Chlorfenapyr Crystal Polymorphism and Insecticidal Activity.

Four crystalline polymorphs of the proinsecticide chlorfenapyr [4-bromo-2-(4-chlorophenyl)-1-ethoxymethyl-5-trifluoromethyl-1H-pyrrole-3-carbonitrile] have been identified and characterized by polarized light optical microscopy, differential scanning calorimetry, Raman spectroscopy, X-ray diffraction, and electron diffraction. Three of the four structures were considered polytypic. Chlorfenapyr polymorphs show similar lethality against fruit flies (Drosophila melanogaster) and mosquitoes (Anopheles quadrimaculatus) with the least stable polymorph showing slightly higher lethality. Similar activities may be expected to be consistent with structural similarities. Knockdown kinetics, however, depend on an internal metabolic activating step, which further complicates polymorph-dependent bioavailability.

Development of a scalar-based geometric parameterization approach for the crystal structure landscape of dithienylethene-based crystalline solids.

Dithienylethenes (DTEs) are a promising class of organic photoswitches that can be used to create crystalline solids with properties controlled by light. However, the ability of DTEs to adopt multiple conformations, only one of which is photoactive, complicates the rational design of these materials. Herein, the synthesis and structural characterization of 19 crystalline solids containing a single DTE molecule are described. A novel D-D analysis of the molecular geometries obtained from rotational potential energy surface calculations and the ensemble of experimental structures were used to construct a crystal landscape for DTE. Of the 19 crystal structures, 17 contained photoinactive DTE rotamers and only 2 were photoactive. These results highlight the challenges associated with the design of these materials. Overall, the D-D analysis described herein provides rapid, effective and intuitive means of linking the molecular structure to photoactivity that could be applied more broadly to afford a general strategy for producing photoactive diarylethene-based crystalline solids.

Photocrystallography of [Ru(bpy)2(dmso)2]2+ reveals an O-bonded metastable state.

We report the first instance of observing the phototriggered isomerization of dmso ligands on a bis sulfoxide complex, [Ru(bpy)2(dmso)2], in the crystalline solid state. The solid-state UV-vis spectrum of the crystal demonstrates an increase in optical density around 550 nm after irradiation, which is consistent with the solution isomerization results. Digital images of the crystal before and after irradiation display a notable color change (pale orange to red) and cleavage occurs along planes, (1̄01) and (100), during irradiation. Single crystal X-ray diffraction data also confirms that isomerization is occurring throughout the lattice and a structure that contains a mix of the S,S and O,O/S,O isomer was attained from a crystal irradiated ex situ. In situ irradiation XRD studies reveal that the percentage of the O-bonded isomer increases as a function of 405 nm exposure time.

Enhancing the Stability of Nicotine via Crystallization Using Enantiopure Tartaric Acid Salt Formers.

Crystallization of nicotine, an oil prone to degradation at room temperature, has been demonstrated to be an effective means of creating nicotine-based materials with tunable thermal properties and improved resistance to photo-induced degradation. Herein, we show that both isomers of enantiomerically pure tartaric acid are highly effective salt formers when combined with nicotine. Both salts exhibit enhanced photostability, and with a melting point of 143.1 °C, the salt prepared using d-(-)-tartaric acid possesses one of the highest melting points for a crystalline nicotine solid reported to date.

Separation of diarylethene-based photoswitchable isomeric compounds by high-performance liquid chromatography and supercritical fluid chromatography.

Diarylethene-based photoswitches have become very popular over the last few decades for potential applications in chemistry, materials science, and biotechnology due to their unique physical and chemical properties. We report the isomeric separation of a diarylethene-based photoswitchable compound using high-performance liquid chromatography. The separated isomers were characterized by ultraviolet-visible spectroscopy and mass spectrometry confirmed the isomeric nature of the compounds. The isomers were purified by preparative high-performance liquid chromatography, providing fractionated samples to study the isomers individually. A total amount of 13 mg of an isomer of interest was fractionated from a solution of 0.4 mg/ml of the isomeric mixture. Because the preparative high-performance liquid chromatographic method required large quantities of solvent, we explored the use of supercritical fluid chromatography as an alternative separation mode which, to the best of our knowledge, is the first time this technique is used to separate diarylethene-based photoswitchable compounds. Supercritical fluid chromatography provided faster analysis times while maintaining sufficient baseline resolution for the separated compounds and consuming less organic solvent in the mobile phase compared to high-performance liquid chromatography. It is proposed that the supercritical fluid chromatographic method be upscaled and used in future fractionation of the diarylethene isomeric compounds, becoming a more environmentally benign approach for compound purification.

