Effects of methoxy-substituted metalloporphyrins in catalytic alkene epoxidation by n-Bu4NHSO5

2010 ◽  
Vol 14 (04) ◽  
pp. 335-342 ◽  
Author(s):  
Amineh Aghabali ◽  
Nasser Safari
Keyword(s):  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
High Activity ◽  
Solvent Mixture ◽  
Steric Effects ◽  
Reaction Condition ◽  
Reaction Solution ◽  
Phenyl Rings ◽  
Active Intermediate ◽  
The Stability

TPPMnOAc and four different kinds of manganese tetraphenylporphyrin acetates were synthesized using different numbers of methoxy substituents in various positions of the phenyl rings. These porphyrins were used as catalysts in the epoxidation of various alkenes with tetra-n-butylammonium hydrogen monopersulfate (n- Bu 4 NHSO 5) as the oxidant and imidazole as the axial base. The following order of catalytic activity was obtained: TPPMnOAc ≥ T (2,3- OMeP ) PMnOAc > T (4- OMeP ) PMnOAc > T (3,4- OMeP ) PMnOAc > T (2,4,6- OMeP ) PMnOAc . By studying the UV-vis spectra in the reaction solution, the stability of the applied methoxy porphyrins and the effect of this factor on obtained yields were investigated. Lower catalytic activity in some of the methoxy porphyrins emphasized steric effects and special hydrogen bonding among the reaction elements. However, the stability of T (2,3- OMeP ) PMnOAc under our reaction condition was considerable and high activity was observed. By adding small amounts of alcohol to the reaction solution, the effect of the solvent mixture was previewed and steps were taken to identify the active intermediate of the catalyst in these conditions.

An assessment of oxime-oximato hydrogen bonding: A structural and thermodynamic study of copper(II) complexes

1978 ◽  
Vol 31 (4) ◽  
pp. 723 ◽  
Author(s):  
EA Daniel ◽  
FC March ◽  
HKJ Powell ◽  
WT Robinson ◽  
JM Russell
Keyword(s):  
Hydrogen Bonding ◽  
Methyl Ether ◽  
Complex Cation ◽  
Steric Effects ◽  
Apical Position ◽  
X Ray ◽  
Methyl Substitution ◽  
Perchlorate Ion ◽  
Nitrogen Donor ◽  
The Stability

Copper(II) complexes formed by the diamine dioxime ligand 4,4,9,9- tetramethyl-5,8-diazadodecane-2,11-dione dioxime (H2dddo) and its O-methyl ether (Hddmo) and bis-O-methyl ether (dddm) have been studied. The log K (potentiometric) and ΔH (calorimetric) values are reported for formation of the four-coordinate complexes [Cu(Hddmo)]2+ and [Cu(dddm)]2+ and for the deprotonation of [Cu(Hddmo)]2+ to give [Cu(ddmo)]+ at 25°C, I = 0.1 M NaCl. (log K = 12.11 � 0.04, 9.10�0.02 and -6.76�0.09; ΔH= -43�2, -17.9�0.4 and +21.9�0.9 kJ mol-1 respectively.) Comparison with data for [Cu(H2dddo)]2+ and [Cu(Hdddo)]+ affords information about the relative contributions of (i) oxime deprotonation (c. 105.6), and (ii) oxime oximato hydrogen bonding (c. 103.5), to the stability of these (non-conjugated) dioxime complexes. The formation of intramolecular (oxime-oximato) hydrogen bonds is favoured by a positive ΔS; intermolecular bonds (oximato-solvent) give rise to a negative ΔS. ��� A single-crystal X-ray molecular structure determination is reported for the complex Cu(dddm)-(ClO4)2. In the solid state the complex cation is square pyramidal with one perchlorate ion weakly coordinated in the apical position and the four nitrogen donor atoms forming a distorted square plane about the copper atom. Steric effects associated with O-methyl substitution are assessed. Steric hindrance between adjacent =NOR groups does not increase measurably when =NOH is replaced by =NOMe.

Investigation of axial ligand effects on catalytic activity of manganese porphyrin, evidence for the importance of hydrogen bonding in cytochrome-P450 model reactions

2014 ◽  
Vol 18 (05) ◽  
pp. 354-365 ◽  
Author(s):  
Elnaz Mesbahi ◽  
Nasser Safari ◽  
Mahin Gheidi
Keyword(s):  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
Product Formation ◽  
Axial Ligand ◽  
Active Species ◽  
Manganese Porphyrin ◽  
Axial Ligands ◽  
Epoxidation Reaction ◽  
Phenyl Rings ◽  
Hydroxy Groups

