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Topological spin textures, such as magnetic skyrmions observed in certain chiral magnets, are one of the most interesting ordered phases in condensed matter. A skyrmion is a swirling spin structure carrying a topological quantum number. Skyrmions were first observed in MnSi, in 2009, and later observed in Cu 2 OSeO 3 , a chiral antiferromagnet with T N = 58 K that can be synthesized by reacting CuO and SeO2 at 600 ° C . Using a transport agent (typically ammonium chloride) in a chemical vapour transport reaction, single crystals can be grown. As skyrmion lattices may find use in nanotechnological devices, such as data storage systems and in other applications, the magnetic properties of nano-sized compounds deserve to be investigated. The following work presents the synthesis and magnetic studies of the nanocrystalline form of Cu 2 OSeO 3 obtained by an alternative route, thermal decomposition of CuSeO3·2 H2O. This procedure afforded nanostructured samples of reasonable purity ( > 95 % ) . Structural, morphological and magnetic characterization of these samples are reported, aiming to study the effect of nanostructuring on the magnetic phases, in particular the presence and stability of the skyrmionic lattice.

A new phosphonic acid, (2-oxo-2-(thiophen-2-yl)ethyl) phosphonic acid (OTEPA), was synthesized and its molecular and crystal structures investigated using several experimental techniques complemented by different types of calculations. The experimental techniques used include infrared and Raman spectroscopies and single crystal X-ray crystallography. Calculations were performed at both molecular mechanics and DFT(B3LYP)/6–311++G(d,p) levels of approximation, for the isolated molecule. The conformational space of OTEPA was investigated and the most stable conformers characterized both structurally and spectroscopically. It was found that in the lower energy conformers of OTEPA an intramolecular H-bond exists between one of the OH groups of the phosphonic acid fragment and the carbonyl oxygen atom. The two lowest energy conformers have the sulphur atom of the thiophene ring eclipsed with the carbonyl oxygen atom, allowing for the establishment of an O⋯S stabilizing contact, similar to the N⋯S type contact found previously in other molecular systems. Noteworthy, in the crystalline phase the OTEPA molecules do not assume one of the most stable conformations for the isolated molecule, but exist in a conformation similar to that of high-energy conformers, which have predicted energies relative to the conformational ground state higher than 13 kJ mol−1. The infrared spectra of the monomeric molecules of the compound isolated in a low temperature solid argon matrix and of the crystal of the neat compound were also investigated and assigned, together with the Raman spectrum of the crystalline compound.

A new polymorph of a thioimidazole disulfide (2-[(1H-imidazol-2-yl) disulfanyl]-1H-imidazole; IDI) was prepared, which exhibits a rare crystal structure with 4 symmetry independent molecules (Z′ = 4; Z = 16) and all possible conformers predicted for the isolated molecule within the crystal unit cell. The crystal structure is non-centrosymmetric, Ia monoclinic space group, with cell parameters: a = 7.45910(10) A, b = 44.1680(8) A, c = 11.3522(2) A, and β = 103.0240(10)°. The four symmetry independent molecules establish an extensive hydrogen bond network involving NH groups as proton donors and N atoms of neighboring molecules as acceptors. A computational structural investigation of the isolated molecule of the compound was performed at the DFT(B3LYP)/6-311++G(d,p) level of theory in order to characterize in detail its conformational space, and these results were taken into account to evaluate the role of conformational flexibility and intermolecular interactions in the observed crystal packing. The excep...

Topological insulators are a quantum state of matter that has recently created a great interest among the scientific community, with Bi 2 Se 3 being one of the most extensively studied materials. Here, we demonstrate that polycrystalline nanostructured samples of Bi 2 Se 3 preserve the existence of topological surface states, where electrons cannot be localised. The nanosheet crystals were synthesised by a microwave-assisted method and their structure, composition and morphology thoroughly characterised. The transport properties of a textured polycrystalline sample with strong preferred orientation along the c-axis were measured, showing the presence of the weak anti-localisation effect and Shubnikov-de Haas oscillations. These features are robust against the presence of non-magnetic impurities and structural defects.

