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A novel anhydrous 1:1 and 2:1 complexes of quinoline betaine (QB) with perchloric acid have been prepared and their structures determined by X-ray diffraction. The 1:1 complex betaine is protonated and the carboxylate group forms a hydrogen bond with the ClO4 ion: O⋯O distance is 2.820(3) A˚. In the 2:1 complex, the carboxylate group of a pair of QB molecules are bridged by a proton to form dimeric cation in non-planar configuration, [(QB)2H]+, featuring a very strong hydrogen bond of the length 2.453(3) A˚. The FTIR spectrum of the 1:1 complex shows a strong absorption at ca. 3100 cm−1 due to the νOH vibration. Broad and intense absorption in the 1500–400 cm−1 region in the spectrum of the 2:1 complex is typical for the very short hydrogen bonds. B3LYP calculations predict slightly shorter hydrogen bonds with different orientation of the ring vs. COOH group than these observed in crystals. [Copyright &y& Elsevier]

The crystals of 1:1 complex of 1,2-bis(N-benzyl-N-methylaminomethyl) benzene with HClO4 were studied using X-ray diffraction and FT-IR spectroscopy. The space group is P1̄ with a=10.637(2), b=15.163(3), c=15.233(3) Å 77 K and Z=4. The two symmetry independent, NHN+ intramolecular hydrogen bonds are asymmetric. Cation (a) D⋯A 2.778(4) Å, D–H 0.989(30) Å, H⋯A 1.827(30) Å, D–H⋯A 160.5° (26), cation (b) D⋯A 2.822(4) Å, D–H 0.891(30), H⋯A 1.970(30) Å, D–H⋯A (30). The IR spectrum of the crystals shows a broad intense band and a low intense continuous absorption indicating relatively low proton polarizability in the intramolecular hydrogen bond. In acetonitrile the proton in the intramolecular hydrogen bond shows very high proton polarizability demonstrated by the continuous absorption in IR spectrum. [Copyright &y& Elsevier]

Some transformations of (10R)- and (10S)-bromo-10,11-dihydroquinine 2a and 2b have been investigated in order to obtain insights into their unexplored chirality. The (10R)-diastereomer 2a converts stereoselectively into (4S)-(E-propenyl)-(6S,7R)-(6-methoxy-quinol-4-yl)-8-oxa-(1R)-azabicyclo[4.3.0]nonane 10, which is the product of a novel rearrangement of the parent quinine 1 and displays the N(1)-(S)-configuration (10a) in the solid state. The (10S)-diastereomer 2b afforded 10 and its (Z)-propenyl isomer 15 (in the ratio 55:45), as well as (Z)-3,10-didehydro-10,11-dihydro-quinine 19. On treatment with acid the alkaloid 10 yields [(4S)-(E)-propenyl)-(2S)-piperidinyl]-6-methoxyquinoline-(αR)-methanol 12. Closure of the oxazolidine ring in 12 gives 14, the 9,9-dimethyl-derivative of 10, with the N(1) configuration inverted. The molecular structures of 10a and 14, determined by X-ray diffraction, show their similar conformations except for the axial (E)-propenyl substituent, disordered in two orientations in 10a and ordered in another position in 14. [Copyright &y& Elsevier]

Reports on the third polymorph (MH3) of maleic hydrazide, studied by X-ray diffraction and shown to be monoclinic, space group P2[sub 1]/n. Finding that the polymorph MH3 is the prevailing form along with the rare triclinic polymorph MH1; Accommodation of the supramolecular conformations to the requirements of close pacing of the aggregates in crystal lattices.

Examines the concept of a general four-circle diffractometer by introducing axial misalignments into mathematical formulae. Description of diffractometer geometry; Advantage of using diffractometer formalism for routine measurements; Propagation of errors arising from the misalignment of axes.

The half-chair conformation of the dynamically disordered molecular ring of 2-methyl-1-3-cyclohexanedione. C7H10O2 transforms to a sofa below Tc = 244K, when the crystal undergoes a continuous phase transition induced by the onset of halting large-amplitude vibration of methylene groups C(4)H2. The temperature dependence of the crystal structure has been investigated by X-ray diffraction. The Ibam symmetry of the crystal reduces below T.. to space group Pccn. the mechanism of the phase transition and of the conversion of the ring conformation is discussed. [ABSTRACT FROM AUTHOR]

The pressure‐induced transformation of plane‐square complex nickel(II) bis(N,N‐diethyldithiocarbamate) between its soft dithiocarbamate (form I) and thioureide (form II) mesomeres is coupled to the interchange of anagostic Ni⋅⋅⋅H−C interactions from methylene to the methyl group, respectively. At 1.23 GPa, the clearly visible giant anomalous compressibility of the crystal reveals a potential‐energy difference of 5.4 kJ mol−1 between the two complex forms. The structural and spectroscopic results, which are supported by quantum‐mechanical calculations, connect this solid‐state phase transition with the mesomeric transition, and this is accompanied by the conformational transformation of anagostic Ni⋅⋅⋅H−C rearrangement and formation of the charge‐assisted S−⋅⋅⋅H−C bond under pressure. [ABSTRACT FROM AUTHOR]

Highly favoured N–HO bonded honeycomb layers in guanidinium nitrate, C(NH2)3+NO3−, have been destabilized by a pressure of 0.6 GPa, and the novel motif of 3-dimensional N–HO bonded aggregation in high-pressure phase IV determined for in situgrown single-crystal by X-ray diffraction. The mechanism of the transition involves the collapse of voids present in phases I, II and III. In the P/T phase diagram a large hysteresis of the phase IV boundaries is caused by the strongly reconstructive character of the transition and pressure dependent H-accepting capacity of oxygen atoms. [ABSTRACT FROM AUTHOR]

