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Structure-Property Relationships of Donor/Acceptor-Functionalized Tetrakis(phenylethynyl)benzenes and Bis(dehydrobenzoannuleno)benzenes Michael M. Haley et al., J. Am. Chem. Soc. 2005 , 127 , 2464. Tobe Laboratory Mariko Ohno. Conjugated pathways present in the TPEB and DBA systems.
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Structure-Property Relationships of Donor/Acceptor-Functionalized Tetrakis(phenylethynyl)benzenes and Bis(dehydrobenzoannuleno)benzenesMichael M. Haley et al.,J. Am. Chem. Soc. 2005,127, 2464 Tobe Laboratory Mariko Ohno
Conjugated pathways present in the TPEB and DBA systems ・ linear-conjugated (path a) ・ cross-conjugated (path b) ・ "bent" conjugated (path c)
TPEBs and BisDBAs tetrakis(phenylethynyl)benzene bis(dehydrobenzo[14]annuleno)benzene bis(dehydrobenzo[15]annuleno)benzene
1H NMR Spectra of Bis[14]-and[15]DBAs Bis[15] DBA13 δ= 8.42 ppm Bis[14] DBA14 δ= 8.24 ppm
The aggregation Aggregate sizses of dimers 15, 16, 18, 19 17 Aggregates much larger than dimer Concentration-dependent chemical shifts chemical shifts of the aromatic protons of DBA 15 in CD2Cl2 at 20 ℃ The upfield shifts of the protons
Summary • The authors noticed an enhancement of the optical activity transitioning from neutral to tetra-donor to donor/acceptor systems as seen by large red shifts of the UV-vis λmax and the development of strong charge-transfer bands. • The tetra-donor compounds provided the best efficiency for fluorescence. • In both absorbance and emission, protonation of the donor groups quenched or altered the optical enhancements. • Self-association properties for the donor/acceptor DBAs to form dimers in solution were observed. • An interesting ordered polymerization triggered by self-association was observed for only one isomer (17) in only CDCl3, suggesting that the reaction is very sensitive to geometrical and solvent effects.