Single-crystal X-ray Diffraction Research Articles

A lithium-aluminium heterobimetallic dimetallocene.

Homobimetallic dimetallocenes exhibiting two identical metal atoms sandwiched between two η5 bonded cyclopentadienyl rings is a narrow class of compounds, with representative examples being dizincocene and diberyllocene. Here we report the synthesis and structural characterization of a heterobimetallic dimetallocene, accessible through heterocoupling of lithium and aluminylene fragments with pentaisopropylcyclopentadienyl ligands. The Al-Li bond features a high ionic character and profits from attractive dispersion interactions between the isopropyl groups of the cyclopentadienyl ligands. A key synthetic step is the isolation of a cyclopentadienylaluminylene monomer, which also enables the structural characterization of this species. In addition to their structural authentication by single-crystal X-ray diffraction analysis, both compounds were characterized by multinuclear NMR spectroscopy in solution and in the solid state. Furthermore, reactivity studies of the lithium-aluminium heterobimetallic dimetallocene with an N-heterocyclic carbene and different heteroallenes were performed and show that the Al-Li bond is easily cleaved.

Designing a Phenalenyl-Based Dinuclear Ni(II) Complex: An Electrocatalyst with Two Single Ni Sites for the Oxygen Evolution Reaction (OER).

A new dinuclear Ni(II) complex 1, [Ni2II(dtbh-PLY)2], is synthesized from 9-(2-(3,6-di-tert-butyl-2-hydroxybenzylidene)hydrazineyl)-1H-phenalen-1-one, dtbh-PLYH2 ligand, and structurally characterized by various analytical tools including the single-crystal X-ray diffraction (SCXRD) technique. In the solid state, both Ni(II) metal centers in complex 1 exist in a distorted square planar geometry and display the presence of rare Ni···H-C anagostic interactions to form a one-dimensional (1-D) linear motif in the supramolecular array. Complex 1 is further stabilized in the solid state by π-π-stacking interactions between the highly delocalized phenalenyl rings. The redox features of complex 1 have been analyzed by the cyclic voltammetry (CV) technique in solution as well as in the solid state, revealing the crucial involvement of both the Ni(II) metal centers for undergoing quasi-reversible oxidation reactions on the application of an anodic sweep. A complex 1-modified glassy carbon electrode, GC-1, is employed as an electrocatalyst for oxygen evolution reaction (OER) in 1.0 M KOH, giving an OER onset at 1.45 V, and very low OER overpotential, 300 mV vs the reversible hydrogen electrode (RHE) to reach 10 mA cm-2 current density. Furthermore, GC-1 displayed fast OER kinetics with a Tafel slope of 40 mV dec-1, a significantly lower Tafel slope value than those of previously reported molecular Ni(II) catalysts. In situ electrochemical experiments and postoperational UV-vis, Fourier transform infrared (FT-IR), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS) studies were performed to analyze the stability of the molecular nature of complex 1 and to gain reasonable insights into the true OER catalyst.

Enhancing the Analysis of Eu3+ Photoluminescence in Coordination Compounds in the Solid State by Determining their Refractive Index

AbstractThis study is focused on determining the refractive index as a crucial parameter for evaluating the intrinsic quantum yield and the ligand sensitisation efficiency in solid‐state trivalent lanthanide coordination compounds. For this, eight trivalent europium complexes with phenyl‐terpyridine ([EuX3(ptpy)(L)], X=Cl− or NO3−, ptpy=4′‐phenyl‐2,2′ : 6′,2′′‐terpyridine, L=H2O or other molecules) were examined. Their refractive indices were determined using the Becke lines test by immersing transparent material in a series of media with known refractive indices. Using the set of media presented here, determining crystalline materials′ refractive indices from 1.41 to 1.73 with a step of 0.01 is possible. Assessment of the refractive indices of the complexes mentioned above allowed a comprehensive analysis of their photophysical properties in the solid state. Moreover, this method can be extrapolated for other solid‐state materials, offering valuable insights in the broader field of photophysics. In addition to photoluminescence investigations, the compounds presented were characterised by single‐crystal X‐ray diffraction (SCXRD), powder X‐ray diffraction (PXRD), Hirschfeld surface area analysis, UV‐Vis reflectance spectroscopy, hydrolysis sensitivity analysis, and simultaneous thermogravimetry and differential thermal analysis coupled with mass‐spectrometry (STA‐MS).

