Halo and azido copper(II) coordination polymers featuring the gem-diolate forms of di-2-pyridyl ketone

The reactions of di-2-pyridyl ketone, (py)2CO, with [Cu2(O2CMe)4(H2O)2] in the presence of NaN3, HCl and HBr have led to the isolation of complexes {[Cu8{(py)2CO2}4(N3)6(O2CMe)2]·2MeCN·H2O}∞ (1·2MeCN·H2O), [Cu2{(py)2C(OH)O}Cl3]∞ (2) and [Cu2{(py)2C(OH)O}Br3]∞ (3), respectively, where (py)2CO22- and (py)2C(OH)O− are the dianion and the monoanion of the gem-diol form of (py)2CO. Complex 1·2MeCN·H2O is an 1D coordination polymer consisting of centrosymmetric [Cu8{(py)2CO2}4(N3)6(O2CMe)2] cluster units linked through weakly coordinated azido bridges. The (py)2CO22- groups adopt the η1:η2:η2:η1:μ4 coordination mode, while the N3- ions behave as η2:μ and η1: η2:μ3 ligands. The isostructural compounds 2 and 3 are also 1D coordination polymers consisting of {Cu2{(py)2C(OH)O}X3}2 units (X=Cl, Br) linked through double halo bridges. The (py)2C(OH)O- ligand adopts the tridentate, bis-chelating η1:η2: η1:μ mode. A common feature in the three complexes is the presence of interchain H-bonding interactions which result in the formation of 2D networks. The magnetic properties of 1–3 have been studied by variable-temperature dc magnetic susceptibility and variable-field magnetization techniques. The analyses of the magnetic data were performed taking into account only the dominant exchange interactions within dinuclear subunits. The intradinuclear exchange interactions have been found to vary from strongly and moderately antiferromagnetic in 1 to ferromagnetic in 2 and 3. This work demonstrates the flexibility, versatility and synthetic potential of combining (py)2CO with carboxylate and azido or halo ligands.

The synthetic investigation of the general [Cu2(O2CMe)4(H2O)2]/(py)2CO/X− reaction system, where (py)2CO is di-2-pyridyl ketone and X− is Cl−, Br− or N3−, has led to 1D coordination polymers with interesting structures and magnetic properties.Figure optionsDownload as PowerPoint slide