XIV
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International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
116
T8: O–5
Synthesis and characterization of complexes of dibenzo-15-crown-5
(2,3,8,9-dibenzo-1,4,7,10,13-pentaoxacyclopentadec-2-ene) with
potassium halides: Macromolecular assemblies held by noncovalent
interactions for recognition of biologically important alkali metal ion
Namrata Ghildiyal
1
1
Department of Chemistry, H.N.B. Garhwal University, Srinagar-Garhwal, India, e-mail:
namoo_doon@yahoo.co.in
A series of complexes of dibenzo-15-crown-5 (DB15C5) with potassium halides (KX; X= F
-
, Cl
-
, Br
-
and I
-
) was synthesized in acetonitrile and characterized by IR, UV, ESI-MS,
1
H NMR,
13
C NMR and
13
C-
1
H HSQC NMR techniques. The alkali metal ion coordinates to the oxygen
donor atoms of the macrocyclic ring by ion-dipole interactions. The counterion is held to the
coordinated cation by electrostatic forces of attraction. The cation recognition property for
potassium ion by the crown ether, dibenzo-15-crown-5, was investigated by recording the
variation in its fluorescence spectra upon complexation. The stability of these complexes in
chloroform was also confirmed from the studies. The complexes display 2:1, ligand: metal ion,
stoichiometry. These complexes make good models to study noncovalent interactions between
biologically important alkali metal ions and a polar binding site. Synthesis of fluorescent sensors
for metal ion recognition is a versatile and growing field of current research [1, 2].The
substitution of benzo groups in the crown ether,15-crown-5, imparts fluorescent property to the
crown ether. Initial fluorescence studies on KF complex of DB15C5 (Ia) were carried out in
acetonitrile. Fluorescence quenching was observed. However when the solvent was changed to
chloroform, fluorescence enhancement was observed for the complex, Ia. This enhancement of
fluorescence intensity is called complexation enhanced fluorescence. The excitation wavelength
was kept at 270 nm. The benzene ring of DB15C5 (I) showed fluorescence emission λ
max
at 305
nm. A red shift of 8 nm was observed in emission λ
max
for KF complex, Ia. The fluorescence of
benzo crown ethers originates from π-π* transition in the benzene unit. The S
0
-S
1
state energies
undergo changes due to variation in electronic charge densities developed by the interaction of
the cation with the oxygen donor atoms adjacent to the aromatic ring [3, 4].
Fig. 1. Complexation enhanced fluorescence in host-guest assembly
Keywords: dibenzo-15-crown-5; potassium; noncovalent; cation recognition; fluorescence
Acknowledgment
The author wishes to acknowledge SAIF centers in India namely IISC Bangalore for providing 1H NMR and 13C
NMR spectra, IIT- Bombay, Mumbai for mid–IR and some ESI-mass spectra, SAIF, NEHU, Shillong for a few
ESI–mass results, STIC- Cochin where CHN analysis of samples were carried out and Department of Physics, H.
N. B. Garhwal University, Srinagar-Garhwal, Uttarakhand, India for recording fluorescence spectra of the
samples. The author also acknowledges financial assistance provided by UGC and UGC-DAE, Indore Centre,
Indore, India during the research. The supervisor and co-supervisor, Prof. Geeta Joshi nee Pant and Prof. M.S.M.
Rawat are also acknowledged.
References
[1] B. Daly, J. Ling, A.P. de Silva, Chem. Soc. Rev. 44 (2015) 4203.
[2] M.C.-L. Yeung, V.W.-W. Yam, Chem. Soc. Rev. 44 (2015) 4192.
[3] S. Samanta, P.S. Sardar, S.S. Maity, A. Pal, M.B. Roy, S. Ghosh, J. Chem. Sci. 119 (2007) 175.
[4] B. Valeur, I. Leray, Coord. Chem. Rev. 205 (2000) 3.
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
117
T9: O–1
FT-IR and FT-Raman spectra of the anti-HIV nucleoside analogue d4T
(Stavudine). Solid state simulation by DFT methods
M. Alcolea Palafox
1,2
, D. Kattan
1,2
, and A. Nils Kristian
2
1
Departamento de Química-Física I, Facultad de Ciencias Químicas, Universidad Complutense,
Madrid-28040, Spain, e-mail: alcolea@ucm.es
2
Nofima AS – the Norwegian Institute of Food, Fisheries and Aquaculture Research, Osloveien 1,
1430 Ås, Norway
A theoretical and experimental vibrational study of the anti-HIV d4T (stavudine or Zerit)
Nucleoside Analogue was carried out, Fig. 1. Its bio-activity can be explained due to the absence
of the hydroxyl group (O3’-H group) [1–3]. The predicted spectra in the two most stable
conformers of d4T in the biological active anti-form were determined at three DFT levels,
especially by B3LYP/6-31G(d,p), B3LYP/6-311++G(2d,p) and X3LYP/6-31G(d,p).
Comparison of the conformers with those of the natural nucleos–ide thymidine was carried out.
The calculated spectra were scaled by using the linear scaling equation procedure (LSE) [4] and
the polynomic equation. The crystal unit cell of the different polymorphism forms were
simulated through dimer forms by using DFT methods. The scaled spectra of these dimer forms
were compared with the FT-IR and FT-Raman spectra recorded in the solid state. All the
vibrational bands were analyzed and assigned to different normal modes of vibration.
Fig. 1. Structure of d4T.
Fig. 2. Optimized dimer forms of d4T.
The most important findings of this study are the following: 1.- In the isolated state the
stability trend of the five first optimum conformers is the same by several methods and levels.
The spectra corresponding to the monomers C1 and C3 are very similar, with the exception of
the modes corresponding to the O5’-H groups, due to their different orientations. 2.- The
simulated spectra are in accordance to the experimental ones. The stretching bands
corresponding to N-H modes in dimer G and I (Fig. 2) appear at lower wavenumbers than those
corresponding to monomer C1 and dimer V. This fact is due to these G and I dimers are
stabilized by two N-H···O=C intermolecular H-bonds. 3.- The scaled wavenumbers with the
polynomic equations slightly improved the values that with LSE. The scaled values with the
X3LYP method are slightly better than by B3LYP.
Keywords: d4T; scaling; simulated spectra
Acknowledgment
MAP wish to thank to BSCH-UCM PR26/16 for financial support.
References
[1] M. Alcolea Palafox, N. Iza, J. Molec. Struct. 1028 (2012) 181.
[2] M. Alcolea Palafox, N. Iza, Phys. Chem. Chem. Phys. 12 (2010) 881.
[3] M. Alcolea Palafox, N. Iza, M. de la Fuente, R. Navarro, J. Phys. Chem. B 113 (2009) 2458.
[4] M. Alcolea Palafox, V. K. Rastogi, Spectrochim. Acta A 58 (3) (2002) 411.
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