In the title inclusion structure, C20H18N4O4S2·0.5C3H6O, the phen­yl groups form hydro­phobic channels along [001], hosting acetone mol­ecules. The phenyl­sulfon­yl substituent group and the meth­yl group on the cyclo­propane ring are syn with respect to each other, and the two phenyl­sulfon­yl groups are positioned on the same side of the triazolopyridazine ring. [ABSTRACT FROM AUTHOR]

The main directions and achievements in the research on transformations of hydrogen-bonds during the last decade have been briefly outlined. [ABSTRACT FROM AUTHOR]

This study revisits a (001)-oriented layered lead chloride templated by 1,2,4-triazolium, Tz2PbCl4, which recently has been an object of intense research but still suffers from gaps in characterization. Indeed, the divergent reports on the crystal structures of Tz2PbCl4 at various temperatures, devoid of independent verification of chiral phases through second harmonic generation (SHG), have led to an unresolved debate regarding the existence of a low-temperature phase transition (PT) and the noncentrosymmetric nature of the low-temperature phase. Now, by combining differential scanning calorimetry, single-crystal X-ray diffraction, dielectric, as well as linear and nonlinear optical spectroscopies on Tz2PbCl4, we reveal a sequence of reversible PTs at T1 = 361 K (phase I–II), T2 = 339 K (phase II–III), and T3 = 280 K (phase III–IV). No SHG activity could be registered for any of the four crystal phases, as checked by wide-temperature range SHG screening, supporting their centrosymmetry. The dipole relaxation processes indicate a decrease in activation energy with increasing temperature, from 0.60, 0.38, to 0.24 eV observed for phase IV (space group P21/c), phase III (Pnma), and phase II (Cmcm), respectively. This change is interpreted as a result of the diminishing strength of H-bonds as the system transforms from phase IV to III and subsequently to II. The weaker H-bonds facilitate the reorientation of Tz+ cations in the presence of an external electric field. The photoluminescence spectra of Tz2PbCl4 reveal an intriguing interplay of narrow and broadband emission, linked respectively to free excitons and excitons trapped on defects. Notably, as the temperature decreases from 300 K to 16 K, both the emission bands exhibit distinctive blue and red shifts, indicative of increased in-plane octahedral distortion. This dynamic behaviour transforms the photoluminescence of Tz2PbCl4 from greenish-blue at 300 K to yellowish-green at 13 K, enriching our understanding of 2D lead halide perovskites and highlighting the optoelectronic potential of Tz2PbCl4. [ABSTRACT FROM AUTHOR]

Single crystals of isomeric 1,2,3‐tribromobenzene (123TBB), 1,2,4‐tribromobenzene (124TBB) and 1,3,5‐tribromobenzene (135TBB) have been grown from different solvents and their structures determined by X‐ray diffraction at 100, 200 and 270 K. The melting‐point differences of ca 40 K between 135TBB, 123TBB and 124TBB have been correlated with the molecular symmetry and packing preferences in the crystal, as well as with the main types of intermolecular halogen interactions, i.e. Br...Br, Br...C (Br...π) and Br...H. The relationship between symmetry and melting point in Carnelley's rule has been extended to the accessibility of terminal atoms for the formation of intermolecular interactions, their occurrences and distribution, and the close packing. The electrostatic potential mapped on molecular surfaces demonstrates that in more symmetric molecules the more evenly distributed substituents are more accessible and form more optimum intermolecular interactions. [ABSTRACT FROM AUTHOR]

New polymorphs β and γ of bis‐3‐nitrophenyl disulphide, crystallized above 0.3 GPa, are less dense than the ambient‐pressure polymorph α. This counterintuitive density relation results from the high‐entropy nucleation and subsequent kinetic crystallization. The work performed by pressure compensates the high entropy and temperature product, substantiated in varied conformers and increased chemical potential. Pressure‐increased viscosity promotes the kinetic polymorphs, in accordance with empirical Ostwald's rule of stages. It contrasts to mechanochemical techniques, favouring high‐density polymorphs. [ABSTRACT FROM AUTHOR]

Trends in the melting points of analogous halogenated benzene isomers are rationalized in terms of molecular symmetry, crystal structure and interactions. [ABSTRACT FROM AUTHOR]

Cooling [Fe(bbtr)3](BF4)2 (bbtr=1,4‐di(1,2,3‐triazol‐1‐yl)butane) triggers very slow spin crossover below 80 K (T1/2↓=76 K). The spin crossover (SCO) is accompanied by a hysteresis loop (T1/2↑=89 K). In contrast to isostructural perchlorate analogue [Fe(bbtr)3](ClO4)2 in which spin crossover during cooling is preceded by phase transition at TPT=126 K in tetrafluoroborate phase transition does not occur to the beginning of spin crossover (80 K). Studies of mixed crystals [Fe(bbtr)3](BF4)2(1‐x)(ClO4)2x (0.5≤x≤0.9) showed that a phase transition precedes spin crossover, however, for x≅0.46 intersection of T1/2(x) and TPT(x) dependencies takes place. The application of pressure of 1 GPa shifts the spin crossover in [Fe(bbtr)3](BF4)2 to a temperature above 270 K. High‐pressure studies of neat tetrafluoroborate and perchlorate, as well as mixed crystals [Fe(bbtr)3](BF4)2(1‐x)(ClO4)2x (0.1≤x≤0.9), revealed that at 295 K P1/2 value changes linearly with x indicating similar mechanism of spin crossover under elevated pressure in all systems under investigation. Variable pressure single crystal X‐ray diffraction studies confirmed that in contrast to thermally induced spin crossover undergoing differently in tetrafluoroborate and perchlorate an application of high pressure removes this differentiation leading to a similar mechanism depending at first on start spin crossover and then P‐3→P‐1 phase transition occurs. In this report we have shown that 2D coordination polymer [Fe(bbtr)3](BF4)2 (bbtr=1,4‐di(1,2,3‐triazol‐1‐yl)butane) treated to date as spin crossover silent shows thermally induced spin crossover phenomenon. Spin crossover in tetrafluoroborate is extremely slow. Determination of the spin crossover curve required carrying measurement in the settle mode‐cooling from 85 to 70 K took about 600 h (average velocity of change of temperature ca. 0.0004 K/min). [ABSTRACT FROM AUTHOR]

