Band 233, Heft 1

The first microporous framework structures containing uranium and chromium have been synthesized and characterized. Rb 2 [(UO 2 ) 2 (CrO 4 ) 3 (H 2 O) 2 ](H 2 O) 3 ( 1 ) was crystallized from uranyl chromate solution by evaporation. Further evaporation led to increased viscosity of the solution and overgrowing of Rb 2 [(UO 2 ) 2 (CrO 4 ) 3 (H 2 O)](H 2 O) ( 2 ) on the crystals of 1 . With respect to 1 , the framework of 2 is partially dehydrated. Both frameworks differ compositionally by only one water molecule, but this seemingly small difference affects significantly the pore size and overall structural topology of the frameworks, which present very different flexibility of the U–O–Cr links. These are rigid in the pillared framework of 1 , in contrast to 2 where the U–O–Cr angles range from 126.3 to 168.2°, reflecting the substantial flexibility of Cr–O–U connections which make them comparable to the corresponding Mo–O–U links in uranyl molybdates.

2-((2-ethylphenyl)amino)nicotinic acid (2EPNA) was synthesized and its crystal structure was determined. It was observed that alkylation of the phenyl ring with ethyl group disrupts the planar conformation of the molecule by steric repulsion, resulting in formation of an acid-pyridine heterosynthon (instead of acid-acid homosynthon) in the crystal. Crystallization tendency from the melt state of the polymorph was studied by differential scanning calorimetry (DSC). It was revealed that this compound could form a very stable amorphous phase on melt quenching and not crystallize even on re-heating. The formation of acid-pyridine hydrogen bonding in the amorphous state is believed to be responsible for its good glass forming ability.

The room temperature structure with P 2 1 / c symmetry of the zinc(II) complex of pyridine-2,6-dicarboxylic acid was published by Okabe and Oya (N. Okabe, N. Oya, Copper(II) and zinc(II) complexes of pyridine-2,6-dicarboxylic acid. Acta Crystallogr. C . 2000 , 56 , 305). Here we report crystal structure of the low temperature phase β -[Zn(pydcH) 2 ]·3H 2 O, pydc=C 7 H 3 NO 4 , resulting from the phase transition around 200K. The diffraction pattern of the low temperature phase revealed satellite reflections, which could be indexed with q-vector 0.4051(10)b* corresponding to (3+1) D incommensurately modulated structure. The modulated structure was solved in the superspace group X 2 1 / c (0 b 0) s 0, where X stands for a non-standard centring vector (½, 0, 0, ½), and compared with the room temperature phase. It is shown that hydrogen bonds are the main driving force of modulation.

Three picrate salt crystals, namely 5-amino-6-methylquinolin-1-ium 2,4,6-trinitrophenolate ( I ), 3-phenyl-1 H -pyrazol-2-ium 2,4,6-trinitrophenolate ( II ) and 1 H -imidazol-3-ium 2,4,6-trinitrophenolate ( III ) were characterized by X-ray diffraction. Salt I crystallizes in space group of P 2 1 / c , with a =15.096(2), b =7.2864(9), c =15.248(2) Å, β =98.437(2)°, V =1659.1 Å 3 and Z =4. Salt II crystallizes in monoclinic space group P 2 1 / c , with a =13.6230(9), b =6.7421(5), c =17.7508(12) Å, β =106.001(1)°, V =1567.20 Å 3 and Z =4. Whereas salt III crystallizes in triclinic system, space group P 1̅, with a =7.6919(10), b =7.9218(10), c =10.2230(13) Å, α=81.909(2), β =77.985(2), γ=82.629(2)°, V =600.05 Å 3 and Z =2. Protons were transferred from the picric acids to their corresponding bases, forming intermolecular N + –H···O − hydrogen bonds in the three salts. Salts I and II form planes, whereas salt III forms chains via N–H···O and C–H···O hydrogen bonds as their supramolecular assembly. Planes and chains in all these salts were interconnected through π···π interaction. The intermolecular interactions in the crystal structures were quantified and were analysed using Hirshfeld surface analysis.

Binary complex compounds (BCC) [Rh(en) 3 ][Fe(CN) 6 ]·2H 2 O ( I ) and [Rh(en) 3 ][Co(CN) 6 ]·2H 2 O ( II ) have been prepared and characterized by the X-ray diffraction, crystal optic, elemental and thermal analyses. The crystal structures I and II (space group P 2 1 / n ) are described within the monoclinic crystal system, are insular and isostructural. The thermal behavior of BCC I and II is identical, with an exception of a higher temperature (~by 50°C) of II decomposition. In air atmosphere, the ligand removal is followed by the formation of, respectively, Rh+1/2Fe 2 O 3 and Rh+Co that on further heating up to 1000°C convert into RhFeO 3 and RhCoO 1.5 . The residues of annealing at 1000°C in argon atmosphere are Rh+1/2Fe 2 O 3 and Rh+CoO, respectively.