Supramolecular Assemblies in Mn(II) and Zn(II) Metal–Organic Compounds Involving Phenanthroline and Benzoate: Experimental and Theoretical Studies

Two new Mn(II) and Zn(II) metal–organic compounds of 1,10-phenanthroline and methyl benzoates viz. [Mn(phen)2Cl2]2-ClBzH (1) and [Zn(4-MeBz)2(2-AmPy)2] (2) (where 4-MeBz = 4-methylbenzoate, 2-AmPy = 2-aminopyridine, phen = 1,10-phenanthroline, 2-ClBzH = 2-chlorobenzoic acid) were synthesized and characterized using elemental analysis, TGA, spectroscopic (FTIR, electronic) and single crystal X-ray diffraction techniques. The crystal structure analysis of the compounds revealed the presence of various non-covalent interactions, which provides stability to the crystal structures. The crystal structure analysis of compound 1 revealed the formation of a supramolecular dimer of 2-ClBzH enclathrate within the hexameric host cavity formed by the neighboring monomeric units. Compound 2 is a mononuclear compound of Zn(II) where flexible binding topologies of 4-CH3Bz are observed with the metal center. Moreover, various non-covalent interactions, such as lp(O)-π, lp(Cl)-π, C–H∙∙∙Cl, π-stacking interactions as well as N–H∙∙∙O, C–H∙∙∙O and C–H∙∙∙π hydrogen bonding interactions, are found to be involved in plateauing the molecular self-association of the compounds. The remarkable enclathration of the H-bonded 2-ClBzH dimer into a supramolecular cavity formed by two [Mn(phen)2Cl2] complexes were further studied theoretically using density functional theory (DFT) calculations, the non-covalent interaction (NCI) plot index and quantum theory of atoms in molecules (QTAIM) computational tools. Synergistic effects were also analyzed using molecular electrostatic potential (MEP) surface analysis.

Synthesis, disorder and Ising anisotropy in a new spin liquid candidate PrMgAl11O19

Abstract Here we report the successful synthesis of large single crystals of triangular frustrated PrMgAl11O19 using the optical floating zone technique. Single crystal Xray diffraction measurements unveiled the presence of quenched disorder within the mirror plane, specifically ∼7% of Pr ions deviating from the ideal 2d site towards the 6h site. Magnetic susceptibility measurements revealed an Ising anisotropy with the c-axis being the easy axis. Despite a large spin-spin interaction that develops below ∼10 K and considerable site disorder, the spins do not order or freeze down to at least 50 mK. The availability of large single crystals offers a distinct opportunity to investigate the exotic magnetic state on a triangular lattice with an easy axis out of the plane.

Unveiling the Multielectron Acceptor Properties of π-Expanded Pyracylene: Reversible Boat to Chair Conversion.

In this work, the chemical reduction of a hybrid pyracylene-hexa-peri-hexabenzocoronene (HPH) nanographene was investigated with different alkali metals (Na, K, Rb) to reveal its remarkable multielectron acceptor abilities. The UV-vis and 1H NMR spectroscopy monitoring of the stepwise reduction reactions supports the existence of all intermediate reduction states up to the hexaanion for HPH. Tuning the experimental conditions enabled the synthesis of the HPH anions with gradually increasing reduction states (up to -5) isolated with different alkali metal ions as crystalline materials. The single-crystal X-ray diffraction structure analysis demonstrates that the highly negatively charged HPH anions (-4 and -5) exhibit a drastic geometry change from boat-shaped (observed in the neutral parent, mono- and dianions) to a chair conformation, which was proved to be fully reversible by NMR spectroscopy. DFT calculations show that this geometry change is induced by an enhanced interaction between the coordinated metal ions and negatively charged HPH core in the chair conformation.

