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The molecular coordination compound trans-[Cu[Cl.sub.2][(3-Clpy).sub.2]] (3-Clpy = 3-chloropyridine), which is prepared as a microcrystalline powder, is reacted directly with gaseous HCl in the absence of water to yield the crystalline salt [(3-ClpyH).sub.2][Cu[Cl.sub.4]]. The reversible uptake of HCl molecules from the gas phase by a nonporous crystalline solid has proceeded in the absence of any solvent and with retention of crystallinity, despite many changes that are required by this process.

An extensive search was carried out for a dimer-based crystal structure of polymorphs of the 3-azabicyclo[3.3.1]nonane-2,4,-dione. It was found that the imide group of 3-azabicyclo[3.3.1]nonane-2,4,-dione could form two hydrogen bond motifs.

A comprehensive characterization of the structure and dynamics of maleic anhydride is discussed using experimental methods like single-crystal neutron diffraction, infrared, Raman and inelastic neutron scattering (INS) spectroscopies and computational methods like AM1 and two levels of density functional theory. Force fields derived by empirical means and ab initio data predict the INS spectrum.

Low-temperature single crystal or powder X-ray diffraction is used to characterize the crystal structures, including two new polymorphs, of three diastereomerically related salt pairs formed by 1-phenylethylammonium with 2-phenylpropanoate, 2-phenylbutyrate and mandelate ions. The findings demonstrate that the stability difference of the diastereomeric salt pairs of three 1-phenylethylammonium-2-phenylacetate derivatives is related to their resolution efficiency and varies considerably, despite the similarity in their molecular structure and hydrogen-bonding motifs.

The direct elimination of HCl from crystalline materials and the subsequent reversible uptake via a gas-solid reaction is presented. The crystal structures are determined and the transformations require cleavage and formation of covalent bonds as well as noncovalent interactions and involve a change in the coordination geometry at the metal center.

A new resource for studying structure property relationships is presented, namely a systematic database of 36 organic salt structures together with phase specific aqueous solubility data. The salts are derived from four M2+ cations (Mg2+, Ca2+, Sr2+, Ba2+) and nine substituted benzoate anions. The intrinsic solubility of the free acid is found to have a major contribution to make to salt solubility, but despite previous literature assertions, there appears to be little correlation of solubility with the polarity of the organic ions, with cation size, or with hydration state. Importantly, we also show that consideration of the array structure rather than just molecular considerations improves prediction of rank orders of solubility. Thus, three-dimensional intermolecular networks (here formed with hydrogen bonding, M−O−M and M−N−M interactions, and halide interactions) are found to have lower aqueous solubilities than lower dimensional networks. A new resource for studying structure property relationships is presented, namely a systematic database of 36 pharmaceutically relevant organic salt structures (alkali earth metal salts of substituted benzoates) together with phase-specific aqueous-solubility data. [ABSTRACT FROM AUTHOR]

The predictions of the crystal structure of 3-azabicyclo[3.3.1]nonane-2,4-dione submitted in the 2001 international blind test of crystal structure prediction (CSP2001) led to the conclusion that crystal structures containing an alternative hydrogen bonded dimer motif were energetically competitive with the known catemer-based structure. Here we report an extensive search for a dimer-based crystal structure. Using an automated polymorph screen a new catemer-based metastable polymorph (form 2) and two new catemer-based solvates were found, and concurrent thermal studies reproduced form 2 and identified a plastic phase (form 3), whose powder X-ray diffraction pattern was consistent with the cubic space group I23 (a = 7.5856(1) Å). Computational studies on the monomer showed that the imide NH was a weak hydrogen bond donor, rationalizing the occurrence of the plastic phase which involved the breaking of all hydrogen bonds, and modeling of small clusters showed that dimers could easily reorganize to give the catemer. FTIR spectra confirmed the weakness of the hydrogen bond, with the solute showing no self-assembly in solution. It is concluded that the weakness of the NH donor, coupled with the globular shape of the molecule, allows unusually facile transformation between alternative hydrogen bonding motifs during aggregation and nucleation. [ABSTRACT FROM AUTHOR]