4,4'-(Ethene-1,2-diyl)dipyridinium bis(2-hy-droxy-3-meth-oxy-benzoate).

In the title double proton-transfer salt, C12H12N2 2+·2C8H7O4 -, consisting of a 1:2 ratio of 4,4'-(ethene-1,2-diyl)dipyridinium cations (trans bipyridinium ethyl-ene) to 2-hy-droxy-3-meth-oxy-benzoate anions (o-vanillate), the complete cation is generated by crystallographic inversion symmetry and it is linked to adjacent o-vanillate anions by N-H⋯O hydrogen bonds, forming trimolecular assemblies. The trimers are linked by C-H⋯O hydrogen bonds as well as aromatic π-π stacking inter-actions into a three-dimensional network. The anion features an intra-molecular O-H⋯O hydrogen bond.

1,2-Bis(pyridin-4-yl)ethene-4-hy-droxy-3-meth-oxy-benzoic acid (1/1).

In the title 1:1 co-crystal [alternatively called bi-pyridine ethyl-ene-p-vanillic acid (1/1)], C12H10N2·C8H8O4, the dihedral angle between the pyridine rings is 59.51 (5)°. In the crystal, the mol-ecules are linked by O-H⋯N hydrogen bonds, generating [401] chains of alternating C12H10N2 and C8H8O4 mol-ecules.

Enhancing the Photo and Thermal Stability of Nicotine through Crystal Engineering with Gentisic Acid.

The use of crystal engineering to convert liquids into crystalline solids remains a powerful method for inhibiting undesired degradation pathways. When nicotine, a liquid sensitive to both light and air, is combined with the GRAS-listed compound, gentisic acid, the resulting crystalline solid, exhibits enhanced photo and thermal stability. Despite a modest ΔTm of 42.7 °C, the melting point of 155.9 °C for the nicotinium gentisate salt is the highest reported for nicotine-containing crystalline solids. An analysis of the crystal packing and thermodynamic properties provides context for the observed properties.

Switching charge states in quasi-2D molecular conductors.

2D molecular entities build next-generation electronic devices, where abundant elements of organic molecules are attractive due to the modern synthetic and stimuli control through chemical, conformational, and electronic modifications in electronics. Despite its promising potential, the insufficient control over charge states and electronic stabilities must be overcome in molecular electronic devices. Here, we show the reversible switching of modulated charge states in an exfoliatable 2D-layered molecular conductor based on bis(ethylenedithio)tetrathiafulvalene molecular dimers. The multiple stimuli application of cooling rate, current, voltage, and laser irradiation in a concurrent manner facilitates the controllable manipulation of charge crystal, glass, liquid, and metal phases. The four orders of magnitude switching of electric resistance are triggered by stimuli-responsive charge distribution among molecular dimers. The tunable charge transport in 2D molecular conductors reveals the kinetic process of charge configurations under stimuli, promising to add electric functions in molecular circuitry.

Emerged Metallicity in Molecular Ferromagnetic Wires.

