Photophysical Studies on the Interaction of Formamide and Alkyl Substituted Amides with Photoinduced Electron Transfer (PET) Based Acridinedione Dyes in Water

Interaction of photoinduced electron transfer (PET) based acridinedione dye (ADR 1) with amides like formamide, acetamide and dimethylformamide (DMF) were investigated by fluorescence spectral techniques. A fluorescence enhancement accompanied with a blue shift in the emission maximum was observed on the addition of amides to ADR 1 dye, which possess C₆H₄(p-OCH₃) in the 9th position of the basic acridinedione ring. The extent of fluorescence enhancement and the blue shift in the emission maximum of ADR 1 dye is of the order of DMF > acetamide > formamide. DMF, which is more hydrophobic and less polar, results in a higher extent of fluorescence enhancement and a larger shift in the emission maximum towards the blue region. On the addition of amides, the ADR 1 dye prefers to orient towards a more hydrophobic phase surrounded by more number of amide molecules. The fluorescence enhancement of ADR 1 dye is attributed to the suppression of PET process occurring through space. The influence of the hydrophobic nature and the polarity of the amides on the excited state properties of acridinedione dyes are elucidated by steady-state and time resolved fluorescence measurements.     

Photophysical Properties and Photoreduction of 5,10,15,20-Tetrakis-(4-N-Methylpyridyl)Porphyrin in Formamide

The photophysical characteristics and photochemical conversions of 5,10,15,20-tetrakis-(4-N-methylpyridyl)porphyrin in a highly polar solvent, formamide, are investigated. It has been established that no photochemical reactions occur on excitation in the visible spectral region, while UV excitation ( = 347 nm) causes photoreduction of porphyrin molecules followed by the formation of protonated products. The solvent molecules serve as a reducing agent. Photoreduction occurs in both air-saturated and deoxygenated solutions, but the nature of the products formed is different: chlorin molecules are formed in the air-saturated solutions and the successive photoconversion porphyrinphlorinporphometheneporphyrinogene occurs in the deoxygenated solutions.     

(2R,5S)-N-间氟苄基-2,5-二甲基哌嗪的合成

以(2R,5S)-2,5-二甲基哌嗪为原料,经过成盐,单取代反应,用D-酉石酸对光学异构体的手性拆分,用氢氧化钠游离,最终合成(2R,5S)-N-间氟苄基-2,5-二甲基哌嗪,反应总收率为83％.该物质的合成未见文献报道,目标化合物用1H NMR,IR进行结构表征.     

1-(2,6-二溴-4-硝基苯)-3-(4-硝基苯)-三氮烯与锌的显色反应研究

研究了 1- (2 ,6-二溴 - 4 -硝基苯 ) - 3- (4 -硝基苯 ) -三氮烯 (DBNPNPT)与锌的显色反应。在表面活性剂Triton X- 10 0的存在下 ,p H=9.0— 11.0的 Na2 B4 O7- Na OH介质中 ,DBNPNPT与锌 ( )可生成橙黄色络合物。建立以 5 35 nm为参比波长 ,4 4 0 nm为测定波长的双峰双波长测定法 ,该络合物的表观摩尔吸光系数为 1.34× 10 5L· mol-1· cm-1。对葡萄糖酸锌中的锌直接测定 ,结果令人满意     

Photophysical properties of polyacrylic acid with Ru (II) polypyridyl complexes

The nature of the conformational transition of the polymers with Ru (II) polypyridyl complexes covalently attached to poly(acrylic acid) (PAA) and poly(metacrylic acid) (PMAA) has been in studied in aqueous solutions at different pH values. The [PAA-Ru₄]⁸⁺ and [PMAA-Ru₄]⁸⁺ polymers has been investigated by means of the luminescence properties of the Ru(bpy)₃²⁺ moiety by steady-state and time-resolved luminescence spectroscopy. The pH markedly affects the luminescence spectra and quantum yields of both ruthenium-polyacid complexes in aqueous solution. Another feature investigated in this work was a comparative study of their luminescence quenching by acridinic dyes in solution. The analysis of the k_q values obtained indicates that the bimolecular quenching by acridinium and 9-aminoacridinium is more effective in the [PAA-Ru₄]⁸⁺ complex (6.4×10⁹ and 1.4×10⁹ M⁻¹ s⁻¹, respectively) compared to the [PMAA-Ru₄]⁸⁺ (2.6×10⁹ and 1.0×10⁹ M⁻¹ s⁻¹). Also, a similar behavior was evidenced for the Ru solely adsorbed onto pure PAA (9.0×10⁹ and 3.4×10⁹ M⁻¹ s⁻¹) and PMAA (1.8×10⁹ and 1.7×10⁹ M⁻¹ s⁻¹) in aqueous solution. The effect of enhancement of quenching rate constant in [PAA-Ru₄]⁸⁺ system could be ascribed to the higher density of Ru per polymer chain. The average number per chain is similar in both systems, but the molecular weight is lower for [PAA-Ru₄]⁸⁺. Furthermore, the larger hydrophilic environment provided by the PAA exposes the Ru probe to the outer surface of the polymer in solution.     

