X-ray diffraction, spectroscopic and DFT studies of 1-(4-bromophenyl)-3,5-diphenylformazan
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TRUCTURE OF ORGANIC COMPOUNDS
XRay Diffraction, Spectroscopic and DFT Studies of 1(4Bromophenyl)3,5diphenylformazan1 H. Tezcana, N. Tokayb, G. Alpaslanc, and A. Erdönmezd a
Department of Chemistry, Faculty of Education, Gazi University, 06500 TeknikokullarAnkara, Turkey b Department of Chemistry, Faculty of Science, Hacettepe University, 06532 BeytepeAnkara, Turkey c Department of Medical Services and Techniques, Vocational School of Health Services, Giresun University, 28200 Giresun, Turkey d Department of Physics, Faculty of Science and Art, Ondokuz May i s University, 55139 KurupelitSamsun, Turkey email: [email protected] Received March 7, 2013
Abstract—The crystal structure of 1(4bromophenyl)3,5diphenylformazan was determined by Xray single crystal diffraction technique. The crystals are orthorhombic, a = 23.0788(9), b = 7.9606(3), c = 18.6340(12) Å, Z = 8, sp. gr. Pbca, R 1 = 0.074. The structure was also examined using the densityfunctional theory. Its structure stability, and frontier molecular orbital components were discussed and the results were compared with Xray and spectral results. The maximum absorbtion peaks of the UVvis spectrum of the compound have been calculated using the timedependent den sityfunctional theory. It was found a good agreement between the calculated and experimental max imum absorption wavelength. DOI: 10.1134/S1063774513080099
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INTRODUCTION
Various formazans were synthesized, and their structural properties and the effects of substituents on the maximum absorption wavelength (λ max) val ues were investigated [1–6]. Formazans are coloured compounds due to π–π* transitions. Field of uses for formazans depends on this fea ture. Because of this, their spectral properties are very important. Formazans form tetrazolium salts on oxidation [7]. Tetrazolium salts are reduced back to formazans by the enzymes in the cell and stain tissue. That’s why formazan/tetrazolium sys tem is classified as a marker of vitality [8]. Forma zans are used to screen anticancer drugs to deter mine their activities on tumor cell and also to determine of sperm viability [9, 10]. Previously, the crystal structures of several formazans were 1 The article is published in the original.
determined by Xray single crystal diffraction technique [11–15]. Additionally, quantum chemi cal calculations of some formazans have been reported recently [16–18]. The utilization of formazans depends on their colourness which is related to their maximum absorption wavelengths (λ max). It is known that the absorption spectrum is related to the molecular structure. In order to support the spectroscopic data on structures of formazans, both Xray single crystal and the quantum chemical calculation investigations should be carried out. That is why this study is mainly focused on molecular structure of the formazan. In our previous study, 1substituted3,5diphe nylformazans were synthesized by the reaction between benzaldehydephenylhydrazone and diaz onium cations (Scheme).
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