Formation Of Electron Donor-acceptor Complexes Research Articles

Solvent effects on the vibrational structure of the ultraviolet spectra of cyanoaromatics. The influence of electron donor-acceptor interactions—I. 1,2-Dicyanobenzene

A solvatochromic study of the vibronic fine structure of the 1 Lb absorption band of 1,2-dicyanobenzene (DCB), in several non-polar and polar solvents including aliphatic amines was made. The spectral properties were analyzed by means of theoretical parameters as well as by K amlet and T aft's solvatochromic comparison method. The solvatochromic behavior of the 1 Lb absorption band of DCB has been accounted fundamentally as dielectric in nature except for the aliphatic amines as solvents. The anomalous behavior of aliphatic amines is explained by considering that the solute interacts via electron donor-acceptor (EDA) complex formation with these solvents. A qualitative approach based on the use of the ratio of vibronic band intensities is proposed as a sensible method to detect these type of EDA interactions.

Aromatic nucleophilic substitution reactions of 1,2-dinitrobenzene with aliphatic primary amines in n-hexane; catalysis by non-nucleophilic bases

The kinetics of the reactions of 1,2-dinitrobenzene with n-butyl-, s-butyl-, isobutyl-, n-propyl-, and isopropyl-amine in n-hexane at various temperatures have been investigated. The second-order rate coefficients for these reactions increase linearly with the amine concentrations. The values of the ratio of the rate constant for the catalysed process to the rate constant of the uncatalysed step [k3RNH2/k2] are dependent on temperature, so that it is possible to minimize the catalysed or uncatalysed processes simply by temperature variation. Kinetic studies in the presence of non-nucleophilic bases [pyridine, triethylamine (TEA), and tributylamine (TBA)] confirmed the proposal that all these reactions are base-catalysed even for the cases where k3RNH2/k2 is less than 50. The role that electron donor–acceptor complex formation between reactants may play in the mechanism of these reactions is discussed. The influence of electronic and steric effects in the amine structure on the catalytic rate constant has been analysed. It has been shown that the catalysed step is disfavoured by electron-donating substituents and that it is inhibited by steric hindrance. The studies with the addition of the bulky bases TEA and TBA confirmed these conclusions.

Vinyl polymers with pending fluoranthene groups and their charge transfer behavior

AbstractIn the present paper the preparation of vinyl monomers with pending fluoranthene groups and different spacer length, their radical polymerization and their electron donor acceptor (EDA) complex formation with tetracyanoquinodimethane, tetracyanoethylene and SbCl5 are studied. EDA complexes with a spacer length of 3 methylene groups are particularly favored. The electrical conductivity of the complexes as well as of radical cation salts of the polymers generated by anodic oxidation (formation of dark foils) is low (10−5 S/cm) and the ESR signal is very broad ‐ indicating trapped electrons ‐ in contrast to highly crystalline low molecular weight fluoranthene radical cation salts.

Photochemistry of electron donor-acceptor complexes of the bis(fulvalene) dicobalt mono- and dications

Addition of carbon tetrachloride or chloroform to acetonitrile solutions of the bis(fulvalene)dicobalt monocation results in the appearance of new absorption features which are attributed to formation of electron donor-acceptor complexes. The association constants of these complexes aer 2.36 /mole fraction (carbon tetrachloride) and 2.74 /mole fraction (chloroform). Excitation in the absorption bands of the donor-acceptor complexes results in oxidation of the monocation to the dication with high quantum yields. A donor-acceptor complex is also formed when sodium tetraphenylborate is added to acetonitrile solutions of the bis(fulvalene)dicobalt dication. Spectroscopic determination of the association constant of the dication with tetraphenylborate yields a value of 26.3 /mole fraction. Excitation of the absorption bands of the ion-pair results in high quantum yields for formation of the bis(fulvalene) dicobalt monocation. Biphenyl is found in photolyzed solutions as a byproduct of the oxidation of the tetraphenylborate anion.

