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π-π Interaction in Fullerenes
Published in Mihai V. Putz, New Frontiers in Nanochemistry, 2020
Lemi Turker, Caglar Celik Bayar
A supramolecular complex of a novel porphyrin tripod, TPZn3, was formed with a fullerene derivative containing a pyridine moiety, PyC60 (Takai et al., 2010). TPZn3 acted as a donor while PyC60 acted as an acceptor in the complex. The photodynamics of the supramolecular complex (TPZn3-PyC60) was investigated by femtosecond and nanosecond laser flash photolysis measurements in nonpolar media, toluene, and dichlorobenzene. It was concluded that PyC60 was captured inside the cavity of TPZn3 not only by an axial coordination bond formed between Zn2+ and the pyridine moiety but also π-π interactions. According to the DFT B3LYP/3-21G(d) calculation, the distance of an axial coordination bond (Zn-N) was found to be 2.00 Å. The minimum distances between the other porphyrin planes and fullerene were found to be 2.58 and 2.63 Å, respectively. These values of spatial separation suggested possible π-π interactions.
Magnetic Field Effect on Photoinduced Interactions: Its Implications in Distance-Dependent Photoinduced Electron Transfer Between CT-DNA and Metal Complex
Published in Tanmoy Chakraborty, Lalita Ledwani, Research Methodology in Chemical Sciences, 2017
Banabithi Koley Seth, Samita Basu
In nanosecond flash photolysis setup having an Nd:YAG laser, the sample has been excited by 266 nm laser light (10 mJ) with full width at half maximum (FWHM) ≈ 8 ns. Absorption of light from a pulsed Xe lamp (150 W) at right angle to the laser beam has been used to detect the newly generated transient species in the system. The photomultiplier (R928) output has been fed into an Agilent Infiniium oscilloscope (DSO8064A, 600 MHz, 4 Gs/s), and the data have been transferred to a computer through IYONIX software. The MFEs on the transient absorption spectra have been explored by passing direct current through a pair of electromagnetic coils placed inside the sample chamber and the strength of MF has been varied from 0.0 to 0.08 T. All the samples have been deaerated properly by argon gas before experiments to avoid quenching. No degradation of the samples has been observed during the experiment. The software Origin 8.0 has been used for curve fitting.
Application of commercially available fluorophores as triplet spin probes in EPR spectroscopy
Published in Molecular Physics, 2019
Kerstin Serrer, Clemens Matt, Monja Sokolov, Sylwia Kacprzak, Erik Schleicher, Stefan Weber
The positive difference absorption at around 560 nm in the transient absorption spectrum of EB is in good agreement with data from a study that was devised to investigate photoinduced electron transfer between EB and duroquinone [45]. Similarly, our data from RB are in accord with previously published values from a laser-flash photolysis examination [46]: a ground-state bleaching between 480 and 580 nm was observed together with three maxima around 390, 470 and 600 nm that were assigned to the excited triplet state. Transient absorption data on AT12 is, to the best of our knowledge, unavailable. When comparing the lifetimes of the three dyes in water (Table 1), it turns out that EB and RB have comparable values of around 5.5 µs, whereas the one of AT12 is roughly three times larger. The former finding can be expected from the similar chemical structures of EB and RB. The triplet-state lifetimes of both EB and RB are decreased by a factor of two when the temperature is increased by about 15 K, see Table 1. Moreover, the triplet-state lifetimes of all three dye molecules strongly depend on the solvent; an overview of previously published data with our own results is presented in Table 4.
Spectral analyses of trans- and cis-DOCO transients via comb spectroscopy
Published in Molecular Physics, 2018
Thinh Q. Bui, P. Bryan Changala, Bryce J. Bjork, Qi Yu, Yimin Wang, John F. Stanton, Joel Bowman, Jun Ye
The use of time-resolved spectroscopy for the study of elementary reaction processes, a key driver in the fundamental understanding of chemical reaction mechanisms and molecular dynamics [1], has experienced revolutionary transformation beginning from Norrish and Porter’s seminal flash photolysis experiment to ultrafast ‘femtochemistry’ by Ahmed Zewail [2]. The development of ultrafast lasers served as a cornerstone for this transition. Taking a different path, high-resolution spectroscopy and precision measurement have motivated the development of stable lasers and frequency-domain approaches. The great merge of these two scientific paths led to the eventual development of the optical frequency comb [3]. The frequency comb possesses broad spectral bandwidth and high spectral resolution in the frequency domain, making it a suitable light source for high-resolution spectroscopy in what has been termed ‘direct frequency comb spectroscopy’ (DFCS) [4]. The versatility of DFCS has more recently been extended to studies of high-resolution spectroscopy of large molecules [5,6] and chemical kinetics [7–10]. Continuing efforts are focused towards construction of high power frequency comb sources that cover 5–10 µm for future advances in high-resolution molecular spectroscopy and dynamics [11].
Naphthalimide derivatives containing benzyl-sulfur bond as cleavable photoinitiators for near-UV LED polymerization
Published in Journal of Sulfur Chemistry, 2020
Xiuyuan Hu, Jia Yu, Shengling Jiang, Yanjing Gao, Fang Sun
Laser flash photolysis experiments of NABSs were carried out with a Spectra − Physics Quanta – Ray Q-switched nanosecond Nd/YAG laser at λexc = 355 nm (10 ns pulses; energy reduced down to 10 mJ) and an analyzing system consisted of a ceramic xenon lamp, an Acton SpectraPro SP-2300 spectrometer, a monochromator, a fast photomultiplier and a transient digitizer (Princeton Instruments PI-MAX 4). Liquid samples with 10−5 M of NABSs in nitrogen-saturated acetonitrile were contained in a quartz cell with an optical path length of 1 cm.