查看更多>>摘要：Although the photophysics of BODIPY compounds has been widely investigated in the last few years, their analogues N-BODIPY, with nitrogen substitution at the boron center, did not receive comparable attention. In this work we report the synthesis and photochemical characterization of a substituted N-BODIPY compound, by means of a combined theoretical and spectroscopic approach. Compared to a standard BODIPY, the compound under investigation presents a lower fluorescence quantum yield (QY) in the visible region. The excited state relaxation dynamics of the dye was studied in different solvents, showing further fluorescence quenching in polar solvents, and excited state decay rates strongly dependent on the environment polarity. The role of the pendant moieties and the involvement of charge transfer states in the excited state dynamics was experimentally addressed by transient absorption spectroscopy, and further analyzed with TD-DFT calculations, which allowed precise assignment of the transient signals to the correspondent electronic configuration. The complete picture of the N-BODIPY behavior shows the presence of both charge transfer and localized states, influencing the observed photophysics to different amounts, depending on the excitation conditions and the surrounding environment.
查看更多>>摘要：Rose bengal (RB) showed photocatalytic performance for cross dehydrogenative-coupling (CDC) reaction. However, single organic dye only absorbs light of specific wavelength which results a lower light utilization efficiency. In this paper, we proposed a simple and effective approach based on Forster resonance energy transfer (FRET), to improve the performance of RB through the incorporation of rhodamine 6G (Rh6G) into RB solution and constructing a binary dyes system rhodamine 6G-rose bengal (Rh6G-RB). The energy transfer efficiency and antenna effect of Rh6G-RB were up to 58% and 10.8, respectively. The synergistic effect of RB and Rh6G exhibited excellent catalytic performance under low concentration (10(-5) M). The catalytic rate constant (k(d)) for Rh6G-RB reached 0.026 mol/(L.min) at 35 degrees C for aza-Henry reaction of tertiary amines with nitromethane, which was 2.03 and 5.52 times higher than that of single RB and Rh6G respectively. Moreover, the synergy of Rh6G and RB was also observed in Mannich reaction of N-tertiary amine derivatives with acetone, which all afforded the coupling products with good to excellent conversions. Finally, the Rh6G-RB system was also demonstrated an efficient visible light photoredox catalyst in continuous flow fashion. The research opened a new avenue and convenient for developing of binary or ternary organic dyes systems based on FRET and advance the application of these dye systems in photocatalytic organic synthesis.
Palion-Gazda, JoannaMachura, BarbaraSzlapa-Kula, AgataMaron, Anna M. M....
19页
查看更多>>摘要：New rhenium(I) tricarbonyl complexes based on the phenanthroline ligand were designed and synthesized to investigate the role of carbazole (cbz) and pyrrolidine (pyrr) substituents in determining thermal, electrochemical and optoelectronic properties. Both pyrr and cbz are electron-releasing substituents, but they differ in the steric hindrance and electron delocalization ability. The impact of pyrr and cbz on ground-and excited-state properties of [ReCl(CO)(3)(cbz(2)-CH(3)phen)] (1) and [ReCl (CO)(3)(pyrr(2)-CH(3)phen)] (2) were investigated with a range of techniques including cyclic voltammetry, absorbance and emission spectroscopies, transient absorption spectroscopy, and they were discussed in comparison with the model chromophore [ReCl(CO)(3)(CH(3)phen)] (3). Experimental results were supported by theoretical calculations. The most striking difference between the pyrr and cbz groups was seen in their impact on the LUMO energy level. While the attached carbazole groups decreased the LUMO energy of 1, the pyrrolidine ones in 2 resulted in the rise of LUMO energy level compared to the model chromophore. For both 1 and 2, the HOMO got energetically destabilized in agreement with electro-donor abilities of pyrr and cbz substituents. Structural modification of phen backbone resulted also in changes of distribution of occupied MOs of 1 and 2 in relation to 3. Experimentally, it was manifested in noticeable changes of electrochemical and photophysical behaviour of the resulting Re(I) complexes in relation to the model chromophore.
Weisz, AdrianLazo-Portugal, RodrigoPerez-Gonzalez, MarianitaRidge, Clark D....
10页
查看更多>>摘要：The anthraquinone anionic dye Acid Violet 43 (AV43, Colour Index No. 60730) is certifiable in the United States as Ext. D&C Violet No. 2 (EV2) for use as a color additive in externally applied cosmetics. The dye is also permitted in cosmetics in the European Union, Japan, and other countries. To be certified in the U.S., the dye may not contain more than 1% subsidiary colors. The present work was aimed at identifying an impurity, presumed to be a subsidiary color, found in batches of AV43 submitted for certification as EV2. The concentration level of the impurity in a sample of EV2 was enriched from-5.5% to-33%, and the enriched sample, 260 mg, was subjected to high-speed countercurrent chromatography (HSCCC). The resulting 50.7 mg of the isolated impurity was sufficient for its identification by spectroscopic methods as the sulfonated phthaloylcarbazole derivative 6-hydroxy-9-methyl-5H-naphtho[2,3-a]carbazole-5,13(12H)-dione-11-sulfonic acid (AV43C). That previously unreported compound was synthesized (0.5 g) for use as a reference material to quantify the impurity in batches of EV2. Test portions of 29 batches, produced by 11 manufacturers from six countries, were analyzed by HPLC and UHPLC. The levels of AV43C ranged from <0.05% to 5.66% across batches. Carbazolization through an intramolecular Scholl-type reaction in the sulfonation step of the manufacturing process is suggested as the likely source of AV43C formation. Control of the conditions that enable carbazolization is proposed as a way to reduce or eliminate contamination by AV43C.
