Supercritical CO2 Synthesis of Porous Metalloporphyrin Frameworks: Application in Photodynamic Therapy.

A series of porous metalloporphyrin frameworks prepared from the 5,10,15,20-tetra(4-pyridyl)porphyrin (H2TPyP) linker and four metal complexes, M(hfac)2 M = Cu(II), Zn(II), Co(II), and Ni(II) (hfac: 1,1,1,5,5,5-hexafluoroacetylacetonate), were obtained using supercritical CO2 (scCO2) as a solvent. All the materials, named generically as [M-TPyP] n , formed porous metal-organic frameworks (MOFs), with surface areas of ∼450 m2 g-1. All MOFs were formed through the coordination of the metal to the exocyclic pyridine moieties in the porphyrin linker. For Cu(II), Zn(II), and Co(II), incomplete metal coordination of the inner pyrrole ring throughout the structure was observed, giving place to MOFs with substitutional defects and leading to a certain level of disorder and limited crystallinity. These samples, prepared using scCO2, were precipitated as nano- to micrometric powders. Separately, a layering technique from a mixture of organic solvents was used to crystallize high-quality crystals of the Co(II) based MOF, obtained with the formula [{Co(hfac)2}2H2TPyP] n . The crystal structure of this MOF was elucidated by single-crystal synchrotron X-ray diffraction. The Zn(II)-based MOF was selected as a potential photodynamic therapy drug in the SKBR-3 tumoral cell line showing outstanding performance. This MOF resulted to be nontoxic, but after 15 min of irradiation at 630 nm, using either 1 or 5 µM concentration of the product, almost 70% of tumor cells died after 72 h.

Discriminating the origin of calcium oxalate monohydrate formation in kidney stones via synchrotron microdiffraction.

Nephrolithiasis is a multifactor disease that produces nephrolites in the kidneys. Calcium oxalate hydrate (dihydrated, COD, or monohydrated, COM) stones are the most common ones with more than sixty percent incidence worldwide. They are related to different pathologies, COD with hypercalciuria and COM with hyperoxaluria. COD is an unstable species and transforms into COM (herein named TRA to distinguish the origin of the monohydrated species). TRA and COM are chemically and crystallographically identical leading to misdiagnosis and recurrence increase. In the current study, the composition and crystalline structures of several calcium oxalate stones, classified by morpho-constitutional analysis, were examined by IR and synchrotron through-the-substrate micro-X-ray diffraction (tts-µXRD). Both IR and linear diffractogram studies were able to distinguish between the monohydrated and dihydrated phases but not between COM and TRA, as expected. The analysis of 2D diffraction patterns revealed that TRA showed a lower degree of crystallinity and less texture with respect to COM which can be used as a signature to distinguish between the two. This study confirms that despite the subtle differences between COM and TRA, the origin of the monohydrate oxalates can be unraveled using tts-µXRD. This valuable information should be taken into account in order to improve patients' diagnosis and reduce recurrence by considering and treating the origin of the formed stones.

A captured room temperature stable Wheland intermediate as a key structure for the orthogonal decoration of 4-amino-pyrido[2,3-d]pyrimidin-7(8H)-ones.

Wheland intermediates are usually unstable compounds and only a few have been isolated at very low temperatures. During our work on tyrosine kinase inhibitors, we studied the bromination of 7 in order to obtain a dibromo substituted pyrido[2,3-d]pyrimidin-7(8H)-one which could be orthogonally decorated. Surprisingly, treatment of 7 with 3 equiv. of Br2 in acetic acid (AcOH) afforded 12, a captured room temperature stable Wheland bromination intermediate stabilized by the bromination of the imino tautomer of the amino group at C4 of the pyridopyrimidine skeleton. The structure was confirmed by crystal structure determination from powder X-ray diffraction data. Treatment of 12 with DMSO afforded the dibromo substituted compound 13 presenting a bromine atom at C6 and C5-C6 unsaturation. 13 was directly accessed by treating 7 with N-bromosuccinimide (NBS), a protocol extended to other compounds using NBS or N-iodosuccinimide (NIS) to afford 6-halo substituted systems. 26, bearing an iodine at C6 and a p-bromophenylamino at C2, allows the orthogonal decoration of pyridopyrimidines.

Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4].

A novel imidazolium halometallate molten salt with formula (trimim)[FeCl4] (trimim: 1,2,3-trimethylimidazolium) was synthetized and studied with structural and physico-chemical characterization. Variable-temperature synchrotron X-ray powder diffraction (SXPD) from 100 to 400 K revealed two structural transitions at 200 and 300 K. Three different crystal structures were determined combining single crystal X-ray diffraction (SCXD), neutron powder diffraction (NPD), and SXPD. From 100 to 200 K, the compound exhibits a monoclinic crystal structure with space group P21/c. At 200 K, the former crystal system and space group are retained, but a disorder in the organic cations is introduced. Above 300 K, the structure transits to the orthorhombic space group Pbcn, retaining the crystallinity up to 400 K. The study of the thermal expansion process in this temperature range showed anisotropically evolving cell parameters with an axial negative thermal expansion. Such an induction occurs immediately after the crystal phase transition due to the translational and reorientational dynamic displacements of the imidazolium cation within the crystal building. Electrochemical impedance spectroscopy (EIS) demonstrated that this motion implies a high and stable solid-state ionic conduction (range from 4 × 10-6 S cm-1 at room temperature to 5.5 × 10-5 S cm-1 at 400 K). In addition, magnetization and heat capacity measurements proved the presence of a three-dimensional antiferromagnetic ordering below 3 K. The magnetic structure, determined by neutron powder diffraction, corresponds to ferromagnetic chains along the a-axis, which are antiferromagnetically coupled to the nearest neighboring chains through an intricate network of superexchange pathways, in agreement with the magnetometry measurements.

Correction: Crystal structure, magneto-structural correlation, thermal and electrical studies of an imidazolium halometallate molten salt: (trimim)[FeCl4].

[This corrects the article DOI: 10.1039/D0RA00245C.].

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.

Multiscale understanding of tricalcium silicate hydration reactions.

Tricalcium silicate, the main constituent of Portland cement, hydrates to produce crystalline calcium hydroxide and calcium-silicate-hydrates (C-S-H) nanocrystalline gel. This hydration reaction is poorly understood at the nanoscale. The understanding of atomic arrangement in nanocrystalline phases is intrinsically complicated and this challenge is exacerbated by the presence of additional crystalline phase(s). Here, we use calorimetry and synchrotron X-ray powder diffraction to quantitatively follow tricalcium silicate hydration process: i) its dissolution, ii) portlandite crystallization and iii) C-S-H gel precipitation. Chiefly, synchrotron pair distribution function (PDF) allows to identify a defective clinotobermorite, Ca11Si9O28(OH)2.8.5H2O, as the nanocrystalline component of C-S-H. Furthermore, PDF analysis also indicates that C-S-H gel contains monolayer calcium hydroxide which is stretched as recently predicted by first principles calculations. These outcomes, plus additional laboratory characterization, yielded a multiscale picture for C-S-H nanocomposite gel which explains the observed densities and Ca/Si atomic ratios at the nano- and meso- scales.

Magnetic Structure, Single-Crystal to Single-Crystal Transition, and Thermal Expansion Study of the (Edimim)[FeCl4] Halometalate Compound.