Due to its high electron affinity and electron mobility in a wide absorption range of the visible solar spectrum, [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) is often used as an efficient acceptor in organic photovoltaics. In turn, imines are additives to the active layer of organic solar cells, mainly due to the free electron pair of the imine nitrogen atom and the presence of various chemical groups affecting the polarity and conformations of molecules. However, the attainable efficiency is not as high as expected. Therefore, we have systematically investigated two imines and their mixtures with PC71BM by spectroscopic (the high pressure UV–Vis and frequency domain dielectric), thermoelectric, and mechanical methods for organic, flexible photovoltaics. Both the imines, (N,NʹE,N,NʹE)-N,Nʹ-([2,2ʹ:5ʹ,2ʺ-terthiophene]-5,5ʺ-diylbis(methanylylidene))bis(benzo[d]thiazol-2-imine) (SC3) and (6E)-N-((5-(5-(5-((E)-(4-(4-(4-fluorophenyl)thiazol-2-yl)phenylimino)methyl)thiophen-2-yl)thiophen-2-yl)thiophen-2-yl)methylene)-4-(4-(4-fluorophenyl)thiazol-2-yl)benzenamine (SC13), have the same core composed of three thiophene rings but different terminal chains of the molecules. In the imine SC3, the imine bond is followed by benzothiazole rings on both sides of the core, while in SC13, a thiazole ring separates two benzene rings, the terminal one F-substituted. The difference in molecular structure affects the electric properties of the neat imine and its mixed layers. An addition of PC71BM to the imines improves their electric conductivity. The mechanical studies focused on the stress at break and elongation showed superior behaviour compared to fullerene derivative. High pressure systematically reduces the band gap energy, Eg, from 1.68 eV at 0.16 GPa to 1.51 eV at 2.69 GPa for PC71BM, from 1.77 eV at 0.1 MPa to 1.53 eV at 4.15 GPa for SC3, and from 1.99 eV at 0.11 GPa to 1.8 eV at 3.10 GPa for SC13, as determined by the UV–Vis absorbance measurements in a diamond-anvil cell. These Eg reductions reflect the compressed intermolecular interactions that can be used to monitor the structural stability of these compounds. Based on the dielectric studies it was found that the relaxation processes registered for both imines are probably the grain boundary relaxation. Two processes also appear in the systems with PC71BM, but none of them is the one characteristic of imines. The high-frequency process has a dipole character while the low-frequency one is probably the grain boundary relaxation of these systems. The mechanism of quasi-DC conduction in various temperature ranges in the studied systems was also determined. [ABSTRACT FROM AUTHOR]

In a more synthetical approach to the study of ion-specific phenomena, four dipodal bis(guanidinium) siloxanes have been synthesized starting from glycine, β-alanine, γ-aminobutanoic acid, L-proline and 1,3-bis(3-aminopropyl)tetramethyldisiloxane. Together with their non-amide progenitor they were comparatively studied in regards to their interactions with nine different anions: sulphate, chromate, molybdate, benzoate, chloride, azide, nitrite, nitrate and thiocyanate. Their aqueous solubilities, form, 1H NMR and FT-IR spectra were examined while searching for anion-specific interactions falling in- or outside of the Hofmeister series. We show that although the "chao-" and "kosmotropic" ions affect the properties of solutions in a predictable way, more selective cation-anion pairing is responsible for phase separation and crystallinity. As a prominent example, crystal structure of one of the benzoate salts was successfully obtained and reveals a synergy of hydrophobic packing, ionic and hydrogen bonding. Immobilized but still flexible siloxane bridges give rise to crystals described by P 42/n space group and neatly segregated into hydro- and lipophilic sections. [ABSTRACT FROM AUTHOR]

[Display omitted] • Important effect of repulsive interactions for absorption spectra. • Relation of barochromic and solvatochromic effects. • Dielectric Onsager model description of pressure effects on absorption. • Barochromic results for anthracene in liquid and solid n-hexane. The band positions in the UV–VIS absorption spectra of compressed solution of anthracene in n-hexane significantly depend not only on the dispersive but also on the repulsive solute–solvent interactions, what has so far been omitted. Their strength is determined not only by the solvent polarity but also by Onsager cavity radius changing with pressure. The results obtained for anthracene show that repulsive interactions should be included in the interpretation of barochromic and solvatochromic results of aromatic compounds. We show that the barochromic studies in the liquid solvent can be an alternative to solvatochromic studies, e.g. to determine the polarizability of organic molecules in the electronic excited state. The pressure-induced polarity change in n-hexane exceeds that induced by the exchange of n-alkane solvents between n-pentane and n-hexadecane. [ABSTRACT FROM AUTHOR]

