The Role of Triplet State of Oligophenylenevinylenes (OPVs) in their Photooxidative Degradation

Results of triplet-triplet energy transfer from biacetyl to OPVs and OPV triplet statequenching by 1, 4-diazabicyclo[2.2.2] octane (DABCO) suggested that triplet state ofoligophenylenevinylenes(OPVs) directly takes part in their photooxidative degradation instead ofjust generating singlet oxygen.     

Triplet state interaction of Safranine T with inorganic cations in different solvents

The triplet-triplet absorbance of Safranine T (3,7-Diamino-2,8-dimethyl-5-phenylphenaznium chloride) has been studied in a series of polar and non-polar solvents. When non-aqueous solvents are gradually added to the aqueous solution of Safranine T (ST) the lifetime of the triplet state decreases. It has been established that the dye forms weak complex with the solvent molecules. The quenching of triplet state of ST by Fe²⁺, Co²⁺ and Mn²⁺ has been studied in different solvents. The double protonated long-lived triplet species of ST; absorbs at 580 nm. The decay of the triplets follows first order kinetics. The quencher generates reduced semidye from ³ST by electron transfer mechanism. The reduction of ³ST by Mn²⁺ and Fe²⁺ is thermodynamically allowed but electron transfer from Co²⁺ to ST is endoergic. The mechanism of quenching by Co²⁺ can be explained as compensation by charge transfer mechanism between ³ST and Co²⁺.     

非线形CS2 分子单重态和三重态的密度泛函理论

The geometrical optimizations on nonlinear CS2 in the singlet and triplet states have been made using two Density Function Theory（DFT）methods（B3LYP and B3PW91）with 6-311+G* and aug-cc-pVTZ basis sets. Three Singlet states 1A1 and five triplet states（3A2、3B1 and 3B2）have been found,and the frequency analysis confirms that there are no image frequencies for these states,indicating that they are geniune minima at the potential energy surface. At their respective equilibrium geometries,the lowest-lying electronic states are predicted to have an energy ordering by 4t 3B2相似文献   

Triplet state spectroscopic studies on some 5,10,15,20-tetrakis(methoxyphenyl)porphyrins

Extensive triplet state spectroscopic investigations were carried out with a series of 5,10,15,20-tetrakis(methoxyphenyl)porphyrins. Triplet absorption spectra, triplet lifetime, triplet quantum yield and quantum yield for singlet oxygen production were determined with different absorption and emission techniques, using the frequency-doubled beam of a Nd:YAG laser. It has been found that these synthetic porphyrins are effective photosensitizers which can be used as model compounds to investigate the theoretical and instrumental aspects of PDT.     

联苯基团引起的激发三重态重排活性增长

双发色团分子光化学研究兴趣与日俱增。我们在以前报道一个有趣的现象:基态发色团间的分子轨道交叠左右光反应机理。3-甲基-3-联苯基-1-丁烯(1),是有特殊意义的分子。与激发能高达(143 kcal/mol)的孤立双键相比,联苯基的激发能特别低(69 kcal/mool)。如此大的激发能差使乙烯基与联苯 p电子间的交叠通道更加畅通,基态1的稳定构象是 endo 型,1的光化学行为将不同于无环双π甲烷分子。1000 W 高压汞灯照射1的正已烷溶液,     

一种具有长寿命三线态的锌卟啉-苝酰亚胺超分子的光物理过程

通过吡啶基与金属锌卟啉的配位作用, 合成了一种新型卟啉-苝酰亚胺超分子配合(TPPZn-BPHPDI), 通过核磁共振氢谱确认了超分子体系的形成. 采用荧光滴定方法测得锌卟啉与苝酰亚胺配位作用的平衡常数为5.32×10⁴ L/mol. 纳秒瞬态荧光光谱和瞬态吸收光谱显示, 超分子体系内存在着从卟啉三线态向苝酰亚胺三线态的能量传递过程, 产生了寿命长达101 μs的苝酰亚胺三线态分子.     

