Incorporation of a sodium ion guest in the host of copper(II)-Schiff-base complexes: Structural characterization and magnetic study

Three copper(II) complexes, [CuL1], [CuL2] and [CuL3] where L1, L2 and L3 are the tetradentate di-Schiff-base ligands prepared by the condensation of acetylacetone and appropriate diamines (e.g. 1,2-diaminoethane, 1,2-diaminopropane and 1,3-diaminopropane, respectively) in 2:1 ratios, have been prepared. These complexes act as host molecules and include a guest sodium ion by coordinating through the oxygen atoms to result in corresponding new trinuclear complexes, [(CuL1)2Na(ClO4)(H2O)][CuL1] (1), [(CuL2)2Na(ClO4)(H2O)] (2) and [(CuL3)2Na(ClO4)(H2O)] (3) when crystallized from methanol solution containing sodium perchlorate. All three complexes have been characterized by single crystal X-ray crystallography. In all the complexes, the sodium cation has a six-coordinate distorted octahedral environment being bonded to four oxygen atoms from two Schiff-base complexes of Cu(II) in addition to a perchlorate anion and a water molecule. The copper atoms are four coordinate in a square planar environment being bonded to two oxygen atoms and two nitrogen atoms of the Schiff-base ligand. The variable temperature susceptibilities for complexes 1–3 were measured over the range 2–300 K. The isotropic Hamiltonian, H^=g1βHS1+g2βHS2+J12S1S2+g3βHS3 for complex 1 and H^=g1βHS1+g2βHS2+J12S1S2 for complexes 2 and 3 has been used to interpret the magnetic data. The best fit parameters obtained are: g1 = g2 = 2.07(0), J = −1.09(1) cm−1 for complex 1, g1 = g2 = 2.06(0), J = −0.55(1) cm−1 for complex 2 and g1 = g2 = 2.07(0), J = −0.80(1) cm−1 for 3. Electrochemical studies displayed an irreversible Cu(II)/Cu(I) one-electron reduction process.

Three Cu(II) complexes, [CuLn] where Ln (n = 1−3) are three tetradentate di-Schiff-base ligands prepared by the condensation of acetyl acetone and diamines (1,2-diaminoethane, 1,2-diaminopropane and 1,3-diaminopropane, respectively), on crystallization from methanol containing NaClO4, give three sodium salt adducts having general formula [(CuLn)2 Na(ClO4)H2O]. Here, the [CuLn] units act as a host molecule and include guest sodium cation by bridging through the oxygen atoms of the ligand to form the tri-nuclear adducts.Figure optionsDownload as PowerPoint slide