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61.
Pi-Tai Chou Ming-Zen Lee Chin-Yen Wel Guo-Ray Wu Lai Kuen Shek Daniel W. J. Kwong 《Photochemistry and photobiology》1999,70(5):745-750
The chemiluminescence of 1DLgO2 expelled from the UV photolysis of vanadium(V)-peroxo (VP) complexes in aqueous solution was observed for the first time. Using phenalenone photosensitization as a standard reference, the 1O2 quantum yields from the photolysis of 12 VP complexes were measured. No good correlation was found between the relative DNA-photocleavage activities and the 1O2 quantum yields of these complexes. This lack of correlation underscores the significant contribution of the complex-DNA binding interaction in determining the observed DNA-photocleavage activity of the complex. The small 1O2 quantum yields observed in these complexes were interpreted in terms of the minor 1O2 pho-toelimination channel relative to other more efficient relaxation processes. 相似文献
62.
Pi-Tai Chou Chau-Shuen Chiou Wei-Shan Yu Guo-Ray Wu Tai-Huei Wei 《Chemical physics letters》2003,370(5-6):747-755
The spectroscopy and dynamics of the low-lying triplet state of the proton-transfer tautomer in salicylaldehydes have been studied via internal heavy-atom effects coupled with a sensitive near-IR detecting system. For 3,5-diiodosalicylaldehyde a weak proton-transfer keto-tautomer phosphorescence was resolved with a maximum at 710 nm (τp1.8 μs, Φobs5.23×10−4) in a 77 K methylcyclohexane glass. The results, in combination with the time-resolved thermal lensing experiment, further deduced the triplet-state population yield and radiative decay rate to be 0.20 (298 K) and 3.12×102 s−1, respectively. Consequently, the energetics and dynamics of the triplet states during a proton transfer cycle are discussed in detail. 相似文献
63.
Tang KC Chang MJ Lin TY Pan HA Fang TC Chen KY Hung WY Hsu YH Chou PT 《Journal of the American Chemical Society》2011,133(44):17738-17745
Using 7-hydroxy-1-indanone as a prototype (I), which exhibits excited-state intramolecular proton transfer (ESIPT), chemical modification has been performed at C(2)-C(3) positions by fusing benzene (molecule II) and naphthalene rings, (molecule III). I undergoes an ultrafast rate of ESIPT, resulting in a unique tautomer emission (λ(max) ~530 nm), whereas excited-state equilibrium is established for both II and III, as supported by the dual emission and the associated relaxation dynamics. The forward ESIPT (normal to proton-transfer tautomer species) rates for II and III are deduced to be (30 ps)(-1) and (22 ps)(-1), respectively, while the backward ESIPT rates are (11 ps)(-1) and (48 ps)(-1). The ESIPT equilibrium constants are thus calculated to be 0.37 and 2.2 for II and III, respectively, giving a corresponding free energy change of 0.59 and -0.47 kcal/mol between normal and tautomer species. For III, normal and tautomer emissions in solid are maximized at 435 and 580 nm, respectively, achieving a white light generation with Commission Internationale de l'Eclairage (CIE) (0.30, 0.27). An organic light-emitting diode based on III is also successfully fabricated with maximum brightness of 665 cd m(-2) at 20 V (885 mA cm(-2)) and the CIE coordinates of (0.26, 0.35). The results provide the proof of concept that the white light generation can be achieved in a single ESIPT system. 相似文献
64.
A series of metal-metal quadruply bonded compounds [(tBuCO2)3M2]2(mu-TT) where TT = thienothiophenedicarboxylate and M = Mo, 1A, and M = W, 1B and [(tBuCO2)3M2]2(mu-DTT) where DTT = dithienothiophenedicarboxylate and M = Mo, 2A, and M = W, 2B, has been prepared and characterized by elemental analysis, ESI- and MALDI-TOF mass spectrometry and 1H NMR spectroscopy. Their photophysical properties have also been investigated by steady-state absorption as well as transient absorption and emission spectroscopy. The optimized structures and the predicted low energy electronic transitions were obtained by DFT and time-dependent DFT calculations, respectively, on model compounds. These results, in combination with the respective properties of the compounds [(tBuCO2)3M2]2(mu-BTh) (BTh = 2,5'-bithienyldicarboxylate, M = Mo, 3A, and M = W, 3B), allow us to make a comprehensive comparison of the fused (compounds 1A, 1B, 2A, and 2B) and the nonfused thienyl (compounds 3A and 3B) dicarboxylate bridged compounds of molybdenum and tungsten. The electrochemical studies show singly oxidized radical cations that are valence trapped on the EPR time-scale and are classified as Class 1 (M = Mo) or Class 2 (M = W) on the Robin and Day scale for mixed valence compounds. The new compounds exhibit intense metal to bridge ligand charge transfer absorption bands in the far visible and near IR (NIR) region. Both molybdenum and tungsten complexes show dual emission, but for molybdenum, the phosphorescence is dominant while for tungsten the emission is primarily fluorescence. Femtosecond transient absorption spectroscopy shows that the relaxation dynamics of the S1 states which have lifetimes of approximately 10 ps is dominated by intersystem crossing (ISC), leading to T1 states that in turn possess long lifetimes, approximately 70 micros (M = Mo) or 3 micros (M = W). These properties are contrasted with the photophysical properties of conjugated organic systems incorporating metal ions of the later transition elements. 相似文献
65.
