Crystal structures of three uranyl-acetate-bipyridine complexes crystallized from hydraulic fracking fluid.

Hydraulic fracking exposes shale plays to acidic hydraulic fracking fluid (HFF), releasing toxic uranium (U) along with the desired oil and gas. With no existing methods to ensure U remains sequestered in the shale, this study sought to add organic ligands to HFF to explore potential U retention in shale plays. To test this possibility, incubations were set up in which uranyl acetate and one organic bipyridine ligand (either 2,2'-, 2,3'-, 2,4'-, or 4,4'-bipyridine) were added to pristine HFF as the crystallization medium. After several months and complete evaporation of all volatiles, bulk yellow crystalline material was obtained from the incubations, three of which yielded crystals suitable for single-crystal analysis, resulting in two novel structures and a high-quality structure of a previously described compound. The UO2VI acetate complexes bis(acetato-κ2O,O')(2,2'-bipyridine-κ2N,N')dioxidouranium(VI), [U(C2H3O2)2O2(C10H8N2)2] or [2,2'-bipyridine]UVIO2(CH3CO2)2, (I), and bis(acetato-κ2O,O')(2,4'-bipyridine-κN1')dioxidouranium(VI), [U(C2H3O2)2O2(C10H8N2)2] or [2,4'-bipyridine]2UVIO2(CH3CO2)2, (III), contain eight-coordinate UVI in a pseudo-hexagonal bipyramidal coordination geometry and are molecular, packing via weak C-H...O/N interactions, whereas catena-poly[bis(2,3'-bipyridinium) [di-µ-acetato-µ3-hydroxido-µ-hydroxido-di-µ3-oxido-hexaoxidotriuranium(VI)]-2,3'-bipyridine-water (1/1/1)], (C10H9N2)2[U3(C2H3O2)2O8(OH)2]·C10H8N2·H2O or {[2,3'-bipyridinium]2[2,3'-bipyridine][(UVIO2)3(O)2(OH)2(CH3CO2)2·H2O]}n, (II), forms an ionic one-dimensional polymer with seven-coordinate pentagonal bipyramidal UVI centers and hydrogen-bonding interactions within each chain. The formation of these crystals could indicate the potential for bipyridine to bind with U in shale during fracking, which will be explored in a future study via ICP-MS (inductively coupled plasma mass spectrometry) analyses of U concentration in HFF/bipyridine/shale incubations. The variation seen here between the molecular structures may indicate variance in the ability of bipyridine isomers to form complexes with U, which could impact their ability to retain U within shale in the context of fracking.

Synthesis, Structure, and Photophysical Properties of Platinum Compounds with Thiophene-Derived Cyclohexyl Diimine Ligands.

Platinum(II) and platinum(IV) compounds were prepared by the stereoselective and regioselective reactions of thiophene-derived cyclohexyl diimine C^N^N-ligands with [Pt2Me4(µ-SMe2)2]. Newly synthesized ligands were characterized by NMR spectroscopy and elemental analysis, and Pt(II)/Pt(IV) compounds were characterized by NMR spectroscopy, elemental analysis, high-resolution mass spectrometry, and single-crystal X-ray diffraction. UV-vis absorbance and photoluminescence measurements were performed on newly synthesized complexes, as well as structurally related Pt(II)/Pt(IV) compounds with benzene-derived cyclohexyl diimine ligands, in dichloromethane solution, as solids, and as 5% by weight PMMA-doped films. DFT and TD-DFT calculations were performed, and the results were compared with the observed spectroscopic properties of the newly synthesized complexes. X-ray total scattering measurements and real space pair distribution function analysis were performed on the synthesized complexes to examine the local- and intermediate-range atomic structures of the emissive solid states.

Spectroscopic, crystallographic, and Hirshfeld surface characterization of nine-membered-ring-containing 9-meth-oxy-3,4,5,6-tetra-hydro-1H-benzo[b]azonine-2,7-dione and its parent tetra-hydro-car-ba-zole.

