Perhalogenated 2-pyridylporphyrin complexes: synthesis, self-coordinating aggregation properties, and catalytic studies

2002 ◽  
Vol 06 (01) ◽  
pp. 50-57 ◽  
Author(s):  
Júlio S. Rebouças ◽  
Maria Eliza M. D. de Carvalho ◽  
Ynara M. Idemori
Keyword(s):  
Nmr Spectroscopy ◽  
First Generation ◽  
Reduction Potential ◽  
Catalyst Concentration ◽  
Acid Base ◽  
H Nmr ◽  
Highly Active ◽  
Ph Dependent ◽  
Metal Insertion ◽  
Kinetics Of

The synthesis of 2, 3, 7, 8, 12, 13, 17, 18-octabromo-meso-tetrakis(2-pyridyl)porphyrin, H 2 Br 8 T 2 PyP , is described, including the comparison of four attempted methods for the demetallation of ZnBr 8 T 2 PyP . One of the methods represents a strategy of demetallation based on the acid-base properties of the macrocycle, the solvent-dependent kinetics of metal insertion into porphyrins and the pH -dependent solubility of the 2-pyridylporphyrin derivatives in water. Self-coordinating aggregation of ZnBr 8 T 2 PyP in non-coordinating solvents was verified by 1 H NMR spectroscopy. The Mn(III)/Mn(II) redox potential for MnBr 8 T 2 PyPCl is 0.38 V higher than the reduction potential measured for its first-generation analogue, MnT 2 PyPCl . Cyclohexane hydroxylation by iodosylbenzene was performed in CH3 CN catalyzed by MnBr 8 T 2 PyPCl and MnT 2 PyPCl . MnBr 8 T 2 PyPCl was highly active, even at low concentration (5 × 10−5 M ), but perhalogenation did not account for oxidative robustness. At such a low catalyst concentration, MnT 2 PyPCl exhibited no activity as inferred by comparison to blank experiments.

scholarly journals Amino-functionalized (meth)acryl polymers by use of a solvent-polarity sensitive protecting group (Br-t-BOC)

2016 ◽  
Vol 12 ◽  
pp. 245-252
Author(s):  
Helmut Ritter ◽  
Monir Tabatabai ◽  
Markus Herrmann
Keyword(s):  
Free Radical ◽  
Nmr Spectroscopy ◽  
Free Amino ◽  
Solvent Polarity ◽  
Protecting Group ◽  
Amino Groups ◽  
Neighboring Group ◽  
H Nmr ◽  
Polarity Sensitive ◽  
Kinetics Of

We describe the synthesis of bromo-tert-butyloxycarbonyl (Br-t-BOC)-amino-protected monomers 2-((1-bromo-2-methylpropan-2-yl)oxycarbonylamino)ethyl (meth)acrylate 3a,b. For this purpose, 2-isocyanatoethyl (meth)acrylate 1a,b was reacted with 1-bromo-2-methylpropan-2-ol (2a). The free radical polymerization of (Br-t-BOC)-aminoethyl (meth)acrylates 3a,b yielded poly((Br-t-BOC)-aminoethyl (meth)acrylate) 6a,b bearing protected amino side groups. The subsequent solvolysis of the Br-t-BOC function led to the new polymers poly(2-aminoethyl (meth)acrylate) 8a,b with protonated free amino groups. The monomers and the resulting polymers were thoroughly characterized by 1H NMR, IR, GPC and DSC methods. The kinetics of the deprotection step was followed by 1H NMR spectroscopy. The solvent polarity and neighboring group effects on the kinetics of deprotection are discussed.

scholarly journals A pyridinium/anilinium [2]catenane that operates as an acid–base driven optical switch

2018 ◽  
Vol 14 ◽  
pp. 1908-1916 ◽  
Author(s):  
Sarah J Vella ◽  
Stephen J Loeb
Keyword(s):  
Nmr Spectroscopy ◽  
Crown Ether ◽  
Optical Switch ◽  
Protonation State ◽  
Acid Base ◽  
H Nmr ◽  
Recognition Sites ◽  
Yellow Orange ◽  
Deep Yellow ◽  
Orange Color

A two-station [2]catenane containing a large macrocycle with two different recognition sites, one bis(pyridinium)ethane and one benzylanilinium, as well as a smaller DB24C8 ring was synthesized and characterized. 1H NMR spectroscopy showed that the DB24C8 ring can shuttle between the two recognition sites depending on the protonation state of the larger macrocycle. When the aniline group is neutral, the DB24C8 ring resides solely at the bis(pyridinium)ethane site, while addition of acid forms a charged benzylanilinium site. The DB24C8 then shuttles between the two charged recognition sites with occupancy favoring the bis(pyridinium)ethane site by a ratio of 4:1. The unprotonated [2]catenane has a deep yellow/orange color when the DB24C8 ring resides solely at the bis(pyridinium)ethane site and changes to colorless when the crown ether is shuttling (i.e., circumrotating) back and forth between the two recognition sites thus optically signalling the onset of the shuttling dynamics.

