π-π Interactions between Pyrylium and Phenyl Rings in the Crystal

1997 ◽  
Vol 52 (4) ◽  
pp. 485-489 ◽  
Author(s):  
Teodor Silviu Balaban ◽  
Nina G. Furmanova
Keyword(s):  
Charge Transfer ◽  
Crystal Structures ◽  
Crystallographic Axis ◽  
Π Interactions ◽  
Charge Transfer Interaction ◽  
Π Stacking ◽  
Phenyl Rings ◽  
A Charge

Abstract The crystal structures of two isomeric phenyl-substituted pyrylium perchlorates, 2,6-di-methyl-4-phenylpyrylium (1) and 2,4-dim ethyl-6-phenylpyrylium (2), have been determined. Both cations are planar in the crystal so that the electron deficient pyrylium rings can interact strongly with the phenyl rings of adjacent molecules forming stacks along the shortest crystallographic axis. The phenyl rings may act as donors in a charge transfer interaction which is more pronounced in 1 than in 2. Charge transfer appears as a non-mandatory consequence of the π-π stacking. The structures demonstrate the electrostatic nature of these interactions conforming to the model of Hunter and Sanders [ 1 ].

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

Syntheses, Structures, Characterisation, and Spectroscopic Properties of CuI and AgI Complexes with Extended C–H···π and π···π Interactions

2014 ◽  
Vol 67 (6) ◽  
pp. 887 ◽  
Author(s):  
Ting-Hong Huang ◽  
Min-Hua Zhang
Keyword(s):  
Charge Transfer ◽  
Room Temperature ◽  
Spectroscopic Properties ◽  
Acetonitrile Solution ◽  
Fluorescent Properties ◽  
Π Interactions ◽  
Π Stacking ◽  
Ligand Charge Transfer ◽  
The One ◽  
Stacking Patterns

Based on the ligands N,N′-bis(pyridin-2-ylmethylene)benzene-1,4-diamine (pmb) and N,N′-bis(pyridin-2-ylmethylene)biphenyl-4,4′-diamine (pmbb), the three compounds [Cu2(pmb) (PPh3)2(Cl)2] (1), [Cu2(pmbb)(CH3CN)2(PPh3)2](BF4)2·2DMF (2), and [Ag2(pmbb)(PPh3)2] (ClO4)2 (3) have been synthesised and characterised. Structural analysis reveals that all of these complexes contain 1D supramolecular arrays, with different variations in π-stacking patterns and intermolecular C–H···π interactions. Crystal structures of 1 and 2 contain 1D tape-like arrays formed by C–H···π and π···π interactions, and an ordered-layer-lattice of DMF and BF4– in 2 is located between the one-dimensional array. For 3, π-stacking interactions lead to the construction of 1D supramolecular arrays and a 2D network. The results indicate that C–H···π and π···π interactions play an important role in the construction of the supramolecular structure. In addition, the absorption peaks of complexes 1 and 3 in the solid state at room temperature show intraligand charge transfer and metal-to-ligand charge transfer absorptions. The optical and fluorescent properties of 2 were also studied in acetonitrile solution at room temperature.

Modulation of the catalytic activity of Pt nanoparticles through charge-transfer interactions with metal–organic frameworks

2017 ◽  
Vol 53 (50) ◽  
pp. 6720-6723 ◽  
Author(s):  
Shotaro Yoshimaru ◽  
Masaaki Sadakiyo ◽  
Aleksandar Staykov ◽  
Kenichi Kato ◽  
Miho Yamauchi
Keyword(s):  
Catalytic Activity ◽  
Charge Transfer ◽  
Co Oxidation ◽  
Oxidation Reaction ◽  
Metal Organic Frameworks ◽  
Pt Nanoparticles ◽  
Charge Transfer Interaction ◽  
Co Oxidation Reaction ◽  
Metal Organic ◽  
A Charge

A charge transfer interaction between Pt nanoparticles and MOFs modulated the catalytic activity of Pt for a CO oxidation reaction.

scholarly journals Different N—H...π interactions in two indole derivatives

2016 ◽  
Vol 72 (5) ◽  
pp. 699-703 ◽  
Author(s):  
Jamie R. Kerr ◽  
Laurent Trembleau ◽  
John M. D. Storey ◽  
James L. Wardell ◽  
William T. A. Harrison
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Intermolecular Interaction ◽  
Aromatic Ring ◽  
Stacking Interactions ◽  
Indole Derivatives ◽  
Asymmetric Unit ◽  
Π Interactions ◽  
Π Stacking

We describe the syntheses and crystal structures of two indole derivatives, namely 6-isopropyl-3-(2-nitro-1-phenylethyl)-1H-indole, C19H20N2O2, (I), and 2-(4-methoxyphenyl)-3-(2-nitro-1-phenylethyl)-1H-indole, C23H20N2O3, (II); the latter crystallizes with two molecules (AandB) with similar conformations (r.m.s. overlay fit = 0.139 Å) in the asymmetric unit. Despite the presence of O atoms as potential acceptors for classical hydrogen bonds, the dominant intermolecular interaction in each crystal is an N—H...π bond, which generates chains in (I) andA+AandB+Binversion dimers in (II). A different aromatic ring acts as the acceptor in each case. The packing is consolidated by C—H...π interactions in each case but aromatic π–π stacking interactions are absent.

