Intermolecular Interactions between Encapsulated Aromatic Compounds and the Host Framework of a Crystalline Sponge

The crystalline sponge [{(ZnI2)3(tris(4-pyridyl)-1,3,5-triazine)2·x(solvent)}n] has been used to produce a range of novel encapsulation compounds with acetophene, trans-cinnamaldehyde, naphthalene, anthracene, and benzylcyanide. Using additional data from previously reported encapsulation compounds, three systematic series have been created and analyzed to investigate the behavior of guest molecules within the sponge framework and identify the dominant intermolecular interactions

Applying the Crystalline Sponge Method to Agrochemicals: Obtaining X-ray Structures of the Fungicide Metalaxyl-M and Herbicide S-Metolachlor

The crystalline sponge method is a technique that provides the ability to elucidate the absolute structure of noncrystalline or hard to crystallize compounds through single-crystal X-ray diffraction by removing the need to obtain crystals of the target compound. In this study the crystalline sponges {[(ZnX_{2})_{3}(2,4,6-tris(4-pyridyl)-1,3,5-trazine)_{2}].x(solvent)}n (X = I, Br) were used to obtain X-ray structures of the agrochemical active ingredients metalaxyl-M and S-metolachlor. The effect of the temperature used during guest uptake and the influence of changing the host framework ZnX_{2} nodes on guest encapsulation were investigated. Additionally, three compounds containing chemical fragments similar to those of metalaxyl-M and S-metolachlor (phenylacetaldehyde, N-ethyl-o-toluidine, and methyl phenylacetate) were also encapsulated. This allowed for the effect of guest size on the position that guests occupy within the host frameworks to be examined. The disorder experienced by the guest compounds was documented, and an analysis of the intermolecular host–guest interactions (CH···π and π ···π) used for guest ordering within the host frameworks was also undertaken in this study

One-step protecting-group-free synthesis of azepinomycin in water

We report an efficient, atom economical general acid-base catalyzed one-step multi-gram synthesis of azepinomycin from commercially available compounds in water. We propose that the described pH-dependent Amadori rearrangement, which couples an amino-imidazole and simple sugar, is of importance as a potential step toward predisposed purine nucleotide synthesis at the origins of life

Are oxygen and sulfur atoms structurally equivalent in organic crystals?

New guidelines for the design of structurally equivalent molecular crystals were derived from structural analyses of new cocrystals and polymorphs of saccharin and thiosaccharin, aided by a computational study. The study shows that isostructural crystals may be obtained through an exchange of >C?O with >C?S in the molecular components of the solids, but only if the exchanged atom is not involved in hydrogen bonding

Photophysics of a mono-nuclear tetrahedral silver(I)N4 core and its copper(I) analog

A neutral ligand L is prepared by condensation of benzil dihydrazone and acetone in 1:2 mol ratio and used for the syntheses of [CuL2]ClO4, [CuL2]PF6, [AgL2]ClO4 and [AgL2]PF6. The X-ray crystal structures of L and the two perchlorate salts have been determined. The metal complexes are found to be mononuclear containing tetrahedral N4 coordination spheres for Cu(I) and Ag(I). Cyclic voltammetrically, the Cu(II/I) and Ag(II/I) potentials are 1.23 and 0.76 V vs NHE respectively in CH2Cl2 at a Pt electrode. The reason for the such a low Ag(II/I) potential is that the silver(I) complex is adsorbed on the electrode surface with a free energy of adsorption of ∼ −14.99 kcal mol−1. DFT calculations at the BP86/LanL2DZ level show that the HOMO’s in [CuL2]ClO4 and [AgL2]ClO4 are both metal based and the LUMO’s have no contribution from the metals. Both complexes show weak emissions from the MLCT states upon excitation at 270 nm in ethanol solution at room temperature. Changing the counterion to PF6− leads to higher quantum yields for these processes. It is consistent with the general observation that ClO4− being more coordinating than PF6−, it binds the metals in the MLCT state to form exciplexes leading to a lower ϕ or total quenching. At 77 K in ethanol glass, L, [CuL2]+ and [AgL2]+ show ligand centered (LC) emissions. Thus the MLCT and LC states are thermally equilibrated in the silver(I) and copper(I) complexes. In keeping with this, a mixture of the two processes, MLCT and LC emissions, is observed at room temperature for [AgL2]ClO4 and [CuL2]ClO4 when they are incorporated in a rigid polymethyl methacrylate matrix

Stereoselective synthesis of 1,2-diamine containing indolines by a conjugate addition nitro-Mannich reaction.