N–π Electron donor–acceptor complexes. II. Aliphatic amines with dinitrobenzenes

The interaction of several aliphatic amines as n-donors and dinitrobenzenes (DNB) as π-acceptors has been studied in n-hexane. The formation of electron donor – acceptor (EDA) complexes is proposed to explain the spectroscopic behaviour of the mixtures. The stability constants (Ks) for these complexes have been calculated by an iterative procedure. For a given acceptor, the donor strength of RNH2 > R2NH > R3N was found. This order is explained by considering the role that steric effect may play in the EDA complex formation. On the other hand, the fact that for a given donor Ks follows the order 1,2-DNB > 1,3-DNB > 1,4-DNB, and that 1,2-DNB reacts with primary amines, led to the proposal of orientational complexes. These EDA complexes may be considered intermediates in aromatic nucleophilic substitution reactions.

Application of organic compounds to metal-hydrogen systems as a technique for improving sorption properties: A new class of hydrogen absorbers

A technique for using organic materials to improve the sorption properties of magnesium-based hydrogen storage media is presented. Two approaches are possible. First, Mg 2Ni and SmMg 3 reversibly absorb hydrogen under more moderate conditions when they have been modified with various organic compounds (anthracene, phenanthrene, chrysene, perylene, naphthacene, phthalonitrile, tetracyanoethylene or chloranil). The hydriding behaviour of modified Mg 2Ni and SmMg 3 is associated with the formation of electron donor-acceptor (EDA) complexes by charge transfer between the alloy particles and the organic modifiers. The process of hydrogen uptake is explained by “hydrogen spill-over”, in which hydrogen species in an atomiclike form which have been activated at the EDA sites rapidly migrate to react with the adjoining alloy particles. Second, small solvated magnesium particles formed by clustering in low temperature organic matrices (tetrahydrofuran, benzene, pentane or ethyl ether) are exceptionally active and immediately begin to absorb hydrogen without requiring “activation”. The hydrogen sorption characteristics of these magnesium-organic compound systems are elucidated. The exceptional activity of these systems can be partially interpreted in terms of their structural geometry compared with that of pure magnesium. The organic matrix in which the magnesium atoms are dispersed and in which crystal growth proceeds has pronounced effects on the shape, size and catalytic properties of the particles formed.

Hydrogen absorption in modified intermetallic compound systems

The modification of Mg 2Ni by various organic compounds was investigated with a view to improving its hydrogen absorption properties. In particular Mg 2 Ni reversibly absorbed hydrogen under more moderate conditions when it had been modified with tetracyanoethylene or phthalonitrile. Studies of the treated materials using electron spin resonance and electronic spectra showed the formation of electron donor-acceptor (EDA) complexes owing to the high electron affinity of the organic species used. It is believed that the EDA complexes formed on the surface layer provide sites for hydrogen activation which is followed by the diffusion of excess hydrogen into the underlying intermetallic phase. This is consistent with the results of X-ray analysis and thermodynamic measurements.

Binding of three molecules in the excited state

It is shown that three neutral molecules can form a stable trimer if one of them is in the excited state. The formation of termolecular electron donor-acceptor complexes of sequence DDA and DAA arises from charge-resonance interaction.

The quenching of biacetyl phosphorescence by alkenes: a dissection of rate effects on exciplex formation and exciplex decay for ketone triplet quenching

Abstract : Rate constants for the quenching of biacetyl phosphorescence by alkenes at room temperature in benzene have been measured. Quenching constants correlate with the ionization potentials of the alkenes. Rate data from phosphorescence quenching for a number of ketones are compared and trends associated with formation and decay of electron donor-acceptor complexes of excited ketone triplets and alkene quenchers. (Author)

High-pressure kinetics of electron donor–acceptor complex formation and cycloaddition between tetracyanoethylene and enol ethers

