A comparison of the isostructural [Co(NH)NO]XNO and [Co(NH)ONO]XNO, X = Cl or Br in relation to nitro-nitrito linkage isomerization and photomechanical effects.

A new photoactive cobalt coordination compound, [Co(NH)NO]BrNO (I), was obtained. Its crystal structure was shown to be isostructural with previously known [Co(NH)NO]ClNO (II) for which linkage isomerization accompanied with mechanical response of the crystal has been already reported. Single crystals of I are transformed into nitrito isomer [Co(NH)ONO]BrNO (III) on irradiation with blue light (λ = 465 nm) without being destroyed.

Structural changes in Rochelle salt on phase transitions revisited in a multi-temperature single-crystal X-ray diffraction study.

Phase transitions in Rochelle salt [sodium potassium L(+)-tartrate tetrahydrate] are revisited in a single-crystal X-ray diffraction multi-temperature study on cooling from 308 to 100 K across the high-temperature paraelectric (PE) ↔ ferroelectric ↔ low-temperature PE phase transition points. The results of structure refinement using three different models (a harmonic with and without disorder, and an anharmonic) were compared. The temperature dependencies of anisotropic displacement parameters (ADPs) and U, which can be calculated directly from ADPs, for the low-temperature PE phase indicate clearly the dynamic nature of disorder of the K1 atoms.

Hysteretic Room-Temperature Magnetic Bistability of the Crystalline 4,7-Difluoro-1,3,2-Benzodithiazolyl Radical.

The title radical R⋅, synthesized by reduction of the corresponding cation R, is thermally stable up to ~380 K in the crystalline state under anaerobic conditions. With SQUID magnetometry, single-crystal and powder XRD, solid-state EPR and TG-DSC, reversible spin-Peierls transition between diamagnetic and paramagnetic states featuring ~10 K hysteretic loop is observed for R⋅ in the temperature range ~310-325 K; ΔH=~2.03 kJ mol and ΔS=~6.

A high-pressure single-crystal X-ray diffraction study of potassium guaninate hydrate, K·CHNO·HO.

The crystal structure of potassium guaninate hydrate, K·CHNO·HO, was studied in the pressure range of 1 atm to 7.3 GPa by single-crystal diffraction using synchrotron radiation and a laboratory X-ray diffraction source. Structural strain was compared to that of the same salt hydrate on cooling, and in 2Na·CHNO·7HO under hydrostatic compression and on cooling.

Two new bismuth salts with succinic acid: synthesis, structural, spectroscopic and thermal characterization.

Two novel bismuth succinate hydrates, namely, poly[[diaqua(μ-butane-1,4-dicarboxylato)hemi(μ-butane-1,4-dicarboxylato)bismuth] monohydrate], {[Bi(CHO)(HO)]·HO} (1), and poly[[μ-aqua-aqua(μ-butane-1,4-dicarboxylato)(μ-butane-1,4-dicarboxylato)-μ-oxido-dibismuth] monohydrate], {[Bi(CHO)O(HO)]·HO} (2), have been synthesized. Their crystal structures were determined by single-crystal X-ray diffraction and the compounds were characterized by IR and Raman spectroscopy, powder X-ray diffraction and thermal analysis. The crystal structure analysis revealed that the compounds are coordination polymers, with 1 having a two-dimensional layered structure and 2 displaying a three-dimensional (3D) framework.

Crystallography relevant to Mars and Galilean icy moons: crystal behavior of kieserite-type monohydrate sulfates at extraterrestrial conditions down to 15 K.

Monohydrate sulfate kieserites ( SO·HO) and their solid solutions are essential constituents on the surface of Mars and most likely also on Galilean icy moons in our solar system. Phase stabilities of end-member representatives ( = Mg, Fe, Co, Ni) have been examined crystallographically using single-crystal X-ray diffraction at 1 bar and temperatures down to 15 K, by means of applying open He cryojet techniques at in-house laboratory instrumentation. All four representative phases show a comparable, highly anisotropic thermal expansion behavior with a remarkable negative thermal expansion along the monoclinic axis and a pronounced anisotropic expansion perpendicular to it.

Charge density studies of multicentre two-electron bonding of an anion radical at non-ambient temperature and pressure.