This contribution addresses standing questions about the nature and consequences of the ion self-assembly and magnetic structures, as well as the molecular motion of the crystalline structure as a function of the temperature, in halometalate materials based on imidazolium cation. We present the magnetic structure and magnetostructural correlations of 1-ethyl-2,3-dimethylimidazolium tetrachloridoferrate, (Edimim)[FeCl4], resolved by neutron diffraction studies. Single-crystal, synchrotron powder X-ray diffraction and powder neutron diffraction techniques have been combined to follow the temperature evolution on its crystallographic structure from 2 K close to its melting point (340 K). In this sense, slightly above room temperature (307 K) (Edimim)[FeCl4] presents a single-crystal to single-crystal transition (SCSC), from phase I (space group P21/n) to phase II (P21/m), accompanied by a notable increase in the disorder of the imidazolium cation, as well as in the metal complex anion. The temperature evolution and solid-phase transitions of the presented compound were followed in detail by synchrotron X-ray powder diffraction (SXPD), which confirms the occurrence of another phase transition at 330 K, phase III (P21/m), the crystal structure of which was elucidated from the SXPD pattern. Moreover, this material presents an anisotropic thermal expansion with a switch from axial positive to negative thermal expansion coefficients as the temperature is raised above the first phase transition, which has been correlated with the molecular motion of the imidazolium-based molecules, producing not only a shortening of the counterion···counterion distances but also the occurrence of different quasi-isoenergetic crystal structures as a function of the temperature.

A green metal-organic framework to monitor water contaminants.

The CIM-80 material (aluminum(iii)-mesaconate) has been synthetized in high yield through a novel green procedure involving water and urea as co-reactants. The CIM-80 material exhibits good thermal stability with a working range from RT to 350 °C with a small contraction upon desolvation. Moreover, this material is stable in water at different pH values (1-10) for at least one week, and shows a LC50 value higher than 2 mg mL-1. The new material has been tested in a microextraction methodology for the monitoring of up to 22 water pollutants while presenting little environmental impact: only 20 mg of CIM-80 and 500 µL of acetonitrile are needed per analysis. The analytical performance of the CIM-80 in the microextraction strategy is similar to or even better for several pollutants than that of MIL-53(Al). The average extraction efficiencies range from ∼20% for heavy polycyclic aromatic hydrocarbons to ∼70-100% for the lighter ones. In the case of the emerging contaminants, the average extraction efficiency can reach values up to 70% for triclosan and carbamazepine.

Microscopic Insights on the Multiferroic Perovskite-Like [CH3 NH3 ][Co(COOH)3 ] Compound.

The characterization of the crystal structure, phase transitions, magnetic structure and dielectric properties has been carried out on [CH3 NH3 ][Co(COOH)3 ] (1) perovskite-like metal-organic compound through variable-temperature single-crystal and powder neutron and X-ray diffraction and relative permittivity measurements. The paraelectric to antiferroelectric-like phase transition observed at around 90 K is triggered by a structural phase transition; the structural studies show a change from Pnma space group at RT (1A) to P21 /n space group at low temperature (1B). This phase transition involves the occurrence of small distortions in the framework and counterions. Neutron diffraction studies have shown a magnetic order showing spontaneous magnetization below 15 K, due to the occurrence of a non-collinear antiferromagnetic structure with a weak ferromagnetic component, mainly due to the single-ion anisotropy of the CoII ions.

Ag2Cu3Cr2O8(OH)4: a new bidimensional silver-copper mixed-oxyhydroxide with in-plane ferromagnetic coupling.

Ag2Cu3Cr2O8(OH)4, a new Ag-Cu-Cr-O layered mixed oxide, prepared by soft hydrothermal heterogeneous reactions, is reported. The new phase is an oxyhydroxide and presents a structure with alternating brucite-like Cu-O and Ag-O layers connected by individual chromate groups. The crystallographic structure has been solved and refined from high resolution powder X-ray diffraction data and is supported by density functional theory calculations, yielding a triclinic, space group P1[combining macron], a = 5.3329(1) Å, b = 5.3871(1) Å, c = 10.0735(1) Å, α = 80.476(1)°, ß = 87.020(1)°, γ = 62.383(1)°. Bond valence sums suggest the formulation of Ag+2Cu2+3Cr6+2O8(OH)4, an electronic state fully supported by X-ray photoelectron spectroscopy (XPS) and Cr K-edge X-ray absorption near edge structure (XANES) measurements. Ag2Cu3Cr2O8(OH)4 exhibits bidimensional Cu-O-Cu ferromagnetic correlations that are apparent at much higher temperatures than in other similar Cu-O layered structures, without coupling between Cu-O layers, which represents a unique case in the recent family of silver copper oxides. The role of Ag inducing bidimensionality in copper oxides is therefore expanded further with the presence of chromate anions. Ab initio calculations using density functional theory show that the electronic states involved originate mainly from Cu and OH orbitals, with minor contributions from Cr and the O atoms linking the Cr tetrahedra to the brucitic Cu-O layer, and almost no contribution from Ag. Further modeling of the in-plane magnetic interactions between Cu atoms suggests that the coupled magnetized stripes are responsible for the observed behavior. The results are discussed in relation with previous Ag-Cu mixed oxide phases where metallic behavior or ferro-antiferro transitions had been observed. The structure of this new Ag-Cu-O phase as compared with previous silver copper oxides supports the conclusion that the Ag-Cu layered ordering is favored under oxidizing conditions.