The kinetics of the high-pressure cycloaddition reaction between tetracyanoethylene and enol ethers (n-butyl vinyl ether and ethyl 2-methylpropenyl ether) in chloroform have been studied, by following spectrophotometrically the disappearance of the electron donor–acceptor complex (e.d.a. complex) at 25 °C and up to 1 500 bar. It is concluded that the e.d.a. complex is on the pathway to the zwitterionic intermediate and the final cycloaddition product. The reaction volume ΔV1 of e.d.a. complex formation is –11.0 ± 1.4 and –5.8 ± 1.0 cm3 mol–1 for n-butyl vinyl ether and ethyl 2-methylpropenyl ether, respectively. The volume of activation ΔV2‡ of cycloaddition step from e.d.a. complex to the adduct is –30.8 ± 1.5 and –41.8 ± 1.5 cm3 mol–1 for n-butyl vinyl ether and ethyl 2-methylpropenyl ether, respectively. The variation of ΔV1 and ΔV2‡ is discussed from the viewpoint of the ionization potential and the electron density at the β-carbon atom of the enol ether.

Conductometric studies of electron donor-acceptor complexes

Conductometric method has been used to investigate the electron donor-acceptor complex formation between a variety of electron donors and acceptors in acetonitrile solution. The stoichiometries of these complexes have been established and their σ M values are reported. Effect of electron donors, acceptors and solvents on σ p values has been examined.

High-pressure kinetics of electron donor-acceptor complex formation and cycloaddition with tetracyanoethylene and ethyl vinyl ether

High-pressure kinetics of electron donor-acceptor complex formation and cycloaddition with tetracyanoethylene and ethyl vinyl ether

ChemInform Abstract: BI‐ AND TER‐MOLECULAR ELECTRON DONOR‐ACCEPTOR COMPLEX FORMATION BETWEEN HEXAMETHYLBENZENE AND 1,3,5‐TRINITROBENZENE, AND ALSO BETWEEN NNN′N′‐TETRAMETHYL‐P‐PHENYLENEDIAMINE AND 1,3,5‐TRINITROBENZENE IN SOLUTION

Chemischer InformationsdienstVolume 8, Issue 5 Article ChemInform Abstract: BI- AND TER-MOLECULAR ELECTRON DONOR-ACCEPTOR COMPLEX FORMATION BETWEEN HEXAMETHYLBENZENE AND 1,3,5-TRINITROBENZENE, AND ALSO BETWEEN NNN′N′-TETRAMETHYL-P-PHENYLENEDIAMINE AND 1,3,5-TRINITROBENZENE IN SOLUTION R. J. BAILEY, Search for more papers by this authorJ. A. CHUDEK, Search for more papers by this authorR. FOSTER, Search for more papers by this author R. J. BAILEY, Search for more papers by this authorJ. A. CHUDEK, Search for more papers by this authorR. FOSTER, Search for more papers by this author First published: February 1, 1977 https://doi.org/10.1002/chin.197705097Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume8, Issue5February 1, 1977 RelatedInformation

Bi- and ter-molecular electron donor–acceptor complex formation between hexamethylbenzene and 1,3,5-trinitrobenzene, and also between NNN′N′-tetramethyl-p-phenylenediamine and 1,3,5-trinitrobenzene in solution

The dependence of the line position in the 1H n.m.r. spectra of dilute solutions of the electron acceptor (A) 1, 3, 5-trinitrobenzene on the concentration of excess of the electron donor (D) hexamethylbenzene in various paraffinic solvents has been interpreted in terms of equilibria involving the complex species DA and D2A. The equilibrium quotients have been evaluated on several concentration scales.The same interpretation provides a satisfactory explanation for similar observations involving the interaction of NNN′N′-tetramethyl-p-phenylenediamine with 1, 3, 5-trinitrobenzene. The results are in accord with those obtained from optical measurements.Activity coefficient effects in themselves appear to be too small to provide an alternative explanation of the observed behaviour.

