Plastic crystals are currently attracting interest because their solid-state caloric functionalit... more Plastic crystals are currently attracting interest because their solid-state caloric functionality could be used to tackle climate change in two critical areas: (i) more environmentally friendly cooling and heating driven by pressure and (ii) passive waste heat management. Here, we suggest that plastic crystals could also be used for active pressure-assisted (i.e., barocaloric) waste heat management. In contrast to the barocaloric cooling/heating cycle, for active barocaloric waste heat management, the hysteresis may not be a constraint and transition temperatures above ambient are usually desired. In contrast to passive waste heat management, the application of pressure can be an advantage to actively control the absorption and delivery of heat by the plastic crystal. Here, we have investigated the pressure-induced caloric response at the first-order phase transitions occurring above room temperature of three plastic crystals derived from adamantane: 1-adamantanol, 2-adamantanol, a...
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The crystal structures of dimorphic benzylthiouracil, a drug against hyperthyroidism, have been r... more The crystal structures of dimorphic benzylthiouracil, a drug against hyperthyroidism, have been redetermined and the atom coordinates of the two independent molecules of form I have been obtained for the first time. The dimorphism convincingly demonstrates the conformational versatility of the benzylthiouracil molecule. It has been established through calorimetric studies that the low-temperature form II transforms endothermically (II IH = 5.6(1.5) J g-1) into form I at 405.4(1.0) K. The high-temperature form I melts at 496.8(1.0) K (I LH = 152.6(4.0) J g-1). Crystallographic and thermal expansion studies show that form I is denser than form II, leading to the conclusion that the slope of the II-I equilibrium curve in the pressure-temperature phase diagram is negative. It follows that this dimorphism corresponds to a case of overall enantiotropic behaviour, which implies that both solid phases possess their own stable phase region irrespective of the pressure. Moreover, form II is clearly the stable polymorph under ambient conditions.
Spironolactone form I melts at about 70 degrees lower than form II, which is very unusual for two... more Spironolactone form I melts at about 70 degrees lower than form II, which is very unusual for two co-existing polymorphs. The phase relationships involving this unprecedented case of dimorphism have been investigated by constructing a topological pressure-temperature phase diagram. The transition from polymorph I to polymorph II is unambiguously exothermic while it is accompanied with an increase in the specific volume. This indicates that the dP/dT slope of the I-II equilibrium curve is negative. The convergence of the melting equilibrium lines at high pressure lead to a topological P-T diagram in which polymorph I possesses a stable phase region at high pressure. Thus, forms I and II are monotropically related at ordinary pressure and turn to an enantiotropic relationship at high pressure. Given that polymorph I is the densest form, it negates the rule of thumb that the densest form is also the most stable form at room temperature, similar to the case of paracetamol.
Since the early nineties countless publications have reported promising medicinal applications fo... more Since the early nineties countless publications have reported promising medicinal applications for [60]fullerene (C60) related to its unparalleled affinity towards free radicals. Yet, until now no officially approved C60-based drug has reached the market, notably because of the alleged dangers of C60. Nevertheless, since the publication of the effects of C60 on the lifespan of rodents, a myriad of companies started selling C60 worldwide for human consumption without any approved clinical trial. Nowadays, several independent teams have confirmed the safety of pure C60 while demonstrating that previously observed toxicity was due to impurities present in the used samples. However, a purity criterion for C60 samples is still lacking and there are no regulatory recommendations on this subject. In order to avoid a public health issue and for regulatory considerations, a quality-testing strategy is urgently needed. Here we have evaluated several analytical tools to verify the purity of co...
The formation of co-crystals is often unexpected; however, the Buckminsterfullerene, for which ma... more The formation of co-crystals is often unexpected; however, the Buckminsterfullerene, for which many solvates are known, is an excellent system to study this tendency. In the present paper, C60 and...