Photophysical characterizations of 2-(4-biphenylyl)-5 phenyl-1,3,4-oxadiazole in restricted geometry

Langmuir and Langmuir-Blodgett (LB) films of non-amphiphilic 2-(4-Biphenylyl)-5-phenyl-1,3,4-oxadiazole (abbreviated as PBD) mixed with stearic acid (SA) as well as with the inert polymer matrix poly(methyl methacrylate) (PMMA) have been studied. Surface pressure versus area per molecule (π-A) isotherm studies suggest that PBD molecules very likely stand vertically on the air-water interface and this arrangement allows the PBD molecules to form stacks and remain sandwiched between SA/PMMA molecules. At lower surface pressure, phase separation between PBD and matrix molecules occurs due to repulsive interaction. However, at higher surface pressure, PBD molecules form aggregates. The UV-vis absorption and steady-state fluorescence spectroscopic studies of the mixed LB films of PBD reveal the nature of the aggregates. H-type aggregate predominates in the mixed LB films, whereas I-type aggregate predominates in the PBD-PMMA spin-coated films. The degree of deformation produced in the electronic levels are largely affected by the film thickness and the surface pressure of lifting.     

Quantum Chemical and Corrosion Inhibition Studies of (4-Chlorophenyl)-N-(4-Methylphenyl) Nitrone

The compound (4-chlorophenyl)-N-(4-methylphenyl) nitrone (4CPNMPN) has been selected as one of the new nitrone derivative for our study. The molecular structure of the compound was investigated based on frontier orbital analysis and natural bond orbital (NBO) theory. The present work also focuses on the inhibition efficiency of the compound. It is an attempt to find the correlation between the molecular structure of the compound and possible behaviour like corrosion inhibitors. The NBO analysis and the values of electric dipole moment (μ) of the investigated molecule were computed using DFT calculations. The molecule orbital contributions were studied by using the total (TDOS) density of states. The strong evidences that the compound can be used as an efficient nonlinear optical (NLO) of 4CPNMPN were demonstrated by considerable polarizability and hyperpolarizability values obtained at DFT levels.     

新型锂离子电池正极材料LiMPO_4(M=Fe,Mn)的谱学和电化学研究

采用固相反应与液相反应,合成了新型锂离子电池正极材料LiMPO4(M=Fe,Mn)。粉末X光衍射表明材料均为纯相。对材料的显微拉曼光谱和红外光谱进行了研究和指认。循环伏安研究表明,含锂磷酸盐是一类有潜力的锂离子电池正极材料。     

Photophysical and Analyte Sensing Properties of Cyclometalated Ir(III) Complexes

The synthesis of some heteroleptic, cyclometalated iridium(III) complexes is described. The utility of these [Ir(ppy)₂(N-N)]Cl (ppy = 2-phenylpyridine and N-N = substituted bipyridine, biquinoline, or phenanthroline) complexes as luminescence-based sensors is assessed. The emission intensity of an Ir(III) complex featuring the 3,3′-H_ndcbpy ligand (H_ndcbpy = dicarboxylic acid-2,2′-bipyridine; n = 0,1,2 to indicate deprotonated, mono- and diprotonated species, respectively) is seen to increase in the presence of Pb(II). Insight into the structure and analyte-sensing capability is achieved by X-ray crystallography in conjunction with computational modeling. Complexes incorporating carboxylic acid-functionalized bipyridine and biquinoline as the polypyridyl ligand show pH sensitivity while similar phenanthroline complexes do not.     