Heat transfer coefficients in a continuous oscillatory baffled crystallizer (COBC) with a nominal internal diameter of 15 mm have been determined as a function of flow and oscillatory conditions typically used under processing conditions. Residence time distribution measurements show a near-plug flow with high Peclet numbers on the order of 100-1000 s, although there was significant oscillation damping in longer COBC setups. Very rapid heat transfer was found under typical conditions, with overall heat transfer coefficients on the order of 100 s W m -2 K -1 . Furthermore, poor mixing in the COBC cooling jacket was observed when lower jacket flow rates were implemented in an attempt to decrease the rate of heat transfer in order to achieve more gradual temperature profile along the crystallizer length. Utilizing the experimentally determined overall heat transfer coefficients, a theoretical case study is presented to investigate the effects of the heat transfer rate on temperature and supersaturation profiles and to highlight potential fouling issues during a continuous plug flow cooling crystallization., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

The anhydrate and the stoichiometric tetarto-hydrate of pyrogallol (0.25 mol water per mol pyrogallol) are both storage stable at ambient conditions, provided that they are phase pure, with the system being at equilibrium at a w (water activity) = 0.15 at 25 °C. Structures have been derived from single crystal and powder X-ray diffraction data for the anhydrate and hydrate, respectively. It is notable that the tetarto-hydrate forms a tetragonal structure with water in channels, a framework that although stabilized by water, is found as a higher energy structure on a computationally generated crystal energy landscape, which has the anhydrate crystal structure as the most stable form. Thus, a combination of slurry experiments, X-ray diffraction, spectroscopy, moisture (de)sorption, and thermo-analytical methods with the computationally generated crystal energy landscape and lattice energy calculations provides a consistent picture of the finely balanced hydration behavior of pyrogallol. In addition, two monotropically related dimethyl sulfoxide monosolvates were found in the accompanying solid form screen.

We report the structure of the fifth monohydrate of gallic acid and two additional anhydrate polymorphs and evidence of at least 22 other solvates formed, many containing water and another solvent. This unprecedented number of monohydrate polymorphs and diversity of solid forms is consistent with the anhydrate and monohydrate crystal energy landscapes, showing both a wide range of packing motifs and also some structures differing only in proton positions. By aiding the solution of structures from powder X-ray diffraction data and guiding the screening, the computational studies help explain the complex polymorphism of gallic acid. This is industrially relevant, as the three anhydrates are stable at ambient conditions but hydration/dehydration behavior is very dependent on relative humidity and phase purity.

An extensive experimental screen, coupled with a computational study, revealed seven new solid-state forms of β-resorcylic acid. The known, stable polymorph II° shows a reversible phase transformation to the new, kinetically stable, probably disordered high temperature form I. The study provides a consistent picture of the solid-state of β-resorcylic acid.

Scanning tunneling microscopy (STM) has become a staple surface microscopy technique for a number of research fields ranging from semiconductor research to heterogeneous catalysis. Pharmaceutical compounds, however, remain largely unstudied. Here we report the first STM study of carbamazepine (CBZ), an anti-epileptic drug, on Au(111) and Cu(111) surfaces. The analysis reveals that CBZ adopts unusual chiral molecular architectures on both metals. These previously unreported structures, which are strikingly different from CBZ packing arrangements observed in 3D crystal structures, indicate that the main molecular architecture is driven by a combination of CBZ intermolecular hydrogen bonding and metal-CBZ interactions. Comparison of the 2D molecular structures reveals large differences in local geometry and packing density that are dependent on the nature of the metal surface. These results have implications for the potential role of metal surfaces as heteronuclei or templating agents for controlling polymorph formation, which continues to be a problem for many compounds in the pharmaceutical industry including CBZ.

Yellow crystalline salts (3-XpyH)2[CuCl4] (3-XpyH = 3-halopyridinium, X = Cl, Br) lose HCl upon exposure to air in an open vessel, yielding quantitatively blue crystalline coordination compounds [CuCl2(3-Xpy)2]. The reaction is prevented if the vessel is sealed, but can be driven forward under such conditions by providing a trapping agent for HCl, such as an aqueous solution of AgNO3. The reaction requires cleavage of Cu-Cl and N-H bonds and formation of Cu-N bonds. The metal coordination geometry also changes from distorted tetrahedral to square planar. Remarkably, the reaction is fully reversible upon exposure of the blue coordination compound to vapor from a concentrated aqueous solution of HCl, and the initial yellow crystalline salt results. The structural changes occurring in these reactions have been followed by X-ray powder diffraction, including Rietveld refinement, of the crystal structures.