Due to its high electron affinity and electron mobility in a wide absorption range of the visible solar spectrum, [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) is often used as an efficient acceptor in organic photovoltaics. In turn, imines are additives to the active layer of organic solar cells, mainly due to the free electron pair of the imine nitrogen atom and the presence of various chemical groups affecting the polarity and conformations of molecules. However, the attainable efficiency is not as high as expected. Therefore, we have systematically investigated two imines and their mixtures with PC71BM by spectroscopic (the high pressure UV–Vis and frequency domain dielectric), thermoelectric, and mechanical methods for organic, flexible photovoltaics. Both the imines, (N,NʹE,N,NʹE)-N,Nʹ-([2,2ʹ:5ʹ,2ʺ-terthiophene]-5,5ʺ-diylbis(methanylylidene))bis(benzo[d]thiazol-2-imine) (SC3) and (6E)-N-((5-(5-(5-((E)-(4-(4-(4-fluorophenyl)thiazol-2-yl)phenylimino)methyl)thiophen-2-yl)thiophen-2-yl)thiophen-2-yl)methylene)-4-(4-(4-fluorophenyl)thiazol-2-yl)benzenamine (SC13), have the same core composed of three thiophene rings but different terminal chains of the molecules. In the imine SC3, the imine bond is followed by benzothiazole rings on both sides of the core, while in SC13, a thiazole ring separates two benzene rings, the terminal one F-substituted. The difference in molecular structure affects the electric properties of the neat imine and its mixed layers. An addition of PC71BM to the imines improves their electric conductivity. The mechanical studies focused on the stress at break and elongation showed superior behaviour compared to fullerene derivative. High pressure systematically reduces the band gap energy, Eg, from 1.68 eV at 0.16 GPa to 1.51 eV at 2.69 GPa for PC71BM, from 1.77 eV at 0.1 MPa to 1.53 eV at 4.15 GPa for SC3, and from 1.99 eV at 0.11 GPa to 1.8 eV at 3.10 GPa for SC13, as determined by the UV–Vis absorbance measurements in a diamond-anvil cell. These Eg reductions reflect the compressed intermolecular interactions that can be used to monitor the structural stability of these compounds. Based on the dielectric studies it was found that the relaxation processes registered for both imines are probably the grain boundary relaxation. Two processes also appear in the systems with PC71BM, but none of them is the one characteristic of imines. The high-frequency process has a dipole character while the low-frequency one is probably the grain boundary relaxation of these systems. The mechanism of quasi-DC conduction in various temperature ranges in the studied systems was also determined. [ABSTRACT FROM AUTHOR]

Due to its high electron affinity and electron mobility in a wide absorption range of the visible solar spectrum, [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) is often used as an efficient acceptor in organic photovoltaics. In turn, imines are additives to the active layer of organic solar cells, mainly due to the free electron pair of the imine nitrogen atom and the presence of various chemical groups affecting the polarity and conformations of molecules. However, the attainable efficiency is not as high as expected. Therefore, we have systematically investigated two imines and their mixtures with PC71BM by spectroscopic (the high pressure UV–Vis and frequency domain dielectric), thermoelectric, and mechanical methods for organic, flexible photovoltaics. Both the imines, (N,NʹE,N,NʹE)-N,Nʹ-([2,2ʹ:5ʹ,2ʺ-terthiophene]-5,5ʺ-diylbis(methanylylidene))bis(benzo[d]thiazol-2-imine) (SC3) and (6E)-N-((5-(5-(5-((E)-(4-(4-(4-fluorophenyl)thiazol-2-yl)phenylimino)methyl)thiophen-2-yl)thiophen-2-yl)thiophen-2-yl)methylene)-4-(4-(4-fluorophenyl)thiazol-2-yl)benzenamine (SC13), have the same core composed of three thiophene rings but different terminal chains of the molecules. In the imine SC3, the imine bond is followed by benzothiazole rings on both sides of the core, while in SC13, a thiazole ring separates two benzene rings, the terminal one F-substituted. The difference in molecular structure affects the electric properties of the neat imine and its mixed layers. An addition of PC71BM to the imines improves their electric conductivity. The mechanical studies focused on the stress at break and elongation showed superior behaviour compared to fullerene derivative. High pressure systematically reduces the band gap energy, Eg, from 1.68 eV at 0.16 GPa to 1.51 eV at 2.69 GPa for PC71BM, from 1.77 eV at 0.1 MPa to 1.53 eV at 4.15 GPa for SC3, and from 1.99 eV at 0.11 GPa to 1.8 eV at 3.10 GPa for SC13, as determined by the UV–Vis absorbance measurements in a diamond-anvil cell. These Eg reductions reflect the compressed intermolecular interactions that can be used to monitor the structural stability of these compounds. Based on the dielectric studies it was found that the relaxation processes registered for both imines are probably the grain boundary relaxation. Two processes also appear in the systems with PC71BM, but none of them is the one characteristic of imines. The high-frequency process has a dipole character while the low-frequency one is probably the grain boundary relaxation of these systems. The mechanism of quasi-DC conduction in various temperature ranges in the studied systems was also determined. [ABSTRACT FROM AUTHOR]

The authors reflect on the publication of various studies regarding non-ambient crystallography in the journal "Acta Crystallographica Section B." Topics discussed include the invention of the main device for high-pressure crystallography in study by C. E. Weir and colleagues, the analysis made by G. J. Piermarini and colleagues on the high-pressure phase of benzene, and the research by P. J. Chupas and colleagues on powder diffraction.

In this article, the authors respond to the comments made to their researches on the exhibition of ferroelectric properties in hydrogen bonds. They state that the new chemical elements determined with ferroelectric properties require having systematic studies for their properties. Also investigated is several fundamental property of ferroelectricity which can be reversed through spontaneous polarization in the electric field.

