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5-nitrouracil is a polarizable molecule with a permanent electric dipole moment. Its molecular properties caught the attention of physicists working on nonlinear optics or optoelectronics, but the translation of the molecular assets to the crystalline solid has not been straightforward. This review compares all the known crystal structures incorporating the neutral or ionic 5-nitrouracil, or the two species concomitantly, discussing the effect of the packing in the optimization of the crystalline optical properties. Two new centrosymmetric 5-nitrouracilate salts are also reported for the first time, showing extensive hydrogen bonding between anions and cations. This review also gathers data from nonlinear optical measurements of non-centrosymmetric crystals and thermal stabilities of known polymorphs, showing that a neutral 5-nitrouracil molecule in acentric crystalline environment allows efficient blue-light generation.

In this work, co-crystal screening was carried out for two important dihydrofolate reductase (DHFR) inhibitors, trimethoprim (TMP) and pyrimethamine (PMA), and for 2,4-diaminopyrimidine (DAP), which is the pharmacophore of these active pharmaceutical ingredients (API). The isomeric pyridinecarboxamides and two xanthines, theophylline (THEO) and caffeine (CAF), were used as co-formers in the same experimental conditions, in order to evaluate the potential for the pharmacophore to be used as a guide in the screening process. In silico co-crystal screening was carried out using BIOVIA COSMOquick and experimental screening was performed by mechanochemistry and supported by (solid + liquid) binary phase diagrams, infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). The in silico prediction of low propensities for DAP, TMP and PMA to co-crystallize with pyridinecarboxamides was confirmed: a successful outcome was only observed for DAP + nicotinamide. Successful synthesis of multicomponent solid forms was achieved for all three target molecules with theophylline, with DAP co-crystals revealing a greater variety of stoichiometries. The crystalline structures of a (1:2) TMP:THEO co-crystal and of a (1:2:1) DAP:THEO:ethyl acetate solvate were solved. This work demonstrated the possible use of the pharmacophore of DHFR inhibitors as a guide for co-crystal screening, recognizing some similar trends in the outcome of association in the solid state and in the molecular aggregation in the co-crystals, characterized by the same supramolecular synthons.

New technologies are called upon to play an important role as beneficial tools for meaningful learning in the classroom. In particular, smartphones can be regarded as pocket computers that, in addition to a remarkable memory and computing capacity, incorporate sensors such as accelerometers, gyroscopes, magnetometers, light sensors, etc., which turn them into easily available measurement instruments for practical classes in an educational environment. In this study, the suitability of these devices for demonstrating Classical Mechanics, minimizing the use of resources and class time, has been assessed in two real classrooms (with 16 to 19 year-old students) by conducting experiments related to projectile motion (vertical free fall and parabolic motion). A simple methodology that only involves a mobile phone, a free burst camera application and open-source tools (GIMP and OpenOffice Calc) for data processing is presented. The results obtained in non-perfected conditions led to an estimate of the acceleration of gravity with an error lower than 2%. Further analyses and alternative procedures are also suggested in the discussion section. No major difficulties were encountered with the high school students or with the first year university ones, and a high degree of satisfaction was found. --------------------------------------------------------------------------------- Las nuevas tecnologías están llamadas a jugar un papel importante como herramientas beneficiosas para el aprendizaje significativo en el aula. En particular, los teléfonos inteligentes son verdaderos ordenadores de bolsillo que, además de una notable capacidad de memoria y de cómputo, incorporan sensores como acelerómetros, giroscopios, magnetómetros, sensores de luz, etc. que los convierten en instrumentos de medida fácilmente disponibles para prácticas en un entorno educativo. En el presente estudio, la idoneidad de estos dispositivos para explicar conceptos de Mecánica Clásica, minimizando el uso de recursos y tiempo de clase, ha sido evaluada en dos clases reales (con estudiantes de edades comprendidas entre los 16 y los 19 años) mediante la ejecución de experimentos relacionados con el movimiento de proyectiles (caída libre y trayectoria parabólica). Se presenta una metodología sencilla, que únicamente hace uso de un teléfono móvil, una aplicación fotográfica gratuita para captura de imágenes en ráfaga y herramientas de código abierto (GIMP y OpenOffice Calc) para el procesado de los datos. Los resultados obtenidos en condiciones no optimizadas han conducido a una estimación de la aceleración de la gravedad con un error inferior al 2%. En la discusión de resultados se sugieren análisis más avanzados y otros procedimientos alternativos. No se encontraron problemas significativos en la ejecución de los experimentos ni con los alumnos de enseñanza secundaria ni con los de primer año de carrera, y el grado de satisfacción entre el alumnado fue alto.

