Three forms of squaric acid with pyrazine and pyridine derivatives: an experimental and theoretical study

Korkmaz, Ufuk; Uçar, İbrahim; Bulut, Ahmet; Büyükgüngör, Orhan

doi:10.1007/s11224-011-9819-7

Cited by 23 publications

(9 citation statements)

References 34 publications

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“…The pyridinium rings, [4‐Me(Py)H] + , are planar in the range of the experimental error and have average intramolecular C–C and C–N bond lengths with 1.383 and 1.335 Å, respectively. These values are compatible with analogues bond lengths in methylpyridinium rings . From weighted least‐squares planes calculated through all non‐hydrogen atoms of the pyridine rings the largest deviation of –0.084 Å exists for the methyl group carbon atom in the methylpyridinium cation consisting of C(42)/C(43)/C(44)/C(45)/C(46)/C(47)/N(8) atoms.…”

Section: Resultssupporting

confidence: 70%

Structure, Physicochemical and Biological Properties of an Aqua (2,2′,2′′‐Nitrilotriacetato)‐oxidovanadium(IV) Salt with 4‐Methylpyridinium Cation

Tesmar

Wyrzykowski

Kazimierczuk

et al. 2017

Zeitschrift anorg allge chemie

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The crystal structure of a nitrilotriacetate (nta) oxidovanadium(IV) salt with 4-methylpyridinium cation, [4-Me(Py)H] + , of [4-Me(Py)H][VO(nta)(H 2 O)] stoichiometry was determined. The complex comprises a discrete mononuclear [VO(nta)(H 2]coordination entity that can be rarely found among other known compounds containing nitrilotriacetate oxidovanadium(IV) moieties. The complex was characterized by spectroscopic (IR and EPR) methods, magnetic measurements, and thermogravimetry (TG-FTIR). The stability of the title compound in aqueous solutions was investigated by using the potentiometric titration method. Furthermore, spectrophotometric (UV/Vis) studies have revealed that the compound is capable to scavenge the

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Section: Resultssupporting

confidence: 70%

Structure, Physicochemical and Biological Properties of an Aqua (2,2′,2′′‐Nitrilotriacetato)‐oxidovanadium(IV) Salt with 4‐Methylpyridinium Cation

Tesmar

Wyrzykowski

Kazimierczuk

et al. 2017

Zeitschrift anorg allge chemie

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“…This is counterintuitive as the most hydrolyzed species ( USq2 and USq3 ) are expected to have the largest red shift of the uranyl symmetric stretching mode. The position of the symmetric stretching band does correlate with the smallest centroid-to-centroid distance, suggesting that the π stacking could influence the Raman signal in the solid state. − …”

Section: Resultsmentioning

confidence: 99%

Spectral Analysis of the Uranyl Squarate and Croconate System: Evaluating Differences between the Solution and Solid-State Phases

Basile

Unruh

Streicher

et al. 2017

Crystal Growth & Design

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The design of hybrid materials relies on an understanding of the structural building units present in the reaction, but identifying these building units in solution can be hampered by difficulties in the interpretation of the characteristic spectroscopic signals. The importance of speciation and intermolecular interactions in identifying building units was explored in the uranyl squarate and croconate system with the isolation and characterization of six compounds: (USq1) [C4H12N2][(UO2)(C4O4)2(H2O)]·(H2O), (USq2) [C5H6N][(UO2)(C4O4)(μ2-OH)]·2H2O, (USq3) [C2H10N2]2[(UO2)6(C4O4)3(μ3-O)2(μ2-OH)6], (UCr1) [C4H12N2]2[(UO2)(C5O5)3(H2O)]·3H2O, (UCr2) [C5H6N]4[(UO2)4(C5O5)4(μ2-OH)4(H2O)4], and (UCr3) [C2H10N2]5[(UO2)6(C5O5)6(μ3-O)2(μ2-OH)6(H2O)4]. These compounds are built upon the traditional monomeric, dimeric, and trimeric uranyl oligomers that occur upon hydrolysis of the metal center. A combined solid and solution spectroscopic approach was used to understand the impact of uranyl oligomerization, ligand coordination, and intermolecular interactions. The v 1(UO2 2+) Raman shift and the UV–visible spectrum for each solid uranyl-squarate and uranyl-croconate compound reveals important information regarding the impact of π–π interactions on the chemical properties of uranyl hybrid materials.

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“…Such description of the PE → AFE phase transition also justifies the change in color from yellow in the PE state (Figures S1 and S8) to colorless in the AFE state. On the basis of the reported calculations of the electronic structure of squaric acid and pyrazine derivatives, 21 we expect the highest occupied molecular orbitals, HOMO and HOMO−1, to be represented by π-orbitals of 2,3-Me 2 pyzH + and the lowest unoccupied molecular orbitals, LUMO and LUMO+1, to correspond to π*-orbitals of Hsq − . Thus, the lowest-energy optical absorption bands correspond to charge transfer from the cation-based HOMO/HOMO−1 to the anion-based LUMO/LUMO+1.…”

Section: Journal Of the American Chemical Societymentioning

confidence: 99%

Antiferroelectric Phase Transition in a Proton-Transfer Salt of Squaric Acid and 2,3-Dimethylpyrazine

et al. 2019

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A proton-transfer reaction between squaric acid (H 2 sq) and 2,3-dimethylpyrazine (2,3-Me 2 pyz) results in crystallization of a new organic antiferroelectric (AFE), (2,3-Me 2 pyzH + )(Hsq − )•H 2 O (1), which possesses a layered structure. The structure of each layer can be described as partitioned into strips lined with methyl groups of the Me 2 pyzH + cations and strips featuring extensive hydrogen bonding between the Hsq − anions and water molecules. Variable-temperature dielectric measurements and crystal structures determined through a combination of single-crystal X-ray and neutron diffraction reveal an AFE ordering at 104 K. The phase transition is driven by ordering of protons within the hydrogen-bonded strips. Considering the extent of proton transfer, the paraelectric (PE) state can be formulated as (2,3-Me 2 pyzH + ) 2 (Hsq 2 3− )(H 5 O 2 + ), whereas the AFE phase can be described as (2,3-Me 2 pyzH + )(Hsq − )(H 2 O). The structural transition caused by the localization of protons results in the change in color from yellow in the PE state to colorless in the AFE state. The occurrence and mechanism of the AFE phase transition have been also confirmed by heat capacity measurements and variable-temperature infrared and Raman spectroscopy. This work demonstrates a potentially promising approach to the design of new electrically ordered materials by engineering molecule-based crystal structures in which hydrogen-bonding interactions are intentionally partitioned into quasi-onedimensional regions.

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Three forms of squaric acid with pyrazine and pyridine derivatives: an experimental and theoretical study

Abstract: Three new squarate salts were synthesized and combined with experimental and theoretical study on molecular, vibrational, and electronical properties. Squaric acid was crystallized as HSQ -[SQ: squarate]

Cited by 23 publications

References 34 publications

Structure, Physicochemical and Biological Properties of an Aqua (2,2′,2′′‐Nitrilotriacetato)‐oxidovanadium(IV) Salt with 4‐Methylpyridinium Cation

Structure, Physicochemical and Biological Properties of an Aqua (2,2′,2′′‐Nitrilotriacetato)‐oxidovanadium(IV) Salt with 4‐Methylpyridinium Cation

Spectral Analysis of the Uranyl Squarate and Croconate System: Evaluating Differences between the Solution and Solid-State Phases

Antiferroelectric Phase Transition in a Proton-Transfer Salt of Squaric Acid and 2,3-Dimethylpyrazine

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