A new crystal structure of tert -butanol and water crystallizing as the decahydrate is reported. The crystallization of the mixture in the desired molar ratio was performed in a capillary placed directly on a goniometer of a single crystal diffractometer at 200 K and ambient pressure using focused IR laser radiation. The crystals were grown while the melting zone formed by the IR laser was moved along the capillary. Usually the crystallization process should be long enough (hours) in order to obtain a good quality single crystal. However, in the case of tert -butanol decahydrate, such a long process led to separation of the ice and alcohol. Only fast crystallization taking tens of seconds allowed crystallization of the desired crystalline phase. In the decahydrate tert -butanol molecules are located in channels formed by water molecules. Hydroxyl groups are anchored to the water framework via hydrogen bonds. All water molecules in the structure have hydrogen atoms disordered equally over two sites; the hydroxyl group is likewise disordered. This effect is observed at both, 200 K and 100 K. Raman spectra recorded for the crystalline phase suggest dynamic disorder at higher temperature, converting to static at lower T . The decahydrate of tert -butanol, together with already known its di - and hepta -hydrates, display similar features to those observed for series of tert -butylamine hydrates. The latter structures behave as frozen steps of amine hydration observed as crystal structures leading, at maximum dilution, to hexagonal ice. Hydrates of tert -butanol nicely follow this tendency completing the relationship found for the tert -butylamine: water system.

Four new Ln(III)-based coordination polymers (CPs), [Eu(HL)Cl 2 (DMF) 2 ]·(H 2 L) ( 1 ), [Dy(HL)Cl 2 (DMF) 2 ]·(H 2 L) ( 2 ), [Er(HL)Cl 2 (DMF)(CH 3 OH)]·(DMF) ( 3 ) and [Yb(HL)Cl 2 (DMF)(H 2 O)]·(DMF) ( 4 ) (H 2 L=2,6-bis[(3-methoxysalicylidene)hydrazinocarbonyl]pyridine) have been synthesized through the reaction of Ln(III) chloride and H 2 L by using the vapour diffusion method. Interestingly, Cl − as a template agent plays a vital role in the formation of the target complexes. Single-crystal X-ray diffraction studies indicate that 1 and 2 are isostructural and crystallize in triclinic space group P 1̅, while complexes 3 and 4 are isostructural and crystallize in monoclinic space group C 2/ c . Variable temperature magnetization measurement ( χ M T – T ) demonstrates possible antiferromagnetic interactions in complex 2 . Alternating-current (ac) susceptibility measurement furthermore indicated frequency dependence for both the in-phase (χ′) and out-of-phase (χ″) components in 2 , suggesting that there is a slow relaxation behavior of the magnetization, which is typical of single-molecule magnets (SMMs). This is the first time that Ln(III) CPs based on such a dihydrazone ligand has been reported so far.

DIANNA is a free software developed to simulate atomic models of structures for an ensemble of nanoparticles and to calculate their whole X-ray powder diffraction patterns and the radial distribution function. The main objects of investigation are the particles whose coherent scattering domains do not exceed several nm. DIANNA is based on the ab initio method using the Debye scattering equation. This method makes it possible to obtain information on the atomic structure, shape and size of nanoparticles. It can be applied also to non-periodic materials or coherently ordered nanostructures. Basic program features, methods and some examples are demonstrated.

In our molecular dynamics simulations of the system of identical particles interacting through the harmonic-repulsive pair potential, we observed the formation of a cubic crystal structure that belongs to the Ia 3̅ d (#230) crystallographic space group. This crystal structure has not been previously seen either in experiments or in computer simulations, though its framework topology has been known from theoretical crystallographic considerations. Its unit cell contains 16 atoms, occupying only ( 16b ) Wyckoff site, and arranged as two mutually intertwined unconnected networks with packing fraction of 0.37. The appearance of this structure is explained by the soft repulsive nature of the interaction potential. The observed Ia 3̅ d structure extends the small number of cubic structures formed in single component systems with spherically symmetric pair potentials in MD simulations. We speculate that materials with such structure could be found in soft matter systems or in selected crystals under high pressure.