The concept of co-amorphous systems is introduced in an integrated laboratory experiment, designed for advanced chemistry students, using solvent-free, environmentally friendly mechanochemistry. The dual-drug naproxen-cimetidine co-amorphous system (NPX-CIM) is investigated as an example of the emergent field of medicinal mechanochemistry. Students are trained in solid-state characterization techniques including X-ray powder diffraction, Fourier-transform infrared spectroscopy, and thermal analysis by differential scanning calorimetry. This lab experiment also provides an opportunity to discuss the relevance of different solid forms of pharmaceutics, emphasizing particular properties of disordered materials. This experiment can easily fit the curriculum of any Chemistry or Pharmacy master level degree in courses dealing with instrumental analysis, solid state chemistry, or green chemistry, for classes of 6 to 18 students, in a 5-h lab session. Suggestions to adapt it to the use of a single characterization technique are provided.

An uranyl complex [UO2(TFA)2(DMSO)3] (TFA=deprotonated trifluoroacetic acid; DMSO=dimethyl sulfoxide) has been successfully synthesized by reacting UO2(CH3COO)2·H2O with one equivalent of (CF3CO)2O and DMSO. The complex has been characterized by single-crystal X-ray diffraction, X-ray powder diffraction, elemental analysis, FT-IR spectroscopy, thermal analysis and absorption and emission spectroscopies. The spectroscopic properties of the material make it suitable for its application in the sensing and monitoring of uranyl in the PUREX process.

In the title compound, C18H18O3, a dihydrocoumarin synthesized via a microwave-assisted hydroarylation reaction, the 4-methoxyphenyl ring is inclined to the mean plane of the coumarin moiety by 78.21 (9)°. The pyran ring has a screw-boat conformation and its mean plane is inclined to the fused benzene ring by 13.88 (11)°. In the crystal, molecules are linked via C—H...O hydrogen bonds, forming ribbons along the b-axis direction. The ribbons are linked via C—H...π interactions, forming slabs parallel to the ab plane.

Two novel europium(III) complexes, a monomer and a homodimer, with 1-(4-chlorophenyl)-4,4,4-trifluoro-1,3-butanedione (Hcbtfa) and 5-chloro-1,10-phenanthroline (cphen) ligands, formulated as [Eu(cbtfa)3(cphen)] and [Eu2(cbtfa)4(cphen)2(CH3O)2], have been synthesized. Their structures have been elucidated by X-ray diffraction and their absorption and emission properties have been studied in the solid state. The experimental data has then been used to test the recently released LUMPAC software, a promising tool which can facilitate the design of more efficient lanthanide light-conversion molecular devices by combining ground state geometry, excited state energy, and luminescent properties calculations.

The asymmetric unit of the title compound, C24H16N2·0.5CH3OH, is comprised of two independent bathophenanthroline molecules (systematic name: 4,7-diphenyl-1,10-phenanthroline) and one methanol molecule. The bathophenanthroline molecules are not planar as there is a considerable rotation of all terminal phenyl rings with respect to the central phenanthroline units [dihedral angles in the range 52.21 (12)–62.14 (10)°]. In addition, a non-negligible torsion is apparent in one of the phenanthroline units: the angle between the mean planes of the two pyridine rings is 14.84 (13)°. The methanol solvent molecule is linked to both N atoms of a bathophenanthroline molecule through a bifurcated O—H...(N,N) hydrogen bond.

In the title compound, [K(C10H5ClO2F3)(H2O)]n, the two independent K+ ions are located on a twofold rotation axis. For each of the cations, the distorted cubic coordination environment is defined by two F and four O atoms of symmetry-related 1,4-chlorophenyl-4,4,4-trifluorobutane-1,3-dionate anions and by two O atoms of water molecules. The μ4-bridging character of the anion and the μ2-bridging of the water molecule lead to the formation of layers parallel to (100). The coordinating water molecules are also involved in O—H...O hydrogen bonds that reinforce the molecular cohesion within the layers, which are stacked along [100]. The β-diketonate anion is not planar, with an angle of 31.78 (10)° between the mean planes of the diketonate group and the chlorophenyl ring.