Dynamically slow solid-to-solid phase transition induced by thermal treatment of DimimFeCl4 magnetic ionic liquid.

The results reported here represent the first direct experimental observations supporting the existence of a solid-to-solid phase transition induced by thermal treatment in magnetic ionic liquids (MILs). The phase transitions of the solid phases of 1,3-dimethylimidazolium tetrachloroferrate, DimimFeCl4, are closely related to its thermal history. Two series of solid-to-solid phase transitions can be described in this MIL: (i) from room temperature (RT) phase II [space group (s.g.) = P21] to phase I-a [s.g. = P212121] via thermal quenching or via fast cooling at T > 2 K min(-1); (ii) from phase I-a to phase I-b [s.g. = P21/c] when the temperature was kept above 180 K for several minutes. The latter involves a slow translational and reorientational dynamical process of both the imidazolium cation and the tetrachloroferrate anion and has been characterized using synchrotron and neutron powder diffraction and DFT (density functional theory) studies. The transition is also related to the modification of the super-exchange pathways of low-temperature phases which show a overall antiferromagnetic behavior. A combination of several experimental methods such as magnetometry, Mössbauer and muon spectroscopy together with polarized and non-polarized neutron powder diffraction has been used in order to characterize the different features observed in these phases.

Application of synchrotron through-the-substrate microdiffraction to crystals in polished thin sections.

The synchrotron through-the-substrate X-ray microdiffraction technique (tts-µXRD) is extended to the structural study of microvolumes of crystals embedded in polished thin sections of compact materials [Rius, Labrador, Crespi, Frontera, Vallcorba & Melgarejo (2011 ▸). J.Synchrotron Rad. 18, 891-898]. The resulting tts-µXRD procedure includes some basic steps: (i) collection of a limited number of consecutive two-dimensional patterns (frames) for each randomly oriented crystal microvolume; (ii) refinement of the metric from the one-dimensional diffraction pattern which results from circularly averaging the sum of collected frames; (iii) determination of the reciprocal lattice orientation of each randomly oriented crystal microvolume which allows assigning the hkl indices to the spots and, consequently, merging the intensities of the different frames into a single-crystal data set (frame merging); and (iv) merging of the individual crystal data sets (multicrystal merging) to produce an extended data set suitable for structure refinement/solution. Its viability for crystal structure solution by Patterson function direct methods (δ recycling) and for accurate single-crystal least-squares refinements is demonstrated with some representative examples from petrology in which different glass substrate thicknesses have been employed. The section of the crystal microvolume must be at least of the same order of magnitude as the focus of the beam (15 × 15 µm in the provided examples). Thanks to its versatility and experimental simplicity, this method-ology should be useful for disciplines as disparate as petrology, materials science and cultural heritage.

Anion-π and halide-halide nonbonding interactions in a new ionic liquid based on imidazolium cation with three-dimensional magnetic ordering in the solid state.