9-Meth-oxy-3,4,5,6-tetra-hydro-1H-benzo[b]azonine-2,7-dione, C13H15NO3, (I), and 6-meth-oxy-1,2,3,4-tetra-hydro-car-ba-zole, C13H15NO, (II), represent the structures of a benzoazonine that contains a nine-membered ring and its parent tetra-hydro-car-ba-zole. The mol-ecules of (I) pack together via strong amide N-H⋯O hydrogen bonding and weak C-H⋯O inter-actions, whereas the parent tetra-hydro-car-ba-zole (II) packs with C/N-H⋯π inter-actions, as visualized by Hirshfeld surface characterization.

Crystallographic and spectroscopic characterization of two 1-phenyl-1H-imidazoles: 4-(1H-imidazol-1-yl)benzaldehyde and 1-(4-meth-oxy-phen-yl)-1H-imidazole.

The title compounds, C10H8N2O, (I), and C10H10N2O, (II), are two 1-phenyl-1H-imidazole derivatives, which differ in the substituent para to the imidazole group on the arene ring, i.e. a benzaldehyde, (I), and an anisole, (II). Both mol-ecules pack with different motifs via similar weak C-H⋯N/O inter-actions and differ with respect to the angles between the mean planes of the imidazole and arene rings [24.58 (7)° in (I) and 43.67 (4)° in (II)].

One pot tandem dehydrogenative cross-coupling of primary and secondary alcohols by ruthenium amido-functionalized 1,2,4-triazole derived N-heterocyclic carbene complexes.

One-pot tandem dehydrogenative cross-coupling of primary and secondary alcohols was catalyzed by three ruthenium complexes [1-(R)-4-N-(furan-2-ylmethyl)acetamido-1,2,4-triazol-5-ylidene]Ru(p-cymene)Cl [R = Et (1b), i-Pr (2b), Bn (3b)], of amido-functionalized 1,2,4-triazole derived N-heterocyclic carbene (NHC) ligands. Density Functional Theory (DFT) calculations were employed for the ruthenium (1b) precatalyst to understand this reaction mechanism completely, and the mechanisms adapted are divided categorically into three steps (i) nucleophilic substitution of chloride ions by alcohols, (ii) dehydrogenation of primary and secondary alcohols, and (iii) olefin and ketone hydrogenation. Our mechanistic study reveals that the formation of a deprotonated Ru-alcoholate (A) or (E) intermediate is favorable compared to the protonated form (A') or (E') from (1b) by associative nucleophilic substitution. Though an ionic pathway that proceeds through (A') or (E'), has less barriers in the dehydrogenation and olefin/ketone hydrogenation steps than that of the neutral pathway, proceeding through (A) or (E), a steep energy barrier was observed in the first nucleophilic substitution step, prohibiting the reaction to proceed via the intermediate (A') or (E'). Thus, our thorough mechanistic study reveals that the reaction proceeds via deprotonated Ru-alcoholate (A) or (E) species. Furthermore, the 1,4 addition of an α,ß-unsaturated carbonyl compound is kinetically and thermodynamically favorable over the 1,2 addition, and the experiments support these observations. As a testimony towards practical application in synthesizing bio-active flavonoid based natural products, five different flavan derivatives (16-20), were synthesized by the dehydrogenative coupling reaction using the neutral ruthenium (1-3)b complexes.

Photophysical Properties of Cyclometalated Platinum(II) Diphosphine Compounds in the Solid State and in PMMA Films.

Platinum(II) compounds were synthesized with both chelate cyclometalated ligands and chelate diphosphine ligands. The cyclometalated ligands include phenylpyridine and a benzothiophene-containing ligand. The three new benzothiophene compounds were characterized by nuclear magnetic resonance (NMR) spectroscopy, high-resolution mass spectrometry (HR-MS), and photophysical measurements. In the case of one compound, L1-DPPM, the structure was determined by single crystal X-ray diffraction. The structural coherence of the noncrystalline emissive solid state was measured by X-ray total scattering real space pair distribution function analysis. Quantum yield values of all of the platinum compounds measured in the solid state and in PMMA films were much greater than in solution.