The pressure-temperature phase diagram of morniflumate (niflumic acid βmorpholinoethyl ester) has... more The pressure-temperature phase diagram of morniflumate (niflumic acid βmorpholinoethyl ester) has been obtained by high-pressure thermal analysis. In addition, calorimetric melting data (TI →L = 348.1 ±0.4 K and ∆HI →L = 89 ±2 J g-1) and the specific volumes of the solid and the liquid state have been obtained under normal pressure. Comparison of the measured high-pressure melting data with the equilibrium curve obtained through the Clapeyron equation indicates that the initial slopes are the same (dP/dT = 2.96 ±0.06 MPa K-1) at the melting point under normal pressure. The fact that the Clapeyron equation can be used to construct topological phase diagrams may be of interest for the food and pharmaceutical industries.
Pressure experiments provide a unique opportunity to unravel new insights into glass-forming liqu... more Pressure experiments provide a unique opportunity to unravel new insights into glass-forming liquids by exploring its effect on the dynamics of viscous liquids and on the evolution of the glass transition temperature. Here we compare the pressure dependence of the onset of devitrification, Ton, between two molecular glasses prepared from the same material but with extremely different ambient-pressure kinetic and thermodynamic stabilities. Our data clearly reveal that, while both glasses exhibit different dTon/dP values at low pressures, they evolve towards closer calorimetric devitrification temperature and pressure dependence as pressure increases. We tentatively interpret these results from the different densities of the starting materials at room temperature and pressure. Our data shows that at the probed pressures, the relaxation time of the glass into the supercooled liquid is determined by temperature and pressure similarly to the behaviour of liquids, but using stability-depe...
We demonstrate that solvates of fullerene C 60 form very predictable structures with finely tunab... more We demonstrate that solvates of fullerene C 60 form very predictable structures with finely tunable properties through the choice of the second component or solvent. Cubic co-crystals of C 60 •12CCl 2 Br 2 and C 60 •12CBr 2 (CH 3) 2 were grown at room temperature in saturated solutions of fcc C 60 and the respective solvents (with C 2v molecular symmetry) They are unstable in air and transform spontaneously into the hexagonal co-crystals C 60 •2CCl 2 Br 2 or C 60 •2CBr 2 (CH 3) 2. Whereas, the cubic co-crystals have positive excess volumes (+2% and +5%, respectively), the stable hexagonal crystals, for which structures are given for the first time, possess negative excess volumes (-5% and-4.3%, respectively). The unit-cell volumes for both cubic and hexagonal co-crystals depend exclusively on the van-der-Waals volumes of the constituents and this correlation has been confirmed using previously published data.
The polymorphism of 1 adamantane methanol C 11 H 18 O has been investigated by differential therm... more The polymorphism of 1 adamantane methanol C 11 H 18 O has been investigated by differential thermal analysis and single crystal and powder X ray diffraction. Below the melting temperature (389.5 ± 0.4 K), this compound exhibits an orthorhombic phase (phase I, Pnnm, Z = 12, Z′ = 1.5). The melting enthalpy was determined to be 20.5 ± 0.4 kJ mol −1 , i.e., with an entropy change of (6.34 ± 0.13)R, which is much higher than the quoted value from Timmermans for the melting orientationally disordered phases (2.5R), thus supporting the orientationally ordered character of phase I. This orthorhombic phase I exhibits a statistical disorder of the hydrogen atom related to the oxygen atom, due to the position of one independent molecule on the mirror. At ca. 272 K, phase I transforms continuously through an order−disorder transition to a low temperature monoclinic phase II (P2 1 /n, Z = 12, Z′ = 3). The monoclinic and orthorhombic phases are related by a group−subgroup relationship, which perfectly agrees with the continuous character of the II to I transition. Moreover, by a convenient choice of an order parameter related to the continuous tilt of the c axis, the critical exponent for this transition is found to be close to the theoretical prediction of the three dimensional Ising model (with a critical exponent of ca. 0.27).
