Coordination polymers containing a pyrazole-based ligand and 4,4′-bipyridine as a spacer: enhancing the family of nonzero-dimensional compounds featuring single-ion magnetic behavior

Abstract

Two coordination polymers with molecular formula 1∞[M(L)2(4,4′-bipy)(H2O)2], where M stands for CoII (1) or CuII, (2), and L = 5-amino-1-phenyl-1H-pyrazole-4-carboxylate ligand were obtained by slow solvent diffusion and characterized by spectroscopic techniques, single crystal and powder X-ray diffraction, magnetic measurements, and DFT calculations. Magnetic studies carried out for complex 1 showed the key role played by the zero-field splitting and the experimental fit parameters were correlated to CASSCF calculations. Moreover, AC magnetic measurements for 1 revealed a field-induced slow relaxation of the magnetization and a single-ion magnet behavior. For the copper-containing polymer, two kinds of magnetic interactions were observed in the magnetic data and confirmed by using broken-symmetry DFT calculations: (i) ferromagnetic interchain coupling mediated by the hydrogen-bonds and (ii) antiferromagnetic intrachain interaction through the 4,4′-bipy ligand.