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)2(bpetha)(H2O)]·2H2O}n (1), {[Cu(L)2(bpetha)]·5H2O}n (2), and [Cu(L)2(bpetha)]n (3), where bpetha = 1,2-bis(4-pyridyl)ethane, L1 = acetato, L2 = lactato, and
L3 = 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, π···π stacking and/or C−H···π 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.