The polymorphism of two 2 X adamantane derivatives, X = Cl, X = Br, has been studied by X ray pow... more The polymorphism of two 2 X adamantane derivatives, X = Cl, X = Br, has been studied by X ray powder diffraction and normal and high pressure (up to 300 MPa) differential scanning calorimetry. 2 Br adamantane displays a low temperature orthorhombic phase (space group P2 1 2 1 2 1 , Z = 4) and a high temperature plastic phase (Fm3m, Z = 4) from 277.9 ± 1.0 K to the melting point at 413.4 ± 1.0 K. 2 Cl adamantane presents a richer polymorphic behavior through the temperature range studied. At low temperature it displays a triclinic phase (P1, Z = 2), which transforms to a monoclinic phase (C2/c, Z = 8) at 224.4 ± 1.0 K, both phases being ordered. Two high temperature orientationally disordered are found for this compound, one hexagonal (P6 3 /mcm, Z =6)at ca. 241 K and the highest one, cubic (Fm3m, Z = 4), being stable from 244 ± 1.0 K up to the melting point at 467.5 ± 1.0 K. No additional phase appears due to the increase in pressure within the studied range. The intermolecular interactions are found to be weak, especially for the 2 Br adamantane compound for which the Br•••Br as well as C−Br•••H distances are larger than the addition of the van der Waals radii, thus confirming the availability of this compound for building up diamondoid blocks.
The phase diagram of the two component systems (CH 3) 3 CBr þ Cl 3 CBr has been experimentally de... more The phase diagram of the two component systems (CH 3) 3 CBr þ Cl 3 CBr has been experimentally determined by means of differ ential scanning calorimetry and X ray powder diffraction techniques from the low temperature ordered phases to the liquid state. Before melting, both components have the same orientationally disordered (OD) face centered cubic (FCC) and rhombohedral (R) phases, and the two phase equilibria [FCC þ L] and [R þ FCC] are accounted for by means of the existence of an isomorphic relationship between the OD phases of pure compounds. The thermodynamic assessment of such equilibria enables us to get the excess properties of the involved OD phases and to rationalize the existence of a maximum and a minimum in the [R þ FCC] equilibrium on the basis of the contribution of the entropic term in the excess Gibbs energy function. At low temperature, two complexes, (CH 3) 3 CBr:Cl 3 CBr (1:1) and (CH 3) 3 CBr:2Cl 3 CBr (1:2), appear. The structures of 1:1 and 1:2 complexes have been determined to be monoclinic (P2 1 /n, c, Z = 4) and hexagonal (P6 3 , Z = 6). Within both "ordered" structures, the Cl 3 CBr entities of the asymmetric unit were found to be disordered so that sites have fractional occupancies of 0.75 and 0.25 for Cl and Br atoms, in the same way that it occurs for the low temperature monoclinic (C2/c, Z = 32) phase of Cl 3 CBr. Finally, the existence of complexes is connected with the special intermolecular interactions appearing between a methyl group and a halogen, as previously inferred by Calvet et al. [T. Calvet et al.
The experimental phase diagram of the CBrCl 3 + CBr 4 system has been determined by means of X-ra... more The experimental phase diagram of the CBrCl 3 + CBr 4 system has been determined by means of X-ray powder diffraction and thermal analysis techniques from 200 K to the liquid state. Before melting, the two components have the same orientationally disordered (OD) face-centered cubic phase, and solid-liquid equilibrium is explained by simple isomorphism. The application of multiple crossed isopolymorphism formalism to the low-temperature solid-solid equilibria has enabled the inference of an OD rhombohedral metastable (at normal pressure) phase for CBr 4. Experimental determination of the pressure-volume-temperature and construction of the pressure-temperature phase diagrams for CBr 4 reveal the existence of a high-pressure phase, the rhombohedral symmetry of which is inferred by means of the thermodynamic assessment of the experimental phase diagram and demonstrated by means of high-pressure neutron diffraction measurements. The procedure used in this work confirms the connection between the appearance of metastable phases at normal pressure and their existence at high-pressure.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Distributed under a Creative Commons Attribution-NonCommercial-ShareAlike| 4.0 International License
Plastic crystals are currently attracting interest because their solid-state caloric functionalit... more Plastic crystals are currently attracting interest because their solid-state caloric functionality could be used to tackle climate change in two critical areas: (i) more environmentally friendly cooling and heating driven by pressure and (ii) passive waste heat management. Here, we suggest that plastic crystals could also be used for active pressure-assisted (i.e., barocaloric) waste heat management. In contrast to the barocaloric cooling/heating cycle, for active barocaloric waste heat management, the hysteresis may not be a constraint and transition temperatures above ambient are usually desired. In contrast to passive waste heat management, the application of pressure can be an advantage to actively control the absorption and delivery of heat by the plastic crystal. Here, we have investigated the pressure-induced caloric response at the first-order phase transitions occurring above room temperature of three plastic crystals derived from adamantane: 1-adamantanol, 2-adamantanol, a...
