Caffeine in copper(II) complexes: crystal and molecular structure of di(caffeine)tetrakis(naproxenato)dicopper(II)

The crystal and molecular structure of di(caffeine)tetrakis(naproxenato)- dicopper(II) was determined by direct method and Fourier techniques. The structure was refined by full-matrix least-squares methods to a weighted R factor of 0.0705. The compound is binuclear with square pyramidal geometry at each copper(II) centre. The two copper(II) atoms are bridged by four carboxylate groups, while the apical ligands are caffeine molecules. The Cu–Cu distance is 2.649(2) Å. The Cu atoms are displaced by 0.217 Å from the plane containing four oxygen atoms bonded to Cu towards the apical caffeine molecules. The structural data are compared with those found in similar [Cu2(RCOO)4(caf)2] (caf = caffeine) complexes.