An asymmetric mononuclear cobalt(II) compound derived from 3-bromo-pyridine-2,6-dicarboxylic acid involving in-situ hydrothermal decarboxylation: structure, magnetic property and Hirshfeld surface analysis

A new cobalt(II) compound with the formula [Co(5-Br-pyc)(2,2′-bipy)(H2O)(Cl)]·2H2O (1·H2O) (5-Br-Hpyc = 5-bromo-pyridine-2-carboxylic acid, 2,2′-bipy = 2,2′-bipyridine) has been hydrothermally synthesized and well characterized. The X-ray single-crystal diffraction analysis showed that 1⋅2H2O has crystallizes in the monoclinic system, space group P21/c (no. 14). The Co(II) center was octahedrally bonded by one bidentate chelate 5-Br-pyc anion and one 2,2′-bipy, one water molecule as well as one chloride anion to form the mononuclear structure of 1⋅2H2O. Complex 1⋅2H2O forms a 3D network through abundant O–H⋅⋅⋅O hydrogen bonds and π⋅⋅⋅π stacking interactions. Notably, the 5-Br-Hpyc ligand was in situ generated by decarboxylation of the 3-bromo-pyridine-2,6-dicarboxylic acid (3-Br-H2pydc) precursor selectively on 2-position under hydrothermal conditions. The magnetic properties, the Hirshfeld surface structure and the synthetic process for 1⋅2H2O have been carefully described and discussed.

A new copper(II) complex containing triclopyr: one-pot crystallization, structure, conformation and Hirshfeld surface analyses

A new copper(II) complex [Cu(3,5,6-tcpa)(2,2′-bipy)Cl] (1) has been obtained through the one-pot hydrothermal reaction of copper chloride dihydrate with triclopyr (systematic name 2-((3,5,6-trichloropyridin-2-yl)oxy)acetic acid, abbreviation 3,5,6-Htcpa) and 2,2′-bipyridine (2,2′-bipy) coligands. 1 has crystallized in triclinic crystal system, P 1 ‾ $\overline{1}$ space group. The central copper(II) ion displayed a distorted square–pyramidal geometry and was connected by one chlorido co-ligand (Clˉ), one 3,5,6-tcpa anionic chelator and one chelating 2,2’-bipy ligand to afford a mononuclear structure. 1 is further extended into a 3D network by the non-covalent interactions of H⋯Cl, H⋯O hydrogen bonds, aromatic π⋯π stacking together with Cl⋯Cl halogen bond interactions. The co-crystallization process, the crystal structure of 1 as well as the Hirshfeld surface analysis for 1 have been analyzed and described. In addition, the flexible conformation of phenoxy methylene group among 1, triclopyr acid and its previously reported co-crystallized compound also have been carefully compared and discussed.

The synthesis, crystal structure and conformation analysis of triclopyr ethyl ester

Triclopyr ethyl ester (1) has been co-synthesized through one-pot solvothermal reaction and the crystal structure has been determined by single crystal X-ray structure analysis. The compound C18H16Cl6N2O6 crystallizes in the monoclinic crystal system, P21/c space group with unit-cell parameters: a = 4.9615(2) Å, b = 30.9297(14) Å, c = 15.9155(10) Å, β = 91.466(4)° and Z = 4. Each unit cell is composed of two discrete, similar but reversely arranged triclopyr ethyl ester organic molecules. In the 3D packing plot, 1 is further assembled into a network structure via rich Cl⋯Cl halogen bond interactions. In addition, the crystal structure, the flexible conformation of phenoxy methylene group of 1 has been carefully compared and discussed with those of triclopyr acid.

Exploratory and machine learning analysis of the stability constants of HgII- triazene ligands complexes

Knowing stability constants for the complexes HgII with extracting ligands is very important from environmental and therapeutic standpoints. Since the selectivity of ligands can be stated by the stability constants of cation–ligand complexes, quantitative structure–property relationship (QSPR) investigations on binding constant of HgII complexes were done. Experimental data of the stability constants in ML2 complexation of HgII and synthesized triazene ligands were used to construct and develop QSPR models. Support vector machine (SVM) and multiple linear regression (MLR) have been employed to create the QSPR models. The final model showed squared correlation coefficient of 0.917 and the standard error of calibration (SEC) value of 0.141 log K units. The proposed model presented accurate prediction with the Leave-One-Out cross validation ( Q LOO 2  = 0.756) and validated using Y-randomization and external test set. Statistical results demonstrated that the proposed models had suitable goodness of fit, predictive ability, and robustness. The results revealed the importance of charge effects and topological properties of ligand in HgII - triazene complexation.

THE SYNTHESIS AND PROPERTIES OF A SODIUM SUPRAMOLECULAR CRYSTAL NETWORK CONSTRUCTED WITH FUNCTIONAL PYRAZINE SULFONIC ACID

Sulfonic acid groups with C_3ν symmetry can coordinate with metal ions to produce multidimensional structures due to their flexible coordination modes. They can also penetrate into supramolecular structures through an intriguing bridging pattern and weak interactions. Herein, a novel heterocyclic sodium sulfonate supramolecular structure, namely [Na(Pyr-SO₃)(H₂O)]_n where Pyr-SO₃H is pyrazine sulfonic acid, is synthesized by utilizing NaBF₄ to coordinate with the P–SO₃H ligand through the solvent evaporation method. The single crystal X-ray diffraction (XRD) data indicate that the as-formed structure belongs to the Pbca space group. Additional properties are characterized by powder XRD, thermal analysis, and solid-state fluorescence. In particular, the introduction of a soft alkali metal ion can coordinate with the oxygen atom of the sulfonate ligand and form a Na–O bridging configuration that can not only significantly improve the pyrazine sulfonic acid ligand coordination ability, but also provide a reference for the extended study of functional sulfonate polymers in the future.

A (4,4)-connected zinc(II) coordination polymer constructed with the flexible 2-carboxy phenoxyacetate ligand: synthesis, conformation alteration and fluorescent properties

A new binary ZnII coordination polymer, [Zn(2-cpa)(H2O)] n (2D-Zn) has been prepared by a 120 °C hydrothermal reaction of zinc(II) sulfate heptahydrate and 2-carboxy phenoxyacetic acid (2-H2cpa) in the presence of potassium hydroxide. Single-crystal X-ray diffraction analysis shows that the ZnII ion is located in a deformed ZnO6 octahedron bonded by one water and three 2-carboxy phenoxyacetate (2-cpa) ligands. The 2-cpa exhibits pentadentate double bridging chelate-μ 3 coordination mode and connects adjacent ZnII ions to generate a corrugated (4,4)-connected layer structure. The structures, conformation of 2-cpa and photoluminescence spectra for 2D-Zn have been carefully analyzed and compared with its two closely related compounds ̶ 1D [Zn(2-cpa)(H2O)] n (1D-Zn) and mononuclear [Zn(2-cpa)(H2O)3] (0D-Zn). The results showed that the conformation of 2-cpa in 2D-Zn has the maximum alteration and the corresponding fluorescence emission peak of 2D-Zn has the largest red-shift of 62 nm compared with that of free 2-H2cpa.