Spin-phonon coupling and slow-magnetic relaxation in pristine ferrocenium

We report the spin dynamic properties of non-substituted ferrocenium complexes. Ferrocenium shows a field-induced single-molecule magnet behaviour in DMF solution while cobaltocene lacks slow spin relaxation neither in powder nor in solution. Multireference quantum mechanical calculations give a non-Aufbau orbital occupation for ferrocenium with small first excitation energy that agrees with the relatively large measured magnetic anisotropy for a transition metal S=1/2 system. The analysis of the spin relaxation shows an important participation of quantum tunnelling, Raman, direct and local-mode mechanisms which depend on temperature and the external field conditions. The calculation of spin-phonon coupling constants for the vibrational modes shows that the first vibrational mode, despite having a low spin-phonon constant, is the most efficient process for the spin relaxation at low temperatures. In such conditions, vibrational modes with higher spin-phonon coupling constants are not populated. Additionally, the vibrational energy of this first mode is in excellent agreement with the experimental fitted value obtained from the local-mode mechanism

Supramolecular Hydrogels Consisting of Nanofibers Increase the Bioavailability of Curcuminoids in Inflammatory Skin Diseases

The low bioavailability of curcuminoids (CCMoids) limits their use in the treatment of inflammatory skin diseases. Our work shows that this constraint can be overcome upon their incorporation into supramolecular hydrogels assembled from a gemini-imidazolium amphiphilic gelator. Three structural CCMoid analogues were used to prepare supramolecular hydrogels, and it was observed that the concentration of both the gelator and CCMoid and the proportion of solvents influence the self-assembly process. Moreover, the mechanical properties of the nanostructured gels were studied to find the optimum gels, which were then further characterized microscopically, and their ability to release the CCMoid was evaluated. The physicochemical properties of the CCMoids play a fundamental role in the interaction with the gelator, influencing not only the gelation but also the morphology at the microscopic level, the mechanical properties, and the biopharmaceutical behavior such as the amount of CCMoid released from the gels. The nanostructured supramolecular hydrogels, which contain the CCMoids at much lower concentrations (μg/mL) in comparison to other products, promote the penetration of the CCMoids within the skin, but not their transdermal permeation, thus preventing any possible systemic effects and representing a safer option for topical administration. As a result, the CCMoid-containing hydrogels can effectively reduce skin inflammation in vivo, proving that these supramolecular systems are excellent alternatives in the treatment of inflammatory skin diseases

Single molecule magnets of cobalt and zinc homo- and heterometallic coordination polymers prepared by a one-step synthetic procedure

The synthesis of 1D cobalt and zinc monometallic and heterometallic coordination polymers (CPs) was carried out applying one-pot synthetic methods by using either supercritical carbon dioxide or ethanol as the solvent. A collection of four 1D CPs were thus obtained by the combination of a metal (or a mixture of metals) with the linker 1,4-bis(4-pyridylmethyl)benzene. The used metallic complexes were zinc and cobalt hexafluoroacetylacetonate, which can easily incorporate pyridine ligands in the coordination sphere of the metal centre. Independently of the used solvent, the precipitated phases involving Zn(II), i.e., homometallic CP of Zn(II) and bimetallic CP of Zn(II)/Co(II), were isostructural. Contrarily, homometallic CPs of Co(II) were precipitated as an isostructural phase of Zn(II) or with a different structure, depending on the used solvent. All the structures were resolved by XRD using synchrotron radiation. In addition, the magnetic properties of the new CPs involving Co(II) were studied. Remarkably, at low temperatures with the application of an external field, they acted as field-induced single molecule magnets

Metallosupramolecular chemistry of novel chiral closo-o-carboranylalcohol pyridine and quinoline ligands: Syntheses, characterization, and properties of cobalt complexes

