TY  - JOUR
A1  - Ceyman, Harald
A1  - Rosspeintner, Arnulf
A1  - Schreck, Maximilian H.
A1  - Mützel, Carina
A1  - Stoy, Andreas
A1  - Vauthey, Eric
A1  - Lambert, Christoph
T1  - Cooperative enhancement versus additivity of two-photon-absorption cross sections in linear and branched squaraine superchromophores
JF  - Physical Chemistry Chemical Physics
N2  - The linear and nonlinear optical properties of a series of oligomeric squaraine dyes were investigated by one-photon absorption spectroscopy (1PA) and two-photon absorption (2PA) induced fluorescence spectroscopy. The superchromophores are based on two indolenine squaraine dyes with transoid (SQA) and cisoid configuration (SQB). Using these monomers, linear dimers and trimers as well as star-shaped trimers and hexamers with benzene or triphenylamine cores were synthesised and investigated. The red-shifted and intensified 1PA spectra of all superchromophores could well be explained by exciton coupling theory. In the linear chromophore arrangements we also found superradiance of fluorescence but not in the branched systems. Furthermore, the 2PA showed enhanced cross sections for the linear oligomers but only additivity for the branched systems. This emphasizes that the enhancement of the 2PA cross section in the linear arrangements is probably caused by orbital interactions of higher excited configurations.
KW  - 2-photon absorption
KW  - Vibronic contributions
KW  - One-photon
KW  - Molecules
KW  - Intensity
KW  - Multibranched structures
KW  - Optical properties
KW  - Dyes
KW  - Chromophores
KW  - Design
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188299
VL  - 18
IS  - 24
ER  - 
TY  - JOUR
A1  - Seifert, Sabine
A1  - Shoyama, Kazutaka
A1  - Schmidt, David
A1  - Würthner, Frank
T1  - An electron-poor C\(_{64}\) nanographene by palladium-catalyzed cascade C-C bond formation: one-pot synthesis and single-crystal structure analysis
JF  - Angewandte Chemie-International Edition
N2  - Herein, we report the one-pot synthesis of an electron-poor nanographene containing dicarboximide groups at the corners. We efficiently combined palladium-catalyzed Suzuki-Miyaura cross-coupling and dehydrohalogenation to synthesize an extended two-dimensional pi-scaffold of defined size in a single chemical operation starting from N-(2,6-diisopropylphenyl)-4,5-dibromo-1,8-naphthalimide and a tetrasubstituted pyrene boronic acid ester as readily accessible starting materials. The reaction of these precursors under the conditions commonly used for Suzuki-Miyaura cross-coupling afforded a C\(_{64}\) nanographene through the formation of ten C-C bonds in a one-pot process. Single-crystal X-ray analysis unequivocally confirmed the structure of this unique extended aromatic molecule with a planar geometry. The optical and electrochemical properties of this largest ever synthesized planar electron-poor nanographene skeleton were also analyzed.
KW  - Graphene nanoribbons
KW  - Liquid-crystalline
KW  - dyes/pigments
KW  - polycyclic aromatic hydrocarbons
KW  - two-dimensional nanostructures
KW  - Aromatic-hydrocarbon
KW  - Carbon
KW  - Dyes
KW  - Functionalization
KW  - cascade reactions
KW  - nanographene
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188889
VL  - 55
IS  - 22
ER  -