CCDC no.: 1447423The crystal structure is shown in the gure. Tables 1-3 contain details of the measurement method and a list of the atoms including atomic coordinates and displacement parameters. Source of materialUnder atmospheric conditions, NbCl5 (0.27 g, 1 mmol) was dissolved in acetonitrile (10 mL), and treated with tetraethylammonium chloride (0.165 g, 1 mmol). The mixture was re uxed overnight at 90-100°C and the solvent was removed under vacuum. (0.2604 g, 1.68 mmol) at room temperature. The resulting mixture was stirred for 4 h, and then the volatile material was removed in vacuo. The resulting residue was washed with diethyl ether (2 × 10 mL), giving a grey solid and the solution was left to stand at 255 K for a few days after which red crystals were obtained. Atom Site Experimental detailsThe H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H = 0.98 Å and Uiso(H) = 1.2Ueq(C), respectively. The highest peak (2.37 e. Å −3 ) is located 1.07 Å from O4 and the deepest hole (−0.65 e. Å −3 ) is situated 0.69 Å from Nb1. DiscussionThe ammonium salt of N-nitroso-N-phenylhydroxylamine, is a well-known analytical reagent (cupferron) and it was very popular especially for analytical separations [1, 2]. The chelate-forming derivatives of this ligand is known to form stable complexes with various metals, but only few of them have been structurally characterized [3][4][5][6][7][8][9][10][11][12]. Also some cupferrates were investigated in our group [13][14][15][16][17][18]. This study forms part of ongoing research to investigate the mechanism of the reactions of O,O′-and N,O-bidentate ligands with transition metals used in nuclear industry, such as Hf, Zr, Nb,.In the title structure the Nb atom is heptacoordinated by six oxygen atoms, of three bidentate cupferron ligands and an oxido group. The cupferrate ligand forms a ve-membered ring with a small bite angle (see the gure). The Nb-O distances are between 1.7107 (5) and 2.2267 (7) Å, and the O-Nb-O angles vary between 68.36(2)°and 158.51(2)°. All the bond distances and angles are similar to other relevant niobium(V) structures [27,28].Acknowledgements: Financial assistance from the faculty
C 42 H 32 Cl 2 O 6 P 2 , P1 (no. 2), a = 8.4669(12) Å, b = 9.7245(14) Å, c = 12.2425(17) Å, α = 69.887(6)°, β = 77.758(6)°, γ = 74.915(6)°, CCDC no.: 1527330A part of the title crystal structure is shown in the figure. Tables 1 and 2 contain details on the crystal structure and measurement conditions and a list of the atoms including atomic coordinates and displacement parameters. Source of materialTriphenylphosphineoxide, Ph 3 PO (0.10 g, 0.359 mmol) was dissolved in acetonitrile (5 mL), and treated with 2,5-dichloro-3,6-dihydroxy-2,5-cyclohexadiene-1,4-dione, H 2 CA (0.08 g, 0.359 mmol) at room temperature. The resulting mixture was stirred for 6 h, and then the volatile material was removed in vacuo. The resulting reddish was washed with diethyl ether (2 × 10 mL), and dried in vacuo. The product was dissolved in acetonitrile/methanol (4:1) and the solution was left to stand at 255 K for a few days after which orange plate crystals were obtained. IR(ATR): ν PO = 979(vs) and 1118 (m) cm −1 .
The close chemical similarity of niobium(V) and tantalum(V), only slightly less studied than that of group (IV) and other transition metals, including its sensitivity to trace of moisture, and ease of oxidation causes it being difficult to handle and store. They also exhibit hard metal centres and display similar chemistry [1]. The study of this group 5 metals and their behaviour towards different ligands, which include mono-(halido and pseudo halido) and bidentate hard ligands with O,O'-and N,O-donor atoms are being investigated in our group [2]. Specific bidentate ligands included cupferrate, hopo, mpo, and H2CA (where hopoH = 2-hydroxypyridine-N-oxide, mpoH = 2-mercaptoypyridine-N-oxide, dcbqH2 = 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone and cupferron is N-phenyl-N-nitrosohydroxylamine) are good ligands for hard transition metal centres and form stable complexes. In this presentation, different synthetic procedures and characterization methods for these complexes will be discussed [3]. The compounds that were synthesised include [NbO(cupf)and cis-[NbO2(dcbqH2)2(POPh3)], which have been characterised by IR, NMR, UV/Vis and X-ray diffraction. All these mentioned ligands form a five-membered ring with a small bite angle when coordinated to the M(V) metal centre as compared with previously reported six-membered rings. Different structures and the comparative bonds and packing characteristics in the above, as well as other related compounds, will be discussed in this presentation(see Figure A and B).