We present the first magnetic phase of an ionic liquid with anion-π interactions, which displays a three-dimensional (3D) magnetic ordering below the Néel temperature, TN = 7.7 K. In this material, called Dimim[FeBr4], an exhaustive and systematic study involving structural and physical characterization (synchrotron X-ray, neutron powder diffraction, direct current and alternating current magnetic susceptibility, magnetization, heat capacity, Raman and Mössbauer measurements) as well as first-principles analysis (density functional theory (DFT) simulation) was performed. The crystal structure, solved by Patterson-function direct methods, reveals a monoclinic phase (P21 symmetry) at room temperature with a = 6.745(3) Å, b = 14.364(3) Å, c = 6.759(3) Å, and ß = 90.80(2)°. Its framework, projected along the b direction, is characterized by layers of cations [Dimim](+) and anions [FeBr4](-) that change the orientation from layer to layer, with Fe···Fe distances larger than 6.7 Å. Magnetization measurements show the presence of 3D antiferromagnetic ordering below TN with the existence of a noticeable magneto-crystalline anisotropy. From low-temperature neutron diffraction data, it can be observed that the existence of antiferromagnetic order is originated by the antiparallel ordering of ferromagnetic layers of [FeBr4](-) metal complex along the b direction. The magnetic unit cell is the same as the chemical one, and the magnetic moments are aligned along the c direction. The DFT calculations reflect the fact that the spin density of the iron ions spreads over the bromine atoms. In addition, the projected density of states (PDOS) of the imidazolium with the bromines of a [FeBr4](-) metal complex confirms the existence of the anion-π interaction. Magneto-structural correlations give no evidence for direct iron-iron interactions, corroborating that the 3D magnetic ordering takes place via superexchange coupling, the Fe-Br···Br-Fe interplane interaction being defined as the main exchange pathway.

Charge transfer states in stable neutral and oxidized radical adducts from carbazole derivatives.

In this paper we report the spectral properties of the stable radical adducts 1(•)-3(•), which are formed by an electron donor moiety, the carbazole ring, and an electron acceptor moiety, the polychlorotriphenylmethyl radical. The molecular structure of radical adduct 1(•) in the crystalline state shows a torsion angle of approximately 90° between the phenyl and the carbazole rings due to steric interactions. They exhibit a charge transfer band in the visible range of the electronic spectrum. All of them are chemically oxidized with copper(II) perchlorate to the respective cation species, which show a strong charge transfer band into the near-infrared region of the spectrum. Radical adducts 1(•)-3(•) and the corresponding stable oxidized species 1(+)-3(+) are real organic mixed-valence compounds due to the open-shell nature of their electronic structure. Charge transfer bands of the cation species are stronger and are bathochromically shifted with respect to those of the neutral species due to the greater acceptor ability of the positively charged central carbon atom of the triphenylmethyl moiety. The cationic species 1(+)-3(+) are diamagnetic, as shown by the absence of a signal in the EPR spectrum in acetonitrile solution at room temperature, but they show an intense and unique band in frozen solutions (183 K).

A magnetic ionic liquid based on tetrachloroferrate exhibits three-dimensional magnetic ordering: a combined experimental and theoretical study of the magnetic interaction mechanism.

A new magnetic ionic liquid (MIL) with 3D antiferromagnetic ordering has been synthetized and characterized. The information obtained from magnetic characterization was supplemented by analysis of DFT calculations and the magneto-structural correlations. The result gives no evidence for direct iron-iron interactions, corroborating that the 3D magnetic ordering in MILs takes place via super-exchange coupling containing two diamagnetic atoms intermediaries.

Application of δ recycling to electron automated diffraction tomography data from inorganic crystalline nanovolumes.

δ Recycling is a simple procedure for directly extracting phase information from Patterson-type functions [Rius (2012). Acta Cryst. A68, 399-400]. This new phasing method has a clear theoretical basis and was developed with ideal single-crystal X-ray diffraction data. On the other hand, introduction of the automated diffraction tomography (ADT) technique has represented a significant advance in electron diffraction data collection [Kolb et al. (2007). Ultramicroscopy, 107, 507-513]. When combined with precession electron diffraction, it delivers quasi-kinematical intensity data even for complex inorganic compounds, so that single-crystal diffraction data of nanometric volumes are now available for structure determination by direct methods. To check the tolerance of δ recycling to missing data-collection corrections and to deviations from kinematical behaviour of ADT intensities, δ recycling has been applied to differently shaped nanocrystals of various inorganic materials. The results confirm that it can phase ADT data very efficiently. In some cases even more complete structure models than those derived from conventional direct methods and least-squares refinement have been found. During this study it has been demonstrated that the Wilson-plot scaling procedure is largely insensitive to sample thickness variations and missing absorption corrections affecting electron ADT intensities.

