Synthesis of a Heterometallic [Zn2Ca] Pinwheel Array Stabilized by Amide-Amide Synthons

The rational design of heterometallic compounds bearing s-block metal ions have been a difficult task for chemists owing to their lack of preferential geometries. However, some strategies, such as the design of coordinating pockets with different sizes and/or donor atoms, have offered great results. In this work, this strategy has been tested using Ca(II) as an s-block metal ion and a compound previously obtained by our group with the formula [Zn(μ-ACA)(4-phpy)], which contains tetrahedral N,O- and octahedral O-coordinating pockets as a model structure. From this work, the corresponding heterometallic compound with the formula [ZnCa(μ-ACA)(4-phpy)]·EtOH (1) has been successfully synthesized, and fully characterized, and its crystal structure has been elucidated. Furthermore, we have compiled all the crystal structures containing [ZnM] pinwheel secondary building units (SBUs), where M stands for an s-block metal ion, and the observed tendencies, as well as the promising applications as template SBUs for the preparation of 1D-3D coordination polymers, have been discussed. Finally, solid-state UV-Vis and photoluminescence have been recorded and compared with the homometallic [Zn(μ-ACA)(4-phpy)] compound

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

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(µ-O,O'-ACA)2(ACA)2(4-Phpy)2]n (1) has been obtained by the reaction between Zn(OAc)2·2H2O, α-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(µ-ACA)6(4-Phpy)2]·4CH3CN (2·4CH3CN) and [Zn3(µ-ACA)6(EtOH)2]·4EtOH (3·4EtOH), respectively. These trinuclear species, unavoidably lose their solvent co-crystallized molecules at RT yielding the complexes [Zn3(µ-ACA)6(4-Phpy)2] (2) and [Zn3(µ-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 diffraction 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

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

Altres ajuts: acords transformatius de la UABThe 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 andα-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 framework

Structural influence of the length and functionality of N,N-donor spacers in Cd(II) ladder-type coordination polymers

Altres ajuts: acord transformatiu CRUE-CSICAltres ajuts: Fundació La Caixa (projectes CB615921 i CB616406)The understanding of the effect generated by small differences of the organic ligands on the molecular and supramolecular arrangement of coordination polymers (CPs) is a key factor to control their properties. Therefore, the study of structurally related ligands differing in some factors inter alia functional group orientation, length, or functionality is a crucial task for crystal engineers. In this contribution, the reactions between Cd(OAc)2·2H2O, α-acetamidocinnamic acid (HACA) and different N,N-donor spacers with increasing length (pyrazine, pyz; 4,4'-bipyridine, 4,4'-bipy; 1,2-bis(4-pyridyl)ethylene, 1,2-bpe), as well as additional functionalities (4,4'-azopyridine, 4,4'-azpy) have been successfully performed. Their crystal structures have been elucidated revealing a family of ladder-type 1D CPs showing molecular arrays with single pillars for {[Cd2(μ-ACA)2(ACA)2(pyz)(H2O)2]·2EtOH}n (1), and double pillars for [Cd2(μ-ACA)2(ACA)2(4,4'-bipy)2]n (2), [Cd2(μ-ACA)2(ACA)2(1,2-bpe)2]n (3) and {[Cd2(μ-ACA)2(ACA)2(4,4'-azpy)2]·4,4'-azpy·9H2O}n (4). Remarkably, the effect of the addition of the azo group in 4 compared with 2 and 3 has led to a CP with the same molecular arrangement but different crystal packing, allowing the introduction of one non-coordinated 4,4'-azpy and nine water molecules. Finally, their solid-state UV-Vis and photoluminescence have been measured observing their blue-emitting properties

Amide-driven secondary building unit structural transformations between Zn(II) coordination polymers

Altres ajuts: J.P. acknowledges financial support from the CB615921 project, the CB616406 project from "Fundació La Caixa". D.E. acknowledges the PIF predoctoral fellowship from the Universitat Autònoma de Barcelona.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

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

Synthesis and characterization of Pd(II), Pt(II), Cu(I), Ag(I) and Cu(II) complexes with N,O-hybrid pyrazole ligand

The coordination behavior of N,O-hybrid pyrazole-based metal-organic frameworks are described. 2-(3,5-Pyridyl-1H-pyrazol-1-yl)ethanol (L) and its Pd(II), Pt(II), Cu(I), Ag(I) and Cu(II) complexes with different anions have been synthesized and characterized by elemental analysis, conductivity, mass spectrometry, IR, ¹H, ¹³C{¹H} and ¹⁹⁵Pt{1H} NMR spectroscopies. Complex 1 was also characterized by single crystal X-ray diffraction. For complex 7 has also been possible to perform the UV-Vis and magnetic susceptibility measurements. All complexes are monomers, except the complexes obtained by reaction of the ligand (L) with M(MeCO₂)₂ (M = Pd(II), Pt(II)) or CuBr₂, which are dimers

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