Single-crystal X-ray Structure Research Articles

Design and Synthesis of Lead(II)-Based Electrocatalysts for Oxygen Evolution Reaction.

A well-organized worldwide effort in providing remedies to sustainable clean energy generation and storage has focused on the strategic design and development of stable and efficient earth-abundant metal (Fe, Co, Ni, Pb, etc.)-based electrocatalysts for the oxygen evolution reaction (OER). Unfortunately, examples of Pb-based catalysts for such a process are rare. In this work, based on the dual-linker strategy, we have designed and synthesized two new two-dimensional (2D) coordination polymers of Pb with the hcb topology, [Pb2(tpbn)(adc)2]·4H2O·0.5CH3OH}n (CP1) and {[Pb2(tpbn)(fum)2]·7H2O}n (CP2), in excellent yields by the room-temperature self-assembly of Pb(OAc)2, tpbn, and H2adc or H2fum (where tpbn = N,N',N‴,N‴'-tetrakis-(2-pyridylmethyl)-1,4-diaminobutane, H2adc = acetylene dicarboxylic acid, and H2fum = fumaric acid). In addition to determining their X-ray single crystal structures, the phase purity and thermal stability were established by powder X-ray diffraction and thermogravimetric analysis, respectively. Furthermore, these were also characterized by the microscopic techniques (SEM/EDX and TEM/HRTEM). For their conductive and highly stable nature in alkaline medium, both CP1 and CP2 were tested for their suitability in the OER process. Interestingly, with a subtle change from adc in CP1 to fumarate in CP2 as the dicarboxylate linker, the latter performed much better than the former and displayed an excellent electrochemical stability in basic medium. Remarkably, CP2 has one of the lowest Tafel values (35 mV dec-1) and a low overpotential value (140 mV vs RHE) in 0.5 M KOH compared to those reported for any materials. Such a comparative study with CP1 and CP2, which are the simplest CPs and made with green-chemistry protocols for an easy making in large quantities, provides an outlook to developing the next-generation Pb-based electrocatalysts.

Concise Synthesis of BN-Dibenzo[f,k]tetraphenes with Different BN Substitution Positions and Direct Comparison with Their Carbonaceous Analogue.

Two types of "parental" BN-dibenzo[f,k]tetraphenes (BNDBT-1 and BNDBT-2) have been synthesized via a transition-metal-catalyzed tandem cross-coupling reaction as key steps. Both BNDBT-1 and BNDBT-2 are fully characterized; one of them is unambiguously confirmed by a single X-ray crystal structure. Compared to its all-carbon analogue DBT, BNDBT-1 and BNDBT-2 exhibit a higher highest occupied molecular orbital (HOMO) and lower lowest unoccupied molecular orbital (LUMO) energy, while the BN doping position slightly influences the HOMO and LUMO energies of BNDBT-1 and BNDBT-2. Both BNDBT-1 and BNDBT-2 exhibit red-shifted absorption and emission spectra and higher emission efficiencies, as compared to their carbonaceous analogue DBT. Moreover, organic light emitting diodes were fabricated using BNDBT-1 and BNDBT-2 as emitters, demonstrating their potential applications.

Electrocatalytic CO2 Reduction by Molecular Ruthenium Complexes with Polypyridyl Ligands.

Two series of ruthenium complexes with various polypyridyl ligands have been prepared. One series of complexes (5 examples) are featured with tetradentate polypyridyl ligands and two acetonitrile molecules at the axial positions of the coordination sphere; the other series (3 examples) include combinations of a tridentate polypyridyl ligand, one 2,2'-bipyridine (bpy) or two picolines, and one acetonitrile ligand. All these complexes were fully characterized by their NMR spectra as well as X-ray single crystal structures. Their electronic absorption and redox data were measured and reported. Of the 8 complexes, three candidates effectively catalyze electrochemical CO2 reduction reaction (CO2 RR) in wet acetonitrile medium, generating CO as the major product. All these three catalytically active complexes contain a 2,2':6',2'':6'',2'''-quaterpyridine (qpy) ligand scaffold. A maximum turnover frequency (TOFmax ) of>1000 s-1 was achieved for the electrocatalytic CO2 reduction at a modest overpotential. On the basis of electrochemical and spectroelectrochemical evidences, the CO2 substrate was proposed to bind with the ruthenium center at the two-electron reduced state of the complex and then entered the catalytic cycle.

