Magneto-structural studies on [CuII2{L3-(2-1,1-CO2-)2}2]?MeOH?H2O and [CuII4{L4-(2-1,3-CO2-)(2-1,3-CO2Me)}4](ClO4)4 using carboxylate- / carboxymethylester-appended (2-pyridyl)-alkylamine ligands differing in alkyl chain length

Two discrete complexes [CuII2{L3-(CO2-)2}2]center dot MeOH center dot H2O (1) and [CuII4{L4-(CO2-)(CO2Me)}4](ClO4)4 center dot unknown solvent (2) have been synthesized from the reaction between copper(II) salts and L3-(CO2Me)2 / L4-(CO2Me)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 CuII2(mu 2-1,1-OCO-)22+ structural unit. Each Cu(II) centre has distorted square-pyramidal CuN2O3 coordination, provided by two N (pyridyl and amine) and two carboxylate O from L3-(CO2-)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 {CuII4{(mu 2-1,3-OCO-)(mu 2-1,3-OCOMe)}44+ structural motif. Here also, each Cu(II) centre has distorted square-pyramidal CuN2O3 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).