The crystal structure of 5-(tri-fluoro-meth-yl)picolinic acid monohydrate reveals a water-bridged hydrogen-bonding network.

The title compound [systematic name: 5-(tri-fluoro-meth-yl)pyridine-2-carb-oxy-lic acid monohydrate], C7H4F3NO2·H2O, is the acid hydrate of a pyridine with a carb-oxy-lic acid group and a tri-fluoro-methyl substituent situated para to one another on the aromatic ring. The mol-ecule forms a centrosymmetric water-bridged hydrogen-bonding dimer with graph-set notation R 4 4 (12). Hydrogen-bonding distances of 2.5219 (11) and 2.8213 (11) Šare observed between the donor carb-oxy-lic acid and the bridging water acceptor, and the donor water and carbonyl oxygen acceptor, respectively. The dimers are further linked into a two-dimensional sheet via two longer inter-molecular hydrogen-bonding inter-actions between the second hydrogen atom on the bridging water mol-ecule and both a pyridine nitro-gen atom and carbonyl oxygen with distances of 3.1769 (11) and 2.8455 (11) Å, respectively. The tri-fluoro-methyl groups extend out the faces of the sheet providing for F⋯F and C-H⋯F contacts between the sheets, completing the three-dimensional packing.

Platinum Complexes from C-H Activation of Sterically Hindered [C

Primary amines and benzothiophene-3-carboxaldehyde were reacted to give four large, bulky imine ligands. These imine ligands were reacted with a tetramethyl platinum dimer and by heteroatom-assisted C-H activation, both monometalated compounds and bismetalated compounds were synthesized. In all cases, five-membered platinacycles were formed. The compounds were characterized by NMR spectroscopy, and one bismetalated compound was characterized by single-crystal X-ray diffraction. The UV-vis absorption and emission spectra and the excited-state lifetimes were recorded for these complexes. Density functional theory (DFT) and time-dependent-DFT calculations were performed to aid in the assignment of the absorption and emission spectra of the newly synthesized complexes.

Crystal and geometry-optimized structure of an anthracene-based Diels-Alder adduct.

Computational calculations of an anthracene-based Diels-Alder adduct, namely, 17-ethyl-1-hydroxymethyl-17-azapentacyclo[6.6.5.02,7.09,14.015,19]nonadeca-2,4,6,9,11,13-hexaene-16,18-dione, C21H19NO3, predicting density functional theory (DFT) optimized geometries in the gas phase are compared in terms of accuracy relative to the solid-state crystal structure and computational cost. Crystal structure determination and Hirshfeld surface analysis of the racemic product reveal that the molecules are linked by O-H...O=C hydrogen bonds between the hydroxy and carbonyl groups, accounting for 9.5% of the intermolecular contacts, while H...H contacts represent 56.9% of the total. Boltzmann population analysis of computed relative rotamer abundances in the gas phase are based on lower-level geometry optimization and thermochemical corrections coupled with higher-level electronic energy calculations using the B2PLYP double-hybrid functional. As expected, the choice of density functional has a greater effect than the basis set on accuracy for all levels of theory. For any given functional, increasing the basis set size did not always correlate with increasingly accurate structures. The hybrid functional B3LYP without dispersion correction routinely gave the closest approximations to the crystal structure where the B3LYP/aug-cc-pVDZ combination afforded the best structure (r.m.s. deviation = 0.1314 Å). However, the B3LYP/6-31+G(d,p) level of theory represents the best compromise between accuracy (r.m.s. deviation = 0.1388 Å) and cost as it yielded appreciably accurate results in a fraction of the time compared to other method combinations.

Crystallographic and spectroscopic characterization of racemic Mosher's Acid.

