Difluoroboron Complexes Based on Benzimidazole-Phenolates as Blue Emitters.

Novel four-coordinated boron complexes (1-5) were synthesized via a reaction between BF3·CH3OH and benzimidazole-phenolate ligands (L1-L5), which are N,O-donors. These complexes exhibit intense blue emission in the solution and solid states accompanied by notable fluorescence quantum yields (ΦF). The study of the structure-property relation, through theoretical and experimental approaches, revealed a distinctive trend where compounds incorporating electron-donating substituents (methyl and ethoxy groups) in the phenolate moiety manifest shifts in emission wavelengths across the blue spectrum, concomitant with an increase in ΦF. Furthermore, the incorporation of an aromatic ring into the benzimidazole moiety considerably intensifies the rate of radiative relaxation from excited states. Notably, in the solid phase, either as a crystalline powder or loaded into polymer films, these modified complexes maintain or even surpass ΦF values observed in molecular solutions, ranging from 0.18 to 0.57, depending on the substitution. This characteristic makes these compounds attractive for applications in optoelectronics. All of the compounds were characterized using 1H, 13C, 11B, and 19F NMR, elemental analysis, and the molecular structures were corroborated through single-crystal X-ray diffraction analysis. Computational calculations via time-dependent density functional theory further elucidate the tunability of optical bandgaps through group substitution on ligands, aligning well with experimental observations.

Beryllium compounds for the carbon-halogen bond activation of phenyl halides: the role of non-innocent ligands.

Beryllium is a metallomimetic main-group element, i.e., it behaves similarly to transition metals (TMs) in some bond activation processes. To investigate the ability of Be compounds to activate C-X bonds (X = F-I), we have computationally investigated, using DFT methods, the reaction of (CAAC)2Be (CAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) and a series of five-membered heterocyclic beryllium bidentate ligands with phenyl halides. We have analysed all plausible reaction mechanisms and our results show that, after the initial C-X oxidative addition, migration of the phenyl group occurs towards the less electronegative heteroatom. Our theoretical study highlights the important role of bidentate non-innocent ligands in providing the required electrons for the initial Ph-X oxidative addition. In contrast, the monodentate ligand, CAAC, does not favour this oxidative addition.

Gel dressing based on type I collagen modified with oligourethane and silica for skin wound healing.

Cutaneous wound healing is a complex process that leads the skin reparation with the formation of scar tissue that typically lacks skin appendages. This fact drives us to find new strategies to improve regenerative healing of the skin. This study outlines, the contribution of colloidal silica particles and oligourethane crosslinking on the collagen material properties and the effect on skin wound healing in rats. We characterized the gel properties that are key forin-situgelation, which is accomplished by the latent reactivity of oligourethane bearing blocked isocyanate groups to crosslink collagen while entrapping silica particles. The swelling/degradation behavior and the elastic modulus of the composite gel were consistent with the modification of collagen type I with oligourethane and silica. On the other hand, these gels were characterized as scaffold for murine macrophages and human stem cells. The application of a composite gel dressing on cutaneous wounds showed a histological appearance of the recovered skin as intact skin; featured by the epidermis, hair follicles, sebaceous glands, subcutaneous adipose layer, and dermis. The results suggest that the collagen-based composite dressings are promising modulators in skin wound healing to achieve a regenerative skin closure with satisfactory functional and aesthetic scars.

Oxidative Coordination versus C3 -C(O)Me Bond Cleavage in Acetylacetonate Iridium Complexes.

