Extending Hexaazatriphenylene with Mono-/Bithiophenes in Acceptor–Donor Diads and Acceptor–Donor–Acceptor Triads
María Moreno OlivaAlberto RiañoIratxe Arrechea‐MarcosMar RamosRafael GómezManuel AlgarraRocío Ponce OrtizJuan T. López NavarreteJosé L. SeguraJuan Casado
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Abstract:
Three new hexaazatriphenylene (HAT)-based electron-accepting molecules with octupolar disc-like symmetry that combine the HAT core with six branches of electron-donor thiophenes in two modalities have been synthesized: (i) with six donor thiophenes and bithiophenes delineating a six-donor-to-one-acceptor (6–1) profile and (ii) with six donor–acceptor branches configuring a 6–6–1 acceptor–donor–acceptor triad. The 6-fold accumulation of donors and acceptors in the periphery of the HAT core is expected to tune the molecular electronic and optical properties. An exhaustive analysis of these properties as a function of the 6–1 and 6–6–1 stoichiometry of the molecules is described by combining a palette of experimental spectroscopic techniques such as electronic absorption (from the ground electronic and excited states), emission (fluorescence and phosphorescence), ultraviolet photoelectron spectroscopy, spectroelectrochemistry, and vibrational Raman have been implemented, all combined with electrochemistry and molecular theoretical modeling. A particular focus on the charged species and the charge distribution around the 6–1 and 6–6–1 patterns is conducted. Structure–property relationships have been outlined. The complete understanding of all these properties might help to design improved chromophores based on the HAT structure and to anticipate new properties.Keywords:
Acceptor
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Electron donor
A series of new thiophene-bridged chromophores based on the powerful heterocyclic acceptor 3-(dicyanomethylene)-2,3-dihydrobenzothiophene-1,1-dioxide has been synthesized; the dependence of the linear and second-order nonlinear optical properties and thermal stability of these species upon the donor group and the bridging group have been studied. In addition, the synthesis of a related new acceptor, not containing the fused benzene ring, is described and a chromophore based upon this acceptor is studied.
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Abstract Ausgehend von dem Dimethylester (I) wird das Paracyclophan (IV) (Fdd2; Z=16) synthetisiert.
Tetracyanoquinodimethane
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Bis(phenylsulfone) as a strong electron acceptor of thermally activated delayed fluorescent emitters
Bis(phenylsulfone) was developed as a strong electron acceptor of thermally activated delayed fluorescent emitters. The connection of two electron withdrawing phenylsulfone moieties through meta-position of phenyl produced the bis(phenylsulfone) acceptor and the strong electron acceptor strength of bis(phenylsulfone) enabled preparation of sky-blue and green thermally activated delayed fluorescent emitters in combination with weak carbazole donors. The bis(phenylsulfone) acceptor and carbazole donor combined organic materials performed as thermally activated delayed fluorescent emitters with a high quantum efficiency of 18.3%.
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Abstract Quenching of fluorescence due to electron transfer is observed in monolayer assemblies when electron donor and electron acceptor, both immobile, are either in the same monolayer or in adjacent monolayers. When the donor and acceptor monolayers are separated by two fatty acid interlayers no fluorescence quenching is detected. Two types of light induced electron transfer have been observed. The donor is excited and the electron is transferred from the S 1 state of the donor into the lowest unoccupied orbital of the acceptor. The donor fluorescence is quenched. The acceptor is excited and the electron is transferred from the S 0 state of the donor into the highest occupied orbital of the acceptor. The acceptor fluorescence is quenched. In both processes the initial situation is recovered by back transfer of an electron from the reduced acceptor to the highest occupied orbital of the donor. These electron transfer processes have been studied by varying the concentration of the acceptor. The fluorescence quenching depends on the average distance R̃ between acceptor molecules and values of R̃ 1/2 (average distance in the acceptor layer at which the fluorescence intensity is half of the intensity without electron transfer) have been determined. The value of R̃ 1/2 depends on the energetic position of both the electron donating level and the electron accepting level as calculated from electrochemical and spectroscopic data.
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Novel organic second Nonlinear optical (NLO) chromophore GZP-T based on tricyanocyclopentenone electronic acceptor group were designed and synthesized in this paper. The structure of chromophore GZP-T is characterized by mass spectrum and nuclear magnetic resonance spectroscopy. And chromophore FTC based on traditional tricyanofuran electronic acceptor was also prepared as the contrast. Their delocalized energy levels were estimated by UV–VIS spectra. Their thermal properties were studied by thermogravimetric analysis (TGA). Obviously, chromophore GZP-T showed lower delocalized energy levels and higher thermal decomposition temperature (just about 290 °C). The poled films showed the largest second-order nonlinear optical coefficients of 103.1 and 68.6 pm/V, respectively, for chromophore GZP-T and FTC. These advantages of chromophore GZP-T are attributed to the improvement of first-order hyperpolarizability and the attenuatation of intermolecular dipole interaction by the introduction of tricyanocyclopentenone electronic acceptor. And in another word, tricyanocyclopentenone electronic acceptor may be a promising way to drastically change the nonlinear optical features of the titled compounds and show a direction of designing new electron acceptor in the field of nonlinear optical materials.
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