Various nitrogenous bases, such as imidazoles, pyridines and amines were employed as axial ligands in epoxidation reaction of cyclooctene bytetra-n-butylammonium hydrogen monopersulfate (n- Bu 4 NHSO 5), in the presence of Mn ( III )-tetrakis(2,3-dimethoxyphenyl)porphyrin-acetate ( T (2,3- OMeP ) PorMnOAc ). T (2,3- OMeP ) PorMnOAc is a fairly stable catalyst, with the ability of producing hydrogen bonding. High epoxidation yield of 85 ± 6% was obtained in the presence of imidazole axial ligand with 100% selectivity in 30 min. Higher conversion of around 100% was obtained by pyridine axial base, while selectivity was reduced to 69%. Further epoxidation reactions were also performed using Mn ( III )-Tetrakis(2,3-dihydroxyphenyl)porphyrin-acetate ( T (2,3- OHP ) PorMnOAc ) as catalyst. In addition to the usual electronic and steric effects, it is proposed that the catalytic activity depends on the existence and kind of hydrogen bonding between the axial base and the ortho-methoxy or hydroxy groups on the phenyl rings of manganese porphyrin. The cis to trans ratio of cis-stilbene oxide formed by imidazole and pyridine axial bases were obtained as 7.5 and 2.5 respectively. In addition GC-Ms and UV-vis studies were employed to find the nature of active species and product formation. Our DFT calculations disclosed that pyridine hydrogen bonding with moiety of the macrocycle rings strongly affects the relative energies of S/Q spin states in [ T (2,3- OMeP ) PorMn V ( O )( Py )]+, in that it results in the longer Mn – O bond and reactivity toward substrates.

scholarly journals New hydrogen-bonding organocatalysts: Chiral cyclophosphazanes and phosphorus amides as catalysts for asymmetric Michael additions

2014 ◽  
Vol 10 ◽  
pp. 224-236 ◽  
Author(s):  
Helge Klare ◽  
Jörg M Neudörfl ◽  
Bernd Goldfuss
Keyword(s):  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
High Activity ◽  
Michael Addition ◽  
Bond Activation ◽  
High Catalytic Activity ◽  
Open Chain ◽  
High Hydrogen ◽  
Michael Additions ◽  
Asymmetric Michael Addition

Ten novel hydrogen-bonding catalysts based on open-chain PV-amides of BINOL and chinchona alkaloids as well as three catalysts based on rigid cis-PV-cyclodiphosphazane amides of N 1,N 1-dimethylcyclohexane-1,2-diamine have been developed. Employed in the asymmetric Michael addition of 2-hydroxynaphthoquinone to β-nitrostyrene, the open-chain 9-epi-aminochinchona-based phosphorus amides show a high catalytic activity with almost quantitative yields of up to 98% and enantiomeric excesses of up to 51%. The cyclodiphosphazane catalysts show the same high activity and give improved enantiomeric excesses of up to 75%, thus representing the first successful application of a cyclodiphosphazane in enantioselective organocatalysis. DFT computations reveal high hydrogen-bonding strengths of cyclodiphosphazane PV-amides compared to urea-based catalysts. Experimental results and computations on the enantiodetermining step with cis-cyclodiphosphazane 14a suggest a strong bidentate H-bond activation of the nitrostyrene substrate by the catalyst.

scholarly journals Entrapment of the Fastest Known Carbonic Anhydrase with Biomimetic Silica and Its Application for CO2 Sequestration

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2452
Author(s):  
Chia-Jung Hsieh ◽  
Ju-Chuan Cheng ◽  
Chia-Jung Hu ◽  
Chi-Yang Yu
Keyword(s):  
Carbonic Anhydrase ◽  
High Activity ◽  
Co2 Sequestration ◽  
Residual Activity ◽  
Entrapment Efficiency ◽  
Free Form ◽  
Uncatalyzed Reaction ◽  
The Stability ◽  
Time Required

Capturing and storing CO2 is of prime importance. The rate of CO2 sequestration is often limited by the hydration of CO2, which can be greatly accelerated by using carbonic anhydrase (CA, EC 4.2.1.1) as a catalyst. In order to improve the stability and reusability of CA, a silica-condensing peptide (R5) was fused with the fastest known CA from Sulfurihydrogenibium azorense (SazCA) to form R5-SazCA; the fusion protein successfully performed in vitro silicification. The entrapment efficiency reached 100% and the silicified form (R5-SazCA-SP) showed a high activity recovery of 91%. The residual activity of R5-SazCA-SP was two-fold higher than that of the free form when stored at 25 °C for 35 days; R5-SazCA-SP still retained 86% of its activity after 10 cycles of reuse. Comparing with an uncatalyzed reaction, the time required for the onset of CaCO3 formation was shortened by 43% and 33% with the addition of R5-SazCA and R5-SazCA-SP, respectively. R5-SazCA-SP shows great potential as a robust and efficient biocatalyst for CO2 sequestration because of its high activity, high stability, and reusability.