Conformations of highly hindered aryl ethers: XV. Mesomeric moments in m-dinitrobenzenes

The dipole moments of fourteen m-dinitrobenzenes with different substituents (OMe, CN, CH 3, CHO, Cl, CF 3, COOMe, F, Br, NH 2) in various positions were measured in order to study mesomeric interactions. Inclusion of conformational considerations permitted estimates to be made for the mesomeric moments of these groups at given positions. The values obtained could be applied with consistent results to a total of forty m-dinitrobenzenes, including others previously reported. The mesomeric moment increments deduced, compared with substituted benzenes possessing no nitro groups, were found to be only slightly larger than in non-nitro substituted benzenes (compared with substituted alkanes), which would indicate a reluctance of the extended π system of m-dinitrobenzene to interact with other substituents present, in any way other than by direct extension of the π network. One apparent case of intermolecular electron donor-acceptor complex formation was detected. The measured dipole moment of o-iodoanisole indicates a planar anti conformation for the methoxyl group.

Indoles and auxins : XIII. Identification and analysis of naturally occurring indoles via electron donor-acceptor complexes

The formation of electron donor-acceptor complexes of some representative indoles with a number of electron acceptors has been investigated with particular emphasis on qualitative and quantitative aspects of analysis involving thin-layer chromatography (TLC). This non-destructive method shows a detection limit for indoles, after chromatography, from 0.5 to 1 μg, depending on the structure of the indole and the electron acceptor employed. An in situ method was developed for quantitation of indoles on the sprayed chromatograms and a linear relationship between concentration of the indole and detector response of a TLC scanner for reflectance at the charge transfer band maxima was observed in the range of 0.5–10 μg. With the same electron acceptor, charge transfer band maxima from complexes on a layer of silica gel shift to longer wavelength when substituents on the indoles are changed from electron withdrawing ( e.g. −CN) to electron donating ( e.g. −OH). Separate mass spectra for indoles and complexing reagents can be obtained directly from the complex, as previously observed, at different temperatures. Some of the newer electron acceptors having low vapor pressures allow application of this method at much higher temperatures, i.e. less volatile indoles can be identified in this manner.

Thermodynamic Constants of Tetracyanoethylene Complexes with Methylated Benzenes

Formation constants, and enthalpy, free energy, and entropy changes for the tetracyanoethylene complexes with a complete series of methyl-substituted benzenes have been evaluated from the charge-transfer spectra over a temperature range of 1−50 °C in carbon tetrachloride solutions. From the literature data, it is deduced that various competing side interactions may not be significant compared to 1:1 electron donor–acceptor complex formation under certain experimental conditions. Some correlations among thermodynamic properties and vertical ionization potentials of the donors are discussed.

Thermodynamic study of the formation of electron donor-acceptor complexes by gas-liquid chromatography

Thermodynamic study of the formation of electron donor-acceptor complexes by gas-liquid chromatography

Electron-donor–acceptor complex formation by compounds of biological interest. Part III. Indole complexes

A nuclear magnetic resonance method has been used to determine the association constants of indole, 2-methyl-3-methyl-, 7-methyl-, 3-ethyl-, 3-dimethylaminomethyl-, 3-diethylaminomethyl-indole, benzothiophen, thiophen and pyrrole with either, or both, the electron acceptors 1,4-dinitrobenzene, 1,3,5-trinitrobenzene, in chloroform solution. The chemical shifts of different protons in the indole change relative to one another in the presence of large excesses of 1,3,5-trinitrobenzene. A similar phenomenon is observed in the spectrum of naphthalene.The differences in association constant of the various donors with a given acceptor, and the changes in the chemical shifts of the different protons of the donor with respect to one another, are accounted for by differences in the contribution to the intermolecular π-π interaction by different parts of the donor molecule. In general, positions of highest electron-density make the greatest contribution to this interaction.