Browsing by Author "Mahmudov, Kamran T."
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- 1D Zn(II) coordination polymer of arylhydrazone of 5,5-dimethylcyclohexane-1,3-dione as a pre-catalyst for the Henry reactionPublication . Martins, Nuno M. R.; Mahmudov, Kamran T.; Silva, M. Fátima C. Guedes; Martins, Luisa; Guseinov, Firudin I.; Pombeiro, Armando J. L.Reaction of a new hydrazone of β-diketone, 5-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)isophthalic acid (H3L), with zinc(II) nitrate hexahydrate in a mixture of DMF and water (1:1) under hydrothermal conditions affords the 1D coordination polymer [Zn(μ3-HL)(H2O)2]n ∙ nH2O (1), where one of the carboxylic groups links two Zn(II) centers in a bridging bidentate (syn-syn-type) mode and the remaining one ligates a third metal cation in a monodentate fashion. It was characterized by IR and NMR spectroscopies, ESI-MS, elemental and single-crystal X-ray crystal structural analyses. 1 acts as an efficient pre-catalyst for the Henry reaction at 40 °C in aqueous medium, providing β-nitroalcohols with good yields (67–86%) and diastereoselectivities (syn:anti 77:23–69:31).
- Copper(II) and iron(III) complexes with arylhydrazone of ethyl 2-cyanoacetate or formazan ligands as catalysts for oxidation of alcoholsPublication . Martins, Nuno; Mahmudov, Kamran T.; Guedes Da Silva, M. Fátima C.; Martins, Luisa; Pombeiro, ArmandoThe aquasoluble [Cu(1 kappa N,O-2:2 kappa O-HL1)(S)](2) [S = CH3OH (1), (CH3)(2)NCHO (2)] and [Cu(kappa N-HL1)(en)(2)]center dot CH3OH center dot H2O (3) Cu-II complexes were prepared by the reaction of Cu-II nitrate hydrate with the new ligand (E/Z)-4-(2-(1-cyano-2-ethoxy-2-oxoethylidene)hydrazinyl)-3-hydroxybenzoic acid (H3L1), in the presence (for 3) or absence (for 1 and 2) of ethylenediamine (en), while the Fe-III complex [Fe(kappa N-3-HL2)(2)] (4) was isolated by treatment of iron(III) chloride hexahydrate with the new ligand (1E,1E)-N',2-di(1H-1,2,4-triazol-3-yl)diazenecarbohydrazonoyl cyanide (H3L2), and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. Cooperative E,Z -> E isomerization of H3L1, induced by coordination and ionic interactions, occurs upon interaction with Cu-II in the presence of en. Complexes 1-4 act as catalyst precursors for the solvent-free microwave (MW) assisted selective oxidation of primary or secondary alcohols and diols to the corresponding aldehydes, ketones and diketones, respectively, with yields in the 5-99% range (TONs up to 4.96 x 10(2)) after 60 min of MW irradiation at 120 degrees C. The influence of temperature, time and organic radicals was studied and also the regioselective oxidation of the catalytic systems involving the primary and secondary alcohols.
- New copper(II) tetramer with arylhydrazone of barbituric acid and its catalytic activity in the oxidation of cyclic C5–C8 alkanesPublication . Sutradhar, Manas; Alegria, Elisabete; Roy Barman, Tannistha; Guedes Da Silva, M. Fátima C.; Mahmudov, Kamran T.; Guseynov, Firuddin I.; Pombeiro, Armando2-(2-(2,4,6-Trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazinyl)terephthalic acid (H5L) was synthesized by azocoupling of diazonium salts of 2-aminoterephthalic acid with barbituric acid and characterized by IR, 1H and 13C NMR spectroscopies and ESI-MS analysis. In solution and solid state, H5L exists in the hydrazone form. The reaction of H5L with copper(II) nitrate hydrate in methanol affords the tetramer species [Cu2(μ2-1κNOO′:2κO′O″-H3L)2]2 (1) where carboxylate groups bridge two Cu(II) centers in a bridging chelate μ2-(O,O′,O′) fashion, giving rise to a cyclic Cu4O4 core. A rare and intense intermolecular non-covalent interaction of the type Ocarboxylic(lone pair)⋯π(pyrimidine), with O⋯centroid distance of 2.705 Å, was found in 1. In addition, medium intense N H⋯O and O H⋯O contacts expand the structure to a 3D network. Compound 1 behaves as efficient catalyst in the mild oxidation, by aqueous H2O2 in acidic MeCN/H2O media, of different cyclic C5–C8 alkanes to produce the corresponding alcohols and ketones. Overall product yields up to ca. 25% (based on alkane) were achieved.