Pyrenes bear a propensity to form fluorescent excimers, and thus this chromophore is often found in sensors and fluorescent probes. 2-FunctionaIized pyrenes are of particular interest, however the preparation of these scaffolds is not trivial, involving synthetic routes that require 4,5,9,10-tetrahydropyrene as a key intermediate. Herein, the development and optimization of routes for the synthesis of 2-functionalized pyrene-derived building blocks, with potential to be used as tags in the preparation of fluorescent probes, is described. Additionally, the crystal structures of ethyl 4,5,9,10-tetrahydro-2-pyrene-5-oxopentanoate and 2-acetyl-4,5,9,10-tetrahydropyrene revealed distinct conformations of the saturated tetrahydropyrene rings. (C) 2017 Elsevier Ltd. All rights reserved. FEDER [PTDC/QUI-BIQ/112943/2009, PTDC/MAR-BIO/4132/2014, UID/Multi/04326/2013, UID/FIS/04564/2016] Fundacao para a Ciencia e a Tecnologia (FCT), Portugal info:eu-repo/semantics/publishedVersion

The synthesis of a new hydrazone, 2-oxoacenaphthylen-1(2H)-ylidene nicotinohydrazide, and its structural and spectroscopic characterization is reported. The obtained powder was recrystallized from DMSO and ethanol that afforded small crystals used for single-crystal X-ray diffraction studies. The compound was found to crystallize in two polymorphs, depending on the crystallization conditions. One of the polymorphs (form I) crystallizes in the centrosymmetric P21/c monoclinic space group, the other (form II) crystallizes in the non-centrosymmetric, but achiral, orthorhombic space group P212121. Conformation of the molecules is similar in both polymorphs, but the network of weak intermolecular interactions determining the crystal packing is different. In form II an additional C-H⋯O bond connects molecules related by the screw-axis running parallel to the a-axis. Crystals of both polymorphs were also screened by FT-IR and Raman microscopy; a detailed analysis of the spectra and comparison with those of the isolated molecule calculated by ab-initio HF/MP2 and DFT/B3LYP methods using a correlation consistent cc-pVDZ basis set is presented. In addition, UV-vis and NMR studies were performed in solution.

Three novel copper(I) complexes with three methyl 4-aryl-6-methyl-3,4-dihydropyrimidine-2(1H)-thione-5-carboxylate ligands were synthesized and fully characterized by elemental analysis, magnetic susceptibility, molar conductivity, ESI-MS, FTIR, UV–Vis and NMR. The difference between the three ligands is located in the aryl group: 4-(tert-butyl)phenyl (HL1), 2,6-dichlorophenyl (HL2) and 2,4-dichlorophenyl (HL3). Two ligands and complex 2 were characterized by single-crystal X-ray diffraction. The complex [CuCl(HL2)2]·dmso exhibits an almost perfect trigonal planar coordination geometry crystallizing in a space group P21/n, through the two sulfur atoms of the ligands, one chlorine atom bonded to the copper(I) and solvated with one molecule of dimethyl sulfoxide. The anticancer activity was evaluated in vitro against human colorectal cancer (CRC) cell line (Caco-2). The complexes have cytotoxic effect with IC50 values of 28.46, 25.03 and 38.83 μM respectively. Moreover, complexes 1 and 2 are able to strongly induce apoptosis in this CRC in vitro model.

New copper(I) complexes of four methyl 4-aryl-6-methyl-3,4-dihydropyrimidine-2(1H)-thione-5-carboxylate ligands, where the aryl group is phenyl (HL1), 1-naphthalenyl (HL2), 2-bromophenyl (HL3) and 2-chlorophenyl (HL4), have been synthesized. Structural characterization was carried out using different techniques, such as elemental analysis, mass spectrometry, molar conductivity, magnetic susceptibility, FTIR, UV–Vis/luminescence and NMR spectroscopies, and allowed us to propose the general formula [CuCl(HL)2] for all complexes. Furthermore, X-ray studies of ligands HL2 and HL3 and the complex [CuCl(HL2)2]·3dmso have been performed. The complex crystallizes in the triclinic space group P 1 ¯ and adopts a less common, almost perfect, trigonal planar coordination geometry, through the two sulfur atoms of the ligands and one chlorine atom bonded to the metal. The intramolecular hydrogen bonds between the chlorine and the N1H stabilize the structure of the complex. Evaluation of the in vitro activity against human breast cancer representatives of hormonal receptor positive (MCF7) and triple negative (HCC1806) tumors revealed a higher activity in the complexes than in the ligands. Considering particularly HCC1806 cells for which no targeted treatment is available, complexes [CuCl(HL1)2] and [CuCl(HL3)2] exhibited IC50 values of 5.51 and 5.30 μM, respectively, which are lower than the currently used chemotherapeutic drugs.