离子液体[Bmim][BF_4]中卟啉的三线态动力学

室温离子液体由于其几乎不挥发、稳定性突出、良好的电化学性能以及结构与性能的可设计性等优点,在诸多领域得到了深入的研究和广泛的应用。与传统的普通溶剂不同,离子液体的本质特点之一是其内部的微观结构具有微不均匀性。本文通过对四苯基卟啉(TPP)分子在离子液体[Bmim][BF_4]中的三线态动力学研究,发现在激光作用下,TPP的三线态寿命由2.95μs显著增加到184μs。进一步分析表明,这一现象很可能是由于离子液体的微结构在激光诱导下发生变化,被激光场或者离子诱导极化的氧气分子在离子液体微不均匀性环境中发生重新分布而引起的。     

Fraction of excited-state oxygen formed as b Σg in solution-phase-photosensitized reactions II. Effects of sensitizer substituent

The fraction F_Σ of excited-state oxygen formed as b ¹Σ_g⁺ was determined for a series of triplet-state photosensitizers in CCl₄ solutions. F_Σ was determined by monitoring the intensities of (a) O₂(b ¹Σ_g⁺) fluorescence at 1926 nm (O₂(b ¹Σ_g⁺)→O₂(a ¹Δ_g) and (b) O₂(a ¹ Δ_g) phosphorescence at 1270 nm (O₂(a ¹Δ_g) → O₂(X³Σ_g⁻)). Oxygen excited states were formed by energy transfer from substituted benzophenones and acetophenones. The data indicate that F_Σ depends on several variables including the orbital configuration of the lowest triplet state and the triplet-state energy. The available data indicate that the sensitizer-oxygen charge transfer (CT) state is not likely to influence F_Σ strongly by CT-mediated mixing of various sensitizer-oxygen states.     

GC determination of halogenated olefins by photoionization and hall electrolytic conductivity detectors in series in matrices of hydrofluorocarbons and hydrochlorofluorocarbons

Summary Gas chromatography (GC) with photoionization (PI) and Hall electrolytic conductivity (E1C) detectors connected in series, has been used for the determination of chlorofluorinated olefins. The separation of different standard solutions containing eight chlorofluorinated ethenes in nitrogen and in halogenated matrices has been performed in wide bore capillaries, 0.53 mm i.d., and normal capillaries, 0.32 mm i.d. The quality of separation is obviously influenced by their limited load capacity and by the response time of the Hall detector. At concentrations 1–150 μL L⁻¹ halogenated olefins, both PI and ElC detectors have linear response and can detect minimum levels of 0.2–0.5 ng and 0.4–1.2 ng, respectively. The PID is particularly selective toward halogenated olefins and is extremely useful for the determination of traces of unsaturated halogenated hydrocarbons in a matrix of saturated homologues. The results of this work are of great interest for the detection of chorofluorinated olefins, highly toxic compounds usually formed as by-products in the industrial production of hydrofluorocarbons and hydrochloro-flurocarbons.     

Density functional theory study of the photosensitization mechanisms of indigo

The triplet excited state properties and photosensitization mechanisms of indigo were investigated based on density functional theory calculations. The solvent effects on the photosensitization mechanisms of indigo have also been considered. The thermodynamic feasibility of the possible ¹O₂ and O₂·⁻-photogeneration pathways by triplet excited state indigo in different solvents was explored, in order to gain some deeper insights into the photosensitization characters of the dye.      

Enhancement of the detection sensitivity for volatile organic compounds by using an annular type photoionization detector and a pre-concentration system

Photoionization detector (PID) was developed for a sensitive on-site detection of trace amounts of volatile organic compounds (VOCs) based on an annular type ion collection electrode assembly. An ion collector with an annular geometry could detect more stable ion signals in the PID system when compared to the other types of ion collectors when an UV lamp of 10.6 eV was used as an ionization source. In order to enhance the detection sensitivity, a pre-concentration system, which was developed by adopting a ceramic heater packed with rod shaped molecular sieves, was adopted for a detection of VOCs. The adopted ceramic heaters had a resistance of 10-20 Ohm, and the temperature of the heater was optimized by controlling the heating time of the resistor. The enhancement of the detection sensitivity was found to be 8-10 times with the PID system when compared to the signals measured without a pre-concentrator. The overall detection sensitivity of the developed PID system was estimated as 10 ppb or better.     

Operating the pulsed discharged detector in both the electron-capture and photoionization modes within the same GC analysis

Summary Since the electron-capture detector (ECD) is highly selective, it is imperative to use a more universal ionization detector in conjunction with the ECD in order to detect non-capturing or weakly capturing compounds. Also in an EC study of weakly or moderately strong electron-capturing compounds, it is necessary to identify the EC peak of the compound by identifying the major component with an ionization detector. In this paper we have shown that the pulsed discharge detector can be interchanged between the EC and the helium ionization modes within 4–6 s. The application of this procedure has been illustrated with a mixture of alkane/alkene chlorocompounds. The interchange between EC and argon photoionization modes has also been investigated. The change from EC to argon photoionization also occurs in 4–6 s but the reverse process requires 9 s.     

