Controlling the ligating behaviour of biologically important p-hydroxybenzoate towards copper(II) by the use of nitrogen bases: Synthesis, characterization and single crystal X-ray structure determination of [trans-Cu(en)2(H2O)2](L1)2 · 2H2O and [cis-Cu(L

Two new copper(II) complex salts of composition [trans-Cu(en)2(H2O)2](p-hydroxybenzoate)2 · 2H2O (1) and [cis-Cu(p-hydroxybenzoate)2(3-picoline)2] (2) have been prepared. The newly synthesized complex salts have been characterized by elemental analyses, spectroscopic techniques (UV/visible, IR and EPR) and conductance measurements. The complex salt 1 crystallizes in the monoclinic space group P21/c having cell dimensions a = 11.8907 (2), b = 9.4443 (2), c = 10.8489 (3)Å, β = 100.340 (1)°, V = 1198.54 (5) Å3, Z = 2 and complex salt 2 crystallizes in the monoclinic space group P2/c having cell dimensions a = 9.9924 (3), b = 10.6862 (4), c = 11.6493 (3)Å, β = 108.588 (2)°, V = 1179.03 (6)Å3, Z = 2. X-ray structure determination revealed an ionic structure consisting of one complex cation [trans-Cu(en)2(H2O)2]2+, two [C7H5O3]− ions, two lattice water molecules in 1 and coordinated structure consisting of two p-hydroxybenzoate and two 3-picoline units attached to copper center in 2. In complex salt 1 central metal ion, copper(II) is coordinated to four nitrogen atoms, originating from two chelating ethylenediamine ligands and two oxygen atoms of two coordinated water molecules, showing distorted octahedral geometry around copper metal ion while in complex salt 2 Cu(II) is coordinated to four oxygen atom originating from two p-hydroxybenzoate (bidentate) and two nitrogen atoms of the 3-picoline molecule.