Supramolecular architectures and magnetic behavior of coordination polymers from copper(II) carboxylates and 1,2-bis(4-pyridyl)ethane as a flexible bridging ligand

The combination of the flexible bpetha ligand with different copper(II) carboxylates in a 1:1 molar ratio leads to the formation by self-assembly of three new one-dimensional (1D) polymeric compounds: {[Cu(L-1)(2)(bpetha)(H2O)]center dot 2H(2)O}(n) (1), {[Cu(L-2)(2)(bpetha)]center dot 5H(2)O}(n) (2), and [Cu(L-3)(2)(bpetha)](n) (3), where bpetha = 1,2-bis(4-pyridyl)ethane, L-1 = acetato, L-2 = lactato, and L-3 = 2-methyllactato. These compounds were characterized by elemental analysis, infrared and electronic absorption spectroscopy, and single-crystal X-ray diffraction. X-ray structural analysis revealed that the polymeric compounds created by the bridging bpetha ligand present different 1D structural motifs: linear chains for 1, zigzag chains for 2, and ladderlike chains for 3. Weak interactions such as hydrogen bonding, pi center dot center dot center dot pi stacking and/or C-H center dot center dot center dot pi interactions join the polymeric chains to generate three-dimensional networks. Variable temperature magnetic susceptibility measurements reveal very weak antiferromagnetic coupling between the copper(II) centers in the three compounds.