H-Bonds, π-Stacking and (Water)O-H/π Interactions in (μ4-EDTA)Bis(Imidazole) Dicopper(II) Dihydrate

We synthesized and studied the polymeric compound {[Cu-2(mu(4)-EDTA)(Him)(2)] 2H(2)O}(n) (1). The single-crystal structure is reported along with an in depth characterization of its thermal stability (TGA), spectral properties (FT-IR, Vis-UV and RSE), and magnetic behavior. The crystal consists of infinite 2D-networks built by centrosymmetric dinuclear motifs, constructed by means of a bridging anti,syn-carboxylate group from each asymmetric unit. Each layer guides Him ligands toward their external faces. They are connected by intermolecular (Him)N-H center dot center dot center dot O(carboxylate) bonds and antiparallel pi-pi stacking between symmetry related pairs of Him ligands, and then pillared in a 3D-network with parallel channels, where disordered water molecules are guested. About half of the labile water is lost from these channels over a wide temperature range (r.t. to 210 degrees C) before the other one, most strongly retained by the cooperating action of (water)O1-H(1A)center dot center dot center dot O(carboxylate) and (water) O1-H(1B)center dot center dot center dot pi(Him) interactions. The latter is lost when organic ligands start to burn. ESR spectra and magnetic measurements indicated that symmetry related Cu(II) centers connected by the bridging carboxylate groups behave magnetically not equivalently, enabling an exchange interaction larger than their individual Zeeman energies.

Automated summary

In this study, a polymeric compound was synthesized and studied, with in-depth characterization of its structure, thermal stability, spectral properties, and magnetic behavior. The compound exhibited complex structural features, with a loss of water molecules over a certain temperature range and specific intermolecular interactions. ESR spectra and magnetic measurements revealed non-equivalent behavior of the Cu(II) centers connected by carboxylate groups, leading to an exchange interaction larger than their individual Zeeman energies.