Tunable Solid-State Thermochromism: Alkyl Chain Length-Dependent Conformational Isomerization of Bianthrones.

The introduction of linear alkoxy chains into bianthrone promoted the aggregation of the minor twisted conformer and made it compete with the major folded conformer in the solid-state. Rapid evaporation approach to the methoxy- and n-butoxy-substituted derivatives provided powder mixtures of folded and twisted conformers as metastable solids. Upon heating the powders, different lengths of alkyl chains converged to different conformers via solid-state isomerization reaction with an apparent color change. Monitoring by FT-IR spectroscopy and powder XRD ensured that these isomerization reactions involve only conformational isomerization without pyrolysis. In addition, single crystal X-ray structure analysis revealed that twisted conformers with longer alkyl chains are stabilized in the solid-state by the synergistic effect of their inter-chain hydrophobic interactions and π-π stacking interactions.

Bidentate acylthiourea ligand anchored Pd-PPh3 complexes with biomolecular binding, cytotoxic, antioxidant and antihemolytic properties

Acylthiourea-based Pd(II) complexes (1–5) with a PPh3 moiety bearing the general formula [PdCl(PPh3)(L-R)] [L-R = monoanionic bidentate acylthiourea ligand, where R = C6H5 (L1), C6H4CH3(o) (L2), C6H4OCH2CH3(p) (L3), C10H7 (L4) or C6H4Cl (L5)] have been synthesized and characterized by spectroscopic and analytical tools. The single crystal X-ray structures (1–3) revealed that the acylthiourea ligands coordinated to Pd(II) ion in an uncommon bidentate fashion through S and N atoms, forming a four-member ring. The Pd(II) ion exhibited a square planar geometry fulfilled by the ligand (N, S), one Cl‐ and one triphenylphosphine (PPh3). Calf thymus (CT) DNA and bovine serum albumin (BSA) binding of the complexes have been analyzed by spectroscopic and molecular docking studies. The complexes were tested for their in vitro cytotoxicity on three cancer (cervical, breast and lung) and one normal (human embryo) cell lines. Complex 4 bearing the naphthalene substitution exhibited the highest activity against three cancer cells with the half-maximal inhibitory concentration (IC50) values of 8.6 (cervical), 8.8 (breast) and 9.4 μM (lung). The acridine orange/ethidium bromide (AO/EB) and 4′,6-diamidino-2-phenylindole (DAPI) staining assays indicated that 4 induced cancer cell death through apoptosis. Among the complexes, 4 exhibited the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity of 86.19%. All the complexes were subjected to the hemolysis assay which revealed their biocompatibility with red blood cells (RBCs) with a lysis rate of less than 5 %.

Novel octanuclear copper(I) clusters [Cu8{(N)-(μ4-S)}4(μ3-I)2I2(PPh3)2] produced via reductive S-S bond cleavage of disulfide Schiff base ligands and their use as efficient heterogeneous catalysts in CuAAC click reaction

