Herein, we report the synthesis and characterization, through elemental analysis, electronic spectroscopy, electrochemistry, potentiometric titration, electron paramagnetic resonance, and magnetochemistry, of two dinuclear copper(II) complexes, using the unsymmetrical ligands N',N',N-tris(2-pyridylmethyl)-N-(2-hydroxy-3,5-di-tert-butylbenzyl)-1,3-propanediamin-2-ol (L1) and N',N'-bis(2-pyridylmethyl)-N,N-(2-hydroxybenzyl)(2-hydroxy-3,5-di-tert-butylbenzyl)-1,3-propanediamin-2-ol (L2). The structures of the complexes [Cu(2)(L1)(μ-OAc)](ClO(4))(2)·(CH(3))(2)CHOH (1) and [Cu(2)(L2)(μ-OAc)](ClO(4))·H(2)O·(CH(3))(2)CHOH (2) were determined by X-ray crystallography. The complex [Cu(2)(L3)(μ-OAc)](2+) [3; L3 = N-(2-hydroxybenzyl)-N',N',N-tris(2-pyridylmethyl)-1,3-propanediamin-2-ol] was included in this study for comparison purposes only (Neves et al. Inorg. Chim. Acta2005, 358, 1807-1822). Magnetic data show that the Cu(II) centers in 1 and 2 are antiferromagnetically coupled and that the difference in the exchange coupling J found for these complexes (J = -4.3 cm(-1) for 1 and J = -40.0 cm(-1) for 2) is a function of the Cu-O-Cu bridging angle. In addition, 1 and 2 were tested as catalysts in the oxidation of the model substrate 3,5-di-tert-butylcatechol and can be considered as functional models for catechol oxidase. Because these complexes possess labile sites in their structures and in solution they have a potential nucleophile constituted by a terminal Cu(II)-bound hydroxo group, their activity toward hydrolysis of the model substrate 2,4-bis(dinitrophenyl)phosphate and DNA was also investigated. Double electrophilic activation of the phosphodiester by monodentate coordination to the Cu(II) center that contains the phenol group with tert-butyl substituents and hydrogen bonding of the protonated phenol with the phosphate O atom are proposed to increase the hydrolase activity (K(ass.) and k(cat.)) of 1 and 2 in comparison with that found for complex 3. In fact, complexes 1 and 2 show both oxidoreductase and hydrolase/nuclease activities and can thus be regarded as man-made models for studying catalytic promiscuity.

Layered materials are a very interesting class of compounds obtained by stacking of two-dimensional layers along the basal axis. A remarkable property of these materials is their capacity to interact with a variety of chemical species, irrespective of their charge (neutral, cationic or anionic). These species can be grafted onto the surface of the layered materials or intercalated between the layers, to expand or contract the interlayer distance. Metalloporphyrins, which are typically soluble oxidation catalysts, are examples of molecules that can interact with layered materials. This work presents a short review of the studies involving metalloporphyrin immobilization on two different anionic exchangers, Layered Double Hydroxides (LDHs) and Layered Hydroxide Salts (LHSs), published over the past year. After immobilization of anionic porphyrins, the resulting solids behave as reusable catalysts for heterogeneous oxidation processes. Although a large number of publications involving metalloporphyrin immobilization on LDHs exist, only a few papers have dealt with LHSs as supports, so metalloporphyrins immobilized on LHSs represent a new and promising research field. This work also describes new results on an anionic manganese porphyrin (MnP) immobilized on Mg/Al-LDH solids with different nominal Mg/Al molar ratios (2:1, 3:1 and 4:1) and intercalated with different anions (CO 3 2´o r NO 3´) . The influence of the support composition on the MnP immobilization rates and the catalytic performance of the resulting solid in cyclooctene oxidation reactions will be reported.

Highlights  Niobium-containing SBA-15 silica used as catalysts for a model reaction to biodiesel production.  High niobium content and high calcination temperature maintained SBA-15 mesoporous silica profile.  Solid evaluated as catalyst with low Nb concentration (2 wt.%) showed better catalytic performance.  Nb promoter effect: catalyst stability at low loadings and also lowest heating treatment.

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