Deep-Red Phosphorescent Iridium(III) Complexes Containing 1-(Benzo[b] Thiophen-2-yl) Isoquinoline Ligand: Synthesis,Photophysical and Electrochemical Properties and DFT Calculations

Four new bis-cyclometalated iridium(III) complexes, [Ir(btq) ₂phen] [PF₆] (3a), [Ir(btq) ₂bpy] [PF₆] (3b), [Ir(btq) ₂dtbipy] [PF₆] (3c) and [Ir(btq) ₂pic] (3d) (btq?=?1-(benzo[b] thiophen-2-yl) isoquinoline, phen?=?1,10-phenanthroline, bpy?=?2,2′-bipyridine, dtbipy?=?4,4′-di-tert-butyl-2,2′-bipyridine, pic?=?picolinic acid) have been synthesized and fully characterized. The crystal structure of 3a has been determined by X-ray analysis. The photophysical and electrochemical properties of these new complexes 3a???3d have been studied. The photoluminescence spectra of all Ir(III) complexes exhibit deep-red emission maxima at 682, 682, 683 and 698 nm, respectively. The most representative molecular orbital energy-level diagrams and the lowest energy electronic transitions of 3a???3d have been calculated with density functional theory (DFT) and time-dependent DFT (TD???DFT). The results show that the pic ancillary ligand of complex 3d influences the absorption and emission energies with a further red-shift relative to other three complexes 3a???3c.     

Influence of UV Radiation on Spectral Properties of 2,6-Di(Hydroximethyl)-4-Methylphenol

Russian Physics Journal - The effect of UV radiation on the spectral properties of aqueous solutions of 2,6-di(hydroxymethyl)-4-methylphenol has been studied. Excilamps based on working molecules:...     

Photophysical parameters and fluorescence quenching of 7-diethylaminocoumarin (DEAC) laser dye

The optical properties including electronic absorption spectrum, emission spectrum, fluorescence quantum yield, and dipole moment of electronic transition of 7-diethylaminocoumarin (DEAC) laser dye have been measured in different solvents. Both electronic absorption and fluorescence spectra are red shifted as the polarity of the medium increases, indicating that the dipole moment of molecule increases on excitation. The fluorescence quantum yield of DEAC decreases as the polarity of solvent increases, a result of the role of solvent polarity in stabilization of the twisting of the intramolecular charge transfer (TICT) in excited state, which is a non-emissive state, as well as hydrogen bonding with the hetero-atom of dye. The emission spectrum of DEAC has also been measured in cationic (CTAC) and anionic (SDS) micelles, the intensity increases as the concentration of surfactant increases, and an abrupt change in emission intensity is observed at critical micelle concentration (CMC) of surfactant. 2×10⁻³ mol dm⁻³ of DEAC gives laser emission in the blue region on pumping with nitrogen laser (λ_ex=337.1 nm). The laser parameters such as tuning range, gain coefficient (α), emission cross section (σ_e), and half-life energy have been calculated in different solvents, namely acetone, dioxane , ethanol, and dimethyforamide (DMF). The photoreactivity of DEAC has been studied in CCl₄ at a wavelength of 366 nm. The values of photochemical yield (?_c) and rate constant (k) are determined. The interaction of organic acceptors such as picric acid (PA), tetracyanoethylene (TCNE), and 7,7,8,8-tetracynoquinonedimethane (TCNQ) with DEAC is also studied using fluorescence measurements in acetonitrile (CH₃CN); from fluorescence quenching study we assume the possible electron transfer from excited donor DEAC to organic acceptor forming non-emissive exciplex.     

Proton-conducting composite membranes derived from poly(2,6-dimethyl-1, 4-phenylene oxide) doped with phosphosilicate gels

Proton-conducting composite membranes were prepared by doping phosphosilicate gels into SPPO polymer matrix. The structure of gels was examined by ³¹P MAS-NMR. The composite membranes were characterized in terms of TGA, mechanical property, water uptake and conductivity. It was found that the composite membranes were thermally stable up to 150 °C, and possessed higher mechanical strength than Nafion112, either in dry state or in wet state. The conductivity of composite membranes increased with the increase of the ion exchange capacity (IEC), relative humidity (R.H.) and doping amounts. The water uptakes of composite membranes are much higher than Nafion112 in weight percent form at room temperature, and the highest conductivity value of 0.216 S cm^− 1 was achieved for water equilibrated membranes, 2.5 times higher than 0.0871 S·cm^− 1 for Nafion112 measured under the same condition. It is suggested that the composite membranes should be the promising candidates used in PEMFC.     