Conformational disorder in the structure of monoclinic phase α of 6-chloro-4,4,5,7-tetramethyldihydrocumarin (C12H15ClO2), with four symmetry-independent molecules (Z' = 4) is eliminated either by cooling below 200 K at 0.1 MPa or by compression to above 0.64 GPa at 296 K. However, high-pressure conditions are essential for transforming this compound to triclinic phase β, structurally related to phase α, but with two ordered molecules in the asymmetric unit (Z' = 2). The isothermal compression triggers the α-to-β transition at 1.65 GPa, whereas 0.7 GPa suffices for obtaining phase β by the isochoric recrystallization. In phase α, two pairs of independent molecules are differentiated by the conformational disorder, but its elimination at 200 K does not trigger the phase transition, even at 100 K. [ABSTRACT FROM AUTHOR]

Distortions of the directional requirements in halogen…halogen contacts between hexachloroethane (HCE), C2Cl6, molecules lead to a loose crystal under ambient conditions. Single-crystal X-ray diffraction shows that the orthorhombic HCE phase of space group Pnma, with the molecules in the staggered conformation, extends at least from 85 to 305 K and from 0.1 MPa to 5.42 GPa. At ambient pressure, all intermolecular distances are longer than the sum of van der Waals radii, reached only at the pressure of ca. 1.2 GPa. [ABSTRACT FROM AUTHOR]

A novel and unique crystalline three-component complex was formed of 2-(1-piperidine)ethanol, p -hydroxybenzoic acid and water at the ratio 1:1:1. Its structure has been determined by single-crystal X-ray diffraction. This is an example of a hydrogen-bonded interaction between amino alcohol and benzoic acid molecules. Water acts as a bridge between molecules. The molecules are linked through medium-strong OH⋯O hydrogen bonds from 2.665(6) to 2.813(6) Å and NH⋯O one 2.744(5) Å in length. The molecular structure of 2-(1-piperidinium)ethanol p -hydroxybenzoate hydrate has been characterized by FTIR and Raman spectra and optimized at the B3LYP/6−311++G(d,p) level of theory. The potential energy distributions (PED) have been used to assign the vibrational spectra. Charge delocalization was analyzed using the natural bond orbital (NBO) methods. [ABSTRACT FROM AUTHOR]

The structures of a series of the simplest aliphatic amines determined at high pressure by single crystal X-ray diffraction reveal systematic structure property relations involving intermolecular interactions and molecular symmetries. Five new polymorphs have been found: one of methylamine (phase II, space group Fdd2), two of dimethylamine (phase I, space group C2/c and phase II, P21/c), and two of trimethylamine (phase II, space group P21/n and phase III, P21/m). The methylamine and dimethylamine molecules are arranged according to the NH...N hydrogen bonds. The phase diagrams of methylamines have been outlined up to 6 GPa. [ABSTRACT FROM AUTHOR]

A new high-pressure crystal form of ethane has been revealed above 2.46 GPa/295 K. This phase IV is tetragonal, of space group P42/mnm, with the H atom disordered due to the molecular rotations about the C-C bond. The crystal structure has been determined by single-crystal X-ray diffraction up to 5.90 GPa. The structure of phase IV resembles the previously determined low-temperature plastic phase I (stable below 90.32 K), of cubic space group Im3m, metastable phase II observed between 89.78 and 89.68 K, as well as monoclinic phase III (space group P21/n) stable below 89.68 K. In phases III and IV, the molecules are arranged according to the weak electrostatic complementarity between neighbors. Liquid-ethane convection erodes the crystal plate, hence colorful interference pattern. At 2.46 GPa, ethane crystallizes in a new tetragonal phase IV with rotating molecules. Spectacular convection of liquid ethane above the single-crystal surface has been observed. [ABSTRACT FROM AUTHOR]

A racemic mixture of ( R/S )-pipecolic acid (piperidine-2-carboxylic acid, P2C) forms a stable crystalline aggregate with 2,6-dichloro-4-nitrophenol (DCNP) at the unusual 2:3 ratio ( 1 ). Complex 1 has been characterized by X-ray analysis, Raman, FTIR and NMR spectra, and its structure ( 2 ) has been optimized by the B3LYP/6-31G(d,p) approach. The crystals are monoclinic, P 2 1 / n space group. The piperidine rings adopt chair conformations with the equatorial positions of the carboxylic groups. A P2C zwitterion is linked to two 2,6-dichloro-4-nitrophenol molecules through two non-equivalent short COO⋯HO–C hydrogen bonds and a cation (P2C + H) is hydrogen bonded with the DCNP − anion. These P2C molecules are NH⋯O hydrogen bonded. The FTIR spectrum is in agreement with the X-ray studies. The 13 C CP MAS spectrum confirms the presence of two different P2C and DCNP units in the complex. In the optimized structure of the isolate aggregate, three DCNP molecules are bonded to two pipecolic acid zwitterions. Charge delocalization has been analyzed using the Natural Bond Orbital (NBO) method. [ABSTRACT FROM AUTHOR]

The title compound, C7H6Cl2N4, forms a layered structure stabilized by short C—H⋯N and Cl⋯Cl contacts. [ABSTRACT FROM AUTHOR]

Presents a correction to portions of an article published in a 2001 issue of "Structural Science," where the crystal data of two polymorphs of maleic hydrazide have been printed with errors or omission on Tables 1 and 2.

Presents a correction to the paper "Coupling of the lactone-ring conformation with crystal symmetry in 6-hydroxy-4,4,5,7,8-pentamethyl-3,4-dihydrocoumarin," by Armand Budzianowski and Andrej Katrusiak, published in a 2001 issue of the "Acta Crystallographica."