三线态二苯基卡宾的动力学稳定效应

通过对二苯基重氮甲烷进行光照射产生了一系列于邻位和对位具有不同大小取代基的三线态二苯基卡宾.用紫外可见光谱对其进行了直接观察,并利用激光闪光光解法测定了三线态二苯基卡宾在室温脱氧苯溶液中的寿命,由此表明在邻位和对位里引入庞大的取代基对三线态二苯基卡宾具有更好的稳定效应.     

Circumstances in which radiation is not absorbed, forbidding photoionization: four classes of matrix element zeros

We compare a new class of photoionization matrix element zeros, which we will call relativistic high-energy zeros (RHEZ), occurring at energies on the order mc², to three well-studied classes of zeros, which include Cooper minima, point Coulomb relativistic zeros (PCRZ) and higher energy nonrelativistic Coulomb zeros (HENRCZ). RHEZ differ from the other three types of zeros in several ways. For example, the position of the zero with respect to photon energy in dipole RHEZ matrix elements is completely independent of n, Z, the central potential V, and retardation; has a simple dependence on the bound state l quantum number. Despite the fact that RHEZ occur at such high energies the dipole RHEZ do have some physical consequences.     

Vacuum ultraviolet photoionization and photoelectron studies in the new millennium: recent developments and applications

Vacuum ultraviolet (VUV) photoionization mass spectrometry and photoelectron spectroscopy have played a central role in providing energetic and spectroscopic information for neutrals and cations. The most important data obtainable in a VUV photoionization and photoelectron experiment are ionization energies and 0 K ion dissociation thresholds or appearance energy (AE), from which 0 K bond dissociation energies for neutrals and cations can be deduced. The recent developments in VUV lasers and third-generation synchrotron sources, together with the introduction of the pulsed-field ionization (PFI), photoelectron (PFI-PE), and PFI-photoion (PFI-PI) methods, have revolutionized the field of photoelectron and ion spectroscopy by significantly improving the energy resolution to the range of 0.025–1.0 meV (full width at half maximum, FWHM). These resolutions, which make possible the measurement of photoelectron spectra for many simple molecules at the rotational-resolved level, are ≈100-fold better than those observed in traditional photoelectron studies, making the PFI-PE technique a true spectroscopic method. The recent introduction of the synchrotron-based PFI-PEPICO scheme has shown that AE values for a range of molecules can be determined with an unprecedented precision limited only by the PFI-PE measurement. The synchrotron-based PFI-PEPICO and PFI-PI schemes show great promises for future studies of state- or energy-selected ion-dissociation dynamics and energy-selected ion-molecule reaction dynamics. Further improvement in energy resolution for PFI-PE and PFI-PI measurements has been demonstrated using the two-color photo-induced Rydberg ionization (PIRI) spectroscopic scheme, which involves the photo-induced ionization of intermediate long-lived high-n ( n≥100) Rydberg states. The incorporation of this method by VUV photoexcitation to prepare intermediate high-n ( n≥100) Rydberg states is also expected to greatly increase the energy range of PFI studies. The availability of this array of laser- and synchrotron-based PFI methods, including PFI-PE, PFI-PEPICO, PFI-PI, PFI-ion-pair, and PIRI schemes, ensures an exciting and bright future for VUV photoionization and photoelectron studies in the new millennium.     

Synthesis,characterization and fluorescent properties of lanthanide complexes with two aryl amide ligands

Two aryl amide ligands, N-(p-tolyl)-2-(quinolin-8-yloxy)acetamide (L¹ ) and N-(4-chlorophenyl)-2-(quinolin-8-yloxy)acetamide (L² ), were synthesized. With these ligands, two series of lanthanide(III) complexes were prepared, Ln(L ⁿ )₂(NO₃)₃ (n = 1, 2; Ln = La, Sm, Eu, Gd, Dy), and characterized by the elemental analyses, molar conductivity, ¹H NMR spectra, IR spectra and TG-DTA. The fluorescence properties of the complexes and the triplet state energies of the ligands were studied in detail. In addition, the quantum yields of both Eu(III) complexes and Eu(L⁰)₂(NO₃)₃ [where L⁰ is N-(phenyl)-2-(quinolin-8-yloxy)acetamide] 1 Wu, WN, Yuan, WB, Tang, N, Yang, RD, Yan, L and Xu, ZH. 2006. Spectrochim. Acta A, 65: 912[Crossref], [Web of Science ®] , [Google Scholar] were calculated. The results indicate that among the lowest triplet energies (T) of the three ligands, that of L² is most suitable to the resonance level (⁵D₁) of Eu(III) ion. Furthermore, Eu(L²)₂(NO₃)₃ has the highest fluorescence intensity and quantum yield of the three Eu(III) complexes.     

