Hiram I. Beltrán

Boron-nitrogen macrocycles: a new generation of calix[3]arenes.

The simple condensation reaction of 3,5-di-tert-butyl salicylaldehyde and 3-aminophenylboronic acid leads to a trimeric macrocyclic compound. The ability of this molecule to include small organic molecules was in a first approximation analyzed by (1)H NMR spectroscopy and X-ray crystallography.

An alkaline one-pot metathesis reaction to give a [Cu3(BTC)2] MOF at r.t., with free Cu coordination sites and enhanced hydrogen uptake properties

A one-pot metathesis reaction between trimesic acid sodium salt and Cu(NO3)2 to yield [Cu3(BTC)2] (HKUST-1) in moderate to good yields, even at room temperature (r.t.) is presented, herein, for the first time. To determine if the basic nature of the metathesis reaction afforded any new physicochemical properties to HKUST-1, three variables were monitored: a) the energy source either from i) ultrasound (US), ii) stirring at room temperature (SRT) or iii) solvothermal (ST) treatment, b) the reaction solvent and c) the reaction time. The metathesis reaction provided DMF·H2O, EtOH·H2O or MeOH·H2O solvates. The compounds were thoroughly characterized by FTIR, XRD, nitrogen adsorption BET surface areas and TGA/DSC data, which indicated the formation of [Cu3(BTC)2] MOFs in eight out of ten synthetic entries. Low-pressure hydrogen uptake experiments revealed values as high as 2.44 wt% for the [Cu3(BTC)2] EtOH·H2O solvates. The [Cu3(BTC)2] MeOH·H2O and [Cu3(BTC)2] EtOH·H2O solvates possess high surface areas, the latter being the metathesis prepared MOF with the least H2O→Cu coordination according to TGA, DSC and a thermal desorption gas chromatography–mass spectrometry (GC-MS) coupled technique. This resulted in a material with less chemisorbed H2O and better H2 adsorption capability.

Structural relationship between a host included chain of spirocyclic water hexamers and bulk water – the role of water clusters in self assembly and crystallization processes

Infinite chains of spirocyclic water hexamers are included in the crystal lattice of a tin complex with a curved, hydrophobic surface and only weak intermolecular bonding interactions between the host molecules, so that the enclosed water clusters might be reminiscent of the solvation sphere in solution.

Strecker intermediates as non-pollutant scavengers for cyanides

Using a series of five bis(aminomethyl)ethers, a fast and efficient transformation of sodium cyanide to sodium N-2-hydroxyethylglycinates is reported, where the starting materials are prototypes for application in the mining and oil industries to diminish the pollution of the tailings derived from their processes.

First trial and physicochemical studies on the loading of basic fuchsin, crystal violet and Black Eriochrome T on HKUST-1

The highly porous metal–organic framework based on copper-benzenetricarboxylate (HKUST-1, Cu3(BTC)2, MOF-199) is used for a loading study of basic fuchsin (BF, neutral charge, ϕ = 12.40 A molecular diameter, 50 ppm solution), crystal violet (CV, cationic charge, ϕ = 15.10 A, 50 ppm solution) and Eriochrome Black T (EBT, anionic charge, ϕ = 15.50 A, 80 ppm solution), as chosen molecular probes for physicochemical analysis and interactions. Characterization is carried out using XRD, FTIR, SEM, and TGA, and UV-Vis is used to determine the differential concentration of loaded dye in the MOF. The adsorption process is evaluated by three incorporation methodologies: post-synthesis (PS) and one-pot in organic (OPO) or metallic (OPM) solution. XRD cell parameters reveal the general compactness of the net through ionic (CV and EBT), dipolar (BF, CV and EBT) and van der Waals (BF, CV and EBT) dye–MOF interactions. Enhanced compactness is observed for CV due to its cationic nature and medium size; the effect is not as strong in EBT, which is anionic in nature but bigger in size, and the least compactness is observed for BF, which lacks ionic interaction with the net. The samples have crystal sizes between 34 and 57 nm, which indicate the generation of nanomaterials. The employed procedures yield crystallite size in the following order: PS < OPO < OPM. The (%) adsorption of all the dyes is above 86.93%, which is observed for the EBT-PS sample as the lowest and 99.42% for BF-PS as the highest, which evidences the high displacement of equilibrium in the studied systems to the Cu3(BTC)2·dye occluded state. Thus, MOFs can be suggested as potential adsorbents/loaders of BF/CV/EBT dyes for composite material generation as well as MOF·molecule interaction studies because of their high loading ability and obtained stability as well as facile synthesis.