Presents an error in the article "Conformational transformation coupled with the order—disorder phase transition in 2-methyl-1,3-cyclohexanedione crystals," by Andrezej Katrusiak, which was published in a 1995 issue of the periodical "Acta Crystallographica Section B."

In pentachloroethane, C2HCl5, high pressure initially strongly compresses the C–H…Cl bonds in phase I; however, in phase II which is stable above 0.62 GPa the role of hydrogen bonds is diminished and molecular aggregation is dominated by halogen bonds Cl…Cl. Both phases have been determined by X-ray diffraction and the phase diagram of C2HCl5 has been outlined. The transition between phases I and II retains some relation between their structures and reduces the symmetry from class mmm (space group Pnma) to 2/m (space group P21/n11). The discontinuous transition, with the shear strain exceeding 21°, is so strong that its progress can be visually observed even for powdered samples. The single-crystal growth suggests a surface-roughening transition, as phase I grows in the form of dendrites combining into oval plates, while phase II forms prisms with sharp edges. [ABSTRACT FROM AUTHOR]

High pressure destabilizes the high Z' polymorph of 3-hydroxy-4,5-dimethyl-1-phenylpyridazin-6-one (1α); however, recrystallization is needed for obtaining a low Z', more dense polymorph. Three polymorphs α, β, and γ can be monotonically compressed to 2.0 GPa at least. At ambient pressure 1 crystallizes in space group C2/c, Z' = 4 as polymorph 1α, or as lower-density polymorph 1β, of space group P21/c and Z' = 1. Polymorph β is metastable, and after about one year, it transforms to phase α. The isochoric recrystallization above 0.40 GPa yields a new polymorph γ of space group P21/a and Z' reduced to 1. The γ polymorph retrieved to ambient conditions for months has showed no signs of transformations. The main motif of OH…O bonded chains is retained in all three phases, but high pressure enforced identical conformation of closely packed molecules and their identical crystal environment in phase γ. [ABSTRACT FROM AUTHOR]

Three polymorphs of 2,4,5-triiodo-1H-imidazole (tIIm), all of exceptionally low symmetry (with three and four independent molecules), differ in the contributions of halogen bonds to their cohesion forces. The crystals of phase α, of monoclinic space group P21/c and Z' = 3, were obtained after the first synthesis of the compound and several of its crystallizations. Above 1.9 GPa phase α isostructurally transformed to phase β. The transition, marked by a huge strain visibly changing the crystal shape, could be reversibly repeated on increasing and releasing pressure. Repeated syntheses of tIIm, by using the same recipe as well as the same and varied conditions, resulted exclusively in a new γ phase, of monoclinic space group P21/c and Z' = 4, while phase α disappeared. Each of phases α, β, γ is built of Z' independent molecules and linked by Z' independent NH…N bonds into chains. In phases β and γ new I…I bonds are formed when one of the NH…N bonds is bent to about 130°. [ABSTRACT FROM AUTHOR]

High pressure strongly favors the highest-density polymorph Z of active pharmaceutical ingredient 2-(2,6-xylidino)-5,6-dihydro-4H-1,3-thiazine hydrochloride (xylazine hydrochloride, XylHCl) up to about 0.1 GPa only, but still higher pressure destabilizes this structure. Above 0.1 GPa, XylHCl preferentially crystallizes as solvates with CH2Cl2, CHCl3, or (CH3)2CHOH depending on the solvent used. However, when XylHCl·H2O is dissolved in any of these solvents, the high-pressure crystallizations yield the hydrate XylHCl·H2O only. The single crystals of the CH2Cl2, CHCl3, and (CH3)2CHOH solvates could be grown in situ in a diamond anvil cell, which allowed their structure determination from the single-crystal diffraction data. At 0.4 GPa the XylHCl·H2O hydrate undergoes a pressure-induced phase transition doubling the unit cell dimensions. [ABSTRACT FROM AUTHOR]

The 1:1 complex of piperidine-4-carboxylic acid (isonipecotic acid, P4C) with 2,6-dichloro-4-nitrophenol (DCNP), has been investigated by single-crystal X-ray analysis, Raman and FTIR spectroscopy and theoretical calculations. The hydrogen-bonded-ion-pair complex is observed in the crystalline state with the O⋯H⋯OOC hydrogen bond of 2.453(16) Å. FTIR spectrum shows a broad absorption in the 1600–400 cm −1 region characteristic of very short OHO hydrogen bond, broken by the Evans holes. The complexes are joined through N H⋯O into a H-bonding network. The N H⋯O mode appears as a broad band in the range of 3100–2000 cm −1 . In the structure optimized at the B3LYP/6–311 + +G(d,p) level of theory the proton is transferred from DCNP to P4C, and molecules are joined through the O⋯HOOC hydrogen bond of 2.640 Å. The experimental and theoretical infrared spectra are discussed. Detail interpretation of the vibrational spectra has been carried out with the use of computed Potential Energy Distribution (PED). [ABSTRACT FROM AUTHOR]

Hydrostatic pressure in range 0.1–1.5 GPa is used to modify biological system behaviour mostly in biophysical studies of proteins in solution. Due to specific influence on the system equilibrium high pressure can act as a filter that enables to identify and investigate higher energy protein conformers. The idea of the presented experiments is to examine the behaviour of RNase A molecule under high pressure before and after introduction of destabilizing mutation. For the first time crystal structures of wild-type bovine pancreatic ribonuclease A and its markedly less stable variant modified at position Ile106 were determined at different pressures. X-ray diffraction experiments at high pressure showed that the secondary structure of RNase A is well preserved even beyond 0.67 GPa at room temperature. Detailed structural analysis of ribonuclease A conformation observed under high pressure revealed that pressure influences hydrogen bonds pattern, cavity size and packing of molecule. [ABSTRACT FROM AUTHOR]