A NMR Study of the Exchange Kinetics of the Nonamethylimidodiphosphoramide with its Complexes of Diamagnetic Cations

1978 ◽  
Vol 33 (6) ◽  
pp. 684-685 ◽  
Author(s):  
P. R. Rubini ◽  
L. Rodehüser ◽  
J.-J. Delpuech
Keyword(s):  
Nmr Spectroscopy ◽  
Ligand Exchange ◽  
H Nmr ◽  
Nmr Study ◽  
Exchange Kinetics ◽  
Monodentate Ligands ◽  
Kinetics Of

Abstract The ligand exchange on nonamethylimidodiphosphoramide (NIPA) complexes is found to be very slow comparatively to analogous monodentate ligands; the rates determined by 1H or 31P NMR spectroscopy are: k(25°C)=4.3 × 10-2 s-1; 31.6 s-1 • M-1; 3.7 × 104 S-1 • M-1 and 1.35 × 104 s-1 · M-1 for Mg2+, Ca2+, Sr2+ and Li+ cations respectively. For the Al3+, Ga3+, In3+ and Be2+ ions no exchange could be detected by 1H NMR spectroscopy up to 120 °C, indicating rates lower than about 10-3 s-1

Kinetics of the Dehydration of the β-Cages of Sodium Faujasites as Studied by H-NMR Spectroscopy

1992 ◽  
Vol 96 (4) ◽  
pp. 545-549 ◽  
Author(s):  
W. D. Basler ◽  
H. T. Lechert ◽  
D. Carboo ◽  
A. Knöchel
Keyword(s):  
Nmr Spectroscopy ◽  
H Nmr ◽  
Kinetics Of

The Basicity of Silylamines and Alkylamines: An Equilibrium Study of the Competitive Borane Adduct Formation

1998 ◽  
Vol 53 (10) ◽  
pp. 1103-1108 ◽  
Author(s):  
Gerald Huber ◽  
Hubert Schmidbaur
Keyword(s):  
Nmr Spectroscopy ◽  
Lewis Acid ◽  
Quantum Chemical ◽  
Adduct Formation ◽  
Steric Effects ◽  
Organic Amine ◽  
Acid Base ◽  
Equilibrium Study ◽  
H Nmr ◽  
Equilibrium Reactions

AbstractIn order to investigate the Lewis acid/base chemistry of silylamines in solution, the equilibrium reactions of Me3SiNMe2 / Me3SiNMe2(BH3) and different amines NR3 / amineboranes NR3(BH3) were monitored by 1H NMR spectroscopy in C6D6 and CDCI3 at 60 °C. For the equilibrium of the reference silylamine/-borane and Me3CNMe2 / Me3CNMe2(BH3) values K = 0.35 (AG = 3.1 kJ mol-1) in C6D6 and K = 0.50 (AG = 2.0 kJ mol-1) in CDCl3 have been estimated, showing that both the silylamine and the C/Si-analogous organic amine have very similar donor properties. Small amines like NMe3 proved to be much more powerful donors than the silylamine Me3SiNMe2, whereas bulky amines are less efficient donors, indicating that steric effects play an important role. The formation of BH3 adducts of Me2NSiH3 and (H3Si)3N which could not be followed experimentally owing to the low stability of the products, has been studied by quantum chemical calculations. A comparison with data for Me3N(BH3) shows that the silylamines are poorer donors, but the reason for this remains unclear

ChemInform Abstract: Kinetics of the Dehydration of the β-Cages of Sodium Faujasites as Studied by H NMR Spectroscopy.

ChemInform ◽  
2010 ◽  
Vol 23 (29) ◽  
pp. no-no
Author(s):  
W. D. BASLER ◽  
H. T. LECHERT ◽  
D. CARBOO ◽  
A. KNOECHEL
Keyword(s):  
Nmr Spectroscopy ◽  
H Nmr ◽  
Kinetics Of

Catalytic activity of rhodium(I) complexes containing (ω-trimethylsilylalkyl)diphenylphosphines

1980 ◽  
Vol 45 (8) ◽  
pp. 2219-2223 ◽  
Author(s):  
Marie Jakoubková ◽  
Martin Čapka
Keyword(s):  
Catalytic Activity ◽  
Nmr Spectroscopy ◽  
Ir Spectroscopy ◽  
Electron Density ◽  
Phosphorus Atom ◽  
Proton Acceptor ◽  
Trimethylsilyl Group ◽  
Kinetics Of

Kinetics of homogenous hydrogenation of 1-heptene catalysed by rhodium(I) complexes prepared in situ from μ,μ'-dichloro-bis(cyclooctenerhodium) and phosphines of the type RP(C6H5)2 (R = -CH3, -(CH2)nSi(CH3)3; n = 1-4) have been studied. The substitution of the ligands by the trimethylsilyl group was found to increase significantly the catalytic activity of the complexes. The results are discussed in relation to the electron density on the phosphorus atom determined by 31P NMR spectroscopy and to its proton acceptor ability determined by IR spectroscopy.