查看更多>>摘要：Steric effects have attracted great attention in the fields of synthetic chemistry, spectroscopy, crystallography, as well as surface chemistry. Herein, two pyrene-based compounds with different cyclic ketones acting as a bridge are presented and the influence of the steric effects on the luminescent and molecular packing is investigated. Both luminogens display different optical properties both in dilute and aggregate states. Notably, the pyrenebased cyclopentanone (2) possesses a non-aggregation-induced emission (AIE) feature, whilst pyrene-based cyclohexanone (3) is AIE-active due to steric effects. Furthermore, the mechanochromism properties and pH responsive ability of both pyrenes are investigated by use of fluorescence and XRD technologies. The present work provides insight into how steric effects impact on the molecular conformations and optical properties in these new pyrene-based AIE luminogen systems.
查看更多>>摘要：Hydrazine (N2H4) is a very important chemical reagent which has been widely used in the fields of chemistry industry, aerospace, pesticide production and others. However, N2H4 is highly toxic and prone to induce a variety of diseases. Hence, we designed two fluorescent probes (CH-NO1, CH-NO2) based on chloro-hydroxylmerocyanine (CHMC) with similar recognition groups. The two probes were synthesized by a simple reaction coupling between CHMC dye and two alkyl bromine compounds. Both probes showed specific off-on response to N2H4 in aqueous solution with nanomolar LOD (28 nM for CH-NO1 and 38 nM for CH-NO2), and without interference by a range of amino acids, anions and cations. Moreover, CH-NO1 can be used for both environmental and biological monitoring of N2H4.
查看更多>>摘要：A new type of "turn-on" fluorescence probe coumarin-based DTC was developed for specifically detecting hypochlorite ion (ClO-) with high sensitivity. DTC can display a significant enhancement of fluorescence and emit blue fluorescence at 452 nm after reaction with ClO-. Moreover, probe DTC can detect ClO- without interference from other reactive oxygen species (ROS), and has a low detection limit for ClO- of 96 nM. Meanwhile, DTC can also detect ClO- in the physiological environment, and DTC can be further used as a test paper-strip for portable and rapid detection of ClO-.
Nganga, Joseph B.Jung, Young JaeSi, YunpeiKim, Minyoung...
8页
查看更多>>摘要：We investigate visible-light-induced radical polymerization initiated by methyl fluorescein and its derivatives (e.g., methyl ether of fluorescein, methyl ether ester of fluorescein, and methyl ester of fluorescein), which act as photoredox catalysts. The structural alterations of fluorescein noticeably affect their photoredox catalytic performance, which increases in the following order: methyl ether of fluorescein < methyl ether ester of fluorescein < methyl ester of fluorescein <= fluorescein. Particularly, the methylation on the phenolic hydroxyl group reduces their performance mainly due to the restraint of tautomerization. Based on this systematic investigation, we synthesize methyl ether fluorescein, bearing aryl boronate as an H2O2-selective photoredox catalyst and use it to amplify the signal of H2O2 through the photoinduced radical polymerization. In the presence of H2O2, this photoredox catalyst successfully initiates the polymerization of poly(ethylene glycol) diacrylate and N-vinyl-pyrrolidone, forming a polymeric hydrogel in 1 min under visible-light irradiation. For the naked-eye detection of H2O2, 10 mu M of the catalyst allows a successful detection of H2O2 down to 20 mu M. We envision that our strategy will be highlighted by mechanistic elucidation of photoredox catalysis and synthesis of multifunctional photoredox catalysts. Other benefits include biomedical applications such as colorimetric sensing of a target analyte, cell surface engineering, and cell therapy.
查看更多>>摘要：Photophysical properties including the first hyperpolarizability of a series of chromophores (SP1-SP5) possessing "push-pull " type conjugation were investigated to evaluate the proficiency as non-linear optically active materials. The compounds are based on the 9,9-dimethyl-9H-fluoren-2-amine platform, which acts as a donor unit and different types of acceptors have been incorporated to design SP1-SP5. The first hyperpolarizability (beta(HRS)) value was in the range of 102 x 10(-30) esu to 174 x 10(-30) esu, and the trends in the experimental beta(HRS) have been rationalized in terms of the difference in the dipole moment (delta mu(ge)) of the ground and excited state, oscillator strength of the contributing absorption bands and the band gaps. The intrinsic efficiency of the non-linear response of these dipolar compounds possessing a single major dipolar hyperpolarizability tensor component beta(zzz) was also determined from the intrinsic hyperpolarizability, a real figure of merit of the non-linear optical response. Comparison of the experimental off-resonant first hyperpolarizability, beta(HRS), as well as the intrinsic hyperpolarizability of this set of D-pi-A chromophores, lacking linear conjugation, revealed advantage over the already reported counterparts based on benzothiazole platform.
查看更多>>摘要：The impact of the thickness of the TiO2 blocking layer (50, 150 and 300 nm) on DSSC performance based on a new D-D-pi-A architecture of metal-free organic dyes and commercial N719 was investigated. The blocking layers were prepared by atomic layer deposition. New indolo[3,2,1-jk]carbazole derivatives as sensitizers with a phenothiazine unit and an acetylene linkage containing either an aldehyde or cyanoacrylic acid were designed, synthesized and characterized. However, the lack of anchoring ability of -CHO group with TiO2 was demonstrated. It was found that the blocking layer thickness has an important role in cell performance. Finally, by the optimum thickness of TiO2 film being 50 nm, the highest efficiency was achieved at 3.70, 8.49 and 8.05% for DSSC based on indolo[3,2,1-jk]carbazole derivative, N719 and mixture of these dyes.
NSTL
Elsevier