Mixing phase behavior of trilaurin and monounsaturated triacylglycerols based on palmitic and oleic fatty acids

Differential scanning calorimetry and X-ray diffraction were used to examine the mixing phase behavior of LLL (trilaurinor 1,2,3-trilauroyl-glycerol) and POP (1,3-dipalmitoyl-2-oleoyl-glycerol), PPO (1,2-dipalmitoyl-3-oleoyl-rac-glycerol), orthe 50POP/50PPO blend able to form a molecular compound. This research aims to provide an insight into the molecularinteractions ruling the physical behavior of fat blends of lauric (i.e., coconut oil) and non-lauric lipids (cocoa butter, palmoil, etc.). The results showed eutectic behavior and no mutual solubility of triacylglycerols in stable LLL/POP and LLL/PPO mixtures. Applying high-rate cooling treatments had a positive effect on miscibility, but the high incompatibility ofthe components due to differences in length and degree of unsaturation of fatty acids was still evident in metastable polymorphs.In ternary LLL/(50POP/50PPO) mixtures, on the other hand, molecular compound β-2L crystals formed by POPand PPO showed to favor the solubility of LLL as compared to the binary systems. Accordingly, promoting the presence oftriacylglycerols forming molecular compound in specific fat blends may help reducing eutectic or incompatible interactionsamong triacylglycerol molecules in the solid state. These lead to phase separation and are a major cause of the restrictedapplicability of lauric oils in the confectionery and chocolate industries

An insight into the solid-state miscibility of triacylglycerol crystals

The crystallization properties of triacylglycerols (TAGs) strongly determine the functional properties of natural lipids. The polymorphic and mixing phase behavior of TAG molecules have long been, and still are, a hot topic of research with special relevance for the cosmetic, pharmaceutical, and food industry. To avoid the difficulties arising from the study of whole real fats, studies at the molecular level on mixtures of a limited number of TAGs has become an indispensable tool to identify the underlying causes of the physical properties in lipid systems. In particular, phase diagrams of binary mixtures of TAGs exhibiting a different degree of heterogeneity (monoacid or mixed fatty acids; molecular symmetry; the presence of cis or trans double bonds) have resulted in a significant breakthrough in our knowledge about structure-interaction-function relationships. The present work aims to provide an overview of the main reports regarding binary and ternary TAG systems, from the early studies to the most recent developments

Deliciosos polimorfos

El polimorfismo, tan habitual y conocido por geólogos en minerales como la calcita-aragonito, el diamante-grafito y el grupo de la sílice, se extiende a muchos otros campos. Desde la cristalografía y la mineralogía, dando un gran salto en los materiales pero no en los fenómenos, el polimorfismo también tiene lugar en productos alimentarios. En particular, los triacilgliceroles, los cuales constituyen los componentes mayoritarios de grasas y aceites, tales como el chocolate, el aceite de oliva o el jamón ibérico, muestran un complejo comportamiento polimórfico (Larsson et al., 2006). La caracterización de sus formas cristalinas resulta crucial en aplicaciones de la industria alimentaria para satisfacer las necesidades del consumidor, optimizar procesos industriales o desarrollar nuevos productos. Sin embargo, el polimorfismo también podría ser utilizado como herramienta discriminatoria entre diferentes categorías de un mismo producto alimentario, así como para la detección de acciones fraudulentas (Bayés-García et al., 2016)

Chocolate: a useful model for teaching basic terms on Crystallography and Thermodynamics

By using a simple, attractive and sweet model, as chocolate is, many scientific concepts related to different disciplines, which are often understood as complex and dull by most students, may be introduced. In particular, the student may be able to develop crystallographic concepts and methodologies combined with some thermodynamic aspects, which have been historically known as complex and arduous disciplines. Hence, the student may enjoyably assimilate complicated concepts such as polymorphism, mixing behavior, crystal morphology, crystal size or thermodynamic stability, and may also be capable of understanding their application to daily life. These concepts may be applicable to any kind of material and can be more deeply developed depending on the level required

Amide-Driven Secondary Building Unit Structural Transformations between Zn(II) Coordination Polymers

