XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
120
T9: O–4
DFT and TD-DFT studies of camptothecin aggregation in solutions
Martin Breza
1
1
Department of Physical Chemistry, Slovak Technical University, Radlinskeho 9, SK-81237
Bratislava, Slovakia, e-mail: martin.breza@stuba.sk
Camptothecin,
(S)-4-ethyl-4-hydroxy-1H-pyrano[3‘,4‘:6,7]-indolizino-[1,2-b]-quinoline-
3,14-(4H,12H)-di-one (CPT), is a potent anticancer drug targeting intracellular topoisomerase I.
Experimental UV/Vis spectrum of the biologically active CPT lactone form (Fig. 1) in water
exhibits two strong (λ
1
= 369 nm and λ
2
= 354 nm of comparable heights) and one weak (λ
3
= 334
nm) spectral bands in the problematic 300–400 nm region. According to TD-DFT//B3LYP/6-
31G* calculations of CPT in water solutions, the HOMO → LUMO transition at 367 nm and
the HOMO-1 → LUMO transition at 329 nm reproduce quite well the experimental λ
1
and λ
3
bands, respectively. The existence of the λ
2
band has been explained by the formation of one or
more hydrogen bonds between the D ring C=O site with one or more water molecules [1].
In our previous study [2] we have presented UV/Vis spectra of CPT in DMSO solutions.
Despite vanishing water content the λ
2
absorption band was by ca 20% higher than the λ
1
one.
Based on TD-DFT//DFT/cc-pVDZ studies using B3LYP and B97D DFT functionals of CPT
dimers in various solutions, the λ
2
absorption band might be explained by the formation of head-
to-tail oriented CPT dimers which are held together by π-π inter-actions only. In the next steps
higher H-aggregates may be formed as well.
The aim of our study is to test this idea by means of TD-DFT//DFT/cc-pVDZ calculations of
head-to-tail oriented (CPT)
n
model systems, n = 1 – 4, in DMSO and water solutions. Solvent
effects are approximated by IEFPCM version of the polarizable continuum model. The results of
B3LYP, B3LYP-D, CAM-B3LYP, B97D and wB97XD DFT functionals are compared.
Fig. 1. Molecular structure of CPT in neutral lactone form with standard ring notation.
Keywords: Geometry optimization; Solvent effect; Electron spectra
Acknowledgment
Financial support of H2020-NMP-2014-2015/H2020-NMP-2015-two-stage project No. 685817 (HISENTS)
is appreciated. Calculations were performed in the Computing Centre of the Slovak Academy of Sciences
using the supercomputing infrastructure acquired in projects ITMS 26230120002 and 26210120002 (Slovak
infrastructure for high-performance computing) supported by the Research & Development Operational
Programme funded by the ERDF.
References
[1] N. Sanna, G. Chillemi, L. Gontrani, A. Grandi, G. Mancini, S. Castelli, G. Zagotto, C. Zazza, V.
Barone, A. Desideri, J. Phys. Chem. B 113 (2009) 5369.
[2] D. Dvoranova, M. Bobenicova, S. Soralova, M. Breza, Chem. Phys. Let. 580 (2013) 141.
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
121
T9: O–5
Vibrational structure of compounds derived from biomass
Izabela Czekaj
1
1
Faculty of Chemical Engineering and Technology, Cracow University of Technology,
Warszawska 24, 31-155 Kraków, Poland, e-mail: iczekaj@chemia.pk.edu.pl
Major challenge of society research is to build fuels and chemical intermediates from
available and renewable materials that do not compete with food crops for water or fertilizer,
such as wood biomass or agricultural waste. The urgent needs for a more sustainable production
of chemicals from renewable feedstock, like biomass, have caused intensive research efforts.
However, the production of chemicals from biomass is very challenging process due to chemical
composition diversity. Lignin, cellulose and hemicellulose are the three main biopolymers of
wood biomass, whose build cell walls of plants. From the lignin mainly phenols could be
obtained, while cellulose and hemicellulose are sources of variety of sugars.
In the present work computational study of most dominant cellulose and lignin
compartments and their vibrational structure have been investigated using Density Functional
Theory method. Full geometry optimization of compartments has been done using StoBe code
with cluster model and non-local functional (RPBE) approach. The calculations of the
vibrational frequencies were performed with harmonic approximations as well as an
anharmonicity fit in the Morse potential function, as implemented into StoBe code. In case of
lignin the calculations include three different precursors based on cinamyl alcohol: coumaryl
alcohol, coniferyl alcohol as well as sinapyl alcohol. In case of cellulose, the glucose and its
derivatives (such as lactic acid, hydroxymethylfurfural or dihydroxyacetone) have been
considered. Presented theoretical investigations for variety of lignocellulose derived compounds
give the possibility of obtaining theoretical VBD (Vibrations Basis Database) for experimental
spectra interpretation (Figure 1). Such database could be further used in preliminary
composition assessment of biomass derived substrates, which will be discussed in details.
Fig. 1. A schematic representation of research on lignocellulose: experimental and theoretical.
Keywords: lignocellulose; DFT; vibrational structure; reaction mechanism; zeolites
Acknowledgment
This project has received funding from the European Union’s Horizon 2020 research and innovation
programme under the Marie Skłodowska-Curie grant agreement No. 665778. (Polonez-1
2015/19/P/ST4/02482).
Dostları ilə paylaş: |