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The crystal structures of dimorphic benzylthiouracil, a drug against hyperthyroidism, have been r... more The crystal structures of dimorphic benzylthiouracil, a drug against hyperthyroidism, have been redetermined and the atom coordinates of the two independent molecules of form I have been obtained for the first time. The dimorphism convincingly demonstrates the conformational versatility of the benzylthiouracil molecule. It has been established through calorimetric studies that the low-temperature form II transforms endothermically (II IH = 5.6(1.5) J g-1) into form I at 405.4(1.0) K. The high-temperature form I melts at 496.8(1.0) K (I LH = 152.6(4.0) J g-1). Crystallographic and thermal expansion studies show that form I is denser than form II, leading to the conclusion that the slope of the II-I equilibrium curve in the pressure-temperature phase diagram is negative. It follows that this dimorphism corresponds to a case of overall enantiotropic behaviour, which implies that both solid phases possess their own stable phase region irrespective of the pressure. Moreover, form II is clearly the stable polymorph under ambient conditions.
Spironolactone form I melts at about 70 degrees lower than form II, which is very unusual for two... more Spironolactone form I melts at about 70 degrees lower than form II, which is very unusual for two co-existing polymorphs. The phase relationships involving this unprecedented case of dimorphism have been investigated by constructing a topological pressure-temperature phase diagram. The transition from polymorph I to polymorph II is unambiguously exothermic while it is accompanied with an increase in the specific volume. This indicates that the dP/dT slope of the I-II equilibrium curve is negative. The convergence of the melting equilibrium lines at high pressure lead to a topological P-T diagram in which polymorph I possesses a stable phase region at high pressure. Thus, forms I and II are monotropically related at ordinary pressure and turn to an enantiotropic relationship at high pressure. Given that polymorph I is the densest form, it negates the rule of thumb that the densest form is also the most stable form at room temperature, similar to the case of paracetamol.
Since the early nineties countless publications have reported promising medicinal applications fo... more Since the early nineties countless publications have reported promising medicinal applications for [60]fullerene (C60) related to its unparalleled affinity towards free radicals. Yet, until now no officially approved C60-based drug has reached the market, notably because of the alleged dangers of C60. Nevertheless, since the publication of the effects of C60 on the lifespan of rodents, a myriad of companies started selling C60 worldwide for human consumption without any approved clinical trial. Nowadays, several independent teams have confirmed the safety of pure C60 while demonstrating that previously observed toxicity was due to impurities present in the used samples. However, a purity criterion for C60 samples is still lacking and there are no regulatory recommendations on this subject. In order to avoid a public health issue and for regulatory considerations, a quality-testing strategy is urgently needed. Here we have evaluated several analytical tools to verify the purity of co...
The formation of co-crystals is often unexpected; however, the Buckminsterfullerene, for which ma... more The formation of co-crystals is often unexpected; however, the Buckminsterfullerene, for which many solvates are known, is an excellent system to study this tendency. In the present paper, C60 and...