WOS: 000361161500008, In this work, we report the synthesis of a novel quinoline derivative, ethyl 4-chloro-7-iodoquinoline-3-carboxylate (CIQC), and its structural, conformational and vibrational characterization. The compound was studied in its neat solid phases (crystalline and low-temperature amorphous phases) and as an isolated species in a cryogenic argon matrix (at similar to 15 K). Infrared spectroscopy and single crystal X-ray diffraction were the chosen experimental techniques. The conformational space and the vibrational spectra of the isolated molecules of the compound were also investigated theoretically at the B3LYP/LANL2DZ-Fcc-pVDZ level of approximation. The CIQC molecule exists in four different conformers, with predicted populations of 4225:17:16% at room temperature (rt). The rt equilibrium conformational mixture was successfully trapped in an argon matrix, at 15K, and the vibrational signatures of the conformers were determined. Upon annealing of the matrix of the compound at higher temperatures (similar to 40 K), conversion of the higher energy forms into the most stable conformer was found to take place, in consonance with the low predicted barriers for conformational isomerization. Sublimation of the host matrix argon atoms (at similar to 43 K) led to production of a low-temperature amorphous state of CIQC, containing the lowest but also the higher energy conformers. At T similar to 233-243 K, the amorphous rearranged to the crystalline state, whose molecular unit corresponds to the most stable CIQC conformer, as shown both by infrared spectroscopy and single crystal X-ray diffraction. At room temperature CIQC crystallizes in the hexagonal P6(3)/m space group, with a=b=17.7928(2) angstrom, and c=6.9830(1) angstrom. The molecules lie on a crystallographic mirror plane and are stacked in layers along the c-axis. The main packing motif consists of a group of three molecules, related by a three-fold rotation, joined together by weak C-H ... O hydrogen bonds, Fundacao para a Ciencia e a Tecnologia (FCT) [PEst-OE/QUI/UI0313/2014, PEst-CCMAR/Multi/04326/2013]; QREN-COMPETE-UE; FCT [SFRH/BPD/88372/2012, RECI/BBB-BQB/0230/2012]; [SFRH/BD/81821/2011], The authors gratefully acknowledge Fundacao para a Ciencia e a Tecnologia (FCT), through the projects PEst-OE/QUI/UI0313/2014 (Coimbra Chemistry Centre) and PEst-CCMAR/Multi/04326/2013 (Center of Marine Sciences, CCMAR), cofunded by QREN-COMPETE-UE. Financial support has also been provided within the framework of the FCT post-doctoral grant SFRH/BPD/88372/2012 (N. K.) and the doctoral grant SFRH/BD/81821/2011 (P. H.). NMR spectrometers used are part of The National NMR Facility, supported by FCT (RECI/BBB-BQB/0230/2012).

The reactivity of 2,2-bis(furan-2-yl)propane towards nitroso- and azoalkenes was explored. The expected hetero-Diels–Alder adducts, 4a,7a-dihydro-4H-furo[2,3-e][1,2]oxazines and 4a,7a-dihydrofuro[3,2-c]pyridazines, were obtained in good yield. The furo-oxazines were easily converted into the corresponding bis(furan-2-yl)methanes bearing an open-chain oxime. Interestingly, the synthesized furo-pyridazines showed a different chemical behavior. In the presence of HCl, they underwent a rearrangement giving 6-(2-oxobutyl)-1,6-dihydropyridazine derivatives in a process having as its key step a furan ring-opening reaction. The synthesis of 4a,7a-dihydrofuro[3,2-c]pyridazines from 2-methylfuran and the subsequent acid-catalysed rearrangement to the corresponding 6-(2-oxopropyl)-1,6-dihydropyridazines was also achieved.

