Complexos de zinc i cadmi amb propietats òptiques

L'enginyeria de cristalls té un paper essencial per entendre com s'acoblen lligands orgànics i ions metàl·lics a l'hora de sintetitzar materials amb propietats especials. Investigadors del Departament de Química han sintetitzat quatre compostos de zinc i cadmi amb l'àcid 2-furoic, incloent-hi un polímer de coordinació, i n'han estudiat les propietats òptiques. L'estudi amplia la comprensió dels polímers de coordinació i el paper dels dissolvents a la seva formació.La ingeniería de cristales desempeña un papel esencial para entender cómo se ensamblan ligandos orgánicos e iones metálicos a la hora de sintetizar materiales con propiedades especiales. Investigadores del Departamento de Química han sintetizado cuatro compuestos de zinc y cadmio con el ácido 2-furoico, incluyendo un polímero de coordinación, y han estudiado sus propiedades ópticas. El estudio amplía la comprensión de los polímeros de coordinación y el papel de los disolventes en su formación.Crystal engineering plays an essential role in understanding how organic ligands and metal ions are assembled when synthesizing materials with special properties. Researchers from the Department of Chemistry have synthesized four zinc and cadmium compounds with 2-furoic acid, including a coordination polymer, and have studied their optical properties. The study expands the understanding of coordination polymers and the role of solvents in their formation

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

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

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

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

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

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

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