The pressure-temperature phase diagram of morniflumate (niflumic acid βmorpholinoethyl ester) has... more The pressure-temperature phase diagram of morniflumate (niflumic acid βmorpholinoethyl ester) has been obtained by high-pressure thermal analysis. In addition, calorimetric melting data (TI →L = 348.1 ±0.4 K and ∆HI →L = 89 ±2 J g-1) and the specific volumes of the solid and the liquid state have been obtained under normal pressure. Comparison of the measured high-pressure melting data with the equilibrium curve obtained through the Clapeyron equation indicates that the initial slopes are the same (dP/dT = 2.96 ±0.06 MPa K-1) at the melting point under normal pressure. The fact that the Clapeyron equation can be used to construct topological phase diagrams may be of interest for the food and pharmaceutical industries.
Pressure experiments provide a unique opportunity to unravel new insights into glass-forming liqu... more Pressure experiments provide a unique opportunity to unravel new insights into glass-forming liquids by exploring its effect on the dynamics of viscous liquids and on the evolution of the glass transition temperature. Here we compare the pressure dependence of the onset of devitrification, Ton, between two molecular glasses prepared from the same material but with extremely different ambient-pressure kinetic and thermodynamic stabilities. Our data clearly reveal that, while both glasses exhibit different dTon/dP values at low pressures, they evolve towards closer calorimetric devitrification temperature and pressure dependence as pressure increases. We tentatively interpret these results from the different densities of the starting materials at room temperature and pressure. Our data shows that at the probed pressures, the relaxation time of the glass into the supercooled liquid is determined by temperature and pressure similarly to the behaviour of liquids, but using stability-depe...
We demonstrate that solvates of fullerene C 60 form very predictable structures with finely tunab... more We demonstrate that solvates of fullerene C 60 form very predictable structures with finely tunable properties through the choice of the second component or solvent. Cubic co-crystals of C 60 •12CCl 2 Br 2 and C 60 •12CBr 2 (CH 3) 2 were grown at room temperature in saturated solutions of fcc C 60 and the respective solvents (with C 2v molecular symmetry) They are unstable in air and transform spontaneously into the hexagonal co-crystals C 60 •2CCl 2 Br 2 or C 60 •2CBr 2 (CH 3) 2. Whereas, the cubic co-crystals have positive excess volumes (+2% and +5%, respectively), the stable hexagonal crystals, for which structures are given for the first time, possess negative excess volumes (-5% and-4.3%, respectively). The unit-cell volumes for both cubic and hexagonal co-crystals depend exclusively on the van-der-Waals volumes of the constituents and this correlation has been confirmed using previously published data.
The polymorphism of 1 adamantane methanol C 11 H 18 O has been investigated by differential therm... more The polymorphism of 1 adamantane methanol C 11 H 18 O has been investigated by differential thermal analysis and single crystal and powder X ray diffraction. Below the melting temperature (389.5 ± 0.4 K), this compound exhibits an orthorhombic phase (phase I, Pnnm, Z = 12, Z′ = 1.5). The melting enthalpy was determined to be 20.5 ± 0.4 kJ mol −1 , i.e., with an entropy change of (6.34 ± 0.13)R, which is much higher than the quoted value from Timmermans for the melting orientationally disordered phases (2.5R), thus supporting the orientationally ordered character of phase I. This orthorhombic phase I exhibits a statistical disorder of the hydrogen atom related to the oxygen atom, due to the position of one independent molecule on the mirror. At ca. 272 K, phase I transforms continuously through an order−disorder transition to a low temperature monoclinic phase II (P2 1 /n, Z = 12, Z′ = 3). The monoclinic and orthorhombic phases are related by a group−subgroup relationship, which perfectly agrees with the continuous character of the II to I transition. Moreover, by a convenient choice of an order parameter related to the continuous tilt of the c axis, the critical exponent for this transition is found to be close to the theoretical prediction of the three dimensional Ising model (with a critical exponent of ca. 0.27).