A conjugate addition nitro-Mannich reaction followed by nitro reduction and intramolecular N-arylation gives diastereomerically pure substituted 1,2-diamine containing indolines. Placing the N-arylation cyclisation handle on the imine precursor derived from an ortho-bromine substituted aromatic aldehyde gave the corresponding β-nitroamines in 55-72% yields as single diastereoisomers. Nitro reduction was effected with modified quantities of Zn/HCl and a subsequent Pd(0) catalysed Buchwald Hartwig cyclisation gave indoline products in 40-70% yields as single diastereoisomers

Nutritional and environmental regulation of the synthesis of highly unsaturated fatty acids and of fatty-acid oxidation in Atlantic salmon (Salmo salar L.) enterocytes and hepatocytes

The aim was to determine if highly unsaturated fatty acid (HUFA) synthesis and fatty acid oxidation in Atlantic salmon (Salmo salar L.) intestine was under environmental and/or seasonal regulation. Triplicate groups of salmon were grown through a full two-year cycle on two diets containing either fish oil (FO), or a diet with 75% of the FO replaced by a vegetable oil (VO) blend containing rapeseed, palm and linseed oils. At key points in the life cycle, fatty acyl desaturation/elongation (HUFA synthesis) and oxidation activities were determined in enterocytes and hepatocytes using [1-14C]18:3n-3 as substrate. As observed previously, HUFA synthesis in hepatocytes showed peak activity at seawater transfer and declined thereafter, with activity consistently greater in fish fed the VO diet. In fish fed FO, HUFA synthesis in enterocytes in the freshwater stage was at a similar level to that in hepatocytes. However, HUFA synthesis in enterocytes increased rapidly after seawater transfer and remained high for some months after transfer before decreasing to levels that were again similar to those observed in hepatocytes. Generally, enterocyte HUFA synthesis was higher in fish fed the VO diet compared to the FO diet. Oxidation of [1-14C]18:3n-3 in hepatocytes from fish fed FO tended to decrease during the freshwater phase but then increased steeply, peaking just after transfer before decreasing during the remaining seawater phase. At the peak in oxidation activity around seawater transfer, activity was significantly lower in fish fed VO compared to fish fed FO. In enterocytes, oxidation of [1-14C]18:3 in fish fed FO showed a peak in activity just prior to seawater transfer. In fish fed VO, other than high activity at 9 months, the pattern was similar to that obtained in enterocytes from fish fed FO with a high activity around seawater transfer and declining activity in seawater. In conclusion, fatty acid metabolism in intestinal cells appeared to be under dual nutritional and environmental or seasonal regulation. The temporal patterns for fatty acid oxidation were generally similar in the two cell types, but HUFA synthesis in enterocytes peaked over the summer seawater phase rather than at transfer, as with hepatocytes, suggesting possibly different regulatory cues

Synthesis and molecular properties of the 52-electron triiron telluride clusters [Fe3(CO)8(u-Te)2(k2-diphosphine)] - Electrochemical properties and activity as proton reduction catalysts