The variation of charge density of two-electron multicentre bonding (pancake bonding) between semi-quinone radicals with pressure and temperature was studied on a salt of 5,6-di-chloro-2,3-di-cyano-semi-quinone radical anion (DDQ) with 4-cyano--methyl-pyridinium cation (4-CN) using the Transferable Aspheric Atom Model (TAAM) refinement. The pancake-bonded radical dimers are stacked by non-bonding π-interactions. With rising pressure, the covalent character of interactions between radicals increases, and above 2.

Pancake-bonding of semiquinone radicals under variable temperature and pressure conditions.

The effects of temperature (100-370 K) and pressure (0-6 GPa) on the non-localized two-electron multicentric covalent bonds (`pancake bonding') in closely bound radical dimers were studied using single-crystal X-ray diffraction on a 4-cyano-N-methylpyridinium salt of 5,6-dichloro-2,3-dicyanosemiquinone radical anion (DDQ) as the sample compound. On cooling, the anisotropic structural compression was accompanied by continuous changes in molecular stacking; the discontinuities in the changes in volume and b and c cell parameters suggest that a phase transition occurs between 210 and 240 K. At a pressure of 2.

Studying weak inter-actions in crystals at high pressures: when hardware matters.

The quality of structural models for 1,2,4,5-tetra-bromo-benzene (TBB), CHBr, based on data collected from a single crystal in a diamond anvil cell at 0.4 GPa using two different diffractometers belonging to different generations have been compared, together with the effects of applying different data-processing strategies.

Anisotropic lattice softening near the structural phase transition in the thermosalient crystal 1,2,4,5-tetrabromobenzene.

The thermosalient effect (crystal jumping on heating) attracts much attention as both an intriguing academic phenomenon and in relation to its potential for the development of molecular actuators but its mechanism remains unclear. 1,2,4,5-Tetrabromobenzene (TBB) is one of the most extensively studied thermosalient compounds that has been shown previously to undergo a phase transition on heating, accompanied by crystal jumping and cracking. The difference in the crystal structures and intermolecular interaction energies of the low- and high-temperature phases is, however, too small to account for the large stress that arises over the course of the transformation.

Structural aspects of displacive transformations: what can optical microscopy contribute? Dehydration of Sm(CO)·10HO as a case study.

For martensitic transformations the macroscopic crystal strain is directly related to the corresponding structural rearrangement at the microscopic level. optical microscopy observations of the interface migration and the change in crystal shape during a displacive single crystal to single crystal transformation can contribute significantly to understanding the mechanism of the process at the atomic scale. This is illustrated for the dehydration of samarium oxalate decahydrate in a study combining optical microscopy and single-crystal X-ray diffraction.

Isoenergetic Polymorphism: The Puzzle of Tolazamide as a Case Study.

In the present case study of tolazamide we illustrate how many seemingly contradictory results that have been obtained from experimental observations and theoretical calculations can finally start forming a consistent picture: a "puzzle put together". For many years, tolazamide was considered to have no polymorphs. This made this drug substance unique among the large family of sulfonylureas, which was known to be significantly more prone to polymorphism than many other organic compounds.

L-Argininium phosphite - a new candidate for NLO materials.

In order to investigate the possibility of salt formation in the L-Arg-H3PO3-H2O system, single crystals of L-argininium phosphite, C6H15N4O2(+)·H2PO3(-), were prepared by evaporation of an aqueous solution containing equimolar quantities of L-arginine and phosphorous acid. The asymmetric unit contains one L-argininium(+) cation and one phosphite [HPO2(OH)](-) anion. The phosphite anions form chains parallel to [010] by O-H.

Synthesis and structure-activity relationship of novel 1,4-diazabicyclo[2.2.2]octane derivatives as potent antimicrobial agents.

A series of new quaternary 1,4-diazabicyclo[2.2.2]octane derivatives was synthesized and evaluated for activity against several strains of both Gram positive and Gram negative bacteria and one strain of fungus under different inoculum size.

Dynamic single crystals: kinematic analysis of photoinduced crystal jumping (the photosalient effect).

Crystals on the move: If they are subjected to a strong light stimulus, crystals of the cobalt coordination compound [Co(NH3)5(NO2)]Cl(NO3) undergo sudden jumps and leap over distances 10(2)-10(5) times their own size to release the strain that accumulates in their interior. The first quantitative kinematic analysis of this phenomenon is reported. The observed effect could be employed for actuation on the macroscopic scale.

A high-pressure single-crystal to single-crystal phase transition in DL-alaninium semi-oxalate monohydrate with switching-over hydrogen bonds.