Thermal reactions of 1-(thiophene-2-yl)-1H-tetrazoles are reported for the first time. The solution thermolysis of 1-(thiophene-2-yl)-1H-tetrazoles under conventional heating and microwave irradiation afforded the unexpected new thieno[2,3-d]pyrimidines incorporating two thiophene rings, which were obtained as major or only product. The synthesis of these heterocycles was rationalized considering the initial nitrogen elimination to generate imidoylnitrene followed by rearrangement to the corresponding carbodiimide and subsequent cyclization triggered by the nucleophilic attack of the in situ generated 2-aminothiophene. The flash vacuum pyrolysis and solution thermolysis of 1-(thiophene-2-yl)-1H-tetrazoles also gave thieno[2,3-d]imidazoles via intramolecular formal insertion into a C–C bond of the corresponding imidoylnitrene intermediate.

The molecular structure, vibrational spectra and photochemistry of 5-methylhydantoin (C4H6N2O2; 5-MH) were studied by matrix isolation infrared spectroscopy and theoretical calculations at the DFT(B3LYP)/6-311++G(d,p) theory level. The natural bond orbital (NBO) analysis approach was used to study in detail the electronic structure of the minimum energy structure of 5-MH, namely the specific characteristics of the sigma and pi electronic systems of the molecule and the stabilizing orbital interactions. UV irradiation of 5-MH isolated in argon matrix resulted in its photofragmentation through a single photochemical pathway, yielding isocyanic acid, ethanimine, and carbon monoxide, thus following a pattern already observed before for the parent hydantoin and 1-methylhydantoin molecules. The investigation of the thermal properties of 5-MH was undertaken by differential scanning calorimetry (DSC), polarized light thermal microscopy (PLTM) and Raman spectroscopy. Four different polymorphs of 5-MH were identified. The crystal structure of one of the polymorphs, for which it was possible to grow up suitable crystals, was determined by X-ray diffraction (XRD). Two of the additional polymorphs were characterized by powder XRD, which confirmed the molecules pack in different crystallographic arrangements.

A new sodium salt, sodium triphenylacetate has been synthesized and characterized by single-crystal X-ray diffraction: triclinic, P-1 with a = 8.3846(2) angstrom, b = 13.5992(3) angstrom, c = 15.5288(3) angstrom, a = 76.7270(11)degrees, b = 74.4500(11)degrees, c = 84.7410(13)degrees, M-W = 656.65, V = 1659.42(6) angstrom(3), Z = 2. The triphenylacetic molecules bridge the metallic ions forming an infinite columnar structure. Calorimetric data does not support the existence of a mesophase induced by temperature.

The angular dependent magnetoresistance of the superconducting ferromagnet UCoGe is studied in detail at 40 mK to fields of 18 T in a single crystal sample with a low residual resistivity ratio [R(300 K)/R(1 K)=RRR=5]. A ferro-to-ferrimagnetic transition near 9 T that depends only on the field component along the uniaxial magnetic c axis is observed in both transport and susceptibility. Reverse hysteresis in the magnetoresistance in the critical field region indicates a coupling of the superconductivity to the magnetization for fields aligned closely to the ab plane. These results corroborate and advance previous findings on higher residual resistivity ratio samples.

This contribution focuses on the structural and physical properties of U-based Laves phases. It starts with the structural description of the different type of Laves phases, followed by a brief description of the factors that affect their stability. The majority of the uranium Laves phases show a weakly paramagnetic behaviour. The reason is the compact structure of the phases that leads to small a U-U spacing as well as very high coordination numbers, regarding both the uranium and the ligands sublattices, which brings a strong hybridization with non-f states. However, there are some exceptions of uranium Laves phases that do order magnetically (UFe2, UNi2 and the recently discovered U2Fe3Ge compound). These exceptions are discussed in more detail in the present manuscript.