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Abstract
The synthesis, spectroscopic and magnetic properties of two new alkoxo-bridged dinuclear copper(II) complexes are described. Both compounds have the general formula [Cu(μ-OR)(L)2]2X2 · H2O, in which μ-OR = CH3O− or C2H5O−, L = 3-aminopyrazidine-2-carboxylic acid and X = . The title complexes consist of a dinuclear unit with bridging methoxo for [Cu(μ-OCH3)(L)2]2(NO3)2 · H2O (1) and bridging ethoxo for [Cu(μ-OC2H5)(L)2]2(NO3)2 · H2O (2) with two ligands linked to each copper via pyrazidine N atom, providing a square pyramidal CuN2O2 unit. Both compounds have been synthesized in a one-step reaction and characterized by elemental analysis, FTIR, ESR, electronic spectra and by room temperature magnetic moments. The compounds exhibit antiferromagnetic interaction at room temperature. The UV-vis spectra show three absorption bands, attributed to d–d transitions of copper, ligand → metal charge transfer and π → π*; or n → π*; transitions of ligand. The FTIR spectra indicate Cu2O2 ring vibration in 570–450 cm−1 range. Both complexes show a room temperature magnetic moment of about 1.50 B.M. per copper atom. The X-band electron spin resonance (ESR) studies indicate a weak half-field band, characteristic of the Cu(II)–Cu(II) dimer, observed at about 1600 gauss. The observation of this band strongly suggests that the hyperfine structure arises from a spin triplet species. The spectrum of frozen samples in DMF or in DMSO at liquid nitrogen temperature shows a typical Δm = 1 transition.
Acknowledgements
The authors would like to thank the Research Council of Arak University for financial support of this research. The authors also appreciate the Chemistry Institute and DAAD Organization at Chemnitz University in Germany for the services, facilities and physical measurements.