A single-crystal to single-crystal transition in DL-alaninium semi-oxalate monohydrate at a pressure between 1.5 and 2.4 GPa was studied by single-crystal X-ray diffraction and Raman spectroscopy.

Semi-maleate salts of L- and DL-serinium: the first example of chiral and racemic serinium salts with the same composition and stoichiometry.

L-serinium semi-maleate, (I), and DL-serinium semi-maleate, (II), both C3H8NO3(+)·C4H3O4(-), provide the first example of chiral and racemic anhydrous serine salts with the same organic anion. A comparison of their crystal structures with each other, with the structures of the pure components (L-serine polymorphs, DL-serine and maleic acid) and with other amino acid maleates is important for understanding the formation of the crystal structures, their response to variations in temperature and pressure, and structure-property relationships. As in other known crystal structures of amino acid maleates, there are no direct links between the semi-maleate anions in the two new structures.

Application of incoherent inelastic neutron scattering in pharmaceutical analysis: relaxation dynamics in phenacetin.

This study centers on the use of inelastic neutron scattering as an alternative tool for physical characterization of solid pharmaceutical drugs. On the basis of such approach, relaxation processes in the pharmaceutical compound phenacetin (p-ethoxyacetanilide, C(10)H(13)NO(2)) were evidenced on heating between 2 and 300 K. By evaluating the mean-square displacement obtained from the elastic fixed window approach, using the neutron backscattering technique, a crossover of the molecular fluctuations between harmonic and nonharmonic dynamical regimes around 75 K was observed.

Low-temperature phase transition in glycine-glutaric acid co-crystals studied by single-crystal X-ray diffraction, Raman spectroscopy and differential scanning calorimetry.

The occurrence of a first-order reversible phase transition in glycine-glutaric acid co-crystals at 220-230 K has been confirmed by three different techniques - single-crystal X-ray diffraction, polarized Raman spectroscopy and differential scanning calorimetry. The most interesting feature of this phase transition is that every second glutaric acid molecule changes its conformation, and this fact results in the space-group symmetry change from P2(1)/c to P1. The topology of the hydrogen-bonded motifs remains almost the same and hydrogen bonds do not switch to other atoms, although the hydrogen bond lengths do change and some of the bonds become inequivalent.

Effect of pressure on crystalline L- and DL-serine: revisited by a combined single-crystal X-ray diffraction at a laboratory source and polarized Raman spectroscopy study.

Information on the effect of pressure on hydrogen bonds, which could be derived from single-crystal X-ray diffraction at a laboratory source and polarized Raman spectroscopy, has been compared. L-Serine and DL-serine were selected for this case study. The role of hydrogen bonds in pressure-induced phase transitions in the first system and in the structural stability of the second one are discussed.

Glycinium semi-malonate and a glutaric acid-glycine cocrystal: new structures with short O-H...O hydrogen bonds.

Glycinium semi-malonate, C(2)H(6)NO(2)(+)·C(3)H(3)O(4)(-), (I), and glutaric acid-glycine (1/1), C(2)H(5)NO(2)·C(5)H(8)O(4), (II), are new examples of two-component crystal structures containing glycine and carboxylic acids. (II) is the first example of a glycine cocrystal which cannot be classified as a salt, as glutaric acid remains completely protonated. In the structure of (I), there are chains formed exclusively by glycinium cations, or exclusively by malonate anions, and these chains are linked with each other.

Monitoring selected hydrogen bonds in crystal hydrates of amino acid salts: combining variable-temperature single-crystal X-ray diffraction and polarized Raman spectroscopy.

Predicting behaviour of hydrogen bonds with varying temperature, in particular-correlating donor-acceptor distances in the O-H···O hydrogen bonds with the frequencies of O-H stretching vibrations is important for understanding dynamics of biomolecules and phase transitions in crystals. A commonly used correlation suggested earlier in the literature is based on statistical analysis of different compounds [A. Novak, Structure and Bonding, 1974, 18, 177; K.

DL-alaninium semi-oxalate monohydrate.

The structure of the title compound, C(3)H(8)NO(2)(+)·C(2)HO(4)(-)·H(2)O, is formed by two chiral counterparts (L- and D-alaninium cations), semi-oxalate anions and water molecules, with a 1:1:1 cation-anion-water ratio. The structure is compared with that of the previously known anhydrous DL-alaninium semi-oxalate [Subha Nandhini, Krishnakumar & Natarajan (2001). Acta Cryst.