Iridabicycles [Ir{κ3 -N,C,O-(pyC(H)=C(C(O)Me)2 }(Cl)(L-L)](L-L=cod (cod=1,5-cyclooctadiene), 1 a; bipy (bipy=2,2'-bipyridine), 1 b) have been obtained by oxidative coordination of 3-(pyridine-2-yl-methylene)pentane-2,4-dione L1, to the complexes [{Ir(µ-Cl)(cod)}2 ] and [{Ir(µ-Cl)(coe)2 }2 ] (coe=cis-cyclooctene), the latter in the presence of bipy. Remarkably, cleavage of the C3 -C(O)Me bond of L1 has instead been achieved in the reaction with [Ir(Cl)(dmb)2 ] (dmb=2,3-dimethylbutadiene), yielding a compound formulated as [Ir{κ2 -N,C-(pyC(H)C(C(O)Me))}(CO)(µ-Cl)(Me)]2 , 2. Treatment of dimer 2 with DMSO or PMe3 produced the complexes[Ir{κ2 -N,C-(pyC(H)C(C(O)Me)}(CO)Cl(Me)L] (L=DMSO, 3 a; PMe3 , 3 b). Plausible mechanisms for the reactions leading to complexes 1 and 2 are proposed by means of DFT calculations.

Thermal, morphological and structural characterization of a copolymer of starch and polyethylene.

The objective of this paper was to perform a copolymerization between polyethylene and starch in order to obtain new environmentally friendly materials. The copolymer obtained was characterized thermally, morphologically and structurally, including its pasting profile. The starch-g-PE copolymer showed lower thermal stability compared to the control materials. FTIR analysis determined that the chemical bond signal between the starch and polyethylene in the copolymer overlaps with the native starch signals. The signal from this chemical bond was assigned by proton NMR spectroscopy at δ 4.45 ppm. X-ray studies of the copolymer showed a material with more amorphous characteristics compared to native starch. SEM analysis demonstrated the presence of cracks in the starch granules which favored the chemical interaction between the polymers. The pasting behavior of the copolymer was less pronounced compared to native starch. Therefore, the copolymerization of both polymers could be an alternative to recycle polyethylene and make biodegradable materials.

Phytochemical profiles and classification of Agave syrups using 1H-NMR and chemometrics.

BACKGROUND: Agave syrups are natural sweeteners that are highly desirable for human consumption because they have low glycemic index. In this work, we explored the potential of 1H-NMR-Chemometrics as a useful tool in the identification and differentiation of Agave syrups. Also, we evaluated the phytochemical screening and antioxidant capacity of Agave syrup compared to other natural sweeteners. RESULTS: The phytochemical screening stands out for Agave syrups containing higher levels of metabolites with antioxidant activity, mainly saponins, glycosides, and terpenoids. Agave syrup antioxidant activity was in a range from 10% to 53%, while the total phenolic content was from 24 to 300 EAG/100 g, and condensed tannins were between 240 and 1,900 mg CE/g. Additionally, 1H-NMR spectroscopy was used to characterize syrup profiles and chemometrics. PCA group analyses allowed the sweeteners' classification by origin and kind of Agave. CONCLUSION: Thus, we conclude that 1H-NMR and chemometrics can be used for identifying, differentiating, and classifying Agave syrups. Besides, Agave syrups contain significant amounts of antioxidative components and can be considered as an effective source of antioxidant.

Design of Silica-Oligourethane-Collagen Membranes for Inflammatory Response Modulation: Characterization and Polarization of a Macrophage Cell Line.

The polarization of macrophages M0 to M1 or M2 using molecules embedded in matrices and hydrogels is an active field of study. The design of biomaterials capable of promoting polarization has become a paramount need nowadays, since in the healing process macrophages M1 and M2 modulate the inflammatory response. In this work, several immunocytochemistry and ELISA tests strongly suggest the achievement of polarization using collagen-based membranes crosslinked with tri-functionalized oligourethanes and coated with silica. Measuring the amount of TGF-ß1 secreted to culture media by macrophages growth on these materials, and quantifying the macrophage morphology, it is proved that it is possible to stimulate the anti-inflammatory pathway toward M2, having measurements with p ≤ 0.05 of statistical significance between the control and the collagen-based membranes. Furthermore, some physicochemical characteristics of the hybrid materials are tested envisaging future applications: collagenase degradation resistance, water uptake, collagen fiber diameter, and deformation resistance are increased for all the crosslinked biomaterials. It is considered that the biological and physicochemical properties make the material suitable for the modulation of the inflammatory response in the chronic wounds and promising for in vivo studies.