The cobalt(II) complexes CoCl 2(LOH) 2 (LOH = 1-[R(hydroxy)methyl]-2-R′-1,2-dicarba-closo-dodecaborane (R′ = H or Me; R = 2-pyridyl 3a or 4a, 3-pyridyl 3b or 4b, 4-pyridyl 3c or 4c, 2-quinolyl 3d or 4d, 4-quinolyl 3e or 4e)) and CoCl 2(LOH) 4 (5, R′ = H; R = 4-pyridyl) were synthesized and characterized. Deprotonation of alcohol in 3a afforded the square-planar complex Co II(LO) 2 (6) that oxidized slowly in solution and under air to give the cobaltacarborane complex Co III{(η 5-C 2B 9H 10)(CHOH)(η 1-NC 5H 4)}(η 2-NC 5H 4COO) (7). Crystal structures for 3a, 3a·2MeOH, 3b, 3e, 4c, 4e, 5, 6, and 7 have been determined by X-ray diffraction (XRD). Molecular structures show octahedral (3a, 3a·2MeOH, 5), tetrahedral (3b, 3e, 4c, 4e), and square-planar (6) coordination around Co II centers, whereas 2-pyridyl and quinolyl ligands favor a bidentate N,O-coordination mode and 3- and 4-pyridyl and quinolyl ligands favor a monodentate N-coordination. The supramolecular structures are dominated by intermolecular O-H⋯Cl/O hydrogen bonds and π-π interactions in the case of tetrahedral complexes. The magnetic properties of 3a-c were investigated in the temperature range 2-300 K by means of X MT, which corroborated coordination numbers and geometries as well as provided information on the supramolecular interactions among neighboring molecules for all three compounds. Complex 3a shows solvent accessible channels running parallel to the hydrogen bonding network and is able to uptake methanol vapors to convert into 3a·2MeOH. The structure of 3a is related to that for 3a·2MeOH by rotation of complex molecules within the 1D O-H⋯Cl hydrogen bonding networks and insertion of methanol into it. © 2012 American Chemical Society.Fil: Di Salvo, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; EspañaFil: Teixidor, Francesc. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; EspañaFil: Viñas, Clara. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; EspañaFil: Planas, José Giner. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia de los Materiales de Barcelona; EspañaFil: Light, Mark E.. University of Southampton; Reino UnidoFil: Hursthouse, Michael B.. University of Southampton; Reino Unido. King Abdulaziz University; Arabia SauditaFil: Aliaga-Alcalde, Núria. Universidad de Barcelona; Españ

A remark on the spectrum of the Dirac operator on pseudo-Riemannian spin manifolds

It is proved that the eigenvalues of the Dirac operator on even dimensional space- and time-oriented pseudo-Riemannian spin manifolds lie symmetric to the real and to the imaginary axes, and that the Dirac operator does not have residual spectrum if the associated Riemannian metric is complete. (orig.)Available from TIB Hannover: RR 1596(136) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Carving 1D CoII-carboranylcarboxylate system by organic solvents creating stable trinuclear molecular analogous: complete structural and magnetic studies

This work presents a straightforward methodology to achieve small linear trinuclear molecules based on the CoII-carboranylcarboxylate system obtained by carving a 1D polynuclear analogous system with the use of diethylether. The reaction of the carboranylcarboxylic ligand, 1-CH3-2-CO2H-1,2-closo-C2B10H10 (LH) with different cobalt salts leads to the polynuclear compound [Co2(μ-H2O)(1-CH3-2-CO2-1,2-closo- C2B10H10)4(THF)4], 1 and the polymeric [Co(μ-H2O)(1-CH3-2-CO2-1,2-closo-C2B10H10)2]n(H2O)n 2. This latter 1D chain has been obtained by an unprecedented synthetic strategy for the isolation of cobalt(II) compounds.[Co3(μ-H2O)2(1-CH3-2-CO2-1,2-closo-C2B10H10)6(H2O)2(C4H10O)2], 3 is formed by the dissociation of the polymeric structure that forms 2 when a mild coordinating solvent such as diethylether is added. These compounds have been characterized by analytical and spectroscopic techniques. X-ray analysis of 1 and 3 revealed that 1 presents a dinuclear structure whereas 3 is trinuclear; in both cases a six-coordinated CoII compound with water molecules bridging each of the two CoII centres has been observed. The magnetic properties of 1 and 3 show a weak antiferromagnetic behaviour, respectively, between the CoII centres mediated by two carboxylate ligands and a molecule of wate

Crystalline Curcumin bioMOF obtained by precipitation in supercritical CO2and structural determination by Electron Diffraction Tomography

8sinoneThis article analyzes the use of supercritical CO2green technology in the reactive crystallization processes involved in the formation of a bioMOF that contains curcumin and ZnIImetal centers. A new phase with a [Zn(curcumin)]ncomposition, termed sc-CCMOF-1, is presented. The developed scCO2protocol allows high yields of the small-sized crystalline material, which was characterized by the use of the recently developed electron diffraction tomography method applied to the resolution of submicrometric crystals. A remarkable 3D macrostructure with a complex morphology was obtained. To analyze the crystallization mechanism, multiple identical runs were performed under similar experimental conditions to study in each time period the crystal growth progress ex situ by X-ray diffraction and scanning electron microscopy. These experiments indicated that the process to achieve the sc-CCMOF-1 in a crystalline form involves the formation of amorphous or semicrystalline metastable phases that derived into hierarchical stable and crystalline nanoflower aggregates. In addition, a potential therapeutic application of the bioMOF has been tested by studying the released of the curcumin molecule at neutral pH.nonePortolés-Gil, Nuria; Lanza, Arianna; Aliaga-Alcalde, Núria; Ayllón, José A.; Gemmi, Mauro; Mugnaioli, Enrico*; López-Periago, Ana M.; Domingo, ConcepciónPortolés-Gil, Nuria; Lanza, Arianna; Aliaga-Alcalde, Núria; Ayllón, José A.; Gemmi, Mauro; Mugnaioli, Enrico; López-Periago, Ana M.; Domingo, Concepció

