Triple bridged μ-phenoxo-bis(μ-carboxylate) and double bridged μ-phenoxo-μ1,1-azide/μ-methoxide dicopper(II) complexes: Syntheses, structures, magnetochemistry, spectroscopy and catecholase activity

The work in this paper presents syntheses, characterization, crystal structures, catecholase activity, electrospray ionization mass spectroscopy (ES1-MS positive), and magnetic properties of seven triple bridged mu-Phenoxo-bis(mu-carboxylate) dicopper(II) complexes [(Cu2L)-L-II(mu-HCOO)(2)](ClO4)center dot CH3OH (1), [(Cu2L)-L-II(mu-CH3-COO)(2)](ClO4) (2), [(Cu2L)-L-II(mu-CCl3COO)(2)(H2O)](ClO4) (3), [(Cu2L)-L-II(mu-CH3CH2COO)(2)](ClO4) (4), [(Cu2L)-L-II(mu-ClCH2CH2COO)(2)](ClO4) (5), [(Cu2L)-L-II(mu-PhCOO)(2)](ClO4)-CH3CN (6) and [(Cu2L)-L-II(mu-o-ClPhCOO)(2)](ClO4) (7), one double bridged mu-phenoxo-mu(1,1)-azide system [(Cu2L)-L-II(mu(1.1)-N-3)(N-3)(2)] (8) and one double bridged mu-phenoxo-mu-methoxide system [(Cu2L)-L-II(mu-OCH3)(NCO)(2)] (9), derived from a new dinucleating ligand HL, which is the 1:2 condensation product of 2,6-diformy1-4-ethylphenol and 3-dimethylaminopropylamine. The variable-temperature (300-2 IC) 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 mu-phenoxo-bis(mu-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 (CuCuII)-Cu-II or reduced (CuCuI)-Cu-I or mixed-valence CullCul metal centers having double/triple bridging moieties. A complex-substrate aggregate [(Cu2L)-L-II(mu-3,5-DTBC2-)](+) has been identified in the ESI-MS positive spectrum of the mixture of complex 4 and 3,5-DTBCH2. (C) 2012 Elsevier Ltd. All rights reserved.