syntheses-crystallization-spectroscopic-characterization-35-lutidine

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine <em>N</em>-Oxide Dehydrate

The synthesis of 3,5-lutidine N-oxide dehydrate, 1, was achieved in the synthesis route of 2-amino-pyridine-3,5-dicarboxylic acid. Ochiai first used the ...

Benemérita Universidad Autónoma de Puebla

A natural single crystal of the ferrimagnetic oxide FeCrO3, which was found in an opencast mine situated in the San Luis Potosí State in Mexico, has been characterized in order to elucidate some outstanding issues about the actual structure of this material. The single-crystal X-ray analysis unambiguously shows that transition metal cations are segregated in alternating layers normal to the threefold crystallographic axis, affording a structure isomorphous to that of ilmenite (FeTiO3), in the space group R3̅. The possible occurrence of cation antisite and vacancy defects is below the limit of detection available from X-ray data. Structural and magnetic results are in agreement with the coherent slow intergrowth of magnetic phases provided by the two antiferromagnetic corundum-type parent oxides Fe2O3 (hematite) and Cr2O3 (eskolaite). Our results are consistent with the most recent density functional theory (DFT) studies carried out on digital FeCrO3 [Sadat Nabi & Pentcheva (2011). Phys. Rev. B, 83, 214424], and suggest that synthetic samples of FeCrO3 might present a cation distribution different to that of the ilmenite structural type.

At last! The single-crystal X-ray structure of a naturally occurring sample of the ilmenite-type oxide FeCrO3.

The spectroscopic and kinetic characterization of two intermediates from the H₂O₂ oxidation of three dimethyl ester [(proto), (meso), (deuteroporphyrinato) (picdien)]Fe(III) complexes ([FePPPic], [FeMPPic] and [FeDPPic], respectively) pinch-porphyrin peroxidase enzyme models, with s = 5/2 and 3/2 Fe(III) quantum mixed spin (qms) ground states is described herein. The kinetic study by UV/Vis at λmax = 465 nm showed two different types of kinetics during the oxidation process in the guaiacol test for peroxidases (1-3 + guaiacol + H₂O₂ → oxidation guaiacol products). The first intermediate was observed during the first 24 s of the reaction. When the reaction conditions were changed to higher concentration of pinch-porphyrins and hydrogen peroxide only one type of kinetics was observed. Next, the reaction was performed only between pinch-porphyrins-Fe(III) and H₂O₂, resulting in only two types of kinetics that were developed during the first 0-4 s. After this time a self-oxidation process was observed. Our hypotheses state that the formation of the π-cation radicals, reaction intermediates of the pinch-porphyrin-Fe(III) family with the ligand picdien [N,N'-bis-pyridin-2-ylmethyl-propane-1,3-diamine], occurred with unique kinetics that are different from the overall process and was involved in the oxidation pathway. UV-Vis, ¹H-NMR and ESR spectra confirmed the formation of such intermediates. The results in this paper highlight the link between different spectroscopic techniques that positively depict the kinetic traits of artificial compounds with enzyme-like activity. 

Spectroscopic and Kinetic Characterization of Peroxidase-Like π-Cation Radical Pinch-Porphyrin-Iron(III) Reaction Intermediate Models of Peroxidase Enzymes.

The here crystallized oxamide was previously characterized as an unsolvated species [Jímenez-Pérez et al. (2000 ▸). J. Organomet. Chem. 614-615, 283-293], and is now reported with methanol as a solvent of crystallization, C30H44N2O4·CH3OH, in a different space group. The introduction of the solvent influences neither the mol-ecular symmetry of the oxamide, which remains centrosymmetric, nor the mol-ecular conformation. However, the unsolvated mol-ecule crystallized as an ordered system, while many parts of the solvated crystal are disordered. The hy-droxy group in the oxamide is disordered over two chemically equivalent positions, with occupancies 0.696 (4):0.304 (4); one tert-butyl group is disordered by rotation about the C-C bond, and was modelled with three sites for each methyl group, each one with occupancy 1/3. Finally, the methanol solvent, which lies on a twofold axis, is disordered by symmetry. The disorder affecting hy-droxy groups and the solvent of crystallization allows the formation of numerous supra-molecular motifs using four hydrogen bonds, with N-H and O-H groups as donors and the oxamide and methanol mol-ecule as acceptors. 

Crystal structure of trans-N,N'-bis-(3,5-di-tert-butyl-2-hy-droxy-phen-yl)oxamide methanol monosolvate.

In the title compound, also known as 3,5-lutidine -oxide dihydrate, CHNO·2HO, the N-O bond is weakened due to the involvement of the O atom as an acceptor of hydrogen bonds from the two water mol-ecules of crystallization present in the asymmetric unit. Fused (10) ring motifs based on O-H⋯O hydrogen bonds form chains in the [010] direction, which are further connected by weak C-H⋯O inter-molecular contacts. As a result, the lutidine mol-ecules are stacked in an efficient manner, with π-π contacts characterized by a short separation of 3.569 (1) Å between the benzene rings.

Article	Year
At last! The single-crystal X-ray structure of a naturally occurring sample of the ilmenite-type oxide FeCrO3. Acta crystallographica Section B, Structural science, crystal engineering and materials\| PubMed ID: 26428405	2015
Spectroscopic and Kinetic Characterization of Peroxidase-Like π-Cation Radical Pinch-Porphyrin-Iron(III) Reaction Intermediate Models of Peroxidase Enzymes. Molecules (Basel, Switzerland)\| PubMed ID: 27355940	2016
Crystal structure of trans-N,N'-bis-(3,5-di-tert-butyl-2-hy-droxy-phen-yl)oxamide methanol monosolvate. Acta crystallographica. Section E, Crystallographic communications\| PubMed ID: 27555931	2016
Crystal structure of 3,5-di-methyl-pyridine -oxide dihydrate. Acta crystallographica. Section E, Crystallographic communications\| PubMed ID: 27980810	2016

Yasmi Reyes-Ortega

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