Chloranilic acid (2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone, caH2) as a bidentate ligand for Nb(V) as a metal center is presented. The different coordination behavior of caH2 is well illustrated by a monomeric (Et4N)cis-[NbO(ca)2(H2O)OPPh3]·3H2O.THF (5) and a novel tetranuclear compound (Et4N)4[Nb4O4(ca)2(μ2-O)2Cl8]·2CH3CN (6) via self-assembly, respectively. These were obtained in > 80% yields and characterized by IR, UV/Vis and NMR (1H, 13C{1H}, 31P{1H}) spectroscopy and single crystal X-ray diffraction, and they included a systematic assessment of the solid-state behavior. The anionic metal complexes showed different coordination modes at the Nb(V): [Nb4O4(ca)2(μ2-O)2Cl8]4− (6a; distorted octahedral) and cis-[NbO(ca)2(H2O)(OPPh3)]− (5a; D5h distorted pentagonal bipyramidal), respectively. The tetranuclear complex 6a is substitution inert, while cis-[NbO(ca)2(H2O)OPPh3]− (5a) allowed a systematic ligation kinetic evaluation. The substitution of the coordinated triphenylphosphine oxide by a range of pyridine-type entering nucleophiles, 4-N,N-dimethyl-aminopyridine (DMAP), pyridine (py), 4-methylpyridine (4Mepy), 3-chloropyridine (3Clpy) and 3-bromopyridine (3Brpy) in acetonitrile at 31.2 °C was carefully evaluated. The subtle interplay between the main group ligand systems and the hard, early transition metal Nb(V) complex (5a) was well illustrated. The entering monodentate ligands showed a 15-fold reactivity range increase in the order 3Brpy < 3Clpy < 4Mepy < py < DMAP in broad agreement with the Brønsted-donating ability of the nucleophiles. The activation parameters determined for the reaction of 5a with DMAP as the entering ligand yielded ΔH≠kf = 52 ± 1 kJ mol−1 and ΔS≠kf = −108 ± 3 J K−1 mol−1 for the enthalpy and entropy of activation, respectively, indicating an associative substitution mechanism. The study presents an important contribution to the structure/reactivity relationships in Nb(V) complexes stabilized by chloranilic acid as a bidentate ligand.
Injera is Ethiopian ethnic traditional staple food, made from teff and other crops. The country’s superfoods are highly regarded in many Western countries for their excellent nutritional properties (‘very low gluten’), and mineral composition. Injera provides sufficient conditions for fungi to grow and ruin injera by changing the texture and making it inedible. This study aimed to develop an evaporative cooler clay chamber (ECCC) used to extend the shelf life of injera by controlling temperature and relative humidity (RH). This system is an economical and efficient way to lower the temperature and increase RH. The results show the maximum daily ambient temperature reduced from 28.98 °C to 22.90 °C and increased the RH of the storage chamber from 28.78% to 80.94%, respectively. The temperature drops up to 6.08 °C, and the RH rises to 52.16% observed. Additionally, the effects of temperature, RH and potential of hydrogen were studied for identified rotten injera and designed for injera storage. ECCC can store freshly made injera for 9 days before any visible mould stains appear, significantly reducing weight loss with an average cooling efficiency of 79.31%. Therefore, this study might help to develop low-cost cold storage for injera preservation at farms end in Ethiopia.
The structure of the title compound, 4-(dimethylamino)pyridin-1-ium-2,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,4-bis(olate) 4-dimethylaminopyridine water undeca-solvate, C57H87Cl5N12O21, obtained from interaction between chloranilic acid (caH2), and dimethyl aminopyridine (DMAP) has been determined by single crystal X-ray diffraction. The title compound, (DMAPH)5(ca)2.5·(DMAP)·11H2O, crystallized in the triclinic crystal system with space group, P (no. 2), a = 13.3824(15) Å, b = 13.4515(17) Å, c = 19.048(2) Å, α = 86.014(4)°, β = 88.821(4)°, γ = 86.367(4)°, V = 3413.3(7) Å3, Z = 2, T = 100(2) K, μ(MoKα) = 0.294 mm-1, Dcalc = 1.414 g/cm3, 59413 reflections measured (3.76° ≤ 2Θ ≤ 56°), 16405 unique (Rint = 0.0517, Rsigma = 0.0589) which were used in all calculations. The final R1 was 0.0460 (I ≥ 2σ(I)) and wR2 was 0.1271 (all data). Using supramolecular chemistry principles, proton donors (chloranilic acid) and acceptor (DMAP) were combined to generate a multicomponent hydrogen-bonded system. Due to the presence of protonated bases (DMAPH+), the dominant interactions are the N+-H···O hydrogen bonds, whereas the negative charges of an acceptor from the chloranilate dianion (ca2-) are delocalized. Additionally, three sets of water clusters in the title compound were identified, namely a cyclic pentamer, a linear, and an acute-shaped trimer water cluster. It was further observed that strong hydrogen bond interactions occurred between the solvated aqua molecule(s) acting as a proton donor and the neutral DMAP acting as a proton acceptor. The crystal packing is further stabilized by O-H···Cl and C-H···Cl weak halogen interactions. The lattice metric strength is further held by observed π-π stacking interactions (centroid-centroid) with inter centroid distances between sets of the DMAPH rings of 3.624(3), 3.642(4), 3.739(3), 3.863(3) and 3.898(3) Å, respectively.
As you know the current population of Africa is 1,374,451,375 as of Monday, July 26, 2021, based on the latest United Nations estimates. Africa population is equivalent to 16.72% of the total world population. Africa ranks number two among regions of the world (roughly equivalent to "continents"), ordered by population. With over 110 million inhabitants, Ethiopia is one of the most populous landlocked countries in the world, as well as the second-most populous nation on the African continent after Nigeria.
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