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.

Some reactions of dimeric silicon phthalocyanines under alkaline conditions

2002 ◽  
Vol 06 (05) ◽  
pp. 336-339 ◽  
Author(s):  
Viktor N. Myakov ◽  
M. A. Lopatin ◽  
Yu. A. Kurskii
Keyword(s):  
Nmr Spectroscopy ◽  
Crown Ether ◽  
Nmr Spectra ◽  
Ring Current ◽  
Electron System ◽  
H Nmr ◽  
Silicon Phthalocyanines ◽  
Alkaline Conditions

Reactions of bis(hydroxy)- and bis(trimethylsiloxy)diphthalocyaninato silicon with KOH were studied in o-xylene or oligosiloxane in the presence of crown ether 15-cr-5 in vacuo at 190-200 °C by the means of electronic, EPR and 1 H NMR spectroscopy. Under gradual removing of H 2 O , consecutive formation of paramagnetic silicon diphthalocyanine monoanions (λ max 580 nm ), and diamagnetic silicon diphthalocyanine dianions (λ max 550 nm ) have been observed. The dianions react with H 2 O to regenerate silicon diphthalocyanine monoanions and then the starting silicon diphthalocyanine. Reaction of the dianion with O 2 results in a decomposition of silicon diphthalocyanine. 1 H NMR spectra of silicon diphthalocyanine dianion have proven the absence of a ring current in the π-electron system of the dianion.

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.

Synthesis of Porphyrin Heterobinuclear Ligands

1994 ◽  
Vol 59 (3) ◽  
pp. 639-648 ◽  
Author(s):  
Vladimír Král ◽  
Magdalena Pánková ◽  
Jana Günterová ◽  
Martin Bělohradský ◽  
Pavel Anzenbacher
Keyword(s):  
Nmr Spectroscopy ◽  
Cytochrome C ◽  
Crown Ether ◽  
Cytochrome C Oxidase ◽  
Spatial Relation ◽  
Model Systems ◽  
Azacrown Ether ◽  
H Nmr ◽  
Porphyrin Derivatives

A series of mono- or biscrown and azacrown ether porphyrin derivatives IIIb - IIIi, IVb and IVc were synthesized as model systems for cytochrome c oxidase. The arrangement of the porphyrin and the crown ether subunits and their spatial relation has been investigated by 1H NMR spectroscopy. The complexation properties of the synthesized ligands have also been studied.

Speed-Controlled Molecular Shuttles

2002 ◽  
Vol 67 (11) ◽  
pp. 1719-1728 ◽  
Author(s):  
Martin Bělohradský ◽  
Arkadij M. Elizarov ◽  
J. Fraser Stoddart
Keyword(s):  
Nmr Spectroscopy ◽  
Gibbs Energy ◽  
Energy Barrier ◽  
Energy Barriers ◽  
H Nmr ◽  
Recognition Sites ◽  
Molecular Shuttles

Five potential molecular shuttles based on degenerate [2]rotaxanes - wherein the ring component is a bis-1,4-phenylene[34]crown-10 and the dumbbell components are terminated by tetraarylmethane (slippage) stoppers and contain two identical bipyridinium recognition sites and a central 1,3-phenylene unit carrying a CH2OR (R = Me, Et, Ph, i-Pr, and t-Bu) substituent on its C-5 position - have been prepared by acylating the parent hydroxymethyl derivative with the appropriate reagents. Dynamic 1H NMR spectroscopy, carried out on these five potential molecular shuttles in CD3CN solutions, has revealed average Gibbs energy barriers to shuttling of 11.5, 12.0, 14.6, and 14.8 kcal mol-1 for the [2]rotaxanes where R = Me, Et, i-Pr, and Ph, respectively. For the [2]rotaxane where R = t-Bu, the Gibbs energy barrier to shuttling must exceed 17.2 kcal mol-1.

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

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.

Different submicellar solubilization mechanisms revealed by 1H NMR and 2D diffusion ordered spectroscopy (DOSY)

2020 ◽  
Vol 22 (19) ◽  
pp. 11075-11085
Author(s):  
Mengjian Wu ◽  
Zhaoxia Wu ◽  
Shangwu Ding ◽  
Zhong Chen ◽  
Xiaohong Cui
Keyword(s):  
Nmr Spectroscopy ◽  
Sodium Dodecyl Sulfate ◽  
1H Nmr ◽  
Sodium Dodecyl ◽  
Butyl Methacrylate ◽  
H Nmr ◽  
Molecular Scale ◽  
Two Systems ◽  
Dodecyl Sulfate ◽  
Triton X

Different submicellar solubilization mechanisms of two systems, Triton X-100/tetradecane and sodium dodecyl sulfate (SDS)/butyl methacrylate, are revealed on the molecular scale by 1H NMR spectroscopy and 2D diffusion ordered spectroscopy (DOSY).

scholarly journals Tautomerisation in 1-(4-Methylphenylazo)naphthalen-2-ol and 2-(4-Methylphenylazo)-4-methylphenol: A Crystallographic and 13C{1H}NMR Study

1999 ◽  
Vol 23 (3) ◽  
pp. 178-179
Author(s):  
Wendy I. Cross ◽  
Kevin R. Flower ◽  
Robin G. Pritchard
Keyword(s):  
Acetic Acid ◽  
Nmr Spectroscopy ◽  
Resonant Frequency ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Nmr Study ◽  
Acetic Acid Esters ◽  
Acid Esters ◽  
Equivalent Carbon

The acetic acid esters of 1-(4-methylphenylazo)naphthalen-2-ol 1 and 2-(4-methylphenylazo)-4-methylphenol 3 are prepared and characterised by single crystal X-ray diffraction studies and 13C{1H}NMR spectroscopy; the position of the C(2)13C resonance for the ester is used to predict the position of resonant frequency of the equivalent carbon in the parent alcohols and hence, calculate the position of the azo-hydrazone equilibrium in these compounds.

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