The polymorphism of two 2 X adamantane derivatives, X = Cl, X = Br, has been studied by X ray pow... more The polymorphism of two 2 X adamantane derivatives, X = Cl, X = Br, has been studied by X ray powder diffraction and normal and high pressure (up to 300 MPa) differential scanning calorimetry. 2 Br adamantane displays a low temperature orthorhombic phase (space group P2 1 2 1 2 1 , Z = 4) and a high temperature plastic phase (Fm3m, Z = 4) from 277.9 ± 1.0 K to the melting point at 413.4 ± 1.0 K. 2 Cl adamantane presents a richer polymorphic behavior through the temperature range studied. At low temperature it displays a triclinic phase (P1, Z = 2), which transforms to a monoclinic phase (C2/c, Z = 8) at 224.4 ± 1.0 K, both phases being ordered. Two high temperature orientationally disordered are found for this compound, one hexagonal (P6 3 /mcm, Z =6)at ca. 241 K and the highest one, cubic (Fm3m, Z = 4), being stable from 244 ± 1.0 K up to the melting point at 467.5 ± 1.0 K. No additional phase appears due to the increase in pressure within the studied range. The intermolecular interactions are found to be weak, especially for the 2 Br adamantane compound for which the Br•••Br as well as C−Br•••H distances are larger than the addition of the van der Waals radii, thus confirming the availability of this compound for building up diamondoid blocks.
The phase diagram of the two component systems (CH 3) 3 CBr þ Cl 3 CBr has been experimentally de... more The phase diagram of the two component systems (CH 3) 3 CBr þ Cl 3 CBr has been experimentally determined by means of differ ential scanning calorimetry and X ray powder diffraction techniques from the low temperature ordered phases to the liquid state. Before melting, both components have the same orientationally disordered (OD) face centered cubic (FCC) and rhombohedral (R) phases, and the two phase equilibria [FCC þ L] and [R þ FCC] are accounted for by means of the existence of an isomorphic relationship between the OD phases of pure compounds. The thermodynamic assessment of such equilibria enables us to get the excess properties of the involved OD phases and to rationalize the existence of a maximum and a minimum in the [R þ FCC] equilibrium on the basis of the contribution of the entropic term in the excess Gibbs energy function. At low temperature, two complexes, (CH 3) 3 CBr:Cl 3 CBr (1:1) and (CH 3) 3 CBr:2Cl 3 CBr (1:2), appear. The structures of 1:1 and 1:2 complexes have been determined to be monoclinic (P2 1 /n, c, Z = 4) and hexagonal (P6 3 , Z = 6). Within both "ordered" structures, the Cl 3 CBr entities of the asymmetric unit were found to be disordered so that sites have fractional occupancies of 0.75 and 0.25 for Cl and Br atoms, in the same way that it occurs for the low temperature monoclinic (C2/c, Z = 32) phase of Cl 3 CBr. Finally, the existence of complexes is connected with the special intermolecular interactions appearing between a methyl group and a halogen, as previously inferred by Calvet et al. [T. Calvet et al.
The experimental phase diagram of the CBrCl 3 + CBr 4 system has been determined by means of X-ra... more The experimental phase diagram of the CBrCl 3 + CBr 4 system has been determined by means of X-ray powder diffraction and thermal analysis techniques from 200 K to the liquid state. Before melting, the two components have the same orientationally disordered (OD) face-centered cubic phase, and solid-liquid equilibrium is explained by simple isomorphism. The application of multiple crossed isopolymorphism formalism to the low-temperature solid-solid equilibria has enabled the inference of an OD rhombohedral metastable (at normal pressure) phase for CBr 4. Experimental determination of the pressure-volume-temperature and construction of the pressure-temperature phase diagrams for CBr 4 reveal the existence of a high-pressure phase, the rhombohedral symmetry of which is inferred by means of the thermodynamic assessment of the experimental phase diagram and demonstrated by means of high-pressure neutron diffraction measurements. The procedure used in this work confirms the connection between the appearance of metastable phases at normal pressure and their existence at high-pressure.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Distributed under a Creative Commons Attribution-NonCommercial-ShareAlike| 4.0 International License
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