Assembly of trinuclear and tetranuclear building units of Cu ~(2+) towards two 1D magnetic systems: Synthesis and magneto-structural correlations

摘要

Two new 1D coordination polymers, [Cu _3(μ _3-OH)(ppk) _3(μ-N(CN) _2)(OAc)] _n (1) and {[Cu _4(pdmH) _2(pdm) _2(μ _2-OH)(H _2O)]·ClO _4} _n (2) based on two different blocking ligands phenyl-2-pyridylketoxime (ppk) and pyridine-2,6-dimethanol (pdmH 2) have been synthesized and were characterized by X-ray single crystal structural analysis. In compound 1, the hydroxido-bridged trinuclear core, {Cu _3(μ _3-OH)(ppk) _3(OAc)}, acts as secondary building units and are connected by the N(CN) _2 - anions resulting in a one dimensional (1D) coordination polymer. The 1D coordination chains undergo π-π interactions giving rise to a 3D supramolecular framework. In compound 2, tetrameric [Cu _4(pdmH) _2(pdm) _2(H _2O)] ~(2+) cores are linked via hydroxido groups forming a zigzag 1D coordination chain where non-coordinated ClO _4 - ions are intercalated between the chains. Variable temperature magnetic susceptibility study of 1 suggests that Cu(ii) ions in the trinuclear Cu 3(μ 3-OH) cores are antiferromagnetically coupled with J = -459.7 cm ~(-1) and g = 2.11 and the trinuclear cores are further weakly coupled antiferromagnetically (zj′ = -5.25 cm ~(-1)) through the N(CN) 2 - bridging ligand. Investigation of the magnetic properties of 2 reveals that Cu(ii) ions are coupled antiferromagnetically in the tetranuclear core with J = -27.1 cm -1 and g = 2.17; the Cu ~(II) _4 building units are further coupled antiferromagnetically with zj′ = -9.65 cm ~(-1). The experimental magnetic behaviours of 1 and 2 are correlated by first principle DFT calculations which provide a qualitative understanding of the origin of antiferromagnetic interactions in both cases.