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Copper(II) complexes with N-alkyliminodiacetamide ligands. Preparation, structural, spectroscopic and DFT studies and biological evaluation

By the reactions of copper(II) nitrate with N- alkyliminodiacetamide derivatives, RN(CH2CONH2)2 (Rimda ; R = Me (methyl), Et (ethyl), Pr (propyl) and Bu (butyl)), four new water-soluble copper(II) complexes were synthesized, namely [Cu(Meimda)2] (NO3)2 (1), [Cu(Etimda)2](NO3)2 (2), [Cu(Primda)2] (NO3)2 (3) and [Cu(Buimda)2](NO3)2 (4). The complexes were characterized by infrared and UV/Vis spectroscopy and thermal analysis (TG/DTA). The molecular and crystal structures of 1 and 4 were determined by X-ray crystallography. The octahedral coordination environment around the copper(II) ion consists of two O, N, O'- tridentate N-alkyliminodiacetamide ligands and the complexes are trans-isomers with fac- configuration of the chelators. Various hydrogen bond ring motifs e. g. R24(8), R44(12), R21(5), R22(8) and R34(16) were established in the crystal structures of 1 and 4. The molecular geometry and infrared spectra of the complex cations [Cu(Meimda)2]2+, [Cu(Etimda)2]2+, [Cu(Primda)2]2+ and [Cu(Buimda)2]2+ were also studied by DFT calculations using BP86, B3LYP and B97-D computational models. Their calculated spectra and molecular geometries agree very well with the experimental results. The complexes were tested for possible antibacterial and antifungal activity on bacteria (Escherichia coli and Staphylococcus aureus) and fungi (Candida albicans), respectively, and showed low or negligible activity. The complexes also showed relatively high toxic effects on Lemna minor L. (duckweed), a model aquatic organism used to test the toxic effects of metal ions.

Copper(II) complexes ; Iminodiacetamide ligands ; X-ray crystallography ; DFT calculations ; Antimicrobial activity ; Lemna test

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