A catalyst don’t appear in the overall stoichiometry of the reaction it catalyzes, Category: Pyrazines, but it must appear in at least one of the elementary reactions in the mechanism for the catalyzed reaction. 14508-49-7, Name is 2-Chloropyrazine, molecular formula is C4H3ClN2. In an article, author is Luo, Lan,once mentioned of 14508-49-7.
Rare example of chiral and achiral polymorphs of a metal-oxide/organic hybrid compound
Hydrothermal techniques have been used to prepare two new Cu(I)/Mo(VI)-oxide hybrids that represent a rare example of crystallization of both achiral (1) and chiral (2) polymorphic structures with the composition CuMoO3 (p2c) (p2c = pyrazine-2-carboxylate). Their structures were characterized by single-crystal X-ray diffraction (1 – space group: P2(1)/c, Z = 4; a = 8.4965(3) angstrom, b = 12.7471(5) angstrom, c = 7.2850(3) angstrom), beta= 97.147(2)degrees , and 2 – P3(2), Z = 3, a = 7.6789(2) angstrom, c = 10.9164(5) angstrom) and found to consist of highly-distorted MoO5N octahedra that are vertex-bridged to form -O-Mo-O-Mo-O- chains and connected to each other via the coordinating p2c ligands and Cu(I) cations. In the achiral structure of 1, the p2c ligands and Cu(I) cations are coordinated to a single side of the extended -O-Mo-O-Mo-O- chains. In the chiral structure of 2, by contrast, these coordinate via a helical-type arrangement down the 3(2) screw axis with a rotation of 120 degrees between neighboring octahedra. The chiral polymorph is favored with higher pressure and exhibits a correspondingly higher density owing to the greater packing efficiency of the helical chains, with calculated densities (g cm(-3)) of 2.81 and 2.95 for 1 and 2, respectively. Both are found to have nearly identical band gaps of similar to 1.37 eV, which are significantly smaller than in other related Cu/Mo oxides . Density functional theory calculations show that 1 exhibits a slightly lower energy of similar to 89 meV per formula (or similar to 8.6 kJ mol(-1)) as compared to 2 and is thus energetically favored. Given the higher calculated energy of the chiral polymorph, 2, this suggests that the application of higher pressures can provide a convenient driving force for the crystallization of higher-density, helical-chain structures that are noncentrosymmetric.
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