Search

Three linear push-pull compounds comprised of difluoroboron β-diketonate and triphenylamine unit 4,6-Bis(4-(diphenylamino)phenyl)-2,2-difluoro-2H-1,3,2-dioxaborinin-1-ium-2-uide, (E)-6-(4-(Diphenylamino)phenyl)-4(4(diphenylamino)styryl)-2,2-difluoro-2H-1,3,2-dioxaborinin-1ium-2-uide and 4,6-Bis((E)-4-(diphenylamino)styryl)-2,2-difluoro-2H-1,3,2-dioxaborinin-1-ium-2-uide (ABA, ABVA, and AVBVA) have been probed by many spectroscopies. The results clarify the photo-physical property of the compounds where ABVA and AVBVA are linked with vinyl units (V). The solvent-dependent steady absorption and photoluminescence spectra data shows that the vinyl unit and the polarity of the solvent influence the photo-physical properties of the compound. Moreover, the vinyl unit would further enhance the role of the polar environment. The transient absorption measurement then offers excitation relaxation behavior. The results show that excited compounds in cyclohexene go back to the ground state through the intramolecular charge transfer (ICT) state, and the transfer lifetime from the initial excited state to the ICT state would prolong after the introduction of vinyl unit. The relaxation behavior becomes complex when cyclohexene is replaced by tetrahydrofuran. Some excited compounds go directly back to the ground state and others go back to the ground state after passing through the ICT state. In addition, two-photon PL measurements and a Z-scan technique are employed, and this confirms that these compounds have two-photon behavior, but the two-photon absorption section gradually decreases. This decrease is attributed to the spectral shifting affected by the vinyl unit. [ABSTRACT FROM AUTHOR]

Through comparing the linear and nonlinear optical property of two pull-push chromophores, which are composed of difluoroboron β-diketonate functionalized with carbazole and tert-butyl carbazole, the role of tert-butyl in chromosphere has been discussed in detail. The tert-butyl unit would lead to the absorption and fluorescence peak red shift and accelerate the fluorescence relaxation rate of chromophores. Moreover, the tert-butyl unit would affect obviously the two-photon optical property of chromophore according to the Z-scan test. The transient absorption (TA) data shows that these two pull-push chromopphores both own intramolecular charge transfer (ICT) characteristics and the tert-butyl unit accelerate the dynamic rate of ICT generation and relaxation process, which may be responsible for the variance of fluorescence property. [ABSTRACT FROM AUTHOR]

Two push-pull compounds, which are comprised of triphenylamine (TPA) (electron donor units) and functionalized β-diketones difluorboron complexes (electron acceptor units) are probed by many spectroscopies, which offers the relationship between electron acceptor and the intrinsic excited state properties of push–pull chromophores. We found that the photoluminescence (PL) intensity would enhance with the number of electron acceptor. Transient absorption (TA) data shows that intramolecular charge transfer (ICT) process really exists in the two molecules after photoexcitation and this process would be prolonged through increasing the electron-acceptor, which would be responsible for the improvement of PL property. [ABSTRACT FROM AUTHOR]

Highlights: [•] π-Spacer dependent optical properties of fluorenone-based oligomers are studied. [•] Fluorene–ethylene (FE) spacer could modulate the steady-state spectra of oligomers. [•] DFT calculations confirm the ICT nature in the HOMO–LUMO transition. [•] FE spacer could increase the TPPL efficiency and TPA cross-section of oligomers. [•] TA measurement confirms the ICT state exists in the relaxation of excited oligomer. [Copyright &y& Elsevier]