Thiol/disulfide interconversion, catalyzed by metal ions and enzymes, is a fundamental transformation and plays important roles in biological systems. The thiolates, produced in these reactions, are particularly versatile sulfur-containing ligands that can bind to metals or group of metals via a variety of modes and this versatility can lead to the formation of polymeric chains and metal clusters with high nuclearity. Herein, we report the facile one pot synthesis of novel octanuclear copper(I) complexes, [Cu8{(N)-(μ4-S)}4(μ3-I)2I2(PPh3)2] (1–5), by the reaction of copper(I) iodide and disulfide Schiff base molecules (R-CHN˗Ph˗S˗S˗Ph-NCH-R, RMePh = 4-MePh (SB1), RMeOPh = 4-MeOPh (SB2), RMeSPh = 4-MeSPh (SB3), RBrPh = 4-BrPh (SB4), and RFur = 2-furan (SB5)) in the presence of PPh3 in dichloromethane-acetonitrile or chloroform-acetonitrile solution under ambient conditions. Single-crystal X-ray structure analyses of these clusters confirm the presence of Cu8S4I4 core stabilized by the chelating Schiff base thiolate fragment R-CHN˗Ph˗Sˉ produced by the reductive cleavage of disulfide bond, Iˉ, and PPh3. DFT calculations have been performed to describe a speculative mechanism of cluster formation. The octanuclear clusters [Cu8{(N)-(μ4-S)}4(μ3-I)2I2(PPh3)2] (1–5) have been exploited as efficient heterogeneous catalysts for the green synthesis of 1,2,3-triazoles from NaN3, alkyl halides, and alkyne derivatives (CuAAC reaction) under mild conditions.

Constructing Planar C–N Bond-Linked Bi-Triazole High-Energy Explosives via the Formation of Salts

Abstract Energy and safety are the two most concerning properties of energetic materials (EMs). Design and synthesis of planar molecules is considered to be an effective way to obtain high-energy low-sensitivity EMs. In this study, a new C–N bond-linked energetic bi-triazole compound, 3,4′,5-triamine-1,3′-bi(1,2,4-triazole) (1), and its nitrate (1a) and perchlorate salt (1b), as well as a nitrification product, 5-amino-3,4′-dinitramide-1,3′-bi(1,2,4-triazole) (2), and corresponding sodium (2a) and potassium salt (2b) were designed and synthesized. All compounds were fully characterized. The molecular structures of 1, 1a, 1b, 2a, and 2b were confirmed by single-crystal X-ray structure analyses. It was found that 1 exhibits non-planar loose molecular stacking, while 1a, 1b, and 2b exhibit compact face-to-face layered molecular packing structures, and salt 2a exhibits compact wave-like stacking. The physicochemical properties of all compounds, such as density, thermal stability, and mechanical sensitivity, were studied. 1, 1a, 1b, 2a, and 2b have low impact and friction sensitivity and good thermal stability. In addition, Hirshfeld surfaces (HS), independent gradient model (IGM) analyses combined with single-crystal analyses revealed intermolecular interactions in 1, 1a, 1b, 2a, and 2b and clarified the relationship between the structures and molecular properties. The sophisticated hydrogen bonds between the bi-triazole molecules and nitrate/perchlorate ions are the driving force of formation of planar structures. Detonation properties calculated with the professional software package EXPLO5 showed that nitrate 1a (D = 8872 m·s−1, P = 34.8 GPa) and perchlorate 1b (D = 8956 m·s−1, P = 35.1 GPa) exhibit good detonation performance.

The Crystal Structure of Malhmoodite from Custer, South Dakota, USA

ABSTRACT An occurrence of malhmoodite, Fe2+Zr(PO4)2·4H2O, from the Scott's Rose Quartz mine, Custer County, South Dakota, USA, has been identified. It occurs as divergent groups of yellowish, flat-lying platy crystals on football-size masses of altered löllingite with scorodite, parasymplesite, karibibite, schneiderhöhnite, kahlerite, and zircon. An electron probe microanalysis of malhmoodite yielded an empirical formula (based on 12 O apfu) of Fe1.06(Zr1.10Hf0.03)Σ1.13[(P0.93As0.01)Σ0.94O4]2·4H2O. Single-crystal X-ray structure analysis shows that malhmoodite is the Fe-analogue of zigrasite, MgZr(PO4)2·4H2O. Malhmoodite is triclinic with space group P and unit-cell parameters a = 5.31200(10), b = 9.3419(3), c = 9.7062(3) Å, α = 97.6111(13), β = 91.9796(11), γ = 90.3628(12)°, V = 477.10(2) Å3, Z = 2, in contrast to the previously reported monoclinic symmetry with space group P21/c and unit-cell parameters a = 9.12(2), b = 5.42(1), c = 19.17(2) Å, β = 94.8(1)°, V = 944.26 Å3, Z = 4. The crystal structure of malhmoodite is characterized by sheets composed of ZrO6 octahedra sharing all vertices with PO4 tetrahedra. These sheets are parallel to (001) and are joined together by the FeO2(H2O)4 octahedra. The structure determination of malhmoodite, along with that of zigrasite, warrants a re-investigation of synthetic compounds M2+Zr(PO4)2·4H2O (M = Mn, Ni, Co, Cu, or Zn) that have been assumed previously to be monoclinic.