Crotonoids A-H, Labdane-Type Diterpenoids with Anti-Inflammatory Activity from Croton sublyratus.

Croton sublyratus (Euphorbiaceae) is a traditional medicinal plant used by the Thai populace to treat helminthic infections and dermatologic conditions. In present study, eight new labdane-type diterpenoids, crotonoids A-H (1-8) and one known analogue (9) were isolated from the aerial parts of C. sublyratus. Compounds 6 and 7 belong to the rare class of 14,15-dinor-labdane diterpenoids. Compound 8 exhibited a rare 14,15,17-trinor-labdane skeleton. The structures of all these diterpenoids were elucidated by spectroscopic data analysis, electronic circular dichroism calculations, and single-crystal X-ray diffraction analysis. Compound 9 exhibited moderate anti-inflammatory activity via the inhibition of NO production in lipopolysaccharide-induced RAW 264.7 cells.

Highly scalable and robust ribbon-like coordination polymer as green catalyst for Hantzsch condensation in synthesis of DHPs and bioactive drug molecule

Ribbon-like coordination polymers (CP) represents a highly unexplored innovative class of metal-coordination network. Herein, we have developed a highly scalable and chemically robust (pH = 3–10 stable) ribbon-like CP [{Cu(Pim)(L)(H2O)·H2O}]n(1) following a complete environment-friendly green synthesis route. Considering the presence of surface flanked labile coordinated water molecules and their appealing correlation with one-dimensional structural characteristics, such sort of ribbon-like CP was explored for the first time as excellent heterogeneous surface catalyst for largely unexplored three-component Hantzsch condensation for synthesis of different classes of dihydropyridine (DHP). Moreover, 1 is employed to synthesize bio-responsive drug ‘Ethidine’ (possessing high anti-oxidant and anticarcinogenic properties) characterized with Single Crystal X-ray Diffraction (SCXRD) analysis. Several DHP-based products are also analysed through in-depth SCXRD analysis. This report inaugurates the usage of a Cu(II) based ribbon-like CPs as heterogeneous surface catalyst following environmentally benign manner for synthesis of bioactive DHPs and Drugs.

8(S)-[(1R,2S,5R)-2-Isopropyl-5-methylcyclohexyloxy]-3,4-dihydro-2H-[1,4]dithiepino[2,3-c]furan-6(8H)-one

The interaction of propane-1,3-dithiol with the chiral bis-thioether, which combines two 2(5H)-furanone moieties, bridged through their carbon atoms C(4) by the propane-1,3-dithiol fragment, in DMF in the presence of potassium hydroxide or cesium carbonate resulted in the formation of an optically active fused bicyclic sulfur heterocycle, possessing 1,4-dithiepine and unsaturated γ-lactone moieties. The studied reaction follows an unexpected pathway in a basic medium with the thiolate–thiolate exchange. The structure of the novel heterocycle of the 1,4-dithiepinofuranone series is characterized by single-crystal X-ray diffraction.

Evolution of structure and spectroscopic properties of a new 1,3-diacetylpyrene polymorph with temperature and pressure.

A new polymorph of 1,3-diacetylpyrene has been obtained from its melt and thoroughly characterized using single-crystal X-ray diffraction, steady-state UV-Vis spectroscopy and periodic density functional theory calculations. Experimental studies covered the temperature range from 90 to 390 K and the pressure range from atmospheric to 4.08 GPa. Optimal sample placement in a diamond anvil cell according to our previously presented methodology ensured over 80% data coverage up to 0.8 Å for a monoclinic sample. Unrestrained Hirshfeld atom refinement of the high-pressure crystal structures was successful and anharmonic behavior of carbonyl oxygen atoms was observed. Unlike the previously characterized polymorph, the structure of 2°AP-β is based on infinite π-stacks of antiparallel 2°AP molecules. 2°AP-β displays piezochromism and piezofluorochromism which are directly related to the variation in interplanar distances within the π-stacking. The importance of weak intermolecular interactions is reflected in the substantial negative thermal expansion coefficient of -55.8 (57) MK-1 in the direction of C-H...O interactions.

