Exciton Interactions,Excimer Formation,and [2π+2π] Photodimerization in Nonconjugated Curcuminoid-BF2 Dimers

We describe the synthesis of a series of covalently linked dimers of quadrupolar curcuminoid-BF₂ dyes and the detailed investigation of their solvent-dependent spectroscopic and photophysical properties. In solvents of low polarity, intramolecular folding induces the formation of aggregated chromophores, the UV/Vis absorption spectra of which display the optical signature characteristic of weakly-coupled H-aggregates. The extent of folding and, in turn, of ground-state aggregation is strongly dependent on the nature of the flexible linker. Steady-state and time-resolved fluorescence emission spectroscopies show that the Frenkel exciton relaxes into a fluorescent symmetrical excimer state with a long lifetime. Furthermore, our in-depth studies show that a weakly emitting excimer lies on the pathway toward a photocyclomer. Two-dimensional ¹H NMR spectroscopy and density functional theory (DFT) allowed the structure of the photoproduct to be established. To our knowledge, this represents the first example of a [2π+2π] photodimerization of the curcuminoid chromophore.     

Imine‐linked porous organic polymers showing mesoporous microspheres architectures with tunable surface roughness

Different kinds of porous organic polymers (POPs) bearing 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BDP) fluorophores have been developed to generate singlet oxygen upon light illumination. Herein, four imine‐linked POPs were prepared by copolymerization of amine and aldehyde with different ratios of di‐aldehyde A1 and A2. The POPs were investigated by a combination of techniques such as solid ¹³C NMR, FTIR, and nitrogen absorption–desorption isotherms and electronic microscopy. The results demonstrated that these POPs were prone to form hierarchical porous architectures. Scanning electron microscopy and transmission electron microscopy images revealed that the spherical morphologies showed different roughness, that is, BDP‐POPs with more BDP aldehyde A2 presented rougher surface. Finally, these POPs were used to generate singlet oxygen (¹O₂) monitored by 1,3‐diphenylisobenzofuran and bioimaging in HeLa cells. Our results indicated that the ability to generate ¹O₂ is dependent on the amount of BDP. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 319–327     

Substituent effects on the photophysical properties of amino-aurone-derivatives

ABSTRACT

Aurones are potential candidates to be employed as fluorescent probes or as pharmacophores for biological applications. This work describes a density functional theory (DFT) and time-dependent -DFT study at the PBE0/6-31?+?G(d) level of theory to analyse the structural, electronic and photophysical properties of a series of new proposed 4′-amine-aurone derivatives in its E and Z isomeric conformations. The maximum absorption wavelength of the proposed aurones appears in the range 390???514?nm, while the most allowed emission pathways were computed in the range 493–530?nm. The bathochromic shift of these compounds with respect to the non-substituted aurone is modulated by the acceptor strength of the added 4-substituents, in addition to the ability of the substituents to localise the frontier molecular orbitals over the acceptor benzofuranone moiety without losing the tricyclic planarity, which favours the push–pull nature of these molecules. The influence of the 4-substituent is also evidenced in the Stokes shifts for the whole series; as the electron-withdrawing character of the 4-substituents enhances, higher is the polarisation of the structure resulting in higher Stokes shifts. As a result, -CF₃ and -NO₂ substituents were responsible of larger Stokes shifts, then compounds containing these substituents are proposed as potential fluorescence probes for useful applications in biological systems.     

A new coumarin laser dye 3-(benzothiazol-2-yl)-7-hydroxycoumarin

The electronic absorption, and emission spectra as well as fluorescence quantum yield of 3-(benzothiazol-2-yl)-7-hydroxycoumarin (BTHC) were measured in different solvents and are affected by solvent polarity (Δf). The deprotonation of BTHC by triethylamine is a reversible process. BTHC is relatively photostable, the quantum yield of photodecomposition (φ_c) was found to be 2×10⁻⁴ and 2.7×10⁻⁴ in EtOH and DMF, respectively. The fluorescence lifetimes of BTHC were measured in the absence and in the presence of molecular oxygen and were found to be 2.82 and 2.78 ns, respectively. BTHC acts as good laser dye upon pumping with nitrogen laser (λ_ex=337.1 nm) in ethanol and gives laser emission with maxima at 508 and 522 nm.     

