Crystal structure of a mixture of lupeol-acetate tautomers isolated from Hieracium plumulosum A. Kerner, Asteraceae

Transparent single crystals obtained from the purified extract of the plant Hieracium plumulosum A. Kerner, Asteraceae were submitted to spectroscopic and X-ray studies. The spectroscopic (infra-red, mass spectrometry, 1 H and 13 C nuclear magnetic resonance) investigations suggested the presence of two isomers of lupeol acetate (C 32 H 52 O2) with tautomeric relationship. Their mixture crystallizes in the monoclinic system with space group P2 1 : a = 19.170(2) Å, b = 8.128(1) Å, c = 21.832(2) Å, β = 90.24(1)°, V = 3401.7(6) Å, Z = 4 (two molecules in the asymmetric unit), D(x) = 1.095 g cm -3 , μ(CuKα) = 0.488 mm -1 . The structure was solved by direct methods and refined to a final R = 0.071 for 6636 reflections with I > 2o(I). The bond lengths around C20/(C60) are between single and double bonds indicating the superposition of the tautomers, i.e., lup-20(29)-en-3β-ol and lup-19(20)-en-3β-ol acetates. They are distributed with different ratio in the symmetry-independent positions. In addition, the difference maps revealed that toluene solvent molecules are also captured in the lattice. They substantially hindered the refinement of atomic positions in particular for the C19/(C59) functions

Reaction of copper(II) with 1-carboxamide-3,5-dimethylpyrazole, 1-carboxamidine-3,5-dimethylpyrazole, 4-acetyl-3-amino-5-methylpyrazole and 5-amino-4-carboxamide-1-phenylpyrazole

International audienceComplex formation of copper(II) bromide and acetate with 1-carboxamide-3,5-dimethylpyrazole (HL3) and copper(II) bromide with 5-amino-4-carboxamide-1-phenylpyrazole (L2), 4-acetyl-3-amino-5-methylpyrazole (HL4) and 1-carboxamidine-3,5-dimethylpyrazole (HL5), was studied. The obtained compounds, CuBr2(L2)2, Cu(L 3)2, CuBr2(HL4)2, CuBr2(HL5)2 and [CuBr(HL1)(L 3)]2 (HL1 denotes the 3,5-dimethylpyrazole), are characterized by elemental analysis, FT-IR spectrometry, molar conductivity, TG-MS and DSC. The X-ray structure of [CuBr(HL1)(L 3)]2 and Cu(L3)2 is discussed. For [CuBr(HL1)(L3)]2 a dimeric penta-co-ordinated structure has been found; the co-ordination around the metal in Cu(L 3)2 is trans-square planar. To CuBr2(L 2)2 and CuBr2(HL4)2 a nearly tetrahedral, while for CuBr2(HL5)2 an octahedral geometry may be assumed. It means that the geometry of the compounds in the first place depends on the ligand substituents. The course of the complex formation reaction is anion-dependent and may be explained on the basis of Pearson's theory, taking into account the steric factors. A low stability intermediate formation was observed in the thermal decomposition of Cu(L 3)2