Analysis of COF-300 synthesis: probing degradation processes and 3D electron diffraction structure.

Although COF-300 is often used as an example to study the synthesis and structure of (3D) covalent organic frameworks (COFs), knowledge of the underlying synthetic processes is still fragmented. Here, an optimized synthetic procedure based on a combination of linker protection and modulation was applied. Using this approach, the influence of time and temperature on the synthesis of COF-300 was studied. Synthesis times that were too short produced materials with limited crystallinity and porosity, lacking the typical pore flexibility associated with COF-300. On the other hand, synthesis times that weretoo long could be characterized by loss of crystallinity and pore order by degradation of the tetrakis(4-aminophenyl)methane (TAM) linker used. The presence of the degradation product was confirmed by visual inspection, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). As TAM is by far the most popular linker for the synthesis of 3D COFs, this degradation process might be one of the reasons why the development of 3D COFs is still lagging compared with 2D COFs. However, COF crystals obtained via an optimized procedure could be structurally probed using 3D electron diffraction (3DED). The 3DED analysis resulted in a full structure determination of COF-300 at atomic resolution with satisfying data parameters. Comparison of our 3DED-derived structural model with previously reported single-crystal X-ray diffraction data for this material, as well as parameters derived from the Cambridge Structural Database, demonstrates the high accuracy of the 3DED method for structure determination. This validation might accelerate the exploitation of 3DED as a structure determination technique for COFs and other porous materials.

Synthesis, Characterization, and Properties of a Titanium(IV)-Tetrathiafulvalene-Based Complex.

To deeply investigate the interaction between a tetrathiafulvalene (TTF) unit and a Ti(IV) center, a monomeric heteroleptic octahedral Ti(IV) complex containing a diimine ligand composed of a 1,10-phenanthroline core fused with a TTF fragment (ligand 2a) was prepared. The stable complex formulated as Ti(1)2(2a), where 1 is a 2,2'-biphenolato derivative, was efficiently synthesized by following a one-step approach. This complex and its model species [Ti(1)2(2b)] were fully characterized in solution, and their solid-state structures were established by single-crystal X-ray diffraction analysis. Density functional theory calculations allowed the assignment of the frontier orbitals involved in the electronic transitions characterized by ultraviolet-visible absorption spectroscopy. Electrochemical and spectroelectrochemical studies revealed that the TTF unit within Ti(1)2(2a) can undergo two reversible one-electron oxidation processes; a reversible one-electron reduction of the Ti(IV) atom was highlighted. The photophysical measurements performed for this donor-acceptor molecular system indicated that an electron transfer process upon light excitation occurred within Ti(1)2(2a).

Experimental and theoretical investigation on the SR method grown semi-organic Piperazinium Tetrachlorozincate Monohydrate (PTZM) single crystal for optoelectronic applications

Efficient semi organic nonlinear optical (NLO) Piperazinium Tetrachlorozincate monohydrate (PTZM) [C4H12N2][ZnCL4]·H2O single crystals have been grown by slow evaporation solution technique (SEST) and Sankaranarayanan-Ramasamy (SR) method using water as solvent. Single crystal X-ray diffraction (SXRD) analysis reveals the unit cell parameters of the grown crystal. The morphology of the grown crystal was identified by the single crystal XRD analysis. The electrical properties, dielectric constant, dielectric loss and piezoelectric (d33) coefficient were determined. The etch pit density of PTZM crystal has been calculated by using the chemical etching analysis. The laser damage threshold (LDT) analysis was investigated by Nd: YAG laser and the wavelength of laser is 1064 nm. The mechanical stability of the grown PTZM crystal was studied using Vickers microhardness measurement. Utilizing quantum chemical calculations, the PTZM compound is analyzed for vibrational properties, HOMO and LUMO characteristics, NBO interactions, and the determination of first-order hyperpolarizability. The nonlinear susceptibility and first-order hyperpolarizability results provide compelling evidence and affirm the PTZM molecule’s potential as a strong candidate for nonlinear optical (NLO) applications.