紫细菌捕光天线LH2中的超快光物理研究

采用飞秒泵浦探测技术研究了紫细菌外周捕光天线LH2中的超快光动力学过程.从B800蓝侧的激发态动力学中观察到B800到B850的能量传递时间,实验结果与理论计算结果的差别说明激发B800时可能引起B850上激子带的直接激发,或存在由B800到B850上激子态的能量传递通道.在B800红侧激发的动力学过程中,漂白信号前端存在的一个快速光吸收信号主要来源于B850上激子带的直接激发.在天然RS601和突变体GM309的LH2中,800 nm激发时的动力学过程都表现为一个类似的光漂白过程,动力学曲线的衰减时间常量在天然LH2中明显快于突变体中,说明在GM309中B800到B850的激发能传递速率有所降低.而在845 nm激发下两个样品中的快过程类似,但慢过程在GM309中有所增快,激发态中的能量重新分布包括逆向的能量传递也受到类胡萝卜素微结构的影响.     

5,10,15-三(五氟苯基)Corrole及其相似卟啉化合物的光物理特性

采用稳态和时间分辨的瞬态光谱技术对比研究了一种Corrole化合物5,10,15-三(五氟苯基)Corrole(FtsTPC)和一种卟啉化合物5,10,15,20-四(五氟苯基)卟啉(F20TPP)的光物理特性.结果表明:F15TPC的B带吸收峰较宽而F20TPP的强而窄,F15TPC的Q带有两个吸收峰而F20TPP有四个.F15TPC的荧光量子产率为0.15,荧光寿命为4.8 ns,F20TPP的荧光量子产率为0.05,荧光寿命为11.1 ns;与F20TPP相比F15TPC具有发光效率高、荧光寿命短的特点.F15TPC具有较大的发光速率常数和无辐射跃迁速率常数,这可能是由于F15TPC少了一个氟代苯基,致使其发色团本身的电子结构发生变化所致.另外空间结构的不对称性和非共面性也对其光物理性质有影响.     

Electronic properties of polyquinolines and poly(2,6-naphthylene)

We present a Valence Effective Hamiltonian (VEH) study of the electronic properties of polyquinoline, poly(4-phenylquinoline), and poly(2,6-naphthylene). Parameters important with redard to the conductivity properties upon doping, such as ionization potentials, bandwidths, and bandgaps, are obtained from the band structures of the title compounds. Results indicate that these polymers have : (i) large ionization potentials (so that fairly strong acceptors are required for effective p-type doping); (ii) large electron affinities (as a result, n-type doping is feasible); and (iii) quite small bandwidths. This is consistent with the relatively low conductivities reported so far for the doped polymers.     

Probing the Microscopic Aspects of 1-Butyl-3-Methylimidazolium Trifluoroacetate Ionic Liquid and Its Mixture with Water and Methanol: A Photophysical and Theoretical (DFT) Study

Considering the potential of mixed ionic liquid-cosolvent systems in wide range of applications, photophysical and theoretical studies on an industrially important ionic liquid, 1-butyl-3-methylimidazolium trifluoroacetate (BMIMTFA), and also its mixture with water and methanol have been investigated. Two organic dipolar solutes coumarin 153 (C153) and 2-aminonitrofluorene (ANF) have been used as the probe molecule for the present study. Steady-state absorption and emission spectral behavior of C153 has not been significantly influenced by both the cosolvents. However, excitation wavelength dependent measurements with ANF in the BMIMTFA-water and BMIMTFA-methanol show entirely different photophysical response. For BMIMTFA-methanol system the average solvation and rotational time is found to be less than that in BMIMTFA-water system. Quite interestingly, time-resolved fluorescence anisotropy measurements reveal two different solute-solvent coupling constant (C _obs ) even if same mole fraction of water and methanol is used for the mixed solvent systems. Theoretical calculations also reveal stronger intermolecular interaction between IL and methanol than that between IL and water. The present combined photophysical and theoretical calculations seem to suggest different microscopic structural organization in the two binary systems.     

新显色剂4,4'''' -二(2,6-二溴-4-硝基苯基重氮氨基)联苯与汞显色反应的研究

本文研究了新显色剂4，4'-二（2，6－二溴－4－硝基苯基重氮氨基）联苯与Hg(Ⅱ）的显色反应，在表面活性剂Triton X-100的存在下，于pH8.8的Na2B4O7-HCl缓冲溶液中，试剂与Hg（Ⅱ）形成2：2橙红色配合物，其最大吸收峰位于490nm，表观摩尔吸光系数为7.62×10^4L·mol^-1·cm^-1。Hg（Ⅱ）量在0－12μg/25mL范围内符合比耳定律。方法用于废水中微量Hg（Ⅱ）的测定，结果满意。