http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Felouat, Abdellah,D’Alé,o, Anthony,Charaf-Eddin, Azzam,Jacquemin, Denis,Le Guennic, Boris,Kim, Eunsun,Lee, Kwang Jin,Woo, Jae Heun,Ribierre, Jean-Charles,Wu, Jeong Weon,Fages, Fré,dé American Chemical Society 2015 The Journal of physical chemistry A Vol.119 No.24
<P>Controlling photoinduced intramolecular charge transfer at the molecular scale is key to the development of molecular devices for nanooptoelectronics. Here, we describe the design, synthesis, electronic characterization, and photophysical properties of two electron donor–acceptor molecular systems that consist of tolane and BF<SUB>2</SUB>-containing curcuminoid chromophoric subunits connected in a T-shaped arrangement. The two π-conjugated segments intersect at the electron acceptor dioxaborine core. From steady-state electronic absorption and fluorescence emission, we find that the photophysics of the dialkylamino-substituted analogue is governed by the occurrence of two closely lying excited states. From DFT calculations, we show that excitation in either of these two states results in a distinct shift of the electron density, whether it occurs along the curcuminoid or tolane moiety. Femtosecond transient absorption spectroscopy confirmed these findings. As a consequence, the nature of the emitting state and the photophysical properties are strongly dependent on solvent polarity. Moreover, these characteristics can also be switched by protonation or complexation at the nitrogen atom of the amino group. These features set new approaches toward the construction of a three-terminal molecular system in which the lateral branch would transduce a change of electronic state and ultimately control charge transport in a molecular-scale device.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcafh/2015/jpcafh.2015.119.issue-24/acs.jpca.5b03699/production/images/medium/jp-2015-03699g_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b03699'>ACS Electronic Supporting Info</A></P>
Łukasiewicz, Łukasz G.,Ryu, Hye Gun,Mikhaylov, Alexander,Azarias, Cloé,Banasiewicz, Marzena,Kozankiewicz, Bolesław,Ahn, Kyo Han,Jacquemin, Denis,Rebane, Aleksander,Gryko, Daniel T. Wiley (John WileySons) 2017 Chemistry, an Asian journal Vol.12 No.14
<P>Five centrosymmetric and one dipolar pyrrolo[3,2-b]pyrroles, possessing either two or one strongly electron-withdrawing nitro group have been synthesized in a straightforward manner from simple building blocks. For the symmetric compounds, the nitroaryl groups induced spontaneous breaking of inversion symmetry in the excited state, thereby leading to large solvatofluorochromism. To study the origin of this effect, the series employed peripheral structural motifs that control the degree of conjugation via altering of dihedral angle between the 4-nitrophenyl moiety and the electron-rich core. We observed that for compounds with a larger dihedral angle, the fluorescence quantum yield decreased quickly when exposed to even moderately polar solvents. Reducing the dihedral angle (i.e., placing the nitrobenzene moiety in the same plane as the rest of the molecule) moderated the dependence on solvent polarity so that the dye exhibited significant emission, even in THF. To investigate at what stage the symmetry breaking occurs, we measured two-photon absorption (2PA) spectra and 2PA cross-sections (sigma(2PA)) for all six compounds. The 2PA transition profile of the dipolar pyrrolo[3,2-b]pyrrole, followed the corresponding one-photon absorption (1PA) spectrum, which provided an estimate of the change of the permanent electric dipole upon transition, approximate to 18D. The nominally symmetric compounds displayed an allowed 2PA transition in the wavelength range of 700-900nm. The expansion via a triple bond resulted in the largest peak value, sigma(2PA)=770GM, whereas altering the dihedral angle had no effect other than reducing the peak value two- or even three-fold. In the S0S1 transition region, the symmetric structures also showed a partial overlap between 2PA and 1PA transitions in the long-wavelength wing of the band, from which a tentative, relatively small dipole moment change, 2-7D, was deduced, thus suggesting that some small symmetry breaking may be possible in the ground state, even before major symmetry breaking occurs in the excited state.</P>
Š,tefane, Bogdan,Pož,gan, Franc,Kim, Eunsun,Choi, Eunyoung,Ribierre, Jean-Charles,Wu, Jeong Weon,Ponce-Vargas, Miguel,Le Guennic, Boris,Jacquemin, Denis,Canard, Gabriel,Zaborova, Elena,Fages Applied Science Publishers 2017 Dyes and pigments Vol.141 No.-
<P><B>Abstract</B></P> <P>The synthesis, characterization and (TD)-DFT calculations of the electrochemical and photophysical properties of novel ethynylene-analogues of hemicurcuminoids are described. These dyes are both emissive in solution and in the solid state. While compounds that emit through an efficient charge transfer (CT) state show solvatochromic behaviour associated with low fluorescence quantum yields, those lacking of donor groups show high fluorescence quantum yields of 70–80%, in solution. The latter dyes also present the advantage to emit in the solid state in the visible region with fluorescence quantum yields up to 23%. Their condensed phase spectrum can be bathochromically shifted to the near infrared region (742 nm) by appending a strong donor group.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Synthesis of new fluorophores based on hemicurcuminoid boron difluoride. </LI> <LI> Photophysical study reveals strong emission of the dyes not containing charge transfer states. </LI> <LI> Fluorescence properties of dyes in their condensed phase show aggregation induced emission. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>