Crystal structure and Hirshfeld surface analysis of 3-cyano-phenyl-boronic acid.

In the title compound, C7H6BNO2, the mean plane of the -B(OH)2 group is twisted by 21.28 (6)° relative to the cyano-phenyl ring mean plane. In the crystal, mol-ecules are linked by O-H⋯O and O-H⋯N hydrogen bonds, forming chains propagating along the [101] direction. Offset π-π and B⋯π stacking inter-actions link the chains, forming a three-dimensional network. Hirshfeld surface analysis shows that van der Waals inter-actions constitute a further major contribution to the inter-molecular inter-actions, with H⋯H contacts accounting for 25.8% of the surface.

In vitro evaluation of apoptotic effect of bis(acetylacetonato-k2 O,O')(1,10-phenanthroline-k2 N,N')Zn(II) complex.

Phenanthroline derivatives have been reported as potential bioactive compounds because of their ability to interact with DNA. To evaluate the antiproliferative effect of bis(acetylacetonate-k2 O,O)(1,10-phenanthroline-k2 N,N)Zn(II) or Zn(acac)2 (phen) complex, the compound was obtained in a simple manner and further characterized to determine crystal structure, thermal behavior, morphology, and spectroscopic properties. The structure of the complex was confirmed by X-ray single structure as well as by 1H and 13C nuclear magnetic resonance (NMR) in dmso-d6 (dimethyl sulfoxide) solution and in the solid state by 13C CP/MAS. Although preparation of this compound has been described previously, there are no reports on its biological activity; here, we assessed its antiproliferative effect on fibroblasts, A253, FaDu, Cal-27, RH-30, RD, U-373, C6, A-549, MDA-MB-231, and MCF-7 cancer cell lines at different doses (50-100 and 150 µg/ml). The cell viability was determined by MTT assay and high activity was observed for the most of the cell lines, and TUNEL results showed the induction of apoptosis.

Hydrocortisone release from tablets based on bioresorbable poly(ether-ester-urethane)s

Abstract Bioresorbable linear poly(ether-ester-urethane)s with different hydrophilic characteristics were synthesized from triblock copolymers of poly(ε-caprolactone)-poly(ethylene oxide)-poly(ε-caprolactone) (PCL-PEO) as macrodiols, and L-lysine diisocyanate (LDI) or hexamethylenediisocyanate (HDI) were used as the required diisocyanates. Macrodiols were obtained by ring-opening polymerization (ROP) of ε-caprolactone (CL). Polyurethanes were synthesized by the reaction of the triblock copolymers with LDI or HDI in solution using stannous 2-ethylhexanoate as catalyst. Polyurethane tablets were fabricated and investigated as prospective drug delivery systems. The effect of the PEO content on the polymers' performance as drug carriers was evaluated. It was found that water provoked more swelling and erosion of polymers with higher contents of PEO. The hydrocortisone release profiles were analyzed using the Ritger-Peppas approximation. An anomalous release behaviour (values of n higher than 0.5) was found for most of the analyzed samples.

Improved properties of composite collagen hydrogels: protected oligourethanes and silica particles as modulators.

