Synthesis, chemical–optical characterization and solvent interaction effect of novel fluorene-chromophores with D–A–D structure (original) (raw)
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The Journal of Physical Chemistry A, 2015
The article presents the results of spectroscopic studies focused on a selected compound from the 1,3,4-thiadiazole group-2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thia-diazole (FABT)-in a micellar system formed by Triton X-100, a non-ionic detergent. Fluorescence measurements revealed the phenomenon of dual fluorescence whose emergence is related to the particular molecular organisation of the compound, which depends both on the concentration of the detergent and, most of all, the concentration of the compound itself. Dual fluorescence of FABT in a micellar system was observed for the compound dissolved in a methanol aqueous system, i.e., an environment wherein the dual fluorescence of the compound had never been reported before. Based on the interpretation of UV-Vis electronic absorption, resonance light scattering (RLS), emission and excitation fluorescence spectra, as well as measurements of dynamic light scattering (DLS) and Principal Component Analysis (PCA), we were able to relate the occurrence of this effect to the process of molecular aggregation taking place between FABT molecules in the micellar system in question. Results of fluorescence spectra measurements and time-correlated single photon counting (TCSPC) indicate that dual fluorescence occurs at detergent concentrations necessary to form micellar systems, which in turn facilitate the process of aggregation of FABT molecules. The correlation between the observed fluorescence effects and the previous measurements performed for analogues from this group suggests the possibility of charge transfer (CT) within the range of detergent concentrations wherein the aforementioned fluorescence effects are observed. It ought to be emphasised that this type of fluorescence effects are relatively easy to induce, which predisposes this groups of fluorophores as ideal fluorescence probes in the context of biological samples.
Chemical Physics Letters, 2007
The two-photon absorption (TPA) properties of a series of symmetrical fluorene and carbazole derivatives have been studied to determine the role of the central core and the solvent polarity. The molecules bear triphenylamine, oxadiazole and pyrene as electron donating, electron acceptor and p-conjugated edge substituents, respectively. Triphenylamine and pyrene substituents with fluorene-core as well as oxadiazole substituent with carbazole-core constitute the optimum selections for enhanced TPA properties. Studying the effect of the solvent polarity it is shown that maximum TPA cross-sections (as high as 1024 GM) are achieved in a solvent of intermediate polarity.
Frontiers in Chemistry, 2020
Herein, we report the synthesis and characterization of fluorophores containing a 2,1,3-benzoxadiazole unit associated with a π-conjugated system (D-π-A-π-D). These new fluorophores in solution exhibited an absorption maximum at around ∼419 nm (visible region), as expected for electronic transitions of the π-π * type (ε ∼2.7 × 10 7 L mol −1 cm −1), and strong solvent-dependent fluorescence emission (Φ FL ∼0.5) located in the bluish-green region. The Stokes' shift of these compounds is ca. 3,779 cm −1 , which was attributed to an intramolecular charge transfer (ICT) state. In CHCl 3 solution, the compounds exhibited longer and shorter lifetimes, which was attributed to the emission of monomeric and aggregated molecules, respectively. Density functional theory was used to model the electronic structure of the compounds 9a-d in their excited and ground electronic states. The simulated emission spectra are consistent with the experimental results, with different solvents leading to a shift in the emission peak and the attribution of a π-π * state with the characteristics of a charge transfer excitation. The thermal properties were analyzed by thermogravimetric analysis, and a high maximum degradation rate occurred at around 300 • C. Electrochemical studies were also performed in order to determine the band gaps of the molecules. The electrochemical band gaps (2.48-2.70 eV) showed strong correlations with the optical band gaps (2.64-2.67 eV).