The title compound, C10H9F3O3, represents the structure of racemic Mosher's Acid (systematic name: 3,3,3-tri-fluoro-2-meth-oxy-2-phenyl-propanoic acid), a carb-oxy-lic acid that when resolved can be employed as a chiral derivatizing agent. The compound contains a carb-oxy-lic acid group, a meth-oxy group and a tri-fluoro-methyl substituent on an asymmetric benzylic carbon atom. The two independent mol-ecules in the asymmetric unit form a non-centrosymmetric homochiral dimer via inter-molecularly hydrogen-bonded head-to-tail dimers with graph-set notation R 2 2(8) and donor-acceptor hydrogen-bonding distances of 2.6616 (13) and 2.6801 (13) Å.

Crystallographic and spectroscopic characterization of 3-chloro-5-fluoro-salicyl-aldehyde.

The title compound (systematic name: 3-chloro-5-fluoro-2-hy-droxy-benzaldehyde), C7H4ClFO2, is a dihalogenated salicyl-aldehyde derivative that has been studied for its anti-bacterial characteristics. The salicyl-aldehyde engages in intra-molecular hydrogen bonding with an O-H⋯O distance of 2.6231 (19) Šwhile the mol-ecules pack together via weak inter-molecular C-H⋯O, C-H⋯F and F⋯O inter-actions and offset face-to-face π-stacking.

Crystallographic and spectroscopic character-ization of 4-nitro-2-(tri-fluoro-meth-yl)benzoic acid and 4-nitro-3-(tri-fluoro-meth-yl)benzoic acid.

The title compounds, both C8H4F3NO4, represent two isomers of nitro tri-fluoro-methyl benzoic acid. The compounds each contain a nitro functionality para to the carb-oxy-lic acid group, with the tri-fluoro-methyl substituent ortho to the acid group in the 2-isomer and ortho to the nitro group in the 3-isomer. The regiochemistry with respect to the tri-fluoro-methyl group results in steric inter-actions that rotate the carb-oxy-lic acid group or the nitro group out of the aromatic plane in the 2- and 3-isomer, respectively. Each mol-ecule engages in inter-molecular hydrogen bonding, forming head-to-tail dimers with graph-set notation R 2 2(8) and donor-acceptor hydrogen-bonding distances of 2.7042 (14) Šin the 2-isomer and 2.6337 (16) in the 3-isomer. Recrystallization attempts did not yield untwinned crystals.

Synthesis and crystal structures of some bis(3-methyl-1H-indol-2-yl)(salicyl)methanes.

Four 2,2'-bisindolylmethanes (BIMs), a useful class of polyindolyl species joined to a central carbon, were synthesized using salicylaldehyde derivatives and simple acid catalysis; these are 2-[bis(3-methyl-1H-indol-2-yl)methyl]-6-methylphenol, (IIa), 2-[bis(3-methyl-1H-indol-2-yl)methyl]-4,6-dichlorophenol, (IIb), 2-[bis(3-methyl-1H-indol-2-yl)methyl]-4-nitrophenol, (IIc), and 2-[bis(3-methyl-1H-indol-2-yl)methyl]-4,6-di-tert-butylphenol, (IId). BIMs (IIa) and (IIb) were characterized crystallographically as the dimethyl sulfoxide (DMSO) disolvates, i.e. C26H24N2O·2C2H6OS and C25H20Cl2N2O·2C2H6OS, respectively. Both form strikingly similar one-dimensional hydrogen-bonding chain motifs with the DMSO solvent molecules. BIM (IIa) packs into double layers of chains whose orientations alternate every double layer, while (IIb) forms more simply packed chains along the a axis. BIM (IIa) has a remarkably long c axis.

Crystallographic and spectroscopic characterization of 5-chloro-pyridine-2,3-di-amine.