Application of ZnO nanorods loaded on activated carbon for ultrasonic assisted dyes removal: Experimental design and derivative spectrophotometry method

A method based on application of ZnO nanorods loaded on activated carbon (ZnO-NRs-AC) for adsorption of Bromocresol Green (BCG) and Eosin Y (EY) accelerated by ultrasound was described. The present material was synthesized under ultrasound assisted wet-chemical method and subsequently was characterized by FE-SEM, TEM, BET and XRD analysis. The extent of contribution of conventional variables like pH (2.0–10.0), BCG concentration (4–20 mg L⁻¹), EY concentration (3–23 mg L⁻¹), adsorbent dosage (0.01–0.03 g), sonication time (1–5 min) and centrifuge time (2–6 min) as main and interaction part were investigated by central composite design under response surface methodology. Analysis of variance (ANOVA) was adapted to experimental data and guide the best operational conditions mass by set at 6.0, 9 mg L⁻¹, 10 mg L⁻¹, 0.02 g, 4 and 4 min for pH, BCG concentration, EY concentration, adsorbent dosage, sonication and centrifuge time, respectively. At these specified conditions dye adsorption efficiency was higher than 99.5%. The suitability and well prediction of optimum point was tested by conducting five experiments and respective results revel that RSD% was lower than 3% and high quality of fitting was confirmed by t-test. The experimental data were best fitted in Langmuir isotherm equation and the removal followed pseudo second order kinetics. The experimentally obtained maximum adsorption capacities were estimated as 57.80 and 61.73 mg g⁻¹ of ZnO-NRs-AC for BCG and EY respectively from binary dye solutions. The mechanism of removal was explained by boundary layer diffusion via intraparticle diffusion.     

不同发光染料的顶发射有机电致发光器件的研制

通过设计合理的微腔结构,制备了基于绿光染料C545t、黄光染料Rubrene、红光染料DCJTB的3种顶发射有机电致发光器件。研究了不同发光染料对顶发射器件的光谱的影响。研究表明,微腔结构对光谱具有窄化作用。绿光、黄光器件的发光峰波长并未随视角增大而明显变化,体现出良好的光谱角度性,而红光器件却出现了明显的光谱蓝移现象。绿光器件的最大功率效率为8.7 lm/W,当电流密度为45 m A/cm2时,亮度能达到7 205 cd/m2;黄光器件的电流效率最大值为11.5 cd/A,当电流密度为48 m A/cm2时,亮度可达到3 770 cd/m2;红光器件的电流效率最大能达到3.54 cd/A,当电流密度为50 m A/cm2时,可获得1 358 cd/m2的亮度。采用合适的发光材料以及合适的器件结构,不仅可以提高顶发射器件的色纯度及发光效率,还可以改善器件发光光谱的角度依赖性。     

混合表面活性剂对某些吡啶偶氮试剂显色反应的作用

本文研究了表面活性剂对不同电子结构的三种金属离子(Zn~(2+),Cu~(2+),Pd~(2+))与两种分子结构类似但反应官能团不同的吡啶偶氮染料(PAR和5-Cl-PADAB)间的显色反应的作用。试验证明:(1)表面活性剂对显色反应增敏作用的产生,最根本的是由于金属离子的电子结构和试剂的反应官能团的不同,以及由此引起所成显色络合物的结构的不同。(2)表面活性剂对显色络合物的增敏效应,与单个表面活性剂分子对有色络合物的作用有关,更重要的是形成胶束,改变反应微环境。(3)离子型-非离子型混合表面活性剂对显色反应是否产生协同增敏效应和协同增敏效应的大小,决定于两者形成混合胶束的难易。如果显色络合物的结构有利于此两种表面活性剂同时对它起协同作用,则协同增敏效应可进一步提高。     

Directly‐coupled‐column ultra‐fast liquid chromatography with diode array detection method for the rapid quantification of allergenic disperse dyes in water preconcentrated by magnetic solid‐phase extraction

A directly‐coupled‐column ultra‐fast liquid chromatography coupled with diode array detection method for the determination of 12 allergenic disperse dyes in river water at sub‐ppb levels has been developed and successfully validated. The analytical method is based on the use of two different reversed‐phased columns connected through a two‐position switching valve. A baseline separation was achieved by proper selection of stationary phases, mobile phases, and the use of a gradient elution in both dimensions. Furthermore, an easy‐to‐handle magnetic solid‐phase extraction procedure was developed for the preconcentration of 12 allergenic disperse dyes from river water. An enrichment factor of 100 times was obtained. The results showed excellent performance in terms of trueness (76.8–99.0%), precision (intraday: 2.2–8.0%, interday: 3.3–8.2%), and sensitivity (limits of determination, 0.027–1.46 μg/L). Twenty real samples collected from the outfalls in the Yaojiang, Yongjiang and Fenghuajiang estuary were analyzed, and three of the studied compounds were found in one collected sample (12.6 μg/L for disperse blue 7, 11.6 μg/L for disperse blue 106, and 0.22 μg/L for disperse blue 3).