Triphenylverdazyl Radical Research Articles

ChemInform Abstract: Triphenyl Verdazyl Radicals′ Reactivity with Alkyne Carboxylates as a Synthetic Route to 1‐(Phenyldiazenyl)isoquinoline‐3,4‐dicarboxylates.

AbstractOnly one isoquinoline product is formed if the starting radical bears either a C‐phenyl or an aryl with ortho‐ or para‐substituent.

Triphenyl verdazyl radicals’ reactivity with alkyne carboxylates as a synthetic route to 1-(phenyldiazenyl)isoquinoline-3,4-dicarboxylates

A series of 1-(phenyldiazenyl)isoquinoline-3,4-dicarboxylates are synthesized by a unique reaction of triphenyl verdazyl radical with di-substituted electron deficient alkyne carboxylates. This transformation allows for the quick synthesis of this class of compounds in just three steps starting from a hydrazone. A radical mechanism that is consistent for the substitution patterns observed in the series of compounds made is proposed. The final product is obtained by a subsequent retro-Diels–Alder reaction.

Anomalously slow rates of reduction of iron(III) polypyridine complexes by triphenyl verdazyl radicals in acetonitrile

The kinetics and mechanisms of the electron transfer reactions of [Fe(N-N)(3)](ClO(4))(3) [N-N = 2,2'-bipyridine, 1,10-phenanthroline] and [Fe(terpy)(2)](ClO(4))(3) [terpy = 2,2':6,2''-terpyridine] with a range of triphenyl verdazyl radicals have been investigated in acetonitrile at 25 degrees C and I = 0.05 mol dm(-3) (C(4)H(9))(4)NPF(6) using stopped-flow spectrophotometry. It was found that all three iron(III) complexes underwent extensive dissociation in acetonitrile and it was necessary to carry out the reactions in the presence of an excess of the relevant ligand. Under these conditions, reaction of the oxidant with the verdazyl radical resulted in an absorbance change that could be described by a single exponential. This was confirmed by global analysis of time-dependent spectra. A mechanism is proposed that accounts for the kinetic data. The rate constants for the electron transfer reaction are many orders of magnitudes less than would be predicted on the basis of the redox potentials and the self exchange rate constants of the reacting species.

Reaction of the triphenylverdazyl radical with benzotrichloride

Reaction of the triphenylverdazyl radical with benzotrichloride

Luminescence of the free triphenylverdazyl radical and of compounds related to it

Luminescence of the free triphenylverdazyl radical and of compounds related to it

Kinetics of electron transfer between semiquinones and stable radicals

1. Electron transfer leads to the oxidation of semiquinone radicals, and the reduction of nitroxyl and triphenylverdazyl radicals. 2. The value of the preexponential factor for electron transfer between semiquinone and 2,2,6,6-tetramethyl-4-oxypiperidin-1-oxyl radicals is low. 3. Over a rather wide interval of solvent viscosities, electron transfer between the anion radicals of the Na salt of 2,6-disulfo-9,10-anthraquinone (2,6-AQ-) radicals and spiroiminoxyl (II) radicals, and between 2,6-AQ- and triphenylverdzyl radicals (VII), occurs in the kinetic region. 4. The introduction of either glycerin or dioxane into the mixed solvents increased the rate constant for slow electron transfer between the anion radicals of the Na salt of 2,6-disulfo-9,10-anthraquinone and 2,2,6,6-tetramethyl-4-oxypiperidin-1-oxyl radicals.

Quantum‐chemical investigation of spatial and electronic structure of verdazyl and its derivatives

AbstractThe unrestricted HF method in the INDO approximation with optimized geometry was used to describe the electronic structure of the hetero‐ring of verdazyl and the derivatives of the latter. The results obtained are in good agreement with the experimental EPR spectra of triphenylverdazyl radical and its dipole moment. These data may be a basis for understanding and predicting the chemical properties and reactivity of verdazyl and its derivatives.

Kinetics of photochemical reactions of triphenylverdazyl radicals

1. The basic pathways of photochemical destruction of an electronically excited triphenylverdazyl radical (TPV) are stripping of hydrogen from the solvent with the formation of the corresponding leuco-base, as well as its dissociation at the N-N bond with the formation, in particular, of aniline and 1,3-diphenyl-1,2,4-triazole. 2. From the concentration dependence of the rate of quenching of the radical it was found that the product of the rate constant of concentration quenching (kq) by the lifetime of the excited state (Τ) is equal to 5·103 liters/mole. 3. The dipole moment of the radical (2.94 D in the ground state) increases to 9 ± l D upon excitation.

The Magnetic Properties of Verdazyl Free Radicals. VI. ESR Studies of Pairs and Triadst of the Symmetrical Triphenylverdazyl Radical in the 1,3,5-Triphenylbenzene Matrix

Abstract Single-crystal ESR studies have been carried out on symmetrical triphenylverdazyl (TPV) doped in a diamagnetic 1,3,5-triphenylbenzene (TPB) crystal at room temperature. There have appeared seven pairs of fine-structure absorptions in addition to the hyperfine splittings. Three out of the seven pairs have been assigned as zero-field splittings due to radical pairs, while the other three pairs have been identified as from radical triads. The six fine structure tensors have been determined through the angular variation of the resonance-field separations. The structures of the pairs and triads of TPV were discussed on the basis of the fine structure tensors, the crystal structures of TPB and TPV, and the spin distribution in the radical molecule, assuming that the unit cell of the mixed crystal with the radical concentration of less than 11.1% is identical with that of the host crystal, TPB. Within the limits of the X-ray examination, this assumption was found to be reliable. It was found that the molecular planes in each species are almost parallel to the bc-plane and that all the C-phenyl rings lie in the c-direction.

The Magnetic Properties of Verdazyl Free Radicals. III. The Anomalous Magnetic Behavior of Symmetrical Triphenylverdazyl

Abstract The static magnetic susceptibility and the ESR spectra from 1.6 to 300 K have been measured on a powder sample of the titled free radical. The broad maximum in the susceptibility which indicates an antiferromagnetic interaction has been observed at 6.9 K. The broadening of the ESR absorption line and the shift of the g-value have been found in the temperature region below Tmax, in which the susceptibility reached its round maximum. There appeared anomalies in the slope of the susceptibility, the linewidth, and the g-value versus temperature curves in the vicinity of 1.7 K. These anomalies may imply a magnetic-phase transition from the short-range ordered state to the long-range ordered state at about 1.7 K. The existence of a ferromagnetic interaction between the magnetic chains in the triphenylverdazyl radical solid is discussed on the basis of the susceptibility, the spin distribution, and the crystal structure. It is understood qualitatively that the radical with a negative spin density has a latent ferromagnetic interaction in or between the magnetic chains, and that the obsrevation of this interaction greatly depends upon the molecular and crystal structure.

Comparative investigation of the IR spectra of the triphenylverdazyl radical and its corresponding ions and leuco compound

Comparative investigation of the IR spectra of the triphenylverdazyl radical and its corresponding ions and leuco compound