Ferrocene-based amides, amines and alcohols as a platform for the design and synthesis of redox-active hybrids: Synthesis, electrochemical and computational studies

Herein we report on the synthesis and characterization of a number of the simplest ferrocenes, namely Fc-amides (4a-i), Fc-amines (5a-i) and Fc-alcohol (1), as starting materials for the synthesis of redox-active ferrocene-modified compounds. Suitable conditions allowed preparing a seria of various ferrocenes with aliphatic and aromatic substituents in good to high yields. The title products were characterized by 1H, 13C NMR, IR, ESI-MS analytical methods. The structure of ferrocenyl(ortho-chlorophenyl) methanol (1) was determined by single-crystal X-ray diffraction. Geometrical parameters in compound 1 were calculated using the ab initio MP2/6-31G* method and based on the advanced DFT calculations, DFT wb97xd/6-31G* and DFT wb97xd/6-311+G*. Electrochemical investigations by cyclic voltammetry revealed reversible redox processes for the ferrocenyl amides. Potentials were also calculated using two basis sets, 6-31G* and 6-311+G*, and demonstrated a high degree of correlation with experimental results.

A drug–drug cocrystal strategy to regulate stability and solubility: A case study of temozolomide/caffeic acid

Temozolomide (TMZ) is a common clinical drug widely used to treat glioblastoma multiforme and gradual astrocytoma. Despite its widespread use in cancer treatment, issues remain with the solubility and stability of TMZ, which can be addressed by synthesizing novel pharmaceutical cocrystals. This study sought to enhance the physiochemical properties of TMZ. To this end, a pioneering pharmaceutical cocrystal of TMZ and caffeic acid (CAF), 2TMZ–CAF·0·5H2O (2:1:0.5) was synthesized and characterized using a solution method. The cocrystal structure was analyzed by molecular surface electrostatic potential (MESP), Hirshfeld surface analysis, and 2D fingerprinting. They were further characterized by single crystal X-ray diffraction, power X-ray diffraction, proton nuclear magnetic resonance, thermogravimetry-differential scanning calorimetry, dynamic vapor sorption, and Fourier transform infrared spectroscopy. Furthermore, the hygroscopicity, stability, and solubility of the TMZ–CAF cocrystal were investigated to evaluate their pharmaceutical applicability. In the asymmetric unit of the novel synthesized cocrystal, two complementary molecules of TMZ and CAF were found, forming planar hydrogen bonding pairs such as O–H···O, N–H···O, and O–H···N. Moreover, the cocrystals exhibited excellent stability compared to TMZ alone and regulated solubility during accelerated stabilization and dissolution processes. Hence, the cocrystals boast characteristics that can circumvent the rapid release of TMZ. In conclusion, the newly synthesized 2TMZ–CAF·0·5H2O cocrystals demonstrate enhanced physiochemical properties, including improved stability and solubility, compared to pure TMZ. This suggests potential utility in drug delivery systems. Additionally, the findings underscore the growing importance of pharmaceutical cocrystals in drug development, with implications for advancing cancer treatment and drug formulation strategies.

Anticancer potential of isovanillin-based symmetrical azine: Synthesis, structure, molecular modeling, in silico leukemia inhibition and MD simulation

Isovanillin azine, a symmetrical azine easily synthesized by reaction of 3-hydroxy-4-methoxybenzaldehyde (isovanillin) with hydrazine hydrate, was identified as a potential inhibitor of the Human T-cell Leukemia Virus type 1 (HTLV-1) protease (2B7F). The compound was characterized using FT-IR, UV-VIS, 1H NMR, and 13C NMR spectroscopic techniques, as well as by single-crystal X-ray diffraction at 100 K. Additionally, calculations were conducted on the FMOs, particularly the HOMO-LUMO, to determine the forbidden energy gap and assess the compound's properties. To properly and accurately evaluate the effectiveness of our product as an anticancer drug, we investigated its interactions with 2B7F through molecular docking experiment and MD simulation. The results indicate that isovanillin azine has the potential to effectively inhibit 2B7F, laying the groundwork for the development of targeted treatments for HTLV-1-related disorders.