Benzothiazole-Based Cycloplatinated Chromophores: Synthetic, Optical, and Biological Studies
Chemistry (Weinheim an der Bergstrasse, Germany), 2017
Cycloplatinated complexes based on 2-(4-substituted)benzothiazole ligands of type [Pt(R-PBT-κC,N)Cl(L)] (PBT=2-phenylbenzothiazole; R=Br (1), MeN (2); L=dimethyl sulfoxide (DMSO; a), 1,3,5- triaza-7-phosphaadamantane (PTA; b), triphenylphosphine 3,3',3''-trisulfonate (TPPTS; c)) and [Pt(Br-PBT-κC)Cl(PTA)] (3) are presented. On the basis of the photophysical data and time-dependent (TD)-DFT calculations (1 a and 2 a), the low-lying transitions (absorption and emission) were associated with ligand-center (LC) charge transfer, with minor metal-to-ligand charge transfer (MLCT), and intraligand charge transfer (ILCT) [MeN-PBT→PBT] excited states, respectively. Simultaneous fluorescence/phosphorescence bands were found in fluid solutions (and also in the solid state for 2 a), which become dominated by triplet emission bands in rigid media at 77 K. The effect of the concentration on emissive behavior of 2 a, b indicated the occurrence of aggregation-induced luminescence propert...
Dyes and Pigments, 2016
A new fluorophore containing a 2,1,3-benzothiadiazole unit containing alkylated tetrazoles terminal groups as electron donors connected through a π-conjugated system of type D-π-A-π-D was synthesized and electronically and electrochemically characterized. The compound in solution has an absorption maximum in the visible region (~ 417 nm) due to electronic transitions of type 1 ππ* (ε ~ 10 4 M-1 •cm-1) and intense fluorescence emission (Φ F ~ 0.65) located in the blue-green region depending on the solvent used with a Stokes' shift of ca. 75 nm. Evidences of intramolecular charge transfer character in the excited state was observed from the Lippert-Mataga correlation. The AFM images of the spin-coating depositions of compound 9 using chloroform as solvent on silicon substrate showed the formation of films *
Journal of Fluorescence, 2012
Novel 2-(1H-benzimidazol-2-yl)-5-(N,Ndiethylamino) phenol, 2-(1,3-benzoxazol-2-yl)-5-(N,Ndiethylamino) phenol, 2-(1,3-benzothiazol-2-yl)-5-(N,Ndiethylamino) phenol and their derivatives have been synthesized from p-N,N-diethyl amino salicylaldehyde with different substituted o-phenylenediamine or o-aminophenol or o-aminothiophenol and their photo-physical properties were studied. Effects of solvent polarity in the absorptionemission properties of synthesized compounds were investigated. All these compounds shows excited state intramolecular proton transfer pathway having single absorption and dual emission characteristics. The fluorescent compounds were characterised by FT-IR, 1 HNMR, 13 C NMR and Mass spectral analysis. TGA analysis showed these compounds are thermally stable up to 200°C.
Synthesis of Two-Photon Absorbing Unsymmetrical Fluorenyl-Based Chromophores
Chemistry of Materials, 2006
Unsymmetrical fluorenyl-based chromophores, flanked on either side by electron-acceptor (A) and/or electron-donating (D) groups, separated by conjugated (π) moieties, were synthesized. Heck coupling and Wittig reactions were utilized to prepare target fluorene derivatives that possess very high solubility in organic solvents, high thermal stability (up to 395°C), and generally high fluorescence quantum yields (0.6-0.9). The systematic alteration of the structural design allowed for investigation of numerous factors that affect the optical nonlinearity, as well as probing effects of molecular symmetry, solvent polarity, strengths of electron donating and/or withdrawing end groups, and π-conjugation length. A detailed spectroscopic study of these molecules, including absorption, fluorescence emission, excitation, and excitation anisotropy, was conducted. Two-photon absorption (2PA) cross sections (δ) were determined by a nonlinear transmission method employing a femtosecond white-light continuum (WLC) pumpprobe method, with all compounds exhibiting high two-photon absorption under femtosecond excitation. Compound 3 had a peak 2PA cross section, δ, of 1093 × 10 -50 cm 4 s photon -1 molecule -1 at 828 nm. In addition, excitation anisotropy studies permitted the determination of the spectral position of the S 0 f S 1 and S 0 f S 2 electronic transitions.