A reversible structural transformation of the basic copper hydroxides Cu-2(OH)(3)[8-((p-(phenylazo)phenyl)oxy)octanoate] occurs as a result of soaking in hot methanol and acetonitrile. X-ray diffraction patterns indicate that the organic layer in the material exhibits an interdigitated monolayer structure in hot methanol, while it does a membrane-like bilayer structure in acetonitrile. The monolayer phase is paramagnetic down to 3 K, while the bilayer phase shows a weak ferromagnetism below 10.8 K. The reversible packing change of the organic guest molecule is accompanied by drastic modification in the magnetic properties of the inorganic layer.