Heating the 50-electron cluster [Fe3(CO)9 (μ3-Te)2] (1) with the diphosphines Ph2P-R-PPh2 [R = -CH2CH2 (dppe), Z-CH=CH (dppv), 1,2-C6H4 (dppb), -CH2CH2CH2 (dpp), ferrocenyl (dppf), naphthalenyl (dppbn)] in benzene affords the 52-electron diphosphine-containing tellurium-capped triiron clusters [Fe3(CO)8 (μ3-Te)2 (κ2-diphosphine)] (diphosphine = dppe, dppv, dppb, dpp, dppf, dppnd) (2–7) in moderate yields, resulting from both phosphine addition and carbonyl loss. With 1,2-bis(diphenylphosphino) benzene (dppb) a second product is the cubane cluster [Fe4(CO)10 (μ3-Te)4 (κ2-dppb)] (8). Cyclic voltammetry measurements on 2–7 reveals that all clusters show irreversible reductive behaviour at ca. −1.85 V with a series of associated small back oxidation waves, suggesting that reduction leads to significant structural change but that this can be reversed chemically. Oxidation occurs at relatively low potentials and is diphosphine-dependent. The first oxidation appears at ca. +0.35 V for 2–6 with a small degree of reversibility but is as low as +0.14 V for the bis(diphenylphosphino)naphthalene derivative 7 and in some cases is followed by further closely-spaced oxidation. Addition of [Cp2Fe][PF6] to 2–7 results in the formation of new clusters formulated as [Fe3(CO)8 (μ3-Te)2 (κ2-diphosphine)]+, with their IR spectra suggesting oxidation at the diiron centre. This is supported by computational studies (DFT) of the bis(diphenylphosphino)propane cluster 5 showing that the HOMO is the FeFe σ-bonding orbital, while the LUMO is centered on the diphosphine-substituted iron atom and has significant FeTe σ∗-anti-bonding character consistent with the irreversible nature of the reduction. Complexes 2–7 have been examined as proton reduction catalysts in the presence of para-toluenesulfonic acid (TsOH). All are active at their first reduction potential, with a second catalytic process being observed at slightly higher potentials. While their overall electrocatalytic behaviour is similar to that noted for the [Fe2(CO)6{μ-E (CH2)3E}] (E = S, Se, Te), the DFT results suggest that as the added electron is localised on the unique iron atom, the mechanistic aspects of hydrogen formation are likely to be quite different from the more widely studied diiron models

Reaction of electron-deficient 6-methoxyquinolinate-substituted cluster [Os3(CO)9{μ3-η1,κ1-C9H5N(6-OMe)}(μ-H)] with PPh3: Thermally induced ligand isomerization, decarbonylation and orthometallation

The reaction of the electron-deficient 6-methoxyquinolinate-substituted triosmium cluster [Os3(CO)9{μ3-η1,κ1-C9H5N(6-OMe)}(μ-H)] (1) with PPh3 proceeds readily at room temperature to afford the electron-precise adduct [Os3(CO)9(PPh3){μ-η1,κ1-C9H5N(6-OMe)}(μ-H)] (2), in which the PPh3 ligand is bound to the osmium that serves as the coordination site for the hydride and the metallated-carbon atom of the benzoheterocycle. This reaction also leads to a change in the hapticity of the 6-methoxyquinolinate ligand from μ3-η1,κ1 to μ-η1,κ1 as confirmed by X-ray crystallography. Thermolysis of 2 in boiling toluene furnishes five new triosmium clusters (3–7) as a result of ligand isomerization, decarbonylation and orthometallation of the ancillary PPh3 ligand. Clusters 3 and 4 are isomers of 2 and the location of the metal-bound hydride and PPh3 with respect to 6-methoxyquinolinate moiety is the only difference between these isomers. Control experiments show that 5 is a decarbonylation product of 4 which converts into 6 as a result of further decarbonylation with concomitant orthometallation of one of the phenyl rings of the coordinated PPh3 ligand, whilst 7 is formed from 6 through replacement of an equatorial carbonyl of the nitrogen-bound osmium by PPh3 ligand. All the new clusters have been characterized by a combination of analytical and spectroscopic methods as well as by X-ray crystallography in the case of 2, 3, 6 and 7

Investigation on the reactivity of tetranuclear Group 7/8 mixed-metal clusters toward triphenylphosphine

Reactions of the tetranuclear mixed-metal clusters ReM3(CO)13(µ3-thpymS) (1, M = Os; 2, M = Ru; thpymSH = tetrahydropyrimidine-2-thiol) with PPh3 are examined. At room temperature reaction between 1 and PPh3 in the presence Me3NO leads to the formation of mono- and bis-phosphine substituted clusters ReOs3(CO)12(PPh3)(µ3-thpymS) (3) and ReOs3(CO)11(PPh3)2(µ3-thpymS) (4). Cluster 3 also reacts with PPh3 under similar conditions to give 4. In contrast, a similar reaction between 2 and PPh3 furnishes only the mono-phosphine substituted clusters ReRu3(CO)12(PPh3)(µ3-thpymS) (3). All the new clusters have been characterized by analytical and spectroscopic data together with single crystal X-ray diffraction for 1, 3 and 5