( R / S )-Piperidine-3-carboxylic acid (P3C, nipecotic acid) forms a stable 1:1 hydrogen-bonded complex with 2,6-dichloro-4-nitrophenol (DCNP). Both, in crystal and in the optimized theoretically structure by the B3LYP/6-311 + +G(d,p) approach the proton is transferred from DCNP to P3C. The ( R ) and ( S )-stereoisomersic complexes of piperidinium-3-carboxylic acid 2,6-dichloro-4-nitrophenolate, P3C + H·DCNP − , aggregate into centrosymmetric cyclic dimers through the COOH⋯O − and N + H⋯ONO hydrogen bonds of 2.57(1) and 3.06(1) Å, respectively, which in turn are linked into a ladder-type cyclamer through the C H⋯Cl hydrogen bonds of 3.71(1) Å. The title compound is characterized by single-crystal X-ray analysis, Raman and FTIR spectroscopies. The structures of the complexes of the ratio 1:1 (monomer), 2:2 (dimer) and 4:4 (cyclamer) of P3C + H·DCNP − units are optimized by the B3LYP/6-311 + + G(d,p) approach and compared with the solid-state experimental structure. Detail interpretation of the vibrational spectra has been carried out by computing Potential Energy Distribution (PED). Charge delocalization has been analyzed using the Natural Bond Orbital (NBO) method. [ABSTRACT FROM AUTHOR]

Pyrazine molecules aggregate by remarkably similar CH···N hydrogen bonds into four polymorphs. Of eight CH···N bonds to each molecule, six H-bonds are very similar for all pyrazine structures. A diagram of four crystalline phases has been outlined and their low-temperature and high-pressure structures determined. Phase I is metastable and occurs only within the ambient-pressure region of phase II. [ABSTRACT FROM AUTHOR]

The compression and thermal expansion of crystalline 1,2,4-trichlorobenzene, C6H3Cl3, 124TCB, investigated under isobaric and isothermal conditions, are in reverse relation, as for most of crystals, however, the isochoric strain along direction c is clearly different from those along a and b. Single crystals of 124TCB have been in situ grown under isochoric and isobaric conditions, at 270 K/0.1 MPa and 295 K/0.16 GPa, and also at 100 K/0.1 MPa and 295 K/0.64 GPa, when the unit-cell volume is similar. All crystallizations yielded the same phase, of monoclinic space group P21/n, with two symmetry-independent molecules (Z′ = 2). The structure is governed by Cl…Cl and Cl…H interactions and the molecules are all nearly parallel to the [001] direction. Systematic differences of these specific contacts afford rationalizing the isochoric strain of the crystal. The phase diagram of 124TCB has been outlined. [ABSTRACT FROM AUTHOR]

Pressure affects the competition between C-HX hydrogen bonds and X⋯X halogenhalogen interactions. In bromomethane, CH3Br, pressure changes the molecular arrangement of the two solid-state phases of this compound: low-pressure phase α is dominated by halogenhalogen interactions, whereas above 1.5 GPa the β phase is governed by C-H⋯halogen bonds. The CH3Br phase α is isostructural with solid CH3I of orthorhombic space group Pnma, while CH3Br phase β is polar, isostructural with CH3Cl and CH3CN crystals, of orthorhombic space group Cmc21. The crystal structures of CH3Cl (b.p. = 249.1 K) and CH3Br (b.p. = 276.7 K) have been determined by high pressure single-crystal X-ray diffraction up to 4.38 GPa and 2.85 GPa, respectively. In CH3Br, pressure of 1.5 GPa enforces the close packing and opposite electrostatic-potential matching between molecular surfaces in contact. The interweaved C-H⋯X bonded diamondoid networks of β-CH3X are similar to those of acetonitrile, H2O ice VII and solidified X2 halogens. The phase diagrams of CH3Br and CH3Cl have been constructed. [ABSTRACT FROM AUTHOR]

Four new hydrogen-bonded complexes of a simple amino acid glycine (GLY) and its methyl derivatives – sarcosine (N-methylglycine, SAR), dimethylglycine (DMG) and betaine (N,N,N-trimethylglycinium, BET) with squaric acid (3,4-dihydroxy-3-cyclobuten-1,2-dione, H2SQ) are synthesized and characterized by X-ray diffraction, FTIR and NMR spectroscopy. The complexes differ in stoichiometry, interaction with H2SQ and the hydrogen-bonding system. Methylation of glycine gradually reverses the dissociation of squaric acid in co-crystals. This process is correlated with the number of N–H…O bonds to the squaric acid oxygens and the N–H donor capability of glycine derivatives. The effect of the presence of methyl groups on the proton and carbon-13 chemical shifts is studied. The DFT calculations are performed for one unit of complexes and stable zwitterionic structures of SAR, DMG and BET in complex with H2SQ, except the GLY unit, are suggested, which appears as an uncharged (neutral) form. The experimental and computed vibrational spectra of complexes studied are reported. [ABSTRACT FROM AUTHOR]

1,4-Diazabicyclo[2.2.2]octane perchlorate,[C6H13N2]+ClO4–, dabcoHClO4, the first NH+···Nhydrogen-bonded ferroelectric, exhibits at least ten unsolvated polymorphs,depending on temperature and pressure. When crystallized from themethanol solution above 2 GPa, dabcoHClO4crystallizeswith two molecules of methanol to form solvate dabcoHClO4·2CH3OH. This solvate structure has been determinedby single-crystal X-ray diffraction up to 3 GPa. High pressure transformsthe H-bonding pattern and the hierarchy of different cohesion forces.The solvate formation is additionally favored by its molecular volumelower than the sum of the molar equivalents of unsolvated components. [ABSTRACT FROM AUTHOR]

