Synthesis, and structural characterization of mixed ligand copper(II) complexes of N,N,N′,N'-tetramethylethylenediamine incorporating carboxylates

Abstract Two ternary copper(II) complexes of N,N,N′,N'-tetramethylethylenediamine (tmen = C 6 H 16 N 2 ) with benzoic acid and p -aminobenzoic acid, having the formula [Cu(tmen)(BA) 2 (H 2 O) 2 ] ( 1 ), and [Cu(tmen)( p ABA) 2 ]. 1/2 CH 3 OH ( 2 ) {(Where BA 1−  = benzoate 1− (C 6 H 5 CO 2 1− ), p ABA 1−  =  p -aminobenzoate 1- ( p -H 2 NC 6 H 5 CO 2 1− )} have been prepared and characterized by elemental combustion analysis, Uv–Visible spectroscopy, FT-IR spectroscopy, thermal, and single crystal X-ray diffraction analyses. The complex 1 is a monomer with distorted octahedral geometry. In its CuN 2 O 4 chromophore, the Cu(II) centre is coordinated by two N atoms of a symmetrically chelating tmen ligand, by two carboxylate-O atoms from two monodentate benzoate 1− anions, and by two apical aqua-O atoms, which define the distorted octahedral structure. The complex 2 is a monomer with a distorted square planar coordination geometry. In CuN 2 O 2 chromophore, tmen is coordinated to Cu(II) ion in a chelating bidentate fashion, while the two p -aminobenzoate 1- anions coordinate to Cu(II) centre through their carboxylate-O atoms in a monodentate manner, forming a square planar structure. The observed difference between asymmetric ѵ as (OCO) and symmetric ѵ s (OCO) stretching IR vibrations of the carboxylate moieties for 1 and 2 is 220 cm −1 and 232 cm −1 , respectively, which suggests monodentate coordination mode (Δν OCO>200) of the carboxylate groups to Cu(II) ion. Thermogravimetric studies of 1 indicates removal of two water molecules at 171 °C, elimination of a tmen upto 529 °C and of two benzoate groups upto 931 °C. In tga curve of 2, methanol is lost upto 212 °C, while tmen is lost from 212 to 993 °C. The antibacterial activities of these new compounds against various bacterial strains were also investigated.