Precursor Engineering for the Synthesis of Mixed Anionic Metal (Cu, Mn) Chalcogenide Nanomaterials via Solvent-Less Synthesis.

Metal-organic ligands with mixed chalcogenides are potential compounds for the preparation of mixed anionic metal chalcogenide alloys. However, only a few of such ligands are known, and their complexes are not well explored. We have prepared homo- and hetero-dichalcogenoimidodiphosphinate [(EE'PiPr2NH)] (E, E' = Se, Se; S, S; S, Se) complexes of manganese and copper through metathetical reactions. The X-ray single crystal structure of [Mn{(SePiPr2)2N}2] 1 revealed a triclinic crystal system, with a MnSe4 core unit, whereas the crystal structure determination of [Mn{(SPiPr2)(SePiPr2)N}2] 2 indicated a triclinic crystal system with a Mn(S/Se)2 unit. Both metal centers are tetrahedral, with two deprotonated bidentate ligands forming the coordination sphere. The free ligand was found to exhibit a gauche configuration in the solid state. The energies of the various rotamers of dithio-analogue were studied by DFT calculations. The decomposition behavior of complexes with homo- and heterochalcogenides was investigated, and the complexes were employed as single-source precursors to generate manganese and copper chalcogenides through solvent-less melt reactions between 500 and 550 °C. The deposited powders were characterized by powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), transmission electron microscopy (TEM), and elemental mapping. MnS, MnSe2, and MnSSe phases were obtained from the decomposition of respective manganese complexes. In contrast, the decomposition of copper-based complexes yielded Cu2-xSe and the sulfur-doped Cu3Se2 phase from seleno- and mixed thio/seleno-complexes of Cu, respectively. The morphology ranged from random sheet-like structures to agglomerated platelets, while the selected area electron diffraction (SAED) revealed the crystalline nature of the materials. Depending on the nature of the complex and the temperature, different amounts of phosphorus were present as an impurity in the synthesized products.

Pd, Ni, Fe and Cu complexes containing a novel SNS-pincer ligand bearing pyridine: Synthesis and catalytic application to form cyclic carbonates

A new SNS pincer type ligand, 2,6-bis[[(4-bromophenyl)thio]carbonyl]pyridine (L) and its metal complexes (L-Pd, L-Ni, L-Fe, L-Cu) were synthesized and characterized by using X-ray (for ligand), NMR (for ligand), UV-Vis, FT-IR, mass, elemental analysis techniques. The products of reaction with L were new bidentate pincer complex [Pd(κ2-L)(OAc)2] and three tridentate pincer complexes [M(κ3-L)(OAc)2] (M = Fe, Ni, Cu). The molecular structure of ligand (L) was characterized by X-ray single crystal structure determination. The molecular structures of Fe, Cu, and Ni complexes exhibit a five-coordinate distorted trigonal bipyramidal geometry around their metal centers, while the Pd complex exhibits a four-coordinated square plane structure. Moreover, the compounds were used to obtain cyclic carbonates from the reaction of epoxide and CO2 as catalysts. The best performance was obtained in the presence of L-Pd catalyst and DMAP as co-catalyst, with a 93.9% yield and 98.9% selectivity.

9-Trifluoromethylxanthenediols: Synthesis and Supramolecular Motifs.

