Solid-State Dynamics and High-Pressure Studies of a Supramolecular Spiral Gear

The structures and solid-state dynamics of the supramolecular salts of the general formula [(12-crown-4)₂ ⋅DABCOH₂ ](X)₂ (where DABCO=1,4-diazabicyclo[2.2.2]octane, X=BF₄ , ClO₄ ) have been investigated as a function of temperature (from 100 to 360 K) and pressure (up to 3.4 GPa), through the combination of variable-temperature and variable-pressure XRD techniques and variable-temperature solid-state NMR spectroscopy. The two salts are isomorphous and crystallize in the enantiomeric space groups P3₂ 2₁ and P3₁ 2₁ . All building blocks composing the supramolecular complex display dynamic processes at ambient temperature and pressure. It has been demonstrated that the motion of the crown ethers is maintained on lowering the temperature (down to 100 K) or on increasing the pressure (up to 1.5 GPa) thanks to the correlation between neighboring molecules, which mesh and rotate in a concerted manner similar to spiral gears. Above 1.55 GPa, a collapse-type transition to a lower-symmetry ordered structure, not attainable at a temperature of 100 K, takes place, proving, thus, that the pressure acts as the means to couple and decouple the gears. The relationship between temperature and pressure effects on molecular motion in the solid state has also been discussed.

Co-crystallization of racemic amino acids with ZnCl2: an investigation of chiral selectivity upon coordination to the metal centre

A preference for racemic vs. meso-crystal formation has been observed upon the cocrystallization of dl-amino acids with ZnCl₂, as a result of homo vs. heterochiral competition.

Co-crystallization of antibacterials with inorganic salts: paving the way to activity enhancement

Co-crystallization of the antibacterial agents proflavine and methyl viologen with the inorganic salts CuCl, CuCl₂ and AgNO₃ results in enhanced antimicrobial activity with respect to the separate components.

Mechanochemical preparation of molecular and ionic co-crystals of the hormone melatonin

Molecular and ionic co-crystals of melatonin with piperazine, DABCO and CaCl₂ were obtained via kneading with ethanol: the solubility of melatonin in H₂O increases by an order of magnitude when combined with CaCl₂.

Improving solubility and storage stability of rifaximin via solid-state solvation with Transcutol®

Crystallization of rifaximin from Transcutol® affords the new anhydrous τ-form, which combines a high dissolution rate with a high storage stability, as it is not affected by exposure to humidity.

Supramolecular zwitterions based on a novel boronic acid–squarate dianion synthon

We report a novel heterodimeric charge-assisted hydrogen bonding synthon and prove its robustness by preparation of a three-component co-crystal.

Precessional Motion in Crystalline Solid Solutions of Ionic Rotors

The order-disorder phase transition associated with the uprise of reorientational motion in (DABCOH2)²⁺ , in the supramolecular salts of general formula [1⋅(DABCOH₂ )]X₂ (where 1=12-crown-4, DABCO=1,4-diazabicyclo[2.2.2]octane, and X=Cl^- or Br^- ), has been investigated by variable temperature X-ray diffraction on single crystals and powder samples, as well as by DSC and solid-state NMR spectroscopy (SSNMR). The two compounds undergo a reversible phase change at 292 and 290 K, respectively. The two crystalline materials form solid solutions [1⋅(DABCOH₂ )]Cl_2x Br_2(1-x) in the whole composition range (0 < x<1), with a decrease in the temperature of transition to a minimum of ca 280 K, corresponding to x=0.5. Activation energy values for the dynamic processes, evaluated by variable-temperature ¹³ C magic-angle spinning (MAS) SSNMR and line-shape analysis are ca. 50 kJ mol^-1 in all cases. Combined diffraction and spectroscopic evidence has allowed the detection of a novel dynamic process for the (DABCOH₂ )²⁺ dications, based on a room temperature precessional motion that is frozen out below the disorder-order transition; to the best of the authors' knowledge this phenomenon has never been observed before.

Ionic Co-Crystal Formation as a Path Towards Chiral Resolution in the Solid State

The preparation and characterization of a whole family of hydrated ionic co-crystals formed by both enantiopure l-proline and racemic dl-proline with LiX (X=Cl, Br, I) are reported. The chiral preference of the lithium cation for homochiral coordination, both in the formation of crystalline conglomerates (with Cl and Br) and racemates (with Cl and I), in which molecules of opposite chirality are confined to distinct crystal layers, is discussed. Dehydration processes for all hydrated crystals have also been investigated.