scholarly journals One-Dimensional Organic–Inorganic Material (C6H9N2)2BiCl5: From Synthesis to Structural, Spectroscopic, and Electronic Characterizations

2021 ◽  
Vol 22 (4) ◽  
pp. 2030
Author(s):  
Hela Ferjani ◽  
Hammouda Chebbi ◽  
Mohammed Fettouhi
Keyword(s):  
Hydrogen Bonding ◽  
Density Functional ◽  
Crystal Packing ◽  
Diffuse Reflectance Spectrum ◽  
Enrichment Ratio ◽  
One Dimensional ◽  
Organic Part ◽  
Fukui Indices ◽  
The Stability ◽  
The One

The new organic–inorganic compound (C6H9N2)2BiCl5 (I) has been grown by the solvent evaporation method. The one-dimensional (1D) structure of the allylimidazolium chlorobismuthate (I) has been determined by single crystal X-ray diffraction. It crystallizes in the centrosymmetric space group C2/c and consists of 1-allylimidazolium cations and (1D) chains of the anion BiCl52−, built up of corner-sharing [BiCl63−] octahedra which are interconnected by means of hydrogen bonding contacts N/C–H⋯Cl. The intermolecular interactions were quantified using Hirshfeld surface analysis and the enrichment ratio established that the most important role in the stability of the crystal structure was provided by hydrogen bonding and H···H interactions. The highest value of E was calculated for the contact N⋯C (6.87) followed by C⋯C (2.85) and Bi⋯Cl (2.43). These contacts were favored and made the main contribution to the crystal packing. The vibrational modes were identified and assigned by infrared and Raman spectroscopy. The optical band gap (Eg = 3.26 eV) was calculated from the diffuse reflectance spectrum and showed that we can consider the material as a semiconductor. The density functional theory (DFT) has been used to determine the calculated gap, which was about 3.73 eV, and to explain the electronic structure of the title compound, its optical properties, and the stability of the organic part by the calculation of HOMO and LUMO energy and the Fukui indices.

Facile synthesis of cubical Co3O4 supported Au nanocomposites with high activity for the reduction of 4-nitrophenol to 4-aminophenol

RSC Advances ◽  
2016 ◽  
Vol 6 (39) ◽  
pp. 32430-32433 ◽  
Author(s):  
Yuwen Yang ◽  
Yongyun Mao ◽  
Bin Wang ◽  
Xianwei Meng ◽  
Jiao Han ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
High Activity ◽  
Impregnation Method ◽  
Facile Synthesis ◽  
Turn Over Frequency ◽  
Turn Over

A facile impregnation method has been successfully applied for synthesis of a cubical Co3O4 supported Au nanocomposites, which leads to the excellent catalytic activity for the reduction of 4-nitrophenol with a high turn over frequency of 9.83 min−1.

Effect of the ionizing radiation on the catalytic activity of the BASF K-3-10 catalyst in the low-temperature conversion of carbon monoxide by water vapour. Stability of the radiation catalytic effects

1986 ◽  
Vol 51 (8) ◽  
pp. 1571-1578 ◽  
Author(s):  
Alois Motl
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Low Temperature ◽  
Catalytic Effect ◽  
Catalytic Properties ◽  
Beta Radiation ◽  
Fast Neutrons ◽  
Time Interval ◽  
The Stability ◽  
Catalytic Effects

The radiation catalytic properties of the BASF K-3-10 catalyst were studied, namely the dependence of these effects on the time interval between the catalyst irradiation and the reaction itself and also on the length of the catalyst use. The catalytic effects decrease exponentially with the interval between the irradiation and the reaction if the catalyst is kept in the presence of air. The stability of effects induced by various types of radiations increases in the sequence beta radiation - gamma radiation - fast neutrons. The radiation catalytic effect stability in the reaction increases in the same sequence.

scholarly journals Crystal structure of 2-(2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-ylidene)acetonitrile

2015 ◽  
Vol 71 (10) ◽  
pp. o792-o793
Author(s):  
K. Priya ◽  
K. Saravanan ◽  
S. Kabilan ◽  
S. Selvanayagam
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Crystal Packing ◽  
Van Der Waals ◽  
Van Der Waals Forces ◽  
Chair Conformation ◽  
Equatorial Orientation ◽  
Amino Group ◽  
Phenyl Rings

In the title 3-azabicyclononane derivative, C22H22N2, both the fused piperidine and cyclohexane rings adopt a chair conformation. The phenyl rings attached to the central azabicylononane fragment in an equatorial orientation are inclined to each other at 23.7 (1)°. The amino group is not involved in any hydrogen bonding, so the crystal packing is stabilized only by van der Waals forces.

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