Synthesis, spectroscopic and thermal characterization of quinoxaline metal complexes

Abstract

KEYWORDSThe coordination behaviour of the quinoxaline ligand with N and O donation sites, derived from 3-(2-oxo-2-p-tolylethyl)quinoxalin-2(1H)-one (HL), towards some transition metal ions namely Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) are reported. The metal complexes are characterized based on elemental analyses, IR, 1 H NMR, solid reflectance, magnetic moment, molar conductance and thermal analyses (TG, DTG and DTA). The ionization constants of the quinoxaline ligand as well as the stability constants of its metal chelates are calculated spectrophotometrically at 25 o C and ionic strength = 0.1 M (1M NaCl). The chelates are found to have octahedral structure. The ligand and its chelates are subjected to thermal analyses and the different activation thermodynamic parameters are calculated from their corresponding DTG curves to throw more light on the nature of changes accompanying the thermal decomposition process of these compounds. The biological activity of the synthesized ligand and its metal complexes also are screened against the desert locust Schistocerca gregaria (Forsk) (Orthoptera-Acrididae) and its adult longevities. They showed remarkable biological activity. Quinoxaline Transition metal complexes Spectroscopy Thermal analyses DTA/TG Biological activity

Quinoxaline, its derivatives and applications: A State of the Art review

“…Several studies have been described, concerning synthesis and biological activity of a large amount of quinoxalines and 1,4-di-Noxide quinoxaline derivatives, where compounds such as 7-chloro-3-(p-substituted)-phenylaminoquinoxaline-2-carbonitrile-1,4-di-N-oxide, 6,7-dichloro-2-ethoxycarbonyl-3-methylquinoxaline-1,4-di-N-oxide and 3-acetamide-6,7-dichloroquinoxaline-2-carbonitrile-1,4-di-N-oxide derivatives have been shown to possess M. tuberculosis growth inhibition values from 99 to 100% [21,27]. However, it is observed that the lack of the two N-oxide groups lead to the loss of the antimycobacterial activity [27,28].…”

Metal based drugs: design, synthesis and in-vitro antimicrobial screening of Co(II), Ni(II), Cu(II) and Zn(II) complexes with some new carboxamide derived compounds: crystal structures of N-[ethyl(propan-2-yl)carbamothioyl]thiophene-2-carboxamide and its copper(II) complex

“…This in turn, propose tetrahedral geometry for the Co(II) complexes. This is also supported by magnetic moment values (3. ), thus showing their non-electrolytic nature 34 . The magnetic moment values of Co(II) complexes were found in the range of 3.78-3.94 B.M, expected for three unpaired electrons and are in agreement with their tetrahedral geometry 35 .…”

Metal-based ethanolamine-derived compounds: a note on their synthesis, characterization and bioactivity

“…The electronic spectra of Co(II) complexes generally showed 45 three absorption bands in the region 8650-8790, 17 523-17 800 and 29 805-29 841 cm À1 which may be assigned to 4T 1 g!4T 2 g(F), 4T 1 g!4A 2 g(F) and 4T 1 g!4Tg(P) transitions respectively, and are suggestive of octahedral geometry around the Co(II) ion. The electronic spectral data of Ni(II) complexes showed 46 …”