The behavior of coordination polymers (CPs) against external stimuli has witnessed remarkable attention, especially when the resulting CPs present reversible molecular arrays. Accordingly, CPs with these characteristics can lead to differences in their properties owing to these structural differences, being promising for their use as potential molecular switches with diverse applications. Herein, we have synthesized four Zn(II) CPs bearing α-acetamidocinnamic acid (HACA) and 4,4′-bipyridine (4,4′-bipy). The reaction between Zn(OAc)2·2H2O, HACA, and 4,4′-bipy yields {[Zn(ACA)2(4,4′-bipy)]·EtOH}n (1), which was used for the formation of three CPs through dissolution–recrystallization structural transformations (DRSTs): {[Zn(ACA)2(4,4′-bipy)]·2MeOH}n (2), {[Zn2(μ-ACA)2(ACA)2(4,4′-bipy)]·2H2O}n (3), and {[Zn3(μ-ACA)6(4,4′-bipy)]·0.75CHCl3}n (4). The study of the four crystal structures revealed that their secondary building units (SBUs) comprise monomeric, dimeric, and trimeric arrangements linked by 4,4′-bipy ligands. The fundamental role of the utilized solvent and/or temperature, as well as their effect on the orientation of the amide moieties driving the formation of the different SBUs is discussed. Furthermore, the reversibility and interconversion between the four CPs have been assayed. Finally, their solid-state photoluminescence has evinced that the effect of the amide moieties not only predetermine a different SBU but also lead to a different emission in 4 compared with 1–3

Polymorphism, crystal growth, crystal morphology and solid-state miscibility of alkali nitrates

In this review, we recollect and discuss the most relevant advancement in crystallographic aspects of alkali nitrates compounds published since 1975, the year of publication of the last review by Rao et al. about some topics discussed here. This review is focused in five nitrate compounds of the first periodic table column: LiNO3, NaNO3, KNO3, RbNO3 and CsNO3. For each one, we have compiled the information about crystal structure, polymorphism and phase transition, crystal growth and crystal morphology, and the phase diagram and solid-state miscibility results. Considerable numbers of papers have been published in the last 40 years, in particular in relation to binary phase diagrams and solid-state miscibility of alkali nitrates. A variety of phase diagram descriptions appears in the 10 possible binary combinations for the five compounds. To finish, we discuss and propose a geometric model in order to explain the different binary phase diagrams observed between these compounds

Cocrystals Based on 4,4'-bipyridine: Influence of Crystal Packing on Melting Point

The reactions of piperonylic acid (HPip) and cinnamic acid (HCinn) with 4,4'-bipyridine (4,4'-bipy) have been assayed using the same synthetic methodology, yielding two binary cocrystals with different acid:4,4'-bipy molar ratios, (HPip)(4,4'-bipy) (1) and (HCinn)2(4,4'-bipy) (2). The melting point (m.p.) of these cocrystals have been measured and a remarkable difference (DT 78 C) between them was observed. Moreover, the two cocrystals have been characterized by powder X-ray diffraction (PXRD), elemental analysis (EA), FTIR-ATR, 1H NMR spectroscopies, and single-crystal X-ray diffraction. The study of their structural packings via Hirshfeld surface analysis and energy frameworks revealed the important contribution of the pi..pi and C-H...pi interactions to the formation of different structural packing motifs, this being the main reason for the difference of m.p. between them. Moreover, it has been observed that 1 and 2 presented the same packing motifs as the crystal structure of their corresponding carboxylic acids, but 1 and 2 showed lower m.p. than those of the carboxylic acids, which could be related to the lower strength of the acid-pyridine heterosynthons respect to the acid-acid homosynthons in the crystal structures

Virtual assessment achieved two binary cocrystals based on a liquid and a solid pyridine derivative with modulated thermal stabilities