The synthesis of four derivatives and the single-crystal X-ray structures of six 9-trifluoromethylxanthenediols (TFXdiols) I–VI are analyzed in this work. These compounds were obtained through superacid-catalyzed condensation of dihydroxybenzenes with 1,1,1-trifluoroacetone or 2,2,2-trifluoroacetophenone. The title molecules have a convex molecular structure due to their three fused rings of the xanthene moiety. We have found that, similar to resorcinol, the configuration of the hydroxyl groups is of great relevance for the crystal packing favoring either interactions above and below their molecular plane or lateral interactions that create layers. Considering that reports of TFXdiols are very scarce, our findings contribute to a better understanding of the molecular conformation and intermolecular interactions in their crystal structures. A similar analysis was extended to a fortuitous cocrystal obtained between 9-trifluoromethyl-9-(4′-fluorophenyl)-xanthenediol and 1,4-dihydroxybenzene, showing that these structures might be used to obtain cocrystals in the future.

Assembly of π-Stacking Helical Peptides into a Porous and Multivariable Proteomimetic Framework.

The evolution of proteins from simpler, self-assembled peptides provides a powerful blueprint for the design of complex synthetic materials. Previously, peptide-metal frameworks using short sequences (≤3 residues) have shown great promise as proteomimetic materials that exhibit sophisticated capabilities. However, their development has been hindered due to few variable residues and restricted choice of side-chains that are compatible with metal ions. Herein, we developed a noncovalent strategy featuring π-stacking bipyridyl residues to assemble much longer peptides into crystalline frameworks that tolerate even previously incompatible acidic and basic functionalities and allow an unprecedented level of pore variations. Single-crystal X-ray structures are provided for all variants to guide and validate rational design. These materials exhibit hallmark proteomimetic behaviors such as guest-selective induced fit and assembly of multimetallic units. Significantly, we demonstrate facile optimization of the framework design to substantially increase affinity toward a complex organic molecule.

ROS -mediated anticancer response of potent copper(II) drug entities derived from S, O and N, N chelating donor scaffold: Single X-ray crystal diffraction and spectroscopic studies

New Cu(II) anticancer drug entities derived from S, O, and N, N donor chelating scaffolds were synthesized and thoroughly characterized by various spectroscopic and single X-ray diffraction studies. The single X-ray crystal structure of 1 and 2 revealed a monoclinic and triclinic crystal system with space group C 2 / c and P -1, respectively. The biomolecular interaction studies of 1 and 2 with ct-DNA were carried out by employing a battery of biophysical techniques, viz., absorption, emission, circular dichroic, and electrochemical (CV) and corroborative results of these experiments demonstrated avid electrostatic binding via surface groove. The synthesized Cu(II) complexes showed high efficacy as ROS generators involving Cu(II)/Cu(I) redox-active pair as evidenced by cleavage assay in the presence of radical scavengers. The ROS generation in the presence of copper-based complexes is considered one of the most favorable cell death mechanisms for the inhibition of cancers. In vitro anticancer activity of 1 and 2 was, therefore, evaluated against a panel of five human cancer cell lines, namely MCF-7, MDA-MB-231, Hop-62, AW1356, and SiHa, and results of cytotoxicity demonstrated good anticancer response against all tested cancerous strains with GI50 value <10 µM, except by 1 against MDA-MB-231, Hop-62 and AW1356 cell lines. Interestingly, 2 has displayed considerable cytotoxicity against MCF-7, Hop-62, and SiHa cancer cell lines even better than that of standard drug adriamycin. Furthermore, computational DFT studies validated the high binding efficacy and significant cytotoxicity of complex 2, which could be attributed to high positive charge density over the Cu(II) center.

Intermolecular Halogen Bond Detected in Racemic and Optically Pure N-C Axially Chiral 3-(2-Halophenyl)quinazoline-4-thione Derivatives.

