Determination of the structures of antiinflammatory copper(II) dimers of indomethacin by multiple-scattering analyses of X-ray absorption fine structure data.

Copper K-edge X-ray absorption spectroscopic (XAS) measurements were recorded for the veterinary antiinflammatory 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), and [Cu2(OAc)4(OH2)2] at room temperature and 10 K. The bond lengths and bridging O−C−O angles of the dimeric Cu(II) cage (Cu2O10C8) obtained from the multiple-scattering (MS) fitting of the X-ray absorption fine structure (XAFS) using a centrosymmetric model of [Cu2(Indo)4(DMF)2] gave Cu···Cu = 2.62(2) A, mean Cu−OAc = 1.95(2) A, Cu−OL = 2.15(2) A, bridging O−C−O = 125(1)°, Cu displacement from plane 0.19 A compared with the XRD data Cu···Cu = 2.630(1) A, mean Cu−OAc = 1.959 A, Cu−OL = 2.143(5) A, bridging O−C−O angles = 123.2(5)°, Cu displacement from plane 0.20 A. The excellent agreement between the XAFS- and XRD-derived data allowed the structures...