Supramolecular engineering bridges molecular assembly with macromolecular charge-transfer salts, promising the design to construct supramolecular architectures that integrate cooperative properties difficult or impossible to find in conventional lattices. Here, we report the crystal engineering design and kinetic growth of one-dimensional supramolecular wires composed of bis(ethylenedithio)tetrathiafulvalene (ET+) cation and polymeric Cu[N(CN)2]2- anion. A bulk ferromagnetic order is discovered for filling up the gap where strong ferromagnetism is missing in such ET molecule-based charge-transfer salts. Metallicity is induced by electric current from the semiconducting wire, which is attributed to strain effect by tuning its close molecular contact. This structural feature is evidenced through the combination of various mechanistic spectroscopic studies. Electric dipole is established from the close molecular contacts and is suggestive to stabilize ferromagnetic spin interaction through anions bridging spin sites. The breakthrough shown here provides a pathway to explore low-dimensional supramolecular materials exhibiting strong electron correlation, metallicity, and ferromagnetism.

N-[6-(Di-methyl-amino)-9-phenyl-3H-telluro-xan-then-3-yl-idene]-N-methyl-methanaminium hexa-fluoro-phosphate monoclinic polymorph.

The title compound C23H23N2Te+·PF6 -, is a monoclinic polymorph of the previously reported triclinic structure [Calitree et al. (2007 ▸). Organometallics, 26, 6248-6257]. In the crystal, parallel offset π-π stacking [shortest centroid-centroid separation = 3.9620 (9) Å] and ionic inter-actions help to establish the packing.

3',5'-Di-chloro-N,N-diphenyl-[1,1'-biphen-yl]-4-amine.

The title tri-phenyl-amine derivative, C24H17Cl2N, featuring a 3,5-di-chloro-1,1'-biphenyl moiety has been synthesized and structurally characterized. The mol-ecular structure shows rotations of the phenyl rings in the range of 37-40° from the amine plane. In the crystal, the mol-ecules inter-act by van der Waals inter-actions.

Determination of the dehydration pathway in a flexible metal-organic framework by dynamic in situ x-ray diffraction.

Understanding guest exchange processes in metal-organic frameworks is an important step toward the rational design of functional materials with tailor-made properties. The dehydration of the flexible metal-organic framework [Co(AIP)(bpy)0.5(H2O)]•2H2O was studied by novel in situ dynamic x-ray diffraction techniques. The complex mechanism of dehydration, along with the as-yet unreported metastable structures, was determined. The structural information obtained by the application of these techniques helps to elucidate the important guest-host interactions involved in shaping the structural landscape of the framework lattice and to highlight the importance of utilizing this technique in the characterization of functional framework materials.

Partial charge transfer in the salt co-crystal of l-ascorbic acid and 4,4'-bi-pyridine.

In the title 1:2 co-crystal, C10H9N2 +·(C6H7.75O6·C6H7.25O6)-, l-ascorbic acid (LAA) and 4,4'-bi-pyridine (BPy) co-crystallize in the chiral space group P21 with two mol-ecules of LAA, and one mol-ecule of bpy in the asymmetric unit. The structure was modeled in two parts due to possible proton transfer from LAA to the corresponding side of the bpy mol-ecule having an occupancy of approximately 0.25 and part 2 with an occupancy of approximately 0.75. In this structure, LAA forms hydrogen bonds with neighboring LAA mol-ecules, forming extended sheets of LAA mol-ecules which are bridged by bpy mol-ecules. A comparison to a related and previously published co-crystal of LAA and 3-bromo-4-pyridone is presented.

Fe(ii) and Co(ii) N-methylated CYCLEN complexes as paraSHIFT agents with large temperature dependent shifts.

