Copper complexes with new oxaaza-pendant-armed macrocyclic ligands: X-ray crystal structure of a macrocyclic copper(II) complex

Abstract

The synthesis of new oxaaza macrocyclic ligands (2-4) derived from O 1 ,O 7 -bis(2-formylphenyl)-1,4,7-trioxaheptane and functionalized tris(2-aminoethyl)amine are described. Mononuclear copper(II) complexes were isolated in the reaction of the corresponding macrocyclic ligand and copper(II) perchlorate. The structure of the [Cu(2)](ClO 4 ) 2 complex was determined by X-ray diffraction analysis. The copper(II) ion is five-coordinated by all N 5 donor atoms, efficiently encapsulated by the amine terminal pendant-arm, with a trigonal-bipyramidal geometry. The complexes are further characterized by UV-Vis, IR and EPR studies. The electronic reflectance spectra evidence that the coordination geometry for the Cu(II) complexes is trigonal-bipyramidal with the ligands 1 and 2 or distorted square-pyramidal with the ligands 3 and 4. The electronic spectra in MeCN solutions are different from those in the solid state, which suggest that some structural modification may occur in solution. The EPR spectrum of powder samples of the copper complex with 2 presents axial symmetry with hyperfine split at g // with the copper nuclei (I = 3/2), which is characteristic of weakly exchange coupled extended systems. The EPR parameters (g // = 2.230, A // = 156 · 10 À4 cm À1 and g^= 2.085) indicate a d x 2 Ày 2 ground state. The EPR spectra of the complexes with ligands 3 and 4 show EPR spectra with a poorly resolved hyperfine structure at g // . In contrast, the complex with ligand 2 shows no hyperfine split and a line shape which was simulated assuming rhombic g-tensor (g 1 = 2.030, g 2 = 2.115 and g 3 = 2.190).

A Five-Coordinate Copper(II) Complex Constructed from Sterically Hindered 4-Chlorobenzoate and Benzimidazole: Synthesis, Crystal Structure, Hirshfeld Surface Analysis, DFT, Docking Studies and Antibacterial Activity

“…Complex 1 exhibited a broad d-d absorption at 746 nm (13405 cm −1 ). The appearance of a broad absorption is attributed to the d→d electronic transition, which corresponds to those of the distorted square pyramidal geometry [52,58]. This suggests that the CuN 2 O 3 chromophore keeps its identity in the solution state as well.…”

“…The differences in V as (OCO) and V s (OCO) are 210 and 242 cm −1 , which are indicative of the asymmetric bidentate mode of coordination and monodentate mode of coordination of the carboxylato groups to the center Cu(II) [57]. The peaks at 547 and 439 cm −1 are assigned to Cu-O and Cu-N [58] for the p-chlorobenzoate moiety and stretching band for benzimidazole. These illustrations correspond to the crystal structure of Complex 1.…”

Macrocyclic coordination chemistry

“…Copper complexes were produced of novel pendant armed mixed oxa-aza macrocyles, L 51 . 86 The X-ray structure of the mononuclear copper(II) complex with the bis-amine pendant arm shows coordination by all five nitrogen donors in a trigonal bipyramidal geometry.…”

Synthesis and characterization of nickel(II) complexes with three potentially hexadentate Schiff-base ligands and polyamines: X-ray crystal structure determination of one nickel(II) complex

“…Metalloenzymes have several functions, including redox as in superoxide dismutase-like activity [1][2][3][4][5][6], structural and catalytic roles [7][8][9][10][11].…”