Copper Coordination Polymers Based on Single-Chain or Sheet Structures Involving Dinuclear and Tetranuclear Copper(II) Units: Synthesis, Structures, and Magnetostructural Correlations

摘要

Reactions between the potentially pentadentate (N_20_3), trianionic double Schiff-base ligand 2,6-bis[[(2-hydro_xyethyl)imino]methyl]-4-methylphenol (H_3L) and Cu(CH_3CO_2)_2 or Cu(C1O_4)_2, in the presence of NaN_3, give novel coordination polymers with chain {[Cu_2(H_2L)(N_3)_3]_2. H_2O}_n (1) or sheet [Cu_2(H_2L)(N_3)_3]_n (2) and [Cu_2(HL) (N_3)]_n[ClO_4]__n (3) structures, respectively. These clusters are comprised of repeating dinuclear units (1) or their dimers (2 and 3). In these compounds, H_3L acts as a tridentate (N_2O) monoanionic (1), tetradentate (ON_2O) monoanionic (2), or pentadentate (O_3N_2) dianionic (3) ligand. Compound [Cu_2(HL)(N_3)_2(H_2O)] _ 0.5CH_3OH (4) formed from the reaction of Cu(CH_3CO_2)_2 with H_3L under reflux, which did not afford crystals suitable for X-ray studies. X-ray structure determinations have revealed that the basic building block in 1-3 comprises two copper centers bridged through one __-phenolate O atom from H_2L~- or HL~(2-) and one __-azido(N1,N1) ion. Compounds 1-3 unveil three different ways in which this Cu_2 basic unit may be organized in the crystalline phase at the supramolecular level through a variety of bridging interactions involving additional azide ligands or alkoxide groups from the side arms of the ligand H_3L. Bulk magnetization measurements have served to demonstrate that the magnetic interactions are completely dominated by the strong antiferromagnetic coupling occurring within the Cu2 building block, with coupling constants ranging from 330 to 560 cm-1 (in the H= _ JS_1 S_2 convention). These results together have been incorporated with data from the few related copper dimers reported exhibiting the same bridging pattern into a study aimed at extracting possible magnetostructural correlations within this Cu_2 unit. An earlier predicted correlation between Jand the angle formed by the phenoxide bridge and the Cu_2 core has been identified for the first time.