scholarly journals The crystal structures of two isomers of 5-(phenylisothiazolyl)-1,3,4-oxathiazol-2-one

2017 ◽  
Vol 73 (11) ◽  
pp. 1726-1731
Author(s):  
Shuguang Zhu ◽  
Melbourne J. Schriver ◽  
Arthur D. Hendsbee ◽  
Jason D. Masuda
Keyword(s):  
Crystal Structures ◽  
Single Molecule ◽  
Planar Structure ◽  
Dihedral Angles ◽  
Steric Repulsion ◽  
Asymmetric Unit ◽  
Axis Direction ◽  
Planar Conformation ◽  
Π Stacking ◽  
Phenyl Rings

The syntheses and crystal structures of two isomers of phenyl isothiazolyl oxathiazolone, C11H6N2O2S2, are described [systematic names: 5-(3-phenylisothiazol-5-yl)-1,3,4-oxathiazol-2-one, (I), and 5-(3-phenylisothiazol-4-yl)-1,3,4-oxathiazol-2-one, (II)]. There are two almost planar (r.m.s. deviations = 0.032 and 0.063 Å) molecules of isomer (I) in the asymmetric unit, which form centrosymmetric tetramers linked by strong S...N [3.072 (2) Å] and S...O contacts [3.089 (1) Å]. The tetramers are π-stacked parallel to thea-axis direction. The single molecule in the asymmetric unit of isomer (II) is twisted into a non-planar conformation by steric repulsion [dihedral angles between the central isothiazolyl ring and the pendant oxathiazolone and phenyl rings are 13.27 (6) and 61.18 (7)°, respectively], which disrupts the π-conjugation between the heteroaromatic isothiazoloyl ring and the non-aromatic oxathiazolone heterocycle. In the crystal of isomer (II), the strong S...O [3.020 (1) Å] and S...C contacts [3.299 (2) Å] and the non-planar structure of the molecule lead to a form of π-stacking not observed in isomer (I) or other oxathiazolone derivatives.

scholarly journals Compound C2, a product of the reaction of oxygen and the mixed-valence state of cytochrome oxidase. Optical evidence for a type-I copper

1979 ◽  
Vol 177 (3) ◽  
pp. 931-941 ◽  
Author(s):  
B Chance ◽  
C Saronio ◽  
J S Leigh
Keyword(s):  
Charge Transfer ◽  
Cytochrome Oxidase ◽  
Valence State ◽  
Mixed Valence ◽  
Type I ◽  
Blue Copper ◽  
Mixed Valence State ◽  
Charge Transfer Interaction ◽  
A Charge ◽  
Reduced State

Compound C2 is a product of the reaction of O2 and the mixed-valence state of cytochrome oxidase. The mixed-valence state of membrane-bound cytochrome oxidase is obtained at -24 degrees C, by using either ferricyanide or yeast peroxidase complex ES as oxidants, and the configurations of oxidized haem a and its associated copper (a3+Cua2+) and of reduced haem a3 and its associated copper (ac3+.CO.Cua3+) are obtained. The mixed-valence-state cytochrome oxidase mixed with O2 at -24 degrees C and flash-photolysed at -60 to -100 degrees C reacts with O2 and initially forms an oxy compound (A2) similar to that formed from the fully reduced state (A1). Thereafter the course of the reaction differs from that obtained in the fully reduced state, and absorbance increases are observed at 740–750 nm and 609 nm and a decrease at 444 nm, with no increase in absorbance at 655 nm. One possible attribution of the absorbance increases is to charge-transfer interaction between the iron of haem a3 and the copper associated with haem a3, Cua3(2+), having properties of a type-I ‘blue’ copper. A possible attribution of the decrease in absorbance at 444 nm is to liganding of a3(2+). A related explanation is that the 609 nm absorbance involves a charge-transfer interaction of both iron and copper as a mixed-valence binuclear complex, Cua3, having properties of a non-blue copper. Intermediates in addition to Compound C2 are not yet identifiable by chemical or spectroscopic tests. The kinetic and equilibrium properties of Compound C2 are described.

Relative migratory aptitudes in the Schmidt reaction of arylpropanones and 2-arylcyclohexanones

1978 ◽  
Vol 31 (9) ◽  
pp. 1989 ◽  
Author(s):  
RH Prager ◽  
JM Tippett ◽  
AD Ward
Keyword(s):  
Charge Transfer ◽  
Aromatic Ring ◽  
Low Temperatures ◽  
Hydrazoic Acid ◽  
Schmidt Reaction ◽  
Aryl Ring ◽  
Charge Transfer Interaction ◽  
Alkyl Groups ◽  
A Charge ◽  
Electron Donating Groups

The relative migratory aptitude of benzyl and alkyl groups in the reaction of arylpropanones and 2-arylcyclohexanones with hydrazoic acid depends on the solvent, temperature and nature of the substituents in the aryl ring. It is suggested that at low temperatures electron- donating groups in the aromatic ring favour a charge-transfer interaction which affects the relative migratory aptitudes.

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