Heterometallic coordination polymers based on dipeptide schiff base Cu(II) metalloligand: synthesis, structures, and magnetic properties

Three new heterometallic coordination polymers formulated as {[Ca(CuL)(H2O)(5)]center dot H2O}(n) (1), [Sr(CuL)(H2O)(2)](n) (2), and [Ba(CuL)(H2O)(4)](n) (3) have been obtained by reaction of a rigid metalloligand [CuL](2-) (H4L = N-5-sulfosalicylideneglycylglycine) with the corresponding alkaline earth metal cations M2+ (M = Ca, Sr or Ba). Their crystal structures are determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses and IR spectra. The coordination preferences of the alkaline earth metal cations are found to have pronounced effects on the structural topologies. Complex 1 has a distorted ladder-like one-dimensional (1D) structure. In complex 2, Sr(II) ions link metalloligands [CuL](2-) via the sulfonate and carbonyl oxygen atoms to generate a three-dimensional (3D) framework. Complex 3 is arranged in a 3D framework formed by the linkage of copper(II) and barium(II) via carboxylate and sulfonate bridges. Variable-temperature magnetic susceptibility studies indicate that all the complexes exhibit weak antiferromagnetic interactions between the Cu(II) paramagnetic centers.