Formation of self-assembled monolayer of curcuminoid molecules on gold surfaces

We investigated the formation of self-assembled monolayers of two thiophene curcuminoid molecules, 2-thphCCM (1) and 3-thphCCM (2), on polycrystalline gold substrates prepared by immersion of the surfaces in a solution of the molecules during 24 h. The functionalized surfaces were studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Despite the fact that both molecules have the same composition and almost the same structure, these molecules exhibit different behavior on the gold surface, which can be explained by the different positions of the sulfur atoms in the terminal aromatic rings. In the case of molecule 1, the complete formation of a SAM can be observed after 24 h of immersion. In the case of molecule 2, the transition from flat-lying to upright configuration on the surface is still in process after 24 h of immersion. This is attributed to the fact that molecule 2 have the sulfur atoms more exposed than molecule 1.Fil: Berlanga, Isadora. Universidad de Chile; ChileFil: Etcheverry Berríos, Álvaro. Universidad de Chile; ChileFil: Mella, Andy. Universidad de Chile; ChileFil: Jullian, Domingo. Universidad de Chile; ChileFil: Gómez Andrade, Victoria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Chile; ChileFil: Aliaga-Alcalde, Núria. Institució Catalana de Recerca i Estudis Avancats; España. Universitat Autònoma de Barcelona; EspañaFil: Fuenzalida, Victor. Universidad de Chile; ChileFil: Flores, Marcos. Universidad de Chile; ChileFil: Soler, Monica. Universidad de Chile; Chil

Intrinsic Permeation and Anti-Inflammatory Evaluation of Curcumin, Bisdemethoxycurcumin and Bisdemethylcurcumin by a Validated HPLC-UV Method

Curcumin shows anti-inflammatory activity, and it has been widely investigated for neurodegenerative diseases, adjuvant treatment in AIDS and antitumor activity against different tumors, among other activities. The goal of this work was to evaluate the capacity of curcumin and its derivatives (bisdemethoxycurcumin and bisdemethylcurcumin) in preventing the irritant effects of topically applied xylol and to assess the intrinsic capacity of curcuminoids in permeating human skin by ex vivo permeation tests. Its secondary goal was to validate an HPLC method to simultaneously determine the curcuminoids in the samples from the ex vivo permeation studies and drug extraction from the skin. Curcuminoid quantification was performed using an RP-C18 column, at isocratic conditions of elution and a detection wavelength of 265 nm. The method was specific with a suitable peak resolution, as well as linear, precise, and accurate in the range of 0.195–3.125 μg/mL for the three curcuminoids. Bisdemethylcurcumin showed the greatest permeation through the human skin, and it was the curcuminoid that was most retained within the human skin. The anti-inflammatory activity of the curcuminoids was evaluated in vivo using a xylol-induced inflammation model in rats. Histological studies were performed to observe any changes in morphology at the microscopic level, and these three curcuminoids were found to be respectful within the skin structure. These results show that these three curcuminoids are suitable for anti-inflammatory formulations for dermal applications, and they can be properly quantified using HPLC-UV

Multiscale study of mononuclear Co" SMMs based on curcuminoid ligands

This work introduces a novel family of Co" species having a curcuminoid (CCMoid) ligand, 9Accm, attached, namely [Co(9Accm)₂(py)₂] (1) and [Co(9Accm)₂(2,20-bpy)] (2), achieved in high yields by the use of a microwave reactor, and exhibiting two different arrangements for the 9Accm ligands, described as "cis"(2) and "trans"(1). The study of the similarities/differences of the magnetic, luminescent and surface behaviors of the two new species, 1 and 2, is the main objective of the present work. The determined single-crystal structures of both compounds are the only Co"-CCMoid structures described in the literature so far. Both compounds exhibit large positive D values, that of 1 (D = +74 cm⁻¹) being three times larger than that of 2 (D = +24 cm⁻¹), and behave as mononuclear Single-Molecule Magnets (SMMs) in the presence of an external magnetic field. Their similar structures but different anisotropy and SMM characteristics provide, for the first time, deep insight on the spin-orbital effects thanks to the use of CASSCF/NEVPT2 calculations implementing such contributions. Further magnetic studies were performed in solution by means of paramagnetic ¹H NMR, where both compounds (1 and 2) are stable in CDCl₃ and display high symmetry. Paramagnetic NMR appears to be a useful diagnostic tool for the identification of such molecules in solution, where the resonance values found for the methine group (-CH-) of 9Accm vary significantly depending on the cis or trans disposition of the ligands. Fluorescence studies show that both systems display chelation enhancement of quenching (CHEQ) with regard to the free ligand, while 1 and 2 display similar quantum yields. Deposition of 1-2 on HOPG and Si(100) surfaces using spin-coating was studied using AFM; UV photoemission experiments under the same conditions display 2 as the most robust system. The measured occupied density of states of 2 with UV photoemission is in excellent agreement with theoretical DFT calculations