Koshevoy IO Lin CL Hsieh CC Karttunen AJ Haukka M Pakkanen TA Chou PT 《Dalton transactions (Cambridge, England : 2003)》2012,41(3):937-945
A family of the diphosphines PPh(2)C(2)(C(6)H(4))(n)C(2)PPh(2) (n = 0-3), which possess a dialkynyl-arene spacer between the phosphorus atoms, was used for the synthesis of a series of bimetallic gold(I) complexes 1-7. Unlike the corresponding polynuclear Au(i) clusters, which show unique phosphorescence, 1-7 reveal dual emissions consisting of fluorescence and phosphorescence. The results are rationalized, in a semi-quantitative manner, by the trace (1-3) to zero (4-7) contribution of MLCT varying with the number of conjugated phenylene rings. As a result, unlike typical polynuclear Au(I) clusters with 100% triplet state population, the rate constant of the S(1)→T(1) intersystem crossing is drastically reduced to 10(9) s(-1) (4-7)-10(10) s(-1) (1-3), so that the fluorescence radiative decay rate can compete or even dominates. The drastic O(2) quenching of phosphorescence demonstrates the unprotected nature of the emission chromophores in 1-7, as opposed to the well protected, O(2) independent phosphorescence in most multimetallic Au(I) clusters. 相似文献
66.
[structure: see text] Ethynyl-linked benzofuran-naphthyridine compounds show high-yield fluorescence with solvatochromic properties. One of the compounds, ABAN, has successfully formed fluorescent organic nanoparticles (FONs), for which the photophysical properties such as the spectral features and intensity are remarkably different from those at the molecular level (solution) and in bulk material. The results are tentatively rationalized by the FONs inducing coplanarization of the benzofuran-naphthyridine molecule to extend its effective conjugation length and hence increase the oscillator strength. 相似文献
67.
Cheng CC Yu WS Chou PT Peng SM Lee GH Wu PC Song YH Chi Y 《Chemical communications (Cambridge, England)》2003,(20):2628-2629
A new series of pyridyl pyrazolate boron complexes 2a-e have been synthesized, in which 2a-c exhibit remarkable dual fluorescence properties due to the photoinduced electron transfer reaction. 相似文献
68.
Liu WH Wu IC Lai CH Lai CH Chou PT Li YT Chen CL Hsu YY Chi Y 《Chemical communications (Cambridge, England)》2008,(41):5152-5154
3,4-Ethylenedioxythiophene and bis[2-(2-methoxyethoxy)ethoxy]thiophene bridged donor-acceptor molecules for dye-sensitized solar cells have been synthesized, one of which achieved a solar-to-energy conversion efficiency of 7.3%, compared to 7.7% optimized for N719 dye. 相似文献
69.
Pi-Tai Chou Chen-Pin Chang John H. Clements Kuo Meng-Shin 《Journal of fluorescence》1995,5(4):369-375
The synthesis and photophysics of 4-formyl-4-N,N-dimethylamino-1,1-biphenyl are reported. The emission spectrum in various solvent polarities demonstrates solvatochromism, indicating that the fluorescence originates from an electronically excited species with a strong charge transfer character. The change in
[
max(absorption) –
max(emission)] varies from 1500 cm–1 inn-heptane to as much as 7500 cm–1 in acetonitrile. In protic solvents, the unusual excitation energy-dependent steady-state emission (red edge effect), resulting from solvent dielectric relaxation, was observed in media with a low viscosity. The large Stokes-shifted and high-yield fluorescence led to the observation of the efficient lasing action. The frequency tunability of the laser output is strongly solvent dependent, generating a new charge transfer laser dye in the blue-green region. 相似文献
70.
Yang SH Wu KL Chi Y Cheng YM Chou PT 《Angewandte Chemie (International ed. in English)》2011,50(36):8270-8274
Panchromatic sensitizers: A series of ruthenium(II) compounds was prepared that contain three thiocyanate ligands and a novel chelating terpyridine ligand. The latter (see picture: colors indicate orbital occupation) serves as an effective and versatile light-harvesting auxochrome. One compound has a solar conversion efficiency of up to 10.3?%. 相似文献