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| 2. |
- Heffernan, C., et al.
(författare)
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Effects of structurally - related impurities on the crystal growth of curcumin spherulites
- 2022
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Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 24:28, s. 5156-5169
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Tidskriftsartikel (refereegranskat)abstract
- The crystal growth of curcumin in pure propan-2-ol and in this solvent containing two structurally related impurities, demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC), has been investigated by seeded isothermal desupersaturation experiments at 283, 293 and 308 K. In situ attenuated total reflectance UV-visible spectroscopy and focused beam reflectance measurement were used as process analytical technologies to monitor the solution concentration over time and to track the particle counts. Both impurities are found to slow down the growth of curcumin spherulites. The product particles collected after growth in the presence of the impurities present a rougher and more porous surface appearance in comparison to curcumin crystalline material grown in pure solutions. A detailed analysis of the powder X-ray diffraction patterns along with compositional analysis by high performance liquid chromatography of grown crystals reveals that impurities are not incorporated into the solid phase except at the highest impurity concentrations explored. By molecular modelling it is shown that the influence of impurities on the diffractograms of the material grown at high impurity concentrations is consistent with the formation of a solid solution. By fitting the Birth and Spread theory to the experimental growth data it is found that the interfacial energy for growth in the presence of the impurities is higher than that for growth of curcumin in the absence of impurities. Two scenarios are envisaged explaining the results. The first is that 3-D nucleation occurs on the impurity encumbered CUR crystallite generating new crystalline material on which crystal growth may continue. The second scenario envisages that a molecular cluster from the solution attaches to the impurity-encumbered surface and condenses into a crystalline surface nucleus without perfect lattice matching.
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| 3. |
- Heffernan, C., et al.
(författare)
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Influence of Structurally Related Impurities on the Crystal Nucleation of Curcumin
- 2018
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 18:8, s. 4715-4723
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the influence of the structurally related impurities, demethoxycurcumin (DMC) and bisde-methoxycurcumin (BDMC) on the primary nucleation of curcumin (CUR) has been investigated in propan-2-ol. The induction time for nucleation was measured at different CUR driving forces and impurity concentrations 0.10 mmol.dm(-3), 0.30 mmol.dm(-3), and 0.60 mmol.dm(-3) and the results are analyzed by the classical nucleation theory (CNT). The nucleation rate for the impure systems was noticeably lower than the nucleation rate of the pure system, and the times of growth to visibility were much longer for the impure systems. The pre-exponential factors are clearly lower for the impure system compared to the pure CUR system, while the increase in the solid-liquid interfacial energy is small. Density functional theory and metadynamic molecular modeling reveal that the 1:1 bonding between CUR and an impurity molecule is stronger than to another CUR molecule, thus suggesting that the developing CUR nucleus has to overcome a certain energy barrier in order to remove the impurity molecules from their surface, which may explain why nucleation of CUR is more difficult in the presence of the structurally related impurities, DMC and BDMC.
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| 4. |
- Lynch, A., et al.
(författare)
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Face indexing and shape analysis of salicylamide crystals grown in different solvents
- 2019
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Ingår i: CrystEngComm. - : Royal Society of Chemistry. - 1466-8033. ; 21:16, s. 2648-2659
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Tidskriftsartikel (refereegranskat)abstract
- The effect of solvent on salicylamide's crystal habit was investigated. Crystals grown experimentally in acetone, acetonitrile and methanol matched the attachment energy predicted rectangle plate vacuum habit. However, in ethyl acetate irregular hexagonal plate crystals form. This change in habit was found to be caused by the stunted growth of specific crystal faces during the crystallisation process. Single crystal and powder X-ray diffraction was carried out to rule out the possibility of a new polymorph. Given no new polymorphs were discovered, the changing habit makes face indexing of experimentally grown crystals difficult. A combination of experimental and modelling prediction tools was employed for the face indexing process. The interfacial angle between faces combined with preferred orientation P-XRD was found to be the most accurate and reliable method leading to successful identification of each salicylamide crystal face. The surface chemistry of each face was examined on a molecular level with insights into the possible growth attachment sites being made. It is deduced that ethyl acetate is adsorbed more strongly on the faces, the increased size of which, can explain the shape change.
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| 5. |
- Rama Krishna, G., et al.
(författare)
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Prediction of Solid State Properties of Cocrystals Using Artificial Neural Network Modeling
- 2018
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 18:1, s. 133-144
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Tidskriftsartikel (refereegranskat)abstract
- Using Artificial Neural Networks (ANNs), four distinct models have been developed for the prediction of solid-state properties of cocrystals: melting point, lattice energy, and crystal density. The models use three input parameters for the pure model compound (MC) and three for the pure coformer. In addition, as an input parameter the model uses the pKa difference between the MC and the coformer, and a 1:1 MC−conformer binding energy as calculated by a force field method. Notably, the models require no data for the actual cocrystals. In total, 61 CCs (two-component molecular cocrystals) were used to construct the models, and melting temperatures and crystal densities were extracted from the literature for four MCs: caffeine, theophylline, nicotinamide, and isonicotinamide. The data set includes 14 caffeine cocrystals, 9 theophylline cocrystals, 9 nicotinamide cocrystals, and 29 isonicotinamide cocrystals. Model-I is trained using known cocrystal melting temperatures, lattice energies, and crystal densities, to predict all three solid-state properties simultaneously. The average relative deviation for the training set is 2.49%, 6.21%, and 1.88% for the melting temperature, lattice energy, and crystal density, respectively, and correspondingly 6.26%, 4.58%, and 0.99% for the valdation set. Model-II, model-III, and model-IV were built using the same input neurons as in model-I, for separate prediction of each respective output solid−state property. For these models the average relative deviation for the training sets becomes 1.93% for the melting temperature model-II, 1.29% for the lattice energy model-III, and 1.03% for the crystal density model-IV, and correspondingly 2.23%, 2.40%, and 1.77% for the respective validation sets.
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