Molecular structure and vibrational spectra of 2-Ethoxymethyl-6-ethyl-2,3,4,5-tetrahydro-1,2,4-triazine-3,5-dione, a potential chemotherapeutic agent, by density functional methods

https://doi.org/10.1016/j.saa.2014.06.053Get rights and content

Highlights

  • IR, Raman spectra and NBO analysis were reported.

  • The wavenumbers are calculated theoretically using Gaussian09 software.

  • The wavenumbers are assigned using PED analysis.

  • The geometrical parameters are in agreement with XRD data.

Abstract

In this work, the vibrational spectral analysis was carried out using FT-IR and FT-Raman spectroscopy for 2-Ethoxymethyl-6-ethyl-2,3,4,5-tetrahydro-1,2,4-triazine-3,5-dione, which is a potential chemotherapeutic agent derivative. Theoretical calculations were performed by density functional methods. The complete vibrational assignments of the wavenumbers were made on the basis of potential energy distribution. The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with the observed spectra. The frontier orbital energy gap and related properties of the molecule illustrates the high reactivity of the title compound. The first order hyperpolarizability, dipole moment and polarizability are also calculated. Stability of the molecule arising from hyper-conjugative interactions and charge delocalization has been analyzed using natural bond orbital analysis. Molecular electrostatic potential map is also constructed. The calculated geometrical parameters are in agreement with the XRD results.

Introduction

1,2,4-Triazine-3,5(2H,4H)-diones (6-azauracils) represent an important class of biologically-active heterocyclic compounds. Several 1,2,4-triazine-3,5-diones showed antiviral [1], [2], [3], antimicrobial [4], [5], [6], [7], anti-inflammatory activities [8], [9], antimalarial [10], anticancer [11], [12], [13], [14] and antiulcer [15] activities. The title compound was synthesized as a potential antimicrobial agent. It was prepared by treatment of silylated 6-ethyl-1,2,4-triazine-3,5(2H,4H)-dione with chloroethyl ether in the presence of cesium iodide [7]. 1,2,4-triazine molecule is an aza-analogue of pyrimidine. 1,2,4-triazine and its derivatives belong to an important class of hetero aromatic compounds and they exhibit various interesting biochemical properties [16], [17]. Derivatives of 1,2,4-triazine present important core in many natural [18], [19] and synthetic [20], [21] biologically active compounds [22]. These hetero cycles easily undergo different substitution reactions and ring transformation [23], [24] that makes them convenient precursors for the synthesis of other hetero aromatic compounds. The single crystal XRD study of the title compound was reported by El-Brollosy et al. [25]. The present study describes the electronic properties and vibrational spectra of the title compound (molecular formula C8H13N3O3), with the hope that the results of present study would be helpful in future synthesis of more potent chemotherapeutic analogues. The energies, degrees of hybridization, populations of the lone electron pairs of oxygen, energies of their interaction with the anti-bonding orbital of the benzene ring and the electron density distributions and E(2) energies have been calculated by NBO analysis using DFT method to give clear evidence of stabilization originating from the hyper conjugation of various intra-molecular interactions. There has been growing interest in using organic materials for nonlinear optical devices, functioning as second harmonic generators, frequency converters, electro optical modulators etc., because of the large second order electric susceptibilities of organic materials. Since the second order electric susceptibility is related to first hyperpolarizability the search for organic chromophores with large first hyperpolarizability is fully justified.

Section snippets

Experimental details

The title compound was synthesized according to the reported protocol [7] and was re-crystallized from ethanol. The 1,2,4-traizine ring of the title compound C8H13N3O3 is nearly planar. The imino group is hydrogen bond donor to the exocylic O atom at the 5-position of an adjacent molecule, the Nsingle bondH⋯O hydrogen bond generating a chain parallel to the b axis [25]. The FT-IR spectrum (Fig. 1) was recorded using KBr pellets on a DR/JASCO FT-IR 6300 spectrometer, with a spectral resolution 4 cm−1 and

Computational details

Calculations of the title compound were carried out with Gaussian09 software [26] program using B3PW91/6-31G(d)(6D,7F) and B3LYP/6-31G(d)(6D,7F) basis sets to predict the molecular structure and vibrational wavenumbers. Calculations were carried out with Becke’s three parameter hybrid model using the Lee–Yang–Parr correlation functional (B3LYP) method. Molecular geometries were fully optimized by Berny’s optimization algorithm using redundant internal coordinates. Harmonic vibrational

IR and Raman spectra

The calculated (scaled) wavenumbers and observed IR, Raman bands and assignments are given in Table 2. The stretching mode of NH group is generally rive rise to bands [30], [31] in the range 3500–3300 cm−1. For the title compound the NH stretching mode is observed at 3425 cm−1 in the IR spectrum, 3445 cm−1 in the Raman spectrum and theoretical value is 3451 cm−1 (B3LYP). Nsingle bondH group show bands at 1510–1500, 1450–1250 and 740–730 cm−1 [32]. According to literature, if Nsingle bondH is a part of a closed ring [33],

Conclusion

FT-IR, FT-Raman and DFT quantum chemical calculations studies were performed on 2-Ethoxymethyl-6-ethyl-2,3,4,5-tetrahydro-1,2,4-triazine-3,5-dione, in order to identify the structure and vibrational features. On the basis of experimental results and potential energy distribution calculations, assignments of all the fundamental vibrational wavenumbers were done. A good correlation between the scaled wavenumbers and observed values was obtained for the title molecule. The NBO analysis shows

Acknowledgements

The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for funding this work through the Research Group Project No. RGP-VPP-274. The authors are thankful to University of Antwerp for access to the University’s CalcUA supercomputer cluster.

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