Direct Observation of Transient Species Generated from Protonation and Deprotonation of the Lowest Triplet of p-Nitrophenylphenol

Photo-induced proton coupled electron transfer (PCET) is essential in the biological, photosynthesis, catalysis and solar energy conversion processes. Recently, \begin{document}$ p $\end{document}-nitrophenylphenol (HO-Bp-NO₂) has been used as a model compound to study the photo-induced PCET mechanism by using ultrafast spectroscopy. In transient absorption spectra both singlet and triplet states were observed to exhibit PCET behavior upon laser excitation of HO-Bp-NO₂. When we focused on the PCET in the triplet state, a new sharp band attracted us. This band was recorded upon excitation of HO-Bp-NO₂ in aprotic polar solvents, and has not been observed for \begin{document}$ p $\end{document}-nitrobiphenyl which is without hydroxyl substitution. In order to find out what the new band represents, acidic solutions were used as an additional proton donor considering the acidity of HO-Bp-NO₂. With the help of results in strong (\begin{document}$ \sim $\end{document}10\begin{document}$ ^{-1} $\end{document} mol/L) and weak (\begin{document}$ \sim $\end{document}10\begin{document}$ ^{-4} $\end{document} mol/L) acidic solutions, the new band is identified as open shell singlet O-Bp-NO₂H, which is generated through protonation of nitro O in \begin{document}$ ^3 $\end{document}HO-Bp-NO₂ followed by deprotonation of hydroxyl. Kinetics analysis indicates that the formation of radical \begin{document}$ \cdot $\end{document}O-Bp-NO₂ competes with O-Bp-NO₂H in the way of concerted electron-proton transfer and/or proton followed electron transfers and is responsible for the low yield of O-Bp-NO₂H. The results in the present work will make it clear how the \begin{document}$ ^3 $\end{document}HO-Bp-NO₂ deactivates in aprotic polar solvents and provide a solid benchmark for the deeply studying the PCET mechanism in triplets of analogous aromatic nitro compounds.     

Microwave Assisted Synthesis of a New Triplet Iridium(III) Pyrazine Complex

A new cyclometalated iridium(III) complex Ir(DPP)₃ (DPP=2,3-diphenylpyrazine) was pre-pared by reaction of DPP with iridium trichloride hydrate under microwave irradiation. The structure of the complex was confirmed by elemental analysis, ¹H NMR, and mass spec-troscopy. The UV-Vis absorption and photoluminescent properties of the complex were investigated. The complex shows strong ¹MLCT (singlet metal to ligand charge-transfer) and ³MLCT (triplet metal to ligand charge-transfer) absorption at 382 and 504 nm, respec-tively. The complex also shows strong photoluminescence at 573 nm at room temperature.These results suggest the complex to be a promising phosphorescent material.     

Spiroborate-Based Host Materials with High Triplet Energies and Ambipolar Charge-Transport Properties

Organic light-emitting diodes (OLEDs) receive considerable attention because of their commercial use in flat panel displays. Herein, highly efficient spiroborate-based host materials are reported for use in blue OLEDs. Our designed spiroborates ( SBOX ) were simple to synthesize and exhibited high triplet excitation energies, narrow S-T gaps, and balanced charge carrier mobilities. A blue OLED containing one of the designed spiroborates, SBON , as a host exhibited a high external quantum efficiency (27.6 %) and low turn-on voltage (3.7 V) compared to those observed using 3,3′-di(9H-carbazol-9-yl)-1,1′-biphenyl (17.6 % and 4.5 V, respectively), indicating their potential as host materials in OLEDs.     

Measurement of Photoionization Cross Sections of the Excited States of Titanium

Resonance-enhanced multiphoton ionization of the titanium atoms has been investigated in the 293 321 nm wavelength. We couple a laser-ablated metal target into a molecular beam to produce free atoms. Ions produced from photoionization of the neutral atoms are monitored by a home-built time-of-flight mass spectrometer. Photoionization cross sections of the excited states of Ti I were deduced from the dependence of the ion signal intensity on the laser intensity for photon energies close to the ionization threshold. The values obtained range from 0.2 Mb to 6.0 Mb. No significant isotope-dependence was found from measurements of the photoionization cross sections of ^46Ti, ^47Ti, and ^48Ti.