Experimental and theoretical investigation of the molecular and electronic structure of 3-ethoxy-4-isopropylaminocyclobut-3-ene-1,2-dione

SÜLEYMANOĞLU N., USTABAŞ R., Alpaslan Y. B., EYDURAN F., Ocak İskeleli N.

SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, vol.96, pp.35-41, 2012 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 96
  • Publication Date: 2012
  • Doi Number: 10.1016/j.saa.2012.04.083
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.35-41
  • Keywords: Squarmonoesteramides, Crystal structure, FT-IR and NMR spectroscopy, Electronic absorption spectra, DFT calculations, 3-Cyclobuthene, DENSITY-FUNCTIONAL THEORY, SQUARIC ACID, EFFICIENT IMPLEMENTATION, CONDENSATION PRODUCTS, HETEROCYCLIC UREAS, ENERGIES, DERIVATIVES, CONTINUUM, AMIDE, ESTER
  • Ondokuz Mayıs University Affiliated: Yes


The title compound, 3-ethoxy-4-isopropylaminocyclobut-3-ene-1,2-dione (EIAC) has been synthesized and characterized by NMR, FT-IR, UV-vis spectroscopy and single-crystal X-ray diffraction. The H-1 NMR spectra were recorded at 300 K and 315 K in CDCl3 to determine syn/anti conformers of the compound EIAC. Density functional theory (DFT) calculations, optimized geometrical parameters, vibrational frequencies and chemical shift values of syn/anti conformer in CDCl3 have been performed at B3LYP/6-311G(d) level, and compared with the experimental data. The values provided with the calculations support the experimental data of the compound EIAC. The presence of N-H center dot center dot center dot O type intermolecular H bond can be perceived from the difference between experimental calculations and results of FT-IR and NMR calculations. In addition, B3LYP/6-311G(d) basis set has been used to calculate the molecular electrostatic potential, frontier molecular orbitals and electronic absorption spectra. HOMO-LUMO electronic transition of 5.12 eV is derived from the contribution of the bands n -> sigma* or pi -> pi*. FT-IR, NMR and X-ray spectral results and additionally DFT calculations exhibit that the compound EIAC exists in keto-enamine tautomeric form. The experimental H-1 NMR spectra recorded at 300 K and 315 K and theoretical H-1 NMR data indicate that the compound EIAC is in syn conformer. (C) 2012 Elsevier B.V. All rights reserved.