A new partially deprotonated mixed-valence manganese(II,III) hydroxide-arsenate with electronic conductivity: magnetic properties of high- and room-temperature sarkinite.

A new three-dimensional hydroxide-arsenate compound called compound 2 has been synthesized by heating (in air) of the sarkinite phase, Mn(2)(OH)AsO(4) (compound 1), with temperature and time control. The crystal structure of this high-temperature compound has been solved by Patterson-function direct methods. A relevant feature of this new material is that it is actually the first member of the adamite-type family with mixed-valence manganese(II,III) and electronic conductivity. Crystal data: a = 6.7367(5) Å, b = 7.5220(6) Å, c = 9.8117(6) Å, α = 92.410(4)°, ß = 109.840(4)°, γ = 115.946(4)°, P1̅. The unit cell content derived from Rietveld refinement is Mn(8)(O(4)H(x))(AsO(4))(4). Its framework, projected along [111], is characterized by rings of eight Mn atoms with the OH(-)/O(2-) inside the rings. These rings form an almost perfect hexagonal arrangement with the AsO(4) groups placed in between. Bond-valence analysis indicates both partial deprotonation (x ≅ 3) and the presence of Mn in two different oxidation states (II and III), which is consistent with the electronic conductivity above 300 °C from electrochemical measurements. The electron paramagnetic resonance spectra of compound 1 and of its high-temperature form compound 2 show the presence of antiferromagnetic interactions with stronger magnetic coupling for the high-temperature phase. Magnetization measurements of room-temperature compound 1 show a complex magnetic behavior, with a three-dimensional antiferromagnetic ordering and magnetic anomalies at low temperatures, whereas for compound 2, an ordered state is not reached. Magnetostructural correlations indicate that superexchange interactions via oxygen are present in both compounds. The values of the magnetic exchange pathways [Mn-O-Mn] are characteristic of antiferromagnetic couplings. Notwithstanding, the existence of competition between different magnetic interactions through superexchange pathways can cause the complex magnetic behavior of compound 1. The loss of three-dimensional magnetic ordering by heating of compound 1 could well be based on the presence of Mn(3+) ions (d(4)) in compound 2.

(Z)-3-Methyl-N-(7-nitroacridin-3-yl)-2,3-dihydro-1,3-benzothiazol-2-imine from laboratory powder diffraction data.

The title compound, C(21)H(14)N(4)O(2)S, belongs to a family of molecules possessing nonlinear optical properties in solution. Its structure has been solved from laboratory X-ray powder diffraction data using a new direct-space structure solution method, where the atomic coordinates are directly used as parameters and the molecular geometry is described by restraints. The molecular packing is controlled by two systems of π-π interactions and one weak edge-to-face interaction.

Capabilities of through-the-substrate microdiffraction: application of Patterson-function direct methods to synchrotron data from polished thin sections.

Some theoretical and practical aspects of the application of transmission microdiffraction (µXRD) to thin sections (≤30 µm thickness) of samples fixed or deposited on substrates are discussed. The principal characteristic of this technique is that the analysed micro-sized region of the thin section is illuminated through the substrate (tts-µXRD). Fields that can benefit from this are mineralogy, petrology and materials sciences since they often require in situ lateral studies to follow the evolution of crystalline phases or to determine new crystal structures in the case of phase transitions. The capability of tts-µXRD for performing structural studies with synchrotron radiation is shown by two examples. The first example is a test case in which tts-µXRD intensity data of pure aerinite are processed using Patterson-function direct methods to directly solve the crystal structure. In the second example, tts-µXRD is used to study the transformation of laumonite into a new aluminosilicate for which a crystal structure model is proposed.