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Resumen del trabajo presentado a la 20th International Conference on Solid Compounds of Transition Elements, celebrada del 11 al 15 de abril de 2016 en Zaragoza (España)., Graphene, a two-dimensional carbon layer, is expected to contribute to a new revolution in electronics. However, the fact that graphene is not magnetic, just as any other carbon derivative, hinders its application to spintronics, i.e. to magnetic data storage and processing. A way to circumvent this difficulty is by doping graphene with either point-like defects or with molecules having a localized spin, such as free-radical systems. The nature of the ensuing magnetism and the existence of a coupling to graphene’s Dirac electrons remains, however, a subject of controversy. Besides, very little is known about the dynamics of spins in graphene. In this work, we have studied a new hybrid material formed by anchoring Fe4 molecular clusters, with a net spin S = 4, to graphene layers. In crystalline form, these clusters behave as single-molecule magnets, i.e. they show magnetic memory effects and slow relaxation at very low temperatures. Below 1 K, the dominant relaxation process is mediated by pure spin tunneling events. Because of the compact structure of its magnetic core, Fe4 clusters retain their electronic and magnetic properties when they are deposited onto solid substrates. Therefore, they provide an close to ideal situation to study how the spin dynamics is affected by the interaction with graphene. We have performed ac susceptibility experiments, with frequencies ranging from 0.1 Hz up to 200 kHz, using a high-sensitivity micro-SQUID susceptometer installed in a 3He-4He dilution refrigerator that gives access to the close neighbourhood of absolute zero (T > 11 mK). Experiments have been performed on the Ge4@graphene hybrid and on single crystals of Fe4 molecular magnets having different ligands and concentrations. The results confirm that properties such as the net molecular spin and magnetic anisotropy are preserved in the former material. However, the spin dynamics is dramatically affected by the presence of the graphene layer. In particular, the tunneling rate, measured at very low temperature, is enhanced by six orders of magnitude. We argue that the effect is due to a very effective shielding of dipole-dipole interactions between the molecules and to the crystal field generated by the graphene layer, which introduces new terms in the molecular spin Hamiltonian that break spin tunneling selection rules. As a result, the molecular spins enter a new dynamical regime, in which tunneling proceeds coherently. These results show that graphene can provide a useful platform for the coherent control of quantum spins with electric fields.

Peptide-functionalized gold nanoparticles are supramolecular systems that can mimic natural proteins or DNA. In this work, we describe the preparation, the analysis, and the biological evaluation of gold nanoparticles linked to pseudopeptide foldamers containing one to eight L-Ala-D-Oxd (Ala = alanine; Oxd = 4-carboxy-5-methyloxazolidin-2-one) residues. The nanoparticles become increasingly organized as the number of such moieties increases. Moreover, from the analysis of chiroptical signals we find that the chirality of the gold surface becomes more evident with decreasing foldamer length. Finally, these systems display no cytotoxicity towards HeLa cells and are good candidates to promote drug delivery once equipped with biologically active moieties.

We present an implementation of strategies to deposit single-molecule magnets (SMMs) using microcontact printing microCP). We describe different approaches of microCP to print stripes of a sulfur-functionalized dodecamanganese (III, IV) cluster on gold surfaces. Comparison by atomic force microscopy profile analysis of the patterned structures confirms the formation of a chemically stable single layer of SMMs. Images based on chemical contrast, obtained by time-of-flight secondary ion mass spectrometry, confirm the patterned structure.