Alloying barbituric and thiobarbituric acids: from solid solutions to a highly stable keto co-crystal form

Alloying isomorphous crystals of barbituric acid (BA) and thiobarbituric acid (TBA) yields solid solutions of general formula BA_xTBA_1-x (x < 0.8); for x = 0.5 the stable co-crystal BA_0.5TBA_0.5, isomorphous with the parent keto forms, is observed, which melts at 265 °C, i.e. ca. 10 and 20 °C higher than the melting points of BA and TBA, respectively. While the BA_xTBA_1-x solid solutions with x > 0.5 are stable, those with x < 0.5 convert, with time or temperature, to the BA_0.5TBA_0.5 co-crystal.

Solid-state chiral resolution mediated by stoichiometry: crystallizing etiracetam with ZnCl2

Co-crystallization of racemic etiracetam with ZnCl₂ results in a racemic compound or a conglomerate, depending on the amount of ZnCl₂; the unprecedented behaviour was investigated through a racetam/ZnCl₂/solvent phase diagram.

Organic–inorganic ionic co-crystals: a new class of multipurpose compounds

Reacting molecular organic solids with inorganic salts gives access to novel properties via ionic co-crystal formation.

Smart urea ionic co-crystals with enhanced urease inhibition activity for improved nitrogen cycle management

A smart ionic co-crystal of urea with KCl and ZnCl₂, obtainedviamechanochemical and solution methods has been proven to be a very efficient urease inhibitor and to provide soil nutrients to complement N supply.

Preliminary profiling of blood transcriptome in a rat model of hemorrhagic shock

Hemorrhagic shock is a leading cause of morbidity and mortality worldwide. Significant blood loss may lead to decreased blood pressure and inadequate tissue perfusion with resultant organ failure and death, even after replacement of lost blood volume. One reason for this high acuity is that the fundamental mechanisms of shock are poorly understood. Proteomic and metabolomic approaches have been used to investigate the molecular events occurring in hemorrhagic shock but, to our knowledge, a systematic analysis of the transcriptomic profile is missing. Therefore, a pilot analysis using paired-end RNA sequencing was used to identify changes that occur in the blood transcriptome of rats subjected to hemorrhagic shock after blood reinfusion. Hemorrhagic shock was induced using a Wigger's shock model. The transcriptome of whole blood from shocked animals shows modulation of genes related to inflammation and immune response (Tlr13, Il1b, Ccl6, Lgals3), antioxidant functions (Mt2A, Mt1), tissue injury and repair pathways (Gpnmb, Trim72) and lipid mediators (Alox5ap, Ltb4r, Ptger2) compared with control animals. These findings are congruent with results obtained in hemorrhagic shock analysis by other authors using metabolomics and proteomics. The analysis of blood transcriptome may be a valuable tool to understand the biological changes occurring in hemorrhagic shock and a promising approach for the identification of novel biomarkers and therapeutic targets. Impact statement This study provides the first pilot analysis of the changes occurring in transcriptome expression of whole blood in hemorrhagic shock (HS) rats. We showed that the analysis of blood transcriptome is a useful approach to investigate pathways and functional alterations in this disease condition. This pilot study encourages the possible application of transcriptome analysis in the clinical setting, for the molecular profiling of whole blood in HS patients.

Making crystals with a purpose; a journey in crystal engineering at the University of Bologna

The conceptual relationship between crystal reactivity, stability and meta-stability, solubility and morphology on the one hand and shape, charge distribution, chirality and distribution of functional groups over the molecular surfaces on the other hand is discussed, via a number of examples coming from three decades of research in the field of crystal engineering at the University of Bologna. The bottom-up preparation of mixed crystals, co-crystals and photoreactive materials starting from molecular building blocks across the borders of organic, organometallic and metalorganic chemistry is recounted.

Ionic co-crystals of enantiopure and racemic histidine with calcium halides

Ionic co-crystals (ICCs) of l- and dl-histidine with CaCl₂, CaBr₂ and CaI₂ were prepared by mechanochemical and solution methods and were structurally characterized by either single crystal or powder X-ray diffraction methods.

White luminescence achieved by a multiple thermochromic emission in a hybrid organic-inorganic compound based on 3-picolylamine and copper(i) iodide

Three copper(i) complexes have been obtained by the reaction of CuI with 3-picolylamine in acetonitrile solution and characterized by X-ray powder diffraction, both from synchrotron and laboratory radiation. Photophysical investigations in the solid state revealed highly efficient thermally-activated delayed fluorescence (TADF) with photoluminescence quantum yields (PLQYs) up to 18%. Notably, the complex [Cu₂I₂(3pica)]_∞ displays a strong luminescence thermochromism due to the presence of both ^1,3(X + M)LCT excited states and a lower-lying cluster-centered (³CC) one, leading to multiple emission at room temperature; as a result, a white luminescence is achieved with a PLQY of 4.5%.