The two ortho-amino groups of the title compound, C5H6ClN3, twist out of the plane of the mol-ecule to minimize intra-molecular inter-action between the amino hydrogen atoms. In the crystal, the amino groups and the pyridine N atom engage in inter-molecular hydrogen bonding. The mol-ecules pack into spiral hydrogen-bonded columns with offset face-to-face π-stacking.

Electrochemical Reduction of CO2 Catalyzed by Re(pyridine-oxazoline)(CO)3Cl Complexes.

A series of rhenium tricarbonyl complexes coordinated by asymmetric diimine ligands containing a pyridine moiety bound to an oxazoline ring were synthesized, structurally and electrochemically characterized, and screened for CO2 reduction ability. The reported complexes are of the type Re(N-N)(CO)3Cl, with N-N = 2-(pyridin-2-yl)-4,5-dihydrooxazole (1), 5-methyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (2), and 5-phenyl-2-(pyridin-2-yl)-4,5-dihydrooxazole (3). The electrocatalytic reduction of CO2 by these complexes was observed in a variety of solvents and proceeds more quickly in acetonitrile than in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The analysis of the catalytic cycle for electrochemical CO2 reduction by 1 in acetonitrile using density functional theory (DFT) supports the C-O bond cleavage step being the rate-determining step (RDS) (ΔG⧧ = 27.2 kcal mol-1). The dependency of the turnover frequencies (TOFs) on the donor number (DN) of the solvent also supports that C-O bond cleavage is the rate-determining step. Moreover, the calculations using explicit solvent molecules indicate that the solvent dependence likely arises from a protonation-first mechanism. Unlike other complexes derived from fac-Re(bpy)(CO)3Cl (I; bpy = 2,2'-bipyridine), in which one of the pyridyl moieties in the bpy ligand is replaced by another imine, no catalytic enhancement occurs during the first reduction potential. Remarkably, catalysts 1 and 2 display relative turnover frequencies, (icat/ip)2, up to 7 times larger than that of I.

Crystal structure of a fluorescent C-shaped molecule containing closely stacked bithiophene-substituted quinoxaline rings.

Molecules with well-defined structures that feature closely stacked aromatic rings are important for understanding π-π interactions. A previously reported C-shaped molecule with bithiophene-substituted quinoxaline rings suspended from an aliphatic bridge that holds the aromatic rings in close proximity exists as a pair of syn and anti diastereomers. The anti isomer, namely (1α,2ß,4ß,5α,16α,17ß,19ß,20α)-1,5,16,20-tetrachloro-31,31,32,32-tetramethoxy-11,26-bis[5-(thiophen-2-yl)thiophen-2-yl]-7,14,22,29-tetraazanonacyclo[18.10.1.15,16.02,19.04,17.06,15.08,13.021,30.023,28]dotriaconta-6(15),7,9,11,13,21(30),22,24,26,28-decaene chloroform monosolvate, C48H36Cl4N4O4S4·CHCl3, whose X-ray structure is described herein, has cofacial quinoxaline rings with bithiophene rings attached on opposite sides. The molecular structure is approximately C-shaped and consists of an aliphatic spacer with a boat-shaped cyclohexane ring in the middle. The centroid-to-centroid distance between the quinoxaline rings is 3.950 (1) Å, with ring-offset distances of 0.354 (3) and 0.816 (2) Å. The pendant bithiophene rings are oriented parallel to one another, which results from the thiophene rings connected to the quinoxaline rings being oriented such that their S atoms are rotated inward toward one another, but are not overlapped. Intermolecular packing is largely governed by van der Waals forces and a few weak C-H...X (X = N or O) interactions.

Crystal structure of a rare trigonal bipyramidal titanium(IV) coordination complex: tri-chlorido-(3,3'-di-tert-butyl-2'-hy-droxy-5,5',6,6'-tetra-methyl-1,1'-biphenyl-2-olato-κO2)(tetra-hydro-furan-κO)-titanium(IV).