New isoxazolidine derivatives: Synthesis, spectroscopic analysis, X-ray, DFT calculation, biological activity studies

The isoxazolidine skeleton is an important component of biologically active natural products, and many compounds containing isoxazolidine ring exhibit excellent antibacterial and anticancer activities. Based on the variously biological activity of isoxazolidines, a new series of isoxazolidine derivatives were designed and synthesized. All the structure of target compounds was characterized by NMR and HRMS. Especially, compound 8a ((Z)-2-methyl-4-(phenoxymethylene)-3-phenylisoxazolidine) was prepared for single crystal X-ray diffraction and FT-IR. Density functional theory (DFT) calculations were also performed on compound 8a at the B3LYP/6–311 level. In addition, after evaluation with MTT method of compounds 8a-8k against A549 cells, it was found that some compounds performed well antitumor activities.

Synthesis and Structure of a Coordination Polymer of Ni(II) with 2-(4-Bromophenoxy)acetohydrazide

The coordination compound [NiCl2L(2-PrOH)]n (where L is 2-(4-bromophenoxy)acetohydrazide; 2-PrOH is isopropanol) was obtained for the first time. The complex was characterized by means of elemental analyses, molar conductance, thermogravimetric analysis, IR spectroscopy, and single crystal X-ray diffraction analysis. It was determined that the coordination compound exhibits a polymeric structure. The complexing agent is six-coordinated, and its distorted octahedron forms due to the bidentate coordination of 2-(4-bromophenoxy)acetohydrazide through the carbonyl oxygen atom and the amine nitrogen. The oxygen of the molecule of isopropanol, the chlorine atom, and two chlorine atoms serve as bridges between two metal atoms.

Structure-property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives.

Presented here is the design, synthesis, and study of a variety of novel hydrogen-bonding-capable π-conjugated N-heteroacenes, 1,4-dihydropyrazino[2,3-b]quinoxaline-2,3-diones (DPQDs). The DPQDs were accessed from the corresponding weakly hydrogen-bonding dicyanopyrazinoquinoxaline (DCPQ) suspensions with excess potassium hydroxide, resulting in moderate to good yields. Both families of compounds were analyzed by UV-vis and NMR spectroscopy, where the consequences of hydrogen bonding capability could be assessed through the structure-property studies. Conversion of the DCPQs into hydrogen-bonding capable DPQDs results in modulation of frontier MO energies, higher molar extinction coefficients, enhanced crystallinity, and on-average higher thermal stability (where in some cases the 5% weight loss temperature is increased by up to 100 °C). Single crystal X-ray diffraction data could be obtained for three DPQDs. One reveals pairwise hydrogen bonding in the solid state as well as a herringbone packing arrangement rendering it a promising candidate for additional studies in the context of organic optoelectronic devices.

New 19(10 → 9)abeo-euphane-type triterpenoids from Trichilia dregeana leaves and NO production inhibitory activities

Phytochemical investigation of the EtOAc soluble fraction from leaves of Trichilia dregeana Sond. (Meliaceae) afforded naturally rare four new pentacyclic triterpenoids (1–4), together with five known pentacyclic analogs (5–8, and 11) and two steroids (9 and 10). Their structures were elucidated by extensive spectroscopic techniques such as 1D and 2D NMR and HRESIMS data analyses. The absolute configuration of 1 was determined by using the single-crystal X-ray diffraction analysis. The nitric oxide (NO) production inhibitory assay indicated that the EtOAc fraction as well as 4 and 7 inhibited the NO production in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells with the IC50 values of 83.53 μg/mL and 81.31 and 85.71 μM, respectively. Compounds 1–4 are rare 19(10 → 9)abeo-euphane-type triterpenoids bearing a 3,10-ether bridge. To the best of our knowledge, this study is the first isolation of triterpenoids with the 3,10-ether bridge in their skeleton from the genus Trichilia, providing new insights into the chemodiversity of the terpenoids in T. dregeana.