The novel catena-poly-mu-orotatobis(butylamine)copper(II), [Cu(mu-HOr)(ba)(2)](n) (1), and diaqua(orotato)copper(II), [Cu-2(HOr)(2)(H2O)(4]) (2), complexes have been prepared and characterized by elemental analysis, magnetic measurements, FT-IR spectroscopy, EPR spectroscopy, thermal analysis and X-ray diffraction. Both complexes crystallize in the monoclinic space group, C2/c in 1 and P2(1)/n in 2. In the complexes, the copper(H) ion is chelated by a deprotonated pyrimidine nitrogen atom and a carboxylate oxygen atom of the orotate. While the coordination sphere around Cu(II) is completed by two N atoms from butylamine groups and a carboxylic O atom in the axial position from a neighboring molecule in 1, the square-planar environment of Cu(II) is completed by two water atoms and one axial position is occupied by the carbonyl oxygen atom from the symmetry related molecule in 2. The coordination sphere should be described as a square pyramid and (4+1)-geometry in 1 and 2, respectively. While complex I shows a polymeric arrangement, compound 2 has a dimeric arrangement. The non-covalent Cu(II)-pi binding force is very important for stabilizing the crystal structure of 2. The thermal decomposition of the complexes has been predicted by the help of thermal analysis (TG, DTG and DTA). (C) 2009 Elsevier Ltd. All rights reserved.