The rational design of cocrystals triggered by the control of recurrent H-bonded patterns referred to as supramolecular synthons enabled the correlation between their structure and properties, which has been a topic of interest owing to the possibility to modulate them depending on the selected components. Accordingly, melting point has been one of the most studied properties, providing materials with enhanced thermal stability for specific applications. Within this frame, in this work we have selected a liquid and a solid pyridine derivative (dPy), namely 4-acetylpyridine (4-Acpy) and 2-hydroxypyridine (2-OHpy) to combine with carboxylic acids to obtain a pair of cocrystals. An initial virtual screening of some carboxylic acids based on the positive and negative critical points of the molecular electrostatic potential (MEP) surfaces was performed to evaluate the feasibility of cocrystal formation. This enabled us to select 1,3-benzodioxole-5-carboxylic acid (piperonylic acid, HPip) to combine with 4-Acpy and a-acetamidocinnamic acid (HACA) with 2-OHpy. Then, we have obtained the corresponding cocrystal experimentally by means of liquid-assisted grinding (LAG), and their crystal structures were elucidated, revealing the formation of (HPip)(4-Acpy) (1) and (HACA)(Pdon) (2) (Pdon = 2-pyridone), observing the tautomerization of 2-OHpy to Pdon. Both cocrystals were characterized by analytical and spectroscopic techniques. In addition, a Cambridge Structural Database (CSD) survey of 4-Acpy and Pdon in cocrystal systems was performed and the observed preferences regarding their preferable synthons and dimensionalities were shown. Finally, their melting points have been determined, and the resulting values have been correlated with the crystal packing of the compounds, supported by Hirshfeld surface analysis and energy frameworks

Influence of a series of pyridine ligands on the structure and photophysical properties of Cd(II) complexes

Among the group 12 metal ions, the Cd(II) ion presents an ionic radius comparable to that of Hg(II), while its electronegativity resembles that of Zn(II). Thus, these characteristics make it a suitable candidate for the synthesis of fluorescent coordination complexes given that it tends to maximize the chelation enhanced effect (CHEF), while its electronegativity helps to prevent the quenching of fluorescence generated by the heavy atom effect. Accordingly, herein, we performed a systematic study using Cd(II) compounds bearing α-acetamidocinnamic acid (HACA) and different N-, N^N- and N^N^N-pyridine ligands (dPy), namely pyridine (py) (1), 3-phenylpyridine (3-phpy) (2), 2,2′-bipyridine (2,2′-bipy) (3), 1,10-phenantroline (1,10-phen) (4) and 2,2′:6′,2′′-terpyridine (terpy) (5). The elucidation of their crystal structures revealed the formation of one coordination polymer (1), one dimer (3) and three monomers (2, 4, and 5). All the synthesized compounds were characterized via analytical and spectroscopic techniques, and their molecular and supramolecular structures were discussed. The photophysical properties of 1–5 in MeOH were studied and their quantum yields (Φ) were calculated, revealing an enhancement in the Φ value of the complexes generated by the CHEF of dPy

Construction of Zn(II) Linear Trinuclear Secondary Building Units from A Coordination Polymer Based on α-Acetamidocinnamic Acid and 4-Phenylpyridine

The synthesis and characterization of one coordination polymer and two trinuclear complexes are presented. The coordination polymer [Zn2( -O,O'-ACA)2(ACA)2(4-Phpy)2]n (1) has been obtained by the reaction between Zn(OAc)2 2H2O, -acetamidocinnamic acid (HACA), and 4-phenylpyridine (4-Phpy) using EtOH as solvent. Its recrystallization in CH3CN or EtOH yields two trinuclear complexes, both having pinwheel arrays with formulas [Zn3( -ACA)6(4-Phpy)2] 4CH3CN (2 4CH3CN) and [Zn3( -ACA)6(EtOH)2] 4EtOH (3 4EtOH), respectively. These trinuclear species, unavoidably lose their solvent co-crystallized molecules at RT yielding the complexes [Zn3( -ACA)6(4-Phpy)2] (2) and [Zn3( -ACA)6(EtOH)2] (3). In addition, compound 2 has also been obtained reacting Zn(OAc)2 2H2O, HACA, and 4-Phpy in a 1:2:2 ratio using CH3CN as solvent. Compounds 1-3 have been characterized by analytical and spectroscopic techniques. Furthermore, single crystals suitable for X-ray di raction method for compounds 1, 2 4CH3CN, and 3 4EtOH were obtained and their supramolecular interactions have been studied and discussed, showing 2D supramolecular planes for the trinuclear complexes and a 3D supramolecular network for the coordination polymer. Finally, the supramolecular interactions of 2 4CH3CN and 3 4EtOH have been compared using Hirshfeld surface analysis and electrostatic potential calculations