Several complexes of Co(ii) or Fe(ii) with 1,4,7,10-tetraazacyclododecane (CYCLEN) appended with 1,7-(6-methyl)2-picolyl groups are studied as 1H NMR paraSHIFT agents (paramagnetic shift agents) for the registration of temperature. Two of the complexes, [Co(BMPC)]2+ and [Fe(BMPC)]2+, contain methyl groups only on the methyl picolyl pendents. Two other complexes, [Co(2MPC)]2+ and [Fe(2MPC)]2+, contain picolyl groups and also methyl groups on the macrocyclic amines. All macrocyclic complexes are in high spin form as shown by solution magnetic moments in the range of 5.0-5.9µBM and 5.3-5.8µBM for Co(ii) and Fe(ii) complexes, respectively. The 1H NMR spectra of both of the Fe(ii) complexes and one of the Co(ii) complexes are consistent with a predominant diastereomeric form in deuterium oxide solutions. The highly shifted methyl proton resonances for [Co(2MPC)]2+ appear at 164 and -113 ppm for macrocycle and pendent picolyl methyls and show temperature coefficients of -0.58 ppm °C-1 and 0.49 ppm °C-1, respectively. Fe(ii) complexes have less shifted methyl proton resonances and smaller temperature coefficients. The 1H resonances of [Fe(2MPC)]2+ appear at 105 ppm and -46 ppm with corresponding temperature coefficients (CT) of -0.29 ppm °C-1 and 0.22 ppm °C-1, respectively. The relatively narrow linewidths of [Fe(2MPC)]2+, however, produce superior CT/FWHM values of 0.44 and 0.31 °C-1 for the N-methyl and picolyl proton resonances where FWHM is the full width at half maximum of the 1H resonance. The crystal structure of [Co(BMPC)]Cl2 shows a six-coordinate Co(ii) bound to the macrocyclic amines and two pendent picolyl groups. The distorted trigonal prismatic geometry of the complex resembles that of an analogous complex containing four 6-methyl-2-picolyl groups, in which only two picolyl pendents are coordinated.

Hybrid organic-inorganic crystal structure of 4-(di-methyl-amino)-pyridinium di-methyl-ammonium tetra-chlorido-lead(II).

The title compound, (C2H8N)(C7H11N2)[PbCl4], is a hybrid organic-inorganic material. It crystallizes in the space group C2/c and contains one half of a mol-ecule of lead chloride, 4-(di-methyl-amino)-pyridinium, and di-methyl-ammonium in the asymmetric unit. The crystal structure exhibits chains of lead chloride capped by 4-(di-methyl-amino)-pyridinium and di-methyl-ammoium by hydrogen bonding. This creates a one-dimensional zipper-like structure down the a axis. The crystal structure is examined and compared to a similar structure containing lead chloride and di-methyl-benzene-1,4-diaminium.

Solvent exchange in a metal-organic framework single crystal monitored by dynamic in situ X-ray diffraction.

Understanding the processes by which porous solid-state materials adsorb and release guest molecules would represent a significant step towards developing rational design principles for functional porous materials. To elucidate the process of liquid exchange in these materials, dynamic in situ X-ray diffraction techniques have been developed which utilize liquid-phase chemical stimuli. Using these time-resolved diffraction techniques, the ethanol solvation process in a flexible metal-organic framework [Co(AIP)(bpy)0.5(H2O)]·2H2O was examined. The measurements provide important insight into the nature of the chemical transformation in this system including the presence of a previously unreported neat ethanol solvate structure.

Hydrogen-bonded co-crystal structure of benzoic acid and zwitterionic l-proline.

The title compound [systematic name: benzoic acid-pyrrolidin-1-ium-2-carboxyl-ate (1/1)], C7H6O2·C5H9NO2, is an example of the application of non-centrosymmetric co-crystallization for the growth of a crystal containing a typically centrosymmetric component in a chiral space group. It co-crystallizes in the space group P212121 and contains benzoic acid and l-proline in equal proportions. The crystal structure exhibits chains of l-proline zwitterions capped by benzoic acid mol-ecules which form a C(5)[R33(11)] hydrogen-bonded network along [100]. The crystal structure is examined and compared to that of a similar co-crystal containing l-proline zwitterions and 4-amino-benzoic acid.

Crystal structure of the co-crystal of 5-amino-isophthalic acid and 1,2-bis(pyridin-4-yl)ethene.

In the title 1:1 co-crystal, C12H10N2·C8H7NO4, the bi-pyridine moiety shows whole-mol-ecule disorder over two sets of sites in a 0.588 (3): 0.412 (3) ratio. In the crystal, the components form hydrogen-bonded sheets linked by N-H⋯O and O-H⋯N inter-actions, which stack along the a axis. A comparison to a related and previously published co-crystal of 5-amino-isophthalic acid and the shorter 4,4'-bipryidine is presented.