The halogen bond has been widely used as an important supramolecular tool in various research areas. However, there are relatively few studies on halogen bonding related to molecular chirality. 3-(2-Halophenyl)quinazoline-4-thione derivatives have stable atropisomeric structures due to the rotational restriction around an N-C single bond. In X-ray single crystal structures of the racemic and optically pure N-C axially chiral quinazoline-4-thiones, we found that different types of intermolecular halogen bonds (C=S⋯X) are formed. That is, in the racemic crystals, the intermolecular halogen bond between the ortho-halogen atom and sulfur atom was found to be oriented in a periplanar conformation toward the thiocarbonyl plane, leading to a syndiotactic zig-zag array. On the other hand, the halogen bond in the enantiomerically pure crystals was oriented orthogonally toward the thiocarbonyl plane, resulting in the formation of a homochiral dimer. These results indicate that the corresponding racemic and optically pure forms in chiral molecules are expected to display different halogen bonding properties, respectively, and should be separately studied as different chemical entities.

Pyrrolidinecarbodithioate as a planarity chuck in the search for cis-platin analogues of nickel: Spectral, single crystal X-ray structural, BVS, and CSM analysis of some planar nickel(II) mixed ligand complexes

[Ni(pyrdtc)(PPh3)(NCS)] (1), [Ni(pyrdtc)(4-MP)(NCS)] (2), [Ni(pyrdtc)(PPh3)(CN)]·H2O (3), [Ni(pyrdtc)(PPh3)2]ClO4 (4), and [Ni(pyrdtc)(P͡P)]BPh4·2H2O (5) [where pyrdtc: Pyrrolidine carbodithioate/S͡S, PPh3: Triphenylphosphine, 4-MP: Tri(4-methylphenyl)phosphine, dppe/P͡P: 1,2-Bis(diphenylphosphino)ethane] have been prepared from the parent bis-dithiocarbamate, [Ni(pyrdtc)]2 (6). The prepared compounds were characterized by electronic, IR, 1H, 13C, and 31P NMR spectra. In the IR spectra of the compounds, thioureide bands are observed at higher wavenumbers for the mixed ligand complexes 1-5 (1528-1540 cm-1) than the parent compound (1490 cm-1). Cyclic voltammetry showed an increasing order of reduction potentials: 5 &lt;&lt; 1 ~ 2 &lt; 3 &lt; 4 &lt;&lt; [Ni(pyrdtc)2] indicating an alleviation of electron density on nickel in the mixed complexes compared to the parent compound. Single crystal X-ray structure of the complexes displayed planar geometry around nickel which is in keeping with their diamagnetism. Bond Valence Sums calculated with the corrected Rij indicated the divalent nature of nickel with predominant covalent interactions. Continuous shape measure analysis of the mixed ligand chromophores stipulates a planar square environment around central nickel atom and deviation to tetrahedral or trigonal bipyramidal variants are absolutely negated. In this study, CSM analysis of cis-platin, a clinical anti-cancer agent, showed a comparable shape measure as those of the mixed ligand complexes 1-5. Hence, pyrrolidinecarbodithioate acts as a ‘chuck’ in compounds 1-5 to stabilize the planar square shape of the nickel chromophores and provides a suitable template to synthesize analogues of cis-platin.

Field-induced single-molecule magnet behaviour in a series of dinuclear cobalt(III,II) complexes

We present the synthesis, structure and magnetic characterization of four dinuclear cobalt(III,II) complexes: [(NCS)CoIII(Ln)(µ–OAc)CoII(NCS)]·G, with n/G = 1/CH3OH (1), 2/CH3CN (2), 3/- (3) and 4/CH3OH (4), being H2Ln, four closely related reduced Schiff base ligands: H2L1 = (1,3-propanediyl)bis(iminomethylene)bis(6-methoxyphenol), H2L2 = (1,3-propanediyl)bis(iminomethylene)bis(6-ethoxyphenol), H2L3= (2,2-dimethyl-1,3-propanediyl)-bis(iminomethylene)bis(6-methoxyphenol) and H2L4= (2,2-dimethyl-1,3-propanediyl)-bis(iminomethylene)bis(6-ethoxyphenol). The single crystal X-ray structures of complexes 1–4 show that both cobalt centres in the four complexes adopt a distorted octahedral geometry with Co(III) and Co(II) centres residing at inner N2O2 and outer O4 pockets of the reduced Schiff base, respectively. Magnetic measurements show that all complexes behave as Co(II) monomers, confirming the presence of diamagnetic low spin Co(III) ions, which have also been supported by the spin-density calculation using Density Functional Theory. Additionally, complexes 1–4 show a field-induced slow relaxation of the magnetization at low temperatures that follow direct and Raman mechanisms.