In the title molecular salt, C6H10N22+·2ClO4−, the Cl—O bond lengths [anion 1: 1.369 (3)–1.415 (3); anion 2: 1.420 (2)–1.441 (2) Å] and the O—Cl—O angles [anion 1: 105.4 (2)–111.8 (4); anion 2: 107.8 (1)–110.3 (1)°] indicate a slight distortion of the perchlorate anions from regular tetrahedral symmetry. In the crystal, the components are linked into columns along the a-axis direction via N—H...O and C—H...O hydrogen bonds, with stacks of the organic molecules being surrounded by stacks of perchlorate anions.

Molecules of the title compound, C52H38N4O8, are located on an inversion center so that the asymmetric cell contains one half of the molecule. The macrocycle exhibits a ruffled conformation with a maximum deviation of 0.16 Å for the 24 macrocycle atoms: the dihedral angle between adjacent five-membered rings is 5.13 (19)°. The benzene rings are rotated by 70.25 (19)° with respect to their adjacent protonated five-membered rings, and by 65.56 (19)° with respect to the unprotonated rings. The porphyrin conformation is supported by bifurcated N—H...(N,N) hydrogen bonds. The structure contained poorly resolved solvent molecules in voids of volume 217 Å3 per unit cell. The latter were treated using the SQUEEZE routine in PLATON [Spek (2009). Acta Cryst. D65, 148–155]. As the solvent could not be identified exactly, it was not included in the calculation of the overall formula weight, density and absorption coefficient.

In the title compound, {(C5H14N2)[Cd2Cl6]·H2O}n, the asymmetric unit contains one piperazinediium cation, one [Cd2Cl6]2− anion and a water molecule. The coordination geometries of the two Cd2+ cations are distorted octahedral. Adjacent CdII atoms are interconnected alternately by paired chloride bridges, generating polymeric chains parallel to [010]. Neighbouring chains are connected by O—H...Cl hydrogen bonds involving the water molecules, forming layers at z = n/2. The crystal packing is further stabilized by intermolecular N—H...Cl and N—H...O hydrogen bonds, one of which is bifurcated.

The title compound, C6H6N2O2S, is a new polymorphic form of 2-(pyrimidin-2-ylsulfanyl)acetic acid. Unlike the previous orthorhombic polymorph [Pan & Chen (2009) Acta Cryst. E65, o652], the molecules are not planar: the aromatic ring makes an angle of 80.67 (17)° with the carboxyl plane. In the crystal, molecules are linked by O—H...N hydrogen bonds into chains along [overline{1}02].

In the monomeric title complex, [Cu(C6H3BrNO2)(NO3)(H2O)2], the CuII ion is coordinated by a bidentate 6-bromopicolinate ion, one nitrate ion and two water molecules in a geometry intermediate between five- and six-coordinate. Conventional O—H...O hydrogen bonds link the complex molecules, forming layers parallel to the ab plane.

The asymmetric unit of the title compound, (C6H9N2)[Co(C7H3NO4)(C7H4NO4)]·C7H5NO4·3H2O, contains one (6-carboxypyridine-2-carboxylato)(pyridine-2,6-dicarboxylato)cobaltate(II) anion, one phenylhydrazinium cation, one pyridine-2,6-dicarboxylic acid molecule and three uncoordinated water molecules, part of which are disordered. The CoII ion is coordinated by a pyridine-2,6-dicarboxylate ion and a 6-carboxypyridine-2-carboxylate ligand almost perpendicular to each other [the angle between the least-squares planes is 87.38 (4)°] and is surrounded by two O atoms and two N atoms in the equatorial plane and two O atoms in axial positions, resulting in a distorted octahedral coordination geometry. There is an extensive three-dimensional network of O—H...O and N—H...O hydrogen bonds, which link the components.

The molecules of the title compound, C27H28O2, exhibit axial chirality. The planes of the aromatic rings of the tetralin ring systems make an angle of 85.72 (11)°. The non-aromatic rings adopt distorted half-chair conformations. In one of them, two C atoms of the four-atom aliphatic chain are disordered over two sites in a 0.75 (2):0.25 (2) ratio. The substituent phenyl ring is also disordered over two positions in a 0.59 (3):0.41 (3) ratio. There are no conventional hydrogen bonds joining the molecules.