Iodoacetate inactivation of rape alcohol dehydrogenase

1980 ◽  
Vol 45 (5) ◽  
pp. 1601-1607 ◽  
Author(s):  
Marie Stiborová ◽  
Sylva Leblová
Keyword(s):  
Alcohol Dehydrogenase ◽  
Protein Molecule ◽  
Sulfhydryl Groups ◽  
Inactivation Rate ◽  
First Order ◽  
Ph Dependent ◽  
Kinetics Of

Iodoacetate inactivates rape alcohol dehydrogenase (ADH, EC 1.1.1.1). The inactivation rate follows the kinetics of the first order, is pH-dependent, and decreases below pH 7.5. Besides irreversible alkylation of the sulfhydryl groups of the enzyme iodoacetate also forms a reversible complex with rape ADH. The coenzyme (NAD) and its analogs (ATP, ADP, AMP) competitively protect the enzyme against alkylation; o-phenanthroline also protects the enzyme against alkylation yet noncompetitively with respect to iodoacetate. Imidazole and o-phenanthroline compete with one another for binding to the protein molecule of rape ADH. Whereas o-phenanthroline decreases the inactivation rate imidazole increases the rate of iodoacetate inactivation.

Conformational study on ribonucleoside O-phosphonylmethyl derivatives by 1H NMR spectroscopy

1985 ◽  
Vol 50 (8) ◽  
pp. 1899-1905 ◽  
Author(s):  
Milena Masojídková ◽  
Jaroslav Zajíček ◽  
Miloš Buděšínský ◽  
Ivan Rosenberg ◽  
Antonín Holý
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Conformational Study ◽  
H Nmr ◽  
Conformational Properties

Conformational properties of ribonucleoside 5'-O-phosphonylmethyl derivatives have been determined by 1H NMR spectroscopy and compared with those of natural nucleosides and 5'-nucleotides.

Monitoring the encapsulation of chlorin e6 derivatives into polymer carriers by NMR spectroscopy

2019 ◽  
Vol 23 (11n12) ◽  
pp. 1576-1586 ◽  
Author(s):  
Sara Pfister ◽  
Luca Sauser ◽  
Ilche Gjuroski ◽  
Julien Furrer ◽  
Martina Vermathen
Keyword(s):  
Relaxation Time ◽  
Nmr Spectroscopy ◽  
Core Region ◽  
Chlorin E6 ◽  
Polypropylene Glycol ◽  
Polymer Carriers ◽  
H Nmr ◽  
Line Shape Analysis ◽  
Dynamic Methods ◽  
Derivatives Of

The encapsulation of five derivatives of chlorin e6 with different hydrophobicity and aggregation properties into a series of five poloxamer-type triblock copolymer micelles (BCMs) with varying numbers of polyethylene and polypropylene glycol (PEG, PPG) units was monitored using 1H NMR spectroscopy. NMR chemical shift and line shape analysis, as well as dynamic methods including diffusion ordered spectroscopy (DOSY) and T1 and T2 relaxation time measurements of the chlorin and the polymer resonances, proved useful to assess the chlorin–BCM compatibility. The poloxamers had high capability to break up aggregates formed by chlorins up to intermediate hydrophobicity. Physically entrapped chlorins were always localized in the BCM core region. The loading capacity correlated with chlorin polarity for all poloxamers among which those with the lowest number of PPG units were most efficient. DOSY data revealed that relatively weakly aggregating chlorins partition between the aqueous bulk and micellar environment whereas more hydrophobic chlorins are well retained in the BCM core region, rendering these systems more stable. T1 and T2 relaxation time measurements indicated that motional freedom in the BCM core region contributes to encapsulation efficiency. The BCM corona dynamics were rather insensitive towards chlorin entrapment except for the poloxamers with short PEG chains. The presented data demonstrate that 1H NMR spectroscopy is a powerful complementary tool for probing the compatibility of porphyrinic compounds with polymeric carriers such as poloxamer BCMs, which is a prerequisite in the development of stable and highly efficient drug delivery systems suitable for medical applications like photodynamic therapy of tumors.

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