• Title/Summary/Keyword: Theoretical chemistry

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Hydrogen Bonding in Aromatic Alcohol-Water Clusters: A Brief Review

  • Ahn, Doo-Sik;Jeon, In-Sun;Jang, Sang-Hee;Park, Sung-Woo;Lee, Sung-Yul;Cheong, Won-Jo
    • Bulletin of the Korean Chemical Society
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    • v.24 no.6
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    • pp.695-702
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    • 2003
  • Recent experimental and theoretical advances on the aromatic alcohol-water clusters are reviewed, focusing on the structure of the hydrogen bonding between the alcoholic OH group and the binding water molecules. The interplay of experimental observations and theoretical calculations for the elucidation of the structure is demonstrated for phenol-water, benzyl alcohol-water, substituted phenol-water, naphthol-water and tropolone -water clusters. Discussion is made on assigning the role (either proton-donating or -accepting) of the hydroxyl group by measuring the shifts of infrared frequency of the OH stretching mode in the cluster from that of bare aromatic alcohol for the experimental determination of the cluster structure.

Theoretical and Experimental 31P NMR and ESI-MS Study of Hg2+ Binding to Fenitrothion

  • Koo, In-Sun;Ali, Dildar;Yang, Ki-Yull;vanLoon, Gary W.;Buncel, Erwin
    • Bulletin of the Korean Chemical Society
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    • v.30 no.6
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    • pp.1257-1261
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    • 2009
  • We present the theoretical and experimental results of $^{31}P$ NMR and low energy CID MS/MS study of $Hg^{2+}$ binding to fenitrothion (FN). The calculated $^{31}P$ NMR chemical shifts order for FN with $Hg^{2+}$ complex is in good agreement with experimental $^{31}P$ NMR chemical shifts order. The experimental and theoretical $^{31}P$ NMR study of organophosphorus pesticide with $Hg^{2+}$ gives to important information for organophosphorus pesticide metal complexes. ESI-MS and low energy CID MS/MS experiments of $Hg^{2+}$-FN complexes combined with accurate mass measurements give insight into the metal localization and allow unambiguous identification of fragments and hydrolysis products.

Behavior of Poisson Bracket Mapping Equation in Studying Excitation Energy Transfer Dynamics of Cryptophyte Phycocyanin 645 Complex

  • Lee, Weon-Gyu;Kelly, Aaron;Rhee, Young-Min
    • Bulletin of the Korean Chemical Society
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    • v.33 no.3
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    • pp.933-940
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    • 2012
  • Recently, it has been shown that quantum coherence appears in energy transfers of various photosynthetic lightharvesting complexes at from cryogenic to even room temperatures. Because the photosynthetic systems are inherently complex, these findings have subsequently interested many researchers in the field of both experiment and theory. From the theoretical part, simplified dynamics or semiclassical approaches have been widely used. In these approaches, the quantum-classical Liouville equation (QCLE) is the fundamental starting point. Toward the semiclassical scheme, approximations are needed to simplify the equations of motion of various degrees of freedom. Here, we have adopted the Poisson bracket mapping equation (PBME) as an approximate form of QCLE and applied it to find the time evolution of the excitation in a photosynthetic complex from marine algae. The benefit of using PBME is its similarity to conventional Hamiltonian dynamics. Through this, we confirmed the coherent population transfer behaviors in short time domain as previously reported with a more accurate but more time-consuming iterative linearized density matrix approach. However, we find that the site populations do not behave according to the Boltzmann law in the long time limit. We also test the effect of adding spurious high frequency vibrations to the spectral density of the bath, and find that their existence does not alter the dynamics to any significant extent as long as the associated reorganization energy is changed not too drastically. This suggests that adopting classical trajectory based ensembles in semiclassical simulations should not influence the coherence dynamics in any practical manner, even though the classical trajectories often yield spurious high frequency vibrational features in the spectral density.

Two-color Transient Grating Spectroscopy of a Two-level System

  • Kwak, Kyoung-Won;Cho, Min-Haeng;Fleming, Graham R.;Agarwal, Ritesh;Prall, Bradley S.
    • Bulletin of the Korean Chemical Society
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    • v.24 no.8
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    • pp.1069-1074
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    • 2003
  • A theoretical description and experimental demonstration of homodyne-detected two-color transient grating (2-C TG) signal are presented. By treating the coupled bath degrees of freedom as a collection of harmonic oscillators and using a short-time expansion method, approximated nonlinear response functions were obtained. An analytic expression for the two-color transient grating signal was obtained by carrying out relevant Gaussian integrals. The initial rising and decaying parts of the 2-C TG signal is shown to be critically dependent on the ultrafast inertial component of the solvation correlation function. The experimental results confirm the predictions of the theoretical model.