The molecule of the title compound, C18H28N2, composed of two 2,5-dimethylpyrrole groups linked by a hexane chain, lies across a crystallographic inversion centre. The mean plane of the pyrrole ring is almost perpendicular to the mean plane of the central chain, making a dihedral angle of 89.09 (8)°. The crystal structure is stabilized by intermolecular C—H...π interactions.

The title compound, C20H26N4, is composed of two (6-methyl-2-pyridyl)methylene units linked by a 1,6-diamine hexane chain. The molecule has Ci symmetry with the inversion center situated at the mid-point of the central C—C bond. The alkyl chain has an all-trans conformation, with all the non-H atoms sharing the same plane [maximum deviation 0.004 (3) Å]. The pyridylmethylene groups are also planar [maximum deviation 0.009 (3) Å], making an angle of 53.78 (19)° with the hexane chain plane. In the crystal, the molecules assemble in layers, stacking along the a axis. The stacks are hold together by attractive interactions between π electron systems.

In the title compound, C9H13NO2, there are two independent molecules per asymmetric unit. The molecules are very similar and almost planar, with the ethoxycarbonyl group anti to the pyrrole N atom. The two independent molecules are joined into dimeric units by strong hydrogen bonds between NH groups and carbonyl O atoms.

In the title compound, (C3H7N6)2[Cu(C7H3NO5)2]·6H2O, the coordination geometry of the CuII atom can be described as distorted octahedral. The equatorial plane is defined by four O atoms from two 4-hydroxypyridine-2,6-dicarboxylate ligands. The axial positions are occupied by the N atoms of the same ligands. There is an extensive three-dimensional hydrogen-bond network reinforcing crystal cohesion.

In the crystal structure of the title compound, C12H10N6, the molecules deviate slightly from planarity. The plane of the central triazole ring makes angles of 6.13 (9) and 3.28 (10)° with the pyridyl ring planes. Intramolecular N—H...N interactions form six-membered closed rings. The crystal packing also shows weak C—H...π and C—H...N interactions.

The title steroid, C23H35ClO4, is a pregnane derivative prepared by ring opening of the corresponding 5α,6α-epoxy steroid with BiCl3. There are two symmetry-independent molecules in the asymmetric unit that show no significant differences concerning bond lengths and angles. The conformation of the six-membered rings in both molecules is close to a chair form, while the five-membered ring adopts an envelope conformation. All rings in both molecules are trans-fused. The molecules are held together by an extensive O—H...O hydrogen-bonding network.

The title compound, C10H6O8·2C3H7NO2, crystallizes as an adduct with the acid and amino acid molecules in their neutral forms. The asymmetric unit contains one half of a centrosymmetric pyromellitic acid molecule and one sarcosine molecule. The sarcosine has the amine group protonated and the carboxyl group deprotonated, as is usual for amino acids (zwitterionic form). The pyromellitic acid molecules retain the four carboxyl H atoms with the carboxyl groups rotated out of the ring plane [O—C—C—C torsion angles = 24.1 (3) and 61.6 (2)°]. There is a three-dimensional hydrogen-bond network linking the molecules.

In the title compound, [Cu(SO4)(C10H9NO2)2]·2H2O, the CuII ion is chelated by two (2-quinolyl)methanediol ligands and coordinated by a monodentate sulfate ligand in a distorted trigonal–bipyramidal environment, with O atoms occupying the equatorial sites and N atoms in the axial sites. The dihedral angle between the two essentially planar quinoline ring systems is 45.02 (9)°. In the crystal structure, an extensive O—H...O hydrogen-bonding network forms layers parallel to the ab plane.

The crystal structure of the title compound, [Mn(C7H5O2)(C10H6NO2)(C10H7NO2)], contains manganese(II) ions six-coordinated in a distorted octahedral environment. The equatorial plane is occupied by four O atoms, two from the carboxylate group of the benzoate ion, the other two from carboxylate/carboxyl groups of the quinaldate/quinaldic acid molecules. The axial positions are occupied by the N atoms of the quinoline ring systems. The metal ion lies on a twofold rotation axis that bisects the benzoate ligand; the quinaldate and quinaldic acid ligands are therefore equivalent by symmetry, and the carboxylate/carboxyl groups are disordered. The complexes are joined together by hydrogen bonds between the carboxylate/carboxyl groups of adjacent quinaldate/quinaldic acid molecules, forming zigzag chains that run along the c axis.