore represents the first proaromatic radiaannulene.
KW - Annulenes
KW - Aromaticity
KW - Computational chemistry
KW - Conjugation
KW - Donor-acceptor systems
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U2 - 10.1002/chem.201001051
DO - 10.1002/chem.201001051
M3 - Article
C2 - 20648493
AN - SCOPUS:77955836308
SN - 0947-6539
VL - 16
SP - 9592
EP - 9605
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 31
ER -