Anti-inflammatory dinuclear copper(II) complexes with indomethacin. Synthesis, magnetism and EPR spectroscopy. Crystal structure of the N,N-dimethylformamide adduct

Abstract

Veterinary anti-inflammatory Cu(II) complexes of indomethacin (1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid = IndoH), of the general formula [Cu2(Indo)4L2] (L = N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N-methylpyrrolidone (NMP), and water), were studied by zero-field and X-band EPR spectroscopies, electronic spectroscopy, magnetic measurements, and X-ray powder diffraction. The complexes are similar to Cu(II) acetate monohydrate, with a strong antiferromagnetic exchange interaction, J, ranging from -141 to -152 cm-1. Variable temperature magnetic susceptibility data for all of the complexes are similar, with the exception of a [Cu2(Indo)4(H2O)2] complex, which displays an unusual increase in magnetic moment with decreasing temperature from 50 to 10 K. The X-ray powder diffraction patterns of the DMF and DMA dimers show that they are isostructural. Two isostructural H2O complexes were synthesized from different methods yet displayed different variable temperature magnetic susceptibity data. All of the [Cu2(Indo)4L2] complexes crystallize in the triclinic space group P1̄. Single-crystal X-ray diffraction analysis of the DMF complex, [Cu2(Indo)4(DMF)2]· 1.6(DMF), shows that it is similar to the previously reported [Cu2(Indo)4(DMSO)2] with a Cu-Cu bond length of 2.630(1) Å, Cu-ORCOO of 1.960(4)-1.967(4) Å, and Cu-ODMF of 2.143(5) Å and crystal parameters a = 10.848(3) Å,b= 13.336(6) Å, c = 16.457(4) Å, α = 104.67(3)°, β= 100.94(2)°, and γ = 107.16(3)°. The X-ray structure of the DMF dimer does not exhibit strong intermolecular interactions due to the hydrophobic nature of the exterior. This may be important in facilitating its dissolution in micelles and transport through membranes. Show more