• Structure of 8 - hydroxyquinoline betaine monohydrate was solved by X-ray. • The one proton of disordered water molecules is shared between two half-occupied sides. • Three broad bands classify the FTIR spectrum as the ABC type. • PED are used to assign the bands in the vibrational spectrum. • Hirshfeld surface, Mulliken atomic charges, MEP, HOMO-LUMO were computed. • The assignment of 1H and 13C resonance signals are based on the 2D measurements. Molecular structure and properties of 8-hydroxyquinoline betaine monohydrate (1-carboxymethyl-8-hydroxyquinolinium inert salt monohydrate) were studied by X-ray diffraction, DFT calculations, FTIR and NMR spectra. In the crystals, 8-hydroxyquinoline betaine and water are bonded by an intermolecular and asymmetric COO···H 2 O hydrogen bond of 2.782(3) Å. The water molecules are disordered so that one of the proton is shared between two half occupied sites. The hydroxyl group of quinoline is bonded to the neighboring molecule by the O−H···OOC hydrogen bond of 2.571(3) Å. The molecular geometry, Hirshfeld surface, Mulliken atomic charge distribution, molecular electrostatic potential, frontier molecular orbitals, vibrational wavenumbers, magnetic isotropic shielding constants were determined using the density functional theory (DFT/B3LYP) with 6–311++G(d,p) basis set. The FTIR spectrum shows a characteristic ABC structure, typical of medium-short hydrogen bonds. The potential energy distribution (PED) was used to assign the bands in the vibrational spectrum. 1H and 13C NMR spectra were analyzed. [Display omitted] [ABSTRACT FROM AUTHOR]

Under high pressure, crystals of [Zn(m-btcp)2(bpdc)2]·2DMF·H2O, referred to as DMOF are particularly sensitive to the type of pressure-transmitting media (PTM) employed: large PTM molecules seal the pores and DMOF is compressed as a closed system, whereas small PTM molecules are pushed into the pores, thereby altering the stoichiometry of DMOF. Compression in glycerol and Daphne 7474 leads to negative linear compressibility (NLC), while a mixture of methanol : ethanol : water 'hyperfills' the pores of the chiral framework, adjusting its 3-dimensional strain and resulting in pressure-induced amorphization around 1.2 GPa. The uptake of the small-molecule PTM strongly increases the dimensions of DMOF in the direction perpendicular to that of the NLC of the crystal. [ABSTRACT FROM AUTHOR]

Transformations of NH···N hydrogen bondscan beemployed in new classes of electronic materials. Imidazole, a prototypicNH···N bonded crystal, remains centrosymmetric whencompressed to 2.7 GPa. However, its recrystallization at 1.2 GPa leadsto a new polar phase which in turn can be decompressed to 0.5 GPaat least. This transformation and calculated potential-energy functionof the H-atom correlate with the transforming dimensions of the hydrogenbond and reveal high polarity of nonionic NH···N bondedcompounds. [ABSTRACT FROM AUTHOR]

Abstract: The ionophoric antibiotic lasalocid acid has been converted to a novel 6-bromohexyl ester (LASBR) and its structure has been determined in the crystal by X-ray diffraction and in solution by NMR and FT-IR methods. In the crystal two symmetry-independent LASBR molecules are present. The structure of LASBR in solution is slightly different because the strongest intramolecular C(1)Hogen bond in the pseudo-aromatic ring becomes partially broken and a new hydrogen bond between O(4)H and carbonyl group C(13)ed. LASBR forms complexes with Li+, Na+ and K+ cations of exclusively 1:1 stoichiometry. The structures of complexes have been studied and visualized using semi-empirical calculation based on results of spectrometric and spectroscopic investigation. It is demonstrated that in contrast to lasalocid acid the novel ester forms preferential complexes with Li+ cation. [Copyright &y& Elsevier]

Abstract: Effects of methylation for intermolecular interactions and lipophilicity have been studied for a series of methylated 4,5-dihydro-6-hydroxypyridazine-3-carboxylic and 6-hydroxypyridazine-3-carboxylic acids (1 and 2). In solution they exist in equilibrium of the lactam and lactim tautomers, with the reverse preferences for analogs 1 and 2, which affect the syntheses of their methylated derivatives. Carboxylic acid 2 preferably crystallizes as a hydrate, built of carboxylate anions and hydronium cations 2 − H3O+, hydrogen bonded into catemeric patterns involving both ions. In methyl 4,5-dihydro-6-oxopyridazine-3-carboxylate (4A) the molecules are NH⋯O hydrogen bonded into chains. In both structures 2 − H3O+ and 4A, there are relatively strong CH⋯O hydrogen bonds, arranging the molecules into sheets. The increased lipophilicity of the methylated derivatives has been correlated with the formation of CH⋯O bonds. [Copyright &y& Elsevier]

Abstract: The 2:2 hydrogen-bonded complex between Kemp’s triacid (KTA) and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) has been synthesised and studied by X-ray and FT-IR methods. The crystals of KTA–MTBD are orthorhombic, space group is Pbca with a= 15.3435(9)Å, b =13.0764(7)Å, c= 21.2403(14)Å, and Z =8. In the solid state two protonated MTBD and two deprotonated KTA molecules form a hydrogen-bonded dimer. The dimer structure is stabilised by two OH⋯O− middle strength and two N+H⋯Otermolecular hydrogen bonds as well as by two OO− very strong intramolecular hydrogen bonds. The existence of these three types of hydrogen bonds is well visible in the FT-IR spectrum of the complex and is discussed in detail. [ABSTRACT FROM AUTHOR]