Synthesis and crystal structure of a binuclear maleatocopper(II) complex with phenanthroline

The title copper(II) complex Cu₂(C₄H₂O₄)₂(phen)₂]⋅4H₂O (phen = 1,10-phenanthroline) was prepared and its crystal structure was determined by X-ray diffraction method. The crystal belongs to space group C2/c with cell of a = 18.136(5), b = 12.505(5), and c = 14.617(5) Å, β = 103.440(5)^∘ and Z = 4. The Cu(II) atom assumes a square pyramidal coordination geometry with a longer Cu–O3 coordination distance 2.308(3) Å] in the apical direction. The carboxyl O3 atoms from two maleate dianion bridges two Cu(II) atoms to form the binuclear complex with a shorter Cu⋅sCu separation of 3.349(1) Å. The separations of 3.39(1) and 3.41(1) Å between parallel phen rings indicate the existence of aromatic stacking.