Synthesis, crystal structure, DFT studies and Hirshfeld surface analysis of Manganese(II) and Cadmium(II) coordination polymers of 2-aminopyridine and dicyanamide

Mn(II) and Cd(II) metal salts reacted with dicyanamide and 2-aminopyridine resulted in the formation of the ligand-rich linear polymeric chain structures [M(dca)2(2-Ampy)2]n (dca = dicyanamide, 2-Ampy = 2-Aminopyridine; M = Mn (1) or Cd (2)), of the same dimensionality, in which the metal centers are μ1,5-bridged by the dca anions. The complexes were characterized by elemental analysis, IR spectroscopy, UV–vis spectroscopy, thermal analysis and single crystal X-ray structure analysis. These coordination polymers crystallize in the Monoclinic space group Cc. The 3D crystal packing structure results from a combination of N—H/H—-N interactions followed by CH—π stacking interactions. Hirshfeld surface (HS) analysis of the polymers was undertaken to investigate further the intermolecular interactions. DFT calculations on 1 and 2 demonstrated a good correlation between the experimental and theoretical data. The in vitro antimicrobial activity of the manganese complex against selected micro-organisms is also reported.

A facile one-pot synthesis of a new 3,7-diethyl-1H- [1,2,4]triazino [4,3-b] [1,2,4]triazine-4,8-dione: Structural, thermal, and photoluminescent properties

A one-step condensation reaction of α-ketobutyric acid with diaminoguanidine in aqueous medium results in 3,7‑diethyl-1H- [1,2,4]triazino [4,3-b] [1,2,4]triazine-4,8‑dione. The newly formed compound was characterized by FT-IR, UV, 1H NMR, and 13C NMR spectroscopic techniques. The single-crystal X-ray structure of the compound was studied and showed crystallization in a monoclinic system C2/c with a = 22.70(2) Å, b = 5.028(5) Å, c = 17.802(16) Å, α = 90°, β = 93.96(3)°, γ = 90°, Z = 8, and R1/wR2 [I ≥ 2σ(I)] = R1 = 0.0461, wR2 = 0.0904. The structural units are surrounded by CH…O and NH…N interactions that generate zigzag patterns perpendicular to each other. The thermal reactivity and stability were analyzed by TG-DTA (thermogravimetry-differential thermal analysis) in both air and nitrogen atmospheres. In air, the compound showed an endothermic decomposition followed by exothermic combustion via triazine intermediate. In a nitrogen atmosphere, the compound showed endothermic decomposition followed by continuous combustion to produce gaseous products. This compound exhibited photoluminescent emission at λex = 380 nm.

Disilanes with Pentacoordinate Si Atoms by Carbon Dioxide Insertion into Aminodisilanes: Syntheses, Molecular Structures, and Dynamic Behavior.

The insertion of carbon dioxide into the Si–N bonds of aminodisilanes ((RR′N)nMe3–nSi)2 affords carbamoyloxydisilanes ((RR′NC(O)O)nMe3–nSi)2. Some of the obtained insertion products feature pentacoordinate silicon atoms in the solid state and in solution, with two carbamoyloxy moieties bridging the Si–Si bond. The aminodisilanes and their insertion products were extensively analyzed, including single-crystal X-ray structure analyses. The temperature dependence of the higher coordination was investigated using variable temperature NMR experiments.

The benefits of Cu Kβ radiation for the single-crystal X-ray structure determination of crystalline sponges.

The crystalline sponge method facilitates the X-ray structure determination of samples that do not crystallize or are too sparsely available to afford viable crystallization. By including these materials in a metal-organic framework, the structure of the guest molecules can be determined. Some of the inherent difficulties of this method are discussed and the use of Cu Kβ radiation is presented as a simple and effective means to improve the quality of the diffraction data that can be obtained from a sponge crystal.