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

Abstract By the reactions of copper(II) nitrate with N -alkyliminodiacetamide derivatives, RN(CH 2 CONH 2 ) 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 ](NO 3 ) 2 ( 1 ), [Cu(Etimda) 2 ](NO 3 ) 2 ( 2 ), [Cu(Primda) 2 ](NO 3 ) 2 ( 3 ) and [Cu(Buimda) 2 ](NO 3 ) 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. R 2 4 (8), R 4 4 (12), R 2 1 (5), R 2 2 (8) and R 3 4 (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.