The work in this paper presents syntheses, characterization, crystal structures, catecholase activity, electrospray ionization mass spectroscopy (ESI-MS positive), and magnetic properties of seven triple bridged μ-phenoxo-bis(μ-carboxylate) dicopper(II) complexes [CuII 2L(μ-HCOO)2](ClO4)·CH3OH (1), [CuII 2L(μ-CH3COO)2](ClO 4) (2), [CuII 2L(μ-CCl3COO) 2(H2O)](ClO4) (3), [CuII 2L(μ-CH3CH2COO)2](ClO 4) (4), [CuII 2L(μ-CH3CH 2CH2COO)2](ClO4) (5), [Cu II 2L(μ-PhCOO)2](ClO4) ·CH3CN (6) and [CuII 2L(μ-o-ClPhCOO) 2](ClO4) (7), one double bridged μ-phenoxo-μ 1,1-azide system [CuII 2L(μ1,1- N3)(N3)2] (8) and one double bridged μ-phenoxo-μ-methoxide system [CuII 2L(μ-OCH 3)(NCO)2] (9), derived from a new dinucleating ligand HL, which is the 1:2 condensation product of 2,6-diformyl-4-ethylphenol and 3-dimethylaminopropylamine. The variable-temperature (300-2 K) magnetic studies reveal moderate or strong antiferromagnetic interaction in 1-9 with J values of -81.5, -64.8, -136.5, -66.9, -61.4, -49.1, -61.5, -186.3 and >-350 cm- 1 for 1-9, respectively. The seven μ-phenoxo-bis(μ-carboxylate) dicopper(II) complexes 1-7 show catecholase activity with turnover (K cat) numbers lying in the range 18.8-89.1 h-1. The positive ions observed in the ESI-MS spectra of 1-8 are heterobridged dinuclear species having oxidized CuIICuII or reduced Cu ICuI or mixed-valence CuIICuI metal centers having double/triple bridging moieties. A complex-substrate aggregate [CuII 2L(μ-3,5-DTBC2-)]+ has been identified in the ESI-MS positive spectrum of the mixture of complex 4 and 3,5-DTBCH2. © 2012 Elsevier Ltd. All rights reserved.