To test the suitability of adsorbents such as activated carbons, zeolites, and other materials to adsorb acetic acid vapors that are liberated inside museum showcases and may destroy lead objects, the adsorption capacities at the saturation pressure and the isotherms of adsorption at lower pressures were determined. The results obtained show that the NaX zeolite in pellet form and the RB4 activated carbon are the best adsorbents. Additionally, they show that materials with sodium content exhibit an exchange process that may be very important, particularly in the case of NaX zeolite. Some of the parameters determined (saturation capacity, Henry constant, kinetic parameter) seem to be related in a simple manner (although there are adsorbents that do not agree with the general trend). However, a simple relation was not found between the specific surface area previously determined with nitrogen at 77 K and the acetic acid saturation capacity at room temperature.

The homoleptic compounds [U(salan-R2)2] (R = Me (1), tBu (2)) were prepared in high yield by salt-metathesis reactions between UI4(L)2 (L = Et2O, PhCN) and 2 equiv of [K2(salan-R2)] in THF. In contrast, the reaction of the tetradentate ligands salan-R2 with UI3(THF)4 leads to disproportionation of the metal and to mixtures of U(IV) [U(salan-R2)2] and [U(salan-R2)I2] complexes, depending on the ligand to M ratio. The reaction of K2salan-Me2 ligand with U(IV) iodide and chloride salts always leads to mixtures of the homoleptic bis-ligand complex [U(salan-Me2)2] and heteroleptic complexes [U(salan-Me2)X2] in different organic solvents. The structure of the heteroleptic complex [U(salan-Me2)I2(CH3CN)] (4) was determined by X-ray studies. Heteroleptic U(IV) and Th(IV) chloride complexes were obtained in good yield using the bulky salan-tBu2 ligand. The new complexes [U(salan-tBu2)Cl2(bipy)] (5) and [Th(salan-tBu2)Cl2(bipy)] (8) were crystallographically characterized. The salan-tBu2 halide complexes of U(IV) and Th(IV) revealed good precursors for the synthesis of stable dialkyl complexes. The six-coordinated alkyl complexes [Th(salan-tBu2)(CH2SiMe3)2] (9) and [U(salan-tBu2)(CH2SiMe3)2] (10) were prepared by addition of LiCH2SiMe3 to the chloride precursor in toluene, and their solution and solid-state structures (for 9) were determined by NMR and X-ray studies. These complexes are stable for days at room temperature. Preliminary reactivity studies show that CO2 inserts into the An–C bond to afford a mixture of carboxylate products. In the presence of traces of LiCl, crystals of the dimeric insertion product [Th2Cl(salan-tBu2)2(μ-η1:η1-O2CCH2SiMe3)2(μ-η1:η2-O2CCH2SiMe3)] (11) were isolated. The structure shows that CO2 insertion occurs in both alkyl groups and that the resulting carboxylate is easily displaced by a chloride anion.

Reactions of titanium and yttrium trichlorides with 1 equiv of the sodium or potassium salts of the diamine bis(phenolate) H2 tBu2O2NN′ (Me2NCH2CH2-(CH2-2-HO-3,5-C6H2 tBu2)2) led to formation of [TiCl(tBu2O2NN′)(L)] (L = THF, 1; py, 2) and [YCl(tBu2O2NN′)(DME)], 3. Reactions of 1 or 3 with MCH2-(2-NMe2)C6H4 and with M[2-(CH2NMe2)C6H4] (M = Li, K) led to [Ti(tBu2O2NN′)(κ2-(CH2C6H4NMe2))], 5, [Y(tBu2O2NN′)(κ2-(CH2C6H4NMe2))], 6, and [Y(tBu2O2NN′)(κ2-(C6H4CH2NMe2))], 7. [Y(tBu2O2NN′)N(SiMe3)2], 4, was obtained from 3 and KN(SiMe3)2, whereas [(Y(tBu2O2NN′)(CH2SiMe3))2(μ4-O)(μ3-Li)2], 8, formed from reaction of 3 and LiCH2SiMe3. The reaction of 7 with 1 equiv of CH3CN gave [Y(tBu2O2NN′)(NC(CH3)C6H4CH2NMe2)], 10, which displays a chelating ketimide ligand formed by nitrile insertion in the Y−Ph bond. Further reaction with CH3CN led to [Y(tBu2O2NN′)(κ2-(N(H)C(CH3)C(H)C(C6H4CH2NMe2)N(H)], 9, the formation of which involves an imine−enamine tautomerism followed by a second nitrile insertion and 1,3-hydrogen shift. The reaction of 1 with CH3CN gave [TiCl(tBu2O2NN′)(NCCH3)], which upon heating converts to a new paramagnetic species that is likely a chloride-bridged Ti(III) dimer. The EPR study performed reveals that bis(phenolate) Ti(III) complexes do not promote nitrile coupling reactions by electron transfer. The solid state molecular structures of 1−9 revealed that in all the complexes the bis(phenolate) ligand is coordinated to the metal center by the two oxygen atoms and the two nitrogen atoms with trans phenolate arrangement.

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Alentejo's religious buildings reflect undoubtedly the history and character of this southern Portugal region. Conservation of these buildings requires a deep knowledge of their masonry and renders' lime mortars to evaluate correctly their state of conservation, to avoid progression of pathologic situations, and to plan efficient interventions, with repair and substitution materials with similar characteristics. This article presents a synthesis of the main results obtained in the mortar characterization of religious buildings from Alentejo, which include E´vora and Elvas Cathedrals, Me´rtola Mosque, and the Church of Amieira do Tejo. For each monument, several samples were collected from different sites and a set of tests was carried out, including chemical, mineralogical, and micro-structural tests, as well as physical and mechanical tests. The tested mortars correspond to different phases of construction and interventions on the buildings, comprising mainly origin periods from the twelfth to the eighteenth centuries; hence exhibited significant differences in composition and in application techniques. The obtained results of composition have given important information about the provenance of the materials used, including binder and sand types, and also about decay products and their correlation with the mortar's conservation state, which gave important clues on the repair strategy to adopt.

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The adsorption isotherms of H 2 S in selected adsorbents were determined at 298 K, at relative pressures up to about 0.005, aiming the use of these materials in the removal of that pollutant from the museums atmosphere. The Dubinin-Astakhov equation adjusts very well the experimental results, although one cannot interpret the preexponential factor w 0 as the limiting adsorbed amount. The parameter E, related with the adsorption energy, and the parameter n, that can be associated with the surface heterogeneity of the adsorbents, are correlated and the first is also correlated with the adsorbed amounts. It was not found any expectable relationship between the adsorbed amounts and textural parameters of the adsorbents such as the specific surface area or the microporous volume. This points out that the adsorption of H 2 S is highly specific. In general, 13X and Y sodium zeolites seem to be the most effective adsorbents, but at lowest tested pressures, near the concentrations found at museums, a pillared clay prepared from a Wyoming montmorillonite seems to be more efficient.