The results of an experiment with two species of epiphytic angiosperms (Tillandsia caput-medusae and T. bulbosa) for monitoring polycyclic aromatic hydrocarbons (PAHs) in the air of Florence, Italy, are presented. PAHs are compounds known to be dangerous because of their carcinogenic potential, and among cormophytes, tillands (monocotyledons equipped with peculiar, specialised, epidermal trichomes) are considered promising for air pollution biomonitoring. PAHs data were obtained using GC/MS analysis of plant extracts. Analytical data indicated an increasing trend in time of PAHs bioaccumulation. This result was compared with instrumentally recorded parameters such as meteorological (rain) and environmental ones (PM10), indicating that trichome-operated physical capture of aerial particles was prominent in PAHs bioaccumulation on tillands. SEM (scanning electron microscope) observations confirmed the role of the trichomes. This work indicates that tillands are particularly useful, low-cost, biomonitoring organisms inside their area of distribution (all Latin American countries and southern USA) where these plants are easily available, but also wherever the climate allows them to surviveSe presentan los resultados de un experimento con dos especies de angiospermas epífitas (Tillandsia caput-medusae y T. bulbosa) para monitorear hidrocarbonos aromáticos policíclicos (PAHs) en el aire de Florencia, Italia. Los PAHs son compuestos que se sabe son peligrosos por su potencial carcinogénico, y, entre las cormófitas, las tilandsias (monocotiledóneas equipadas con tricomas epidérmicos, especializados y peculiares) son consideradas promisorias para el biomonitoreo de la contaminación del aire. Se obtuvieron datos de PAHs usando el análisis de GC/MS de extractos de plantas. Los datos analíticos indicaron una tendencia creciente de la bioacumulación de PAH’s en el tiempo. Este resultado se comparó con los parámetros registrados instrumentalmente como los meteorológicos (lluvia) y los ambientales (PM10), indicando que la captura física de partículas aéreas por medio de tricomas era prominente en la bioacumulación de PAHs en las tilandsias. Las observaciones de SEM (microscopio electrónico de barrido) confirmaron el papel de los tricomas. Este trabajo indica que las tilandsias son organismos de biomonitoreo, de bajo costo y particularmente útiles dentro de su área de distribución (todos los países Latinoamericanos y el sureste de EUA) donde estas plantas son disponibles fácilmente, pero también donde el clima les permite sobrevivir

The results of an experiment with two species of epiphytic angiosperms (Tillandsia caput-medusae and T. bulbosa) for monitoring polycyclic aromatic hydrocarbons (PAHs) in the air of Florence, Italy, are presented. PAHs are compounds known to be dangerous because of their carcinogenic potential, and among cormophytes, tillands (monocotyledons equipped with peculiar, specialised, epidermal trichomes) are considered promising for air pollution biomonitoring. PAHs data were obtained using GC/MS analysis of plant extracts. Analytical data indicated an increasing trend in time of PAHs bioaccumulation. This result was compared with instrumentally recorded parameters such as meteorological (rain) and environmental ones (PM10), indicating that trichome-operated physical capture of aerial particles was prominent in PAHs bioaccumulation on tillands. SEM (scanning electron microscope) observations confirmed the role of the trichomes. This work indicates that tillands are particularly useful, low-cost, biomonitoring organisms inside their area of distribution (all Latin American countries and southern USA) where these plants are easily available, but also wherever the climate allows them to survive. Se presentan los resultados de un experimento con dos especies de angiospermas epífitas (Tillandsia caputmedusae y T. bulbosa) para monitorear hidrocarbonos aromáticos policíclicos (PAHs) en el aire de Florencia, Italia. Los PAHs son compuestos que se sabe son peligrosos por su potencial carcinogénico, y, entre las cormófitas, las tilandsias (monocotiledóneas equipadas con tricomas epidérmicos, especializados y peculiares) son consideradas promisorias para el biomonitoreo de la contaminación del aire. Se obtuvieron datos de PAHs usando el análisis de GC/MS de extractos de plantas. Los datos analíticos indicaron una tendencia creciente de la bioacumulación de PAH’s en el tiempo. Este resultado se comparó con los parámetros registrados instrumentalmente como los meteorológicos (lluvia) y los ambientales (PM10), indicando que la captura física de partículas aéreas por medio de tricomas era prominente en la bioacumulación de PAHs en las tilandsias. Las observaciones de SEM (microscopio electrónico de barrido) confirmaron el papel de los tricomas. Este trabajo indica que las tilandsias son organismos de biomonitoreo, de bajo costo y particularmente útiles dentro de su área de distribución (todos los países Latinoamericanos y el sureste de EUA) donde estas plantas son disponibles fácilmente, pero también donde el clima les permite sobrevivir