The title compound, [Ti(C24H33O2)Cl3(C4H8O)], is a rare example of a trigonal-bipyramidal titanium coordination complex with three chloride and two oxygen donor ligands. The asymmetric unit contains two independent mol-ecules having essentially the same conformation. The mol-ecules feature the titanium(IV) metal cation complexed with three chloride ligands, a tetra-hydro-furan mol-ecule, and one oxygen atom from the resolved ligand precursor (R)-(+)-5,5',6,6'-tetra-methyl-3,3'-di-t-butyl-1,1'-biphenyl-2,2'-diol, where the remaining phenolic hydrogen atom engages in inter-molecular O-H⋯Cl hydrogen bonding. In one mol-ecule, the THF ligand is disordered over two orientations with refined site occupancies of 0.50 (3).

Crystal structures of 6-chloro-indan-1-one and 6-bromo-indan-1-one exhibit different inter-molecular packing inter-actions.

The two title compounds are analogs of 1-indanone that are substituted at the 6-position with chlorine and bromine. Although very similar in mol-ecular structure, the crystal structures are not isomorphous and reveal that 6-chloro-indan-1-one, C9H7ClO (I), and 6-bromo-indan-1-one, C9H7BrO (II), exhibit unique inter-molecular packing motifs. The mol-ecules of the chloro analog (I) pack with a herringbone packing motif of C-H⋯O inter-actions, whereas the bromo derivative (II) packs with offset face-to-face π-stacking, C-H⋯O, C-H⋯Br and Br⋯O inter-actions. Compound (II) was refined as a two-component non-merohedral twin, BASF 0.0762 (5).

Crystallographic and spectroscopic characterization of (R)-O-acetyl-mandelic acid.

The title compound [systematic name: (R)-(-)-2-acet-oxy-2-phenyl-acetic acid], C10H10O4, is a resolved chiral ester derivative of mandelic acid. The compound contains an acetate group and a carb-oxy-lic acid group, which engage in inter-molecular hydrogen bonding, forming chains extending parallel to [001] with a short donor-acceptor hydrogen-bonding distance of 2.676 (2) Å.

The chemical biology of Cu(II) complexes with imidazole or thiazole containing ligands: Synthesis, crystal structures and comparative biological activity.

The synthesis and characterization of two copper(II) complexes containing 2-(2-pyridyl)benzimidazole (PyBIm) are reported with the biological activity of these two complexes and a third Cu(II) complex containing 2-(2-pyridyl)benzothiazole (PyBTh). Complex 1, [Cu(PyBIm)(NO3)(H2O)](NO3), is a four coordinate, distorted square planar species with one ligand (N,N), nitrate and water bound to Cu(II). The [Cu(PyBIm)3](BF4)2 complex (2) has distorted octahedral geometry with a 3:1 Py(BIm) ligand to metal ratio. The distorted trigonal bi-pyramidal geometry of compound 3, [Cu(PyBTh)2(H2O)](BF4)2, is comprised of two PyBTh ligands and one water. Biological activity of 1-3 has been assessed by analyzing DNA interaction, nuclease ability, cytotoxic activity and antibacterial properties. Complex 3 exhibits potent concentration dependent SC-DNA cleavage forming single- and double-nicked DNA in contrast to the weak activity of complexes 1 and 2. Mechanistic studies indicate that all complexes utilize an oxidative mechanism however 1 and 2 employ O2(-) as the principal reactive oxygen species while the highly active 3 utilizes (1)O2. The interaction between 1-3 and DNA was investigated using fluorescence emission spectroscopy and revealed all complexes strongly intercalate DNA with Kapp values of 2.65 × 10(6), 1.85 × 10(6) and 2.72 × 10(6)M(-1), respectively. Cytotoxic effects of 1-3 were examined using HeLa and K562 cells and show cell death in the micromolar range with the activity of 1 ≈ 2 and were slightly higher than 3. Similar reactivity was observed in the antibacterial studies with E. coli and S. aureus. A detailed comparative analysis of the three complexes is presented.