No abstract

Two new coordination polymers {[MII(HL)(EtOH)2](ClO4)}n, where MII= Co (1) and Ni (2), were synthesized using a Schiff base ligand H2L = 2-{[(E)-1H-imidazol-4-ylmethylidene}amino]benzoic acid. Compounds 1 and 2 are isostructural, presenting a one-dimensional helical chain arrangement. Each metal center has a distorted octahedral geometry bridged by a syn-anti carboxylate group. The fitting of the magnetic susceptibility data in the 1.8–300 K range shows weak intrachain antiferromagnetic interaction for 1 and weak ferromagnetic interaction for 2, with the presence of zero-field splitting (zfs) phenomenon in both compounds. Theoretical calculations confirm the weak intrachain coupling in both compounds, but with a zfs phenomenon dominant at lower temperatures. A positive value for the zfs is also obtained, with a major spin–orbit coupling component.

The synthesis of coordination compounds based on 3d cations has been of great interest not only for their various structures and topologies but also for their possible applications as functional materials in areas such as gas storage/adsorption, catalysis, magnetism, luminescence, among others. [1][2][3] Two new coordination polymers based on Co II and Ni II ylmethylidene]amino}benzoic acid), were synthesized using a new Schiff base ligand. Compounds 1 and 2 are isostructural presenting a one-dimensional helical chain arrangement and crystallizing in a P21/n monoclinic space group. A hexacoordinated cation with an MN2O4 environment is present in the cationic fragment [M(HL)(EtOH)2] + being the charge balanced by a ClO4anion. Furthermore, the carboxylate group of HL-ligand is also acting as syn-anti bridge, producing the assembly of the [M(HL)(EtOH)2] + fragments, thus generating a cationic chain growing through the b axis with an intercation M•••M distance of 5.1257(13) Å and 5.164(4) Å for 1 and 2, respectively. The M-Ox distances are in the range of 2.060(3) Å to 2.136(4) Å for 1 and 1.988(3) to 2.107(4) Å for 2. Meanwhile, the M-Ny distances are 2.076(3) Å and 2.139(3) Å for 1 and 2.041(4) Å and 2.080(4) Å for 2. The resulting MN2O4 moiety presents an elongated octahedral geometry with higher bond distances in the axial position corresponding to the EtOH molecules. Magnetic susceptibility characterization in the 1.8-300 K range reveals intrachain antiferromagnetic interactions for 1 and ferromagnetic interaction for 2 with the presence of the zero-field splitting phenomenon in both compounds.