WOS: 000430989200009, Novel mixed-ligand coordination frameworks, occurring concomitantly namely [Cu(Im)(3)(H(2)Cit)] (1) and [Cu(Im)(2)(HCit)]center dot HIm (2) (with Im = imidazole and H(4)Cit = citric acid) were obtained as a result of the one-pot reaction between imidazole, citric acid and copper chloride. The complexes were structurally characterized by elemental analysis, FTIR spectroscopy and X-ray diffraction. The two structures were found to be connected through 3D hydrogen-bonding networks examined by means of the Hirshfeld surface analysis which highlighted the presence of O-H center dot center dot center dot O, N-H center dot center dot center dot O and C-H center dot center dot center dot O H-bonds together with the pi center dot center dot center dot lp interactions. A topological analysis of the underlying nets corresponding to the two hydrogen-bonded frameworks was carried out. Moreover, quantum chemical calculations were performed using the HF method with 6-31G(d) and LANL2DZ levels in the gas phase, and therefore the optimized structures, the IR, H-1 NMR, C-13 NMR spectra and the electronic structure descriptors were examined in detail. Furthermore, the magnetic properties of (1) and (2) were also investigated. The complexes showed remarkable antimicrobial and antifungal inhibition activities. (C) 2018 Elsevier B.V. All rights reserved., Universite Abbes Laghrour Khenchela (Algeria); TUBITAK ULAKBIM; High Performance and Grid Computing Center (TRUBA Resources, Turkey); Spanish MINECO [MAT2016-78155-C2-1-R]; FPI grant [BES-2011-046948]; Gobierno del Principado de Asturias [GRUPIN14-060]; FEDER, The financial support from Universite Abbes Laghrour Khenchela (Algeria), TUBITAK ULAKBIM, High Performance and Grid Computing Center (TRUBA Resources, Turkey), Spanish MINECO MAT2016-78155-C2-1-R, FPI grant BES-2011-046948 to MSM.A., Gobierno del Principado de Asturias (GRUPIN14-060) and FEDER are acknowledged. A.D. gratefully acknowledges Pr. A. Djelloul and Pr. A. Boumaza (University of Khenchela) for the FTIR measurements.

WOS: 000474406600594, …

With the aim of investigating the impact of lattice solvent on the processability of tetrairon(III) single-molecule magnets by thermal sublimation, two new solvatomorphs of [Fe4(LPh)2(dpm)6] (1) were prepared and structurally characterized along with unsolvated 1 (H3LPh = 2-(hydroxymethyl)-2-phenylpropane-1,3-diol, Hdpm = dipivaloylmethane). All solvatomorphs crystallize in the C2/c space-group whereas solvent-free 1 belongs to a different space group (P21/c). The pitch of the propeller-like tetrairon(III) molecules is distinctly different in solvated vs. unsolvated phases, highlighting the effect of intermolecular interactions and crystal packing. The compounds sublimate at 450 - 490 K (in high vacuum conditions ∼ 10−6-10−7 mbar) affording thick deposits which display different crystallinity depending on the particular starting material used. However, all sublimated samples retain slow magnetic relaxation with thermal activation parameters comparable to those of microcrystalline 1. The results indicate that factors other than mere molecular structure have a limited influence on the processability of these materials by thermal sublimation.

Tetrairon(III) single-molecule magnets [Fe4(pPy)2(dpm)6] (1) (H3pPy=2-(hydroxymethyl)-2-(pyridin-4-yl)propane-1,3-diol, Hdpm=dipivaloylmethane) have been deliberately organized into supramolecular chains by reaction with Ru(II)Ru(II) or Ru(II)Ru(III) paddlewheel complexes. The products [Fe4(pPy)2(dpm)6][Ru2(OAc)4](BF4)x with x=0 (2 a) or x=1 (2 b) differ in the electron count on the paramagnetic diruthenium bridges and display hysteresis loops of substantially different shape. Owing to their large easy-plane anisotropy, the s=1 diruthenium(II,II) units in 2 a act as effective s(eff)=0 spins and lead to negligible intrachain communication. By contrast, the mixed-valent bridges (s=3/2, s(eff)=1/2) in 2 b introduce a significant exchange bias, with concomitant enhancement of the remnant magnetization. Our results suggest the possibility to use electron transfer to tune intermolecular communication in redox-responsive arrays of SMMs.

Some hybrid foldamers of various length, all containing the (4R,5S)-4-carboxy-5-methyloxazolidin-2-one (d-Oxd) moiety alternating with an l-amino acid (l-Val, l-Lys, or l-Ala), were prepared in order to study their preferred conformations and to evaluate their biological activity. Surprisingly, only the longer oligomers containing l-Ala fold into well-established helices, whereas all the other oligomers give partially unfolded turn structures. Nevertheless, they all show good biocompatibility, with no detrimental effects up to 64 μm. After equipping some selected foldamers with the fluorescent tag rhodamine B, a quantitative analysis was performed by dose- and time-response fluorescence-activated cell sorting (FACS) assays with human HeLa cells and primary blood lymphocytes, granulocytes, and monocytes. Among the cell types analyzed, the oligomers associated with monocytes and granulocytes with greatest efficacy, still visible after 24 h incubation. This effect is even more pronounced for foldamers that are able to form stable helices.