This paper reports the structure-property relationship of novel biomedical hydrogels derived from collagen, water-soluble oligourethanes, and silica. The molecular weight (MW) of oligourethanes, synthesized from polyoxyethylene diol and hexamethylene, l-lysine, isophorone or trimethylhexamethylene diisocyanates (P(HDI), P(LDI), P(IPDI) and P(TMDI), respectively), is determined by the chemical structure of the starting aliphatic diisocyanate. Thus, the collagen polymerization process and both the characteristics and mechanics of the formed three-dimensional (3D) network had a direct relation with the oligourethane MW. The crosslinking of collagen with oligourethanes was compatible with orthosilicate polycondensation to deposit silica particles on the fibrillar 3D network. A higher crosslinking index was found in hydrogels formulated with P(HDI) and P(LDI) in comparison with P(TMDI) and P(IPDI). In spite of similar crosslinking extensions, P(LDI) induced an enhanced water uptake and enhanced susceptibility to degradation, contrary to the impact of P(HDI). Fibroblasts and macrophages cultured for 3 days on hydrogels formulated with P(LDI) showed a metabolic activity similar to collagen only hydrogels. However, we observed the highest cell metabolic activity on hydrogels formulated with P(LDI) after 7 day culture. After this time lapse, an enhanced secretion of chemoattractant cytokines transforming growth factor-beta1 (TGF-ß1) and monocyte chemoattractant protein-1 (MCP-1 or CCL-2) was noted in macrophages cultured on hydrogels crosslinked with P(LDI). These tunable composite collagen hydrogels might be excellent candidates for holding and releasing bioactive molecules and nanomaterials intended to regulate cell behavior via their constituents and properties.

Quantum chemical characterization of zwitterionic structures: Supramolecular complexes for modifying the wettability of oil-water-limestone system.

In this work, we present a quantum chemical study pertaining to some supramolecular complexes acting as wettability modifiers of oil-water-limestone system. The complexes studied are derived from zwitterionic liquids of the types N'-alkyl-bis, N-alquenil, N-cycloalkyl, N-amyl-bis-beta amino acid or salts acting as sparkling agents. We studied two molecules of zwitterionic liquids (ZL10 and ZL13), HOMO and LUMO levels, and the energy gap between them, were calculated, as well as the electron affinity (EA) and ionization potential (IP), chemical potential, chemical hardness, chemical electrophilicity index and selectivity descriptors such Fukui indices. In this work, electrochemical comparison was realized with cocamidopropyl betaine (CPB), which is a structure zwitterionic liquid type, nowadays widely applied in enhanced recovery processes.

Hexacoordinated oligosilanes from a hexacoordinated silicon(IV) complex containing an O,N,N,O salen-type and thiocyanato-N ligands.

Two new neutral hexacoordinated silicon complexes with SiN(4)O(2) (6) and SiN(3)O(2)C (7) coordinating frameworks were synthesized by reaction of the O,N,N,O-donor salen-type ligand 1,2-bis[[(2-hydroxy-4-methoxyphenyl)(phenyl)methylene]amino]ethane (H(2)salen*) with Si(NCS)(4) and HMeSi(NCS)(2), respectively. The complexes 6 [Si(salen*)(NCS)(2)] and 7 [Si(salen*)Me(NCS)] were studied in the solid-state by (29)Si and (15)N CP/MAS NMR and in solution by (1)H, (13)C, and (29)Si insensitive nuclei enhanced by polarization transfer (INEPT) NMR, UV/vis and FT-IR spectroscopy. Elemental analysis and single-crystal X-ray diffraction analysis were used to confirm the composition and structure for compounds 6 and 7. Both complexes contain the dianionic salen-type ligand coordinated in an equatorial fashion to the silicon center, while the axial positions are occupied by two thiocyanato-N ligands for 6 and one thiocyanato-N and one methyl ligand for 7. Complex 6, which contains two Si-NCS functional groups, was used as monomer to produce a mixture of linear oligosilanes with a hexacoordinated silicon backbone (formulated SCN-[Si(salen*)](n)-NCS, n = 2-8) 8, via a Wurtz-type coupling reaction. Oligomers 8 were identified by solid-state (29)Si cross polarization-magic angle spinning NMR and solution (1)H and (29)Si NMR spectroscopy, matrix assisted laser desorption ionization-time of flight (MALDI-TOF), gel-permeation chromatography (GPC), FT-IR, UV/vis spectroscopy and thermogravimetric analysis (TGA). Conclusive evidence of the oligomeric nature of 8 was provided by MALDI-TOF spectrometry and was supported by quantitative solution (29)Si NMR and GPC studies.