Magneto-structural studies on [Cu II 2 {L 3 -(μ 2 -1,1-CO 2 – ) 2 } 2 ]•MeOH•H 2 O and [Cu II 4 {L 4 -(μ 2 -1,3-CO 2 – )(μ 2 -1,3-CO 2 Me)} 4 ](ClO 4 ) 4 using carboxylate- / carboxymethylester-appended (2-pyridyl)-alkylamine ligands differing in alkyl chain length

Two discrete complexes [Cu II 2 {L 3 -(CO 2 – ) 2 } 2 ]•MeOH•H 2 O ( 1 ) and [Cu II 4 {L 4 -(CO 2 – )(CO 2 Me)} 4 ](ClO 4 ) 4 •unknown solvent ( 2 ) have been synthesized from the reaction between copper(II) salts and L 3 -(CO 2 Me) 2 / L 4 -(CO 2 Me) 2 [3,3′-[(pyridin-2-ylmethyl)imino]dipropionate dimethylester / 3,3′-[(pyridin-2-ylethyl)imino]dipropionate dimethylester]. Structural analysis reveals that 1 is a monatomic bridging carboxylate dinuclear complex with Cu II 2 (μ 2 -1,1-OCO – ) 2 2+ structural unit. Each Cu(II) centre has distorted square-pyramidal CuN 2 O 3 coordination, provided by two N (pyridyl and amine) and two carboxylate O from L 3 -(CO 2 – ) 2 and the fifth coordination is provided by an O atom belonging to the carboxylate group of an adjacent molecule. Complex 2 is a syn - anti carboxylate-bridged tetranuclear coordination cluster with a {Cu II 4 {(μ 2 -1,3-OCO – )(μ 2 -1,3-OCOMe)} 4 4+ structural motif. Here also, each Cu(II) centre has distorted square-pyramidal CuN 2 O 3 coordination, and an O atom belonging to the carboxylate group of an adjacent molecule completes the fifth coordination. Variable temperature magnetic studies reveal antiferromagnetic coupling in 1 ( J  = –8.37(6) cm −1 ), while 2 exhibits ferromagnetic behaviour ( J = +13.1(1) cm −1 ).