Synthesis, crystal structure and magneto-structural correlation of two bi-bridging 1D copper(ii) chains

Abstract

Two 1D bi-bridging Cu(II) chains, catena-oxalate-bis[1-(2-aminoethyl)pyrrolidine-copper(II)]-0.5(squarate) perchlorate hydrate (1) and catena-pyrazine-oxalate-tetraaquo-dicopper(II) diperchlorate (2) have been synthesised and their molecular structures determined by X-ray crystallography. Compound 1 exhibits a polymeric arrangement with a ladder-like structure running parallel to crystallographic axis a, in which two [(Cu(ampy))₂(ox)] chains (ampy = 1-(2-aminoethyl)pyrrolidine; ox = oxalate) are linked by squarate groups. The oxalate behaves simultaneously as bis-bridging and bis-monodentate towards four coplanar copper ions, a coordination mode which has never been reported for Cu(II). Compound 2 is characterized by a polymeric array with alternate repetition of bridging oxalate and ‘pyz’ (pyz = pyrazine). Low temperature magnetic behaviour reveals the existence of a dominant weak antiferromagnetic interaction within 1 whereas in 2 a strong antiferromagnetic interaction is observed. The results obtained experimentally corroborate the structural parameters in both 1 and 2.