| الوصف: |
The crystal structures of several copper and mixed copper-lanthanoid complexes are reported, using the 6-chloro and 6-methyl derivatives of 2-pyridone as a ligand. With 6-chloro-2-pyridone, a novel dimeric copper complex results, which has been structually and physically studied. This species, under certain conditions, exhibits a dissociation reaction which has been examined using U.V.-vis. and E.P.R. spectroscopy and by cyclic voltammetry. Reaction of this dimeric copper compound with methanol and ethylene glycol results in the formation of tetranuclear and polymeric copper complexes respectively, which have both been structurally characterised. The reaction of this copper dimer with various lanthanoids results in the formation of a series of mixed copper-lanthanoid species based on four structural types. Reactions in methanol dichloromethane result in three structural configurations depending on size of the lanthanoid used (with La and Ce, LnCu3 with five ligands; with Gd, Dy and Er LnCu3 with eight ligands and for Yb Ln2Cu2 with four ligands). The reaction of lanthanum with the dimeric copper species in a variety of solvents gave a further two structures, one of which (in ethanol) has a similar structure to those observed with Gd, Dy and Er in methanol, while in acetonitrile a fourth structural type occurs, based on La2Cu2 with six ligands. With the 6-methyl-2-pyridone an unusual hexanuclear 'metallocrown' results, which has been characterised structually and by proton and sodium-23 NMR. The reaction of this species with lanthanoids in methanol yields a range of closely related mixed copper-lanthanoid compounds all based on Ln2Cu2 (as seen for the product of Yb with the copper dimer in methanol). The only difference between the structures is a change in the coordination number of the lanthanoid between Sm and Gd to accommodate the contraction in lanthanoid size. The mixed phase reaction of this 'metallocrown' with lanthanum nitrate yields an extremely remarkable structure based on a La8Cu12 core. |