Free-lignin cellulose obtained from agar industry residues using a continuous and minimal solvent reaction/extraction methodology

Herein we present a green procedure to obtain cellulose (Cel) polymers with different physicochemical properties at high purity, and underline its two major aspects: sustainability and efficiency. In the first place, regarding sustainability, the source of Cel was residues from agar industries, which are based on red seaweed and hence free of lignin, thus facilitating the extraction of Cel. In the aspect of efficiency, a continuous extraction/reaction system was used to obtain pure Cel from these residues. The extraction/reaction device used in this study normally works in a liquid–liquid extraction fashion, but in this particular case it was successfully employed as a liquid–solid system. This methodology is important, because it concomitantly reduces the time of extraction/reaction procedures in the same flask and also minimizes the amount of solvent used. Thus high purity Cel was obtained using a continuous and minimal solvent extraction/reaction system in neutral/acidic/basic conditions leading to Celn/Cela/Celb polymers in 42/34/43.3% yield. These materials were characterized by 13C cross-polarization magic-angle spinning (CP-MAS) NMR, Fourier transform infrared spectroscopy (FT-IR), CHNS elemental analyses, X-ray diffraction (XRD), size exclusion chromatography (SEC) and compared against microcrystalline cellulose (MCC), confirming chemical integrity. Crystallinity index (CI [%]), was obtained from XRD/CP-MAS NMR data. All samples had slightly higher crystallinity than that of MCC. Molecular weight (MW, g mol−1), polydispersity index (PDI) and degree of polymerization (DP) for Celn, Cela, Celb polymers were all higher than those in MCC. Compared to MCC, the physicochemical characteristics of the isolated Cel polymers varied depending on the treatment, neutral being the mildest. The greener procedures developed herein provide Cel suitable for research and development of Cel derived substances.

The cis-bis(decanoate)tin phthalocyanine/DPPC film at the air/water interface.

Films made of cis-bis-decanoate-tin(IV) phthalocyanine (PcSn10) and racemic dipalmitoylphosphatidylcholine (DPPC) are studied with compression isotherms and Brewster angle microscopy (BAM) at the air/water interface. Films enriched in PcSn10 present phase separation elliptical-shaped domains. These domains present optical anisotropy and molecular order. They are enriched in PcSn10, and the film outside these domains is enriched in DPPC, as shown in by high-angle annular dark-field transmission electron microscopy on Langmuir-Blodgett (LB) transferred films. Film collapse area and atomic force microscopy images of LB transferred films on mica indicate that the films are actually multilayers. A computational survey was performed to determine how the PcSn10 molecules prefer to self-assemble, in films basically made of PcSn10. The relative energetic stability for several dimeric assemblies was obtained, and a crystal model of the film was developed through packing and repeating the PcSn10 molecules, along the crystallographic directions of the unit cell. Our results contribute to understanding the strong interaction between PcSn10 and DPPC at the air/water interface, where even small quantities of DPPC (~1-2%) can modify the film in an important way.

The fungicide effect of HKUST-1 on Aspergillus niger, Fusarium solani and Penicillium chrysogenum

In this work we have evaluated the fungicide effects causing the growth inhibition of Aspergillus niger, Fusarium solani and Penicillium chrysogenum using three metal–organic framework materials (MOFs): HKUST-1 (three-dimensional structure), HKUST-1NP doped with copper oxide nanoparticles (CuO-NPs) and sterilized HKUST-1 (which generated a one-dimensional Cu(BTC)(OH)(H2O)-type structure). The materials were synthesized by stirring at room temperature under atmospheric pressure, and were compared to commercial CuO-NPs to evaluate the toxic effects using a radial growth (inhibition halo) technique. The MOFs were thoroughly dispersed in culture media, and the fungi were cultured on potato dextrose agar plates containing different concentrations of the tested materials. A thorough characterization of the studied materials was carried out through PXRD, FTIR, N2 adsorption, TGA and SEM measurements in order to determine the physicochemical properties. For A. niger, none of the tested materials inhibited its growth; it hence proved to be resistant, due to its ability to leach copper from the compounds. In the case of F. solani, concentrations between 750 to 1000 ppm caused 100% inhibition of growth. For P. chrysogenum, it was observed that increasing the concentration of MOFs up to 1000 ppm caused a concomitant increase in inhibition. This work represents the first report underlining the possible use of MOFs as fungicides, and the results have shown growth inhibition capability in some species, opening up possible new applications in this field.

Novel valproic aminophenol amides with enhanced glial cell viability effect

New valproic acid derivatives were synthesized by coupling valproyl chloride with ortho-aminophenols, resulting in seven N-(ortho-hydroxyphenyl)valproamides. These amides share similar structural characteristics and exhibit tuneable electronic and steric contributions either without particular substituents, or through the inclusion of electro-donating (–Me), electro-withdrawing (–NO2) or pi electro-donating/sigma electro-withdrawing (–Cl) substituents at the aromatic ring. The identity of such derivatives was evidenced through spectroscopic characterization using FTIR, 1H, 13C and HETCOR NMR, as well as by analyzing their melting points. In particular, for three derivatives it was feasible to determine their chemical structures in the crystal phase; all three behaved in a similar fashion and exhibited very similar conformations independent of the attached substituents. The base compound was found to exhibit 15.8 times more activity in C6 cells and 4.4 times more activity in U373 cells compared with VPA. In general, the parent compound, or those having –Me as a substituent, presented a greater effect on C6 cells than U373 cells. However, those with –NO2 and –Cl substituents, as well as VPA, required similar doses for the IC50 in both cell lines. Modification of the base compound with a –Me or –NO2 substituent increased the effect on cell viability to ca. 20 times that of VPA in both C6 and U373, indicating that a larger structure causes an important enhancement in the inhibition of cell viability. In both cell lines, –Cl containing derivatives were the most active compounds. For these derivatives, an activity increase of ca. 59 and 47 times that of VPA was observed for C6 and U373 cells, respectively. An important perspective is that VPA analogues possessing an aromatic ring with a –Cl substituent may become central structures in the search for more potent pharmaceutical prototypes.