[aqhl]

Anh Nguyễn Chí Sơn, BM Hóa Lý, vừa ủng hộ thư viện ChemVN Master thesis (cả 2 bản tiếng Anh và Tiếng Việt) cùng 3 bài báo trên các journal. Nick trên 4rum của anh Sơn là ncson, hiện nay anh tạm thời quy ẩn, nên nhờ mình up hộ lên 4rum. Tháng 8 năm nay anh Sơn sẽ sang học PhD bên USA (University of California, Berkeley). Chúc anh Sơn thành công và đóng góp nhiều paper nữa cho ChemVN. BM cho các bài báo vào folder Hóa Tính toán nhé.

Master Thesis: Linear Dichroism Spectroscopic and Theoretical Investigations of the compound Emodin

Author: Nguyen Chi Son
Roskilde University, Denmark
Issue date: 2004

Abstract: The LD UV-VIS spectra of Emodin (1,3,8-trihydroxy-6-methyl anthraquinone) in stretched PE and PVA have been recorded and analysed. Orientation factor of the observed electronic transition were determined through stepwise reduction. The electronic transition moment direction of observed transition is determined by the assumption of molecule has Cs symmetry. The observed electronic transition moment directions belong to the “long” and “short” molecular symmetry axes. This information leads to the conclusion that Emodin still remembers the exited states of parent molecule, Chrysazin. When changing from PE solvent to PVA solvent, almost electronic transitions have small red shift by 200 – 500 cm-1, except a strong band at 44500 cm-1 don’t move anymore, the electronic transition moment directions of observed transitions still remain.

The LD UV-VIS spectra of Emodin anion in stretched PVA also have been recorded and analysed. The electronic transitions of anion are completely different the electronic transitions of neutral molecule because of redistribution of negative charge. The observed electronic transition moment directions do not belong to the “long” and “short” molecular symmetry axes.

The TD-DFT calculation, B3LYP/6-31G+(d,p)//B3LYP/6-31G(d,p), has a good agreement to the assignment of observed transitions in both transitions and its moment directions.

Các bài báo trên tạp chí quốc tế:

1, A computational study of halomethyllithium carbenoid mixed aggregates with lithium halides and lithium methoxide

Lawrence M. Pratt, Shayla Merry, Son Chi Nguyen, Phung Quan, B.T. Thanh

Tetrahedron, Volume 62, Issue 47, 20 November 2006, Pages 10821-10828

Abstract
Density functional theory calculations were used to examine the formation of lithium halide and lithium alkoxide mixed aggregates with halomethyllithium carbenoids. These mixed aggregates may be the important intermediates in carbenoid reactions where lithium halides are formed as byproducts, or when the mixture has been exposed to small amounts of air. The calculations showed that in the gas phase and in THF solution, mixed dimers, trimers, and tetramers may coexist with free lithium carbenoids, depending on the lithium salt. The calculations also indicated that mixed aggregates may influence the activation free energies of cyclopropanation reactions of lithium carbenoids.

2, Electronic states of emodin and its conjugate base. Synchrotron linear dichroism spectroscopy and quantum chemical calculations

Nguyen Chi Son, Bjarke Knud Vilster Hansen, Søren Vrønning Hoffmann and Jens Spanget-Larsen

Submitted to Physical Chemistry Chemical Physics (PCCP)

Abstract: The electronic transitions of emodin (1,3,8-trihydroxy-6-methyl-9,10-anthraquinone, E) and its conjugate base (3-oxido-6-methyl-1,8-dihydroxy-9,10-anthraquinone, Ecb) were investigated by UV-Vis linear dichroism (LD) spectroscopy on molecular samples aligned in stretched poly(vinylalcohol). The experiments in the UV region were performed with synchrotron radiation, thereby obtaining significantly improved signal to noise ratio compared with traditional technology. The LD spectra provided information on the polarization directions of the observed transitions, thereby leading to resolution of otherwise overlapping, differently polarized transitions. The investigation was supported by PCM-TD-DFT calculations; a mixed discrete/continuum solvation model was applied in the case of the strongly solvated Ecb anion. The calculations led to excellent agreement with the observed transitions, resulting in the assignment of at least 7 excited electronic states in the region 15000 – 50000 cm-1 for each species. A recent assignment of the absorption spectrum of E to a superposition of contributions from 9,10- and 1,10-anthraquinoid tautomeric forms was not supported by the results of the present investigation.

3, Calculation of the solvation state of organolithium compounds: Effects of basis sets and electron correlation methods.

Lawrence M. Pratt, Darrel Jones, Andrea Sease, Donta Busch, Emmanuel Faluade, Son C. Nguyen, Bui T. Thanh

Accepted in International Journal of Quantum Chemistry, 2008

Abstract: The free energies of successive solvation of organolithium species by THF ligands was examined by DFT and ab initio methods. The popular B3LYP method using three different basis sets, and the MPW1PW91/6-31+G(d) DFT method, were compared to MP2 calculations, and when possible, to the G3MP2 method. The DFT methods generally underestimated the exergonic free energies of solvation compared to MP2 and G3MP2.