Structure of 3,4-dihydro-2,4,6-triphenyl-s-tetrazin-1(2H)-yl free radical by crystal-packing analysis and x-ray diffraction

Williams, Donald E.

doi:10.1021/ja01033a052

Cited by 38 publications

(4 citation statements)

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“…The remaining 18% of the total spin density is delocalized over the C-atoms with the majority being distributed over the ortho-and para-positioned carbons of the N-bound phenyl rings. While the DFT-optimized geometry is in good agreement with the X-ray crystal structure 46,47 and earlier low-level ab initio calculations, 48 the theoretical spin density is corroborated by electron paramagnetic resonance data. 49 Both, the extensive delocalization of the unpaired electron and the conformational stability of the electronic ground state rationalize the remarkably high stability of this open-shell species.…”

Section: Molecular and Electronic Structuresupporting

confidence: 77%

Ultrafast primary processes of the stable neutral organic radical, 1,3,5-triphenylverdazyl, in liquid solution

Weinert

Wezisla

Lindner

et al. 2015

Phys. Chem. Chem. Phys.

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Femtosecond spectroscopy with hyperspectral white-light detection was used to elucidate the ultrafast primary processes of the thermodynamically stable organic radical, 1,3,5-triphenylverdazyl, in liquid acetonitrile solution at room temperature. The radical was excited with optical pulses having a duration of 39 fs and a center wavelength of 800 nm thereby accessing its energetically lowest electronically excited state (D1). The apparent spectrotemporal response is understood in terms of an ultrafast primary D1-to-D0 internal conversion that generates the electronic ground state of the radical in a highly vibrationally excited fashion within a few hundred femtoseconds. The replenished electronic ground state subsequently undergoes vibrational cooling on a time scale of a few picoseconds. The instantaneous absorption spectra of the radical derived from the femtosecond pump-probe data are analyzed within the Sulzer-Wieland formalism for calculating the electronic spectra of "hot" polyatomic molecules. The pump-probe spectra together with transient anisotropy data in the region of the D0 → D1 ground-state bleach gives evidence for an additional transient absorption that arises from a dark excited state, which gains oscillator strength with increasing vibrational excitation of the radical by virtue of vibronic coupling.

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Section: Molecular and Electronic Structuresupporting

confidence: 77%

Ultrafast primary processes of the stable neutral organic radical, 1,3,5-triphenylverdazyl, in liquid solution

Weinert

Wezisla

Lindner

et al. 2015

Phys. Chem. Chem. Phys.

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“…Pertinent bond lengths and bond angles of 2 − 4 are given in Table . The data of the central hydrazidinyl moiety N1−N2−C3−N4−N5 are very similar to those of 1,3,5-triphenylverdazyl and other 1,3,5-triarylverdazyls. − As in these compounds the four nitrogens of the verdazyl ring in 2 − 4 are nearly planar and the verdazyl ring has an unsymmetrical boat conformation, with both C3 and C6 being out of the nitrogen plane on the same side. C3 is displaced by only +0.1 Å, while C6 is displaced by +0.6 Å.…”

Section: Resultsmentioning

confidence: 57%

Magnetic Properties and Crystal Structures of 1,5-Diphenylverdazyls with Electron Acceptor Groups in the 3-Position

Mito¹,

Takeda²,

Mukai³

et al. 1997

J. Phys. Chem. B

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The magnetic properties of four diphenylverdazyls (2−5) with electron acceptor groups in the 3-position were studied by measuring the magnetic susceptibility and heat capacity. The crystal structures of 3 and 4 were determined, and for 2 the crystal structure analysis led to an improved refinement. Verdazyl 2 was found to be an antiferromagnet with a Neel temperature of T N = 1.16 ± 0.04 K. Above the transition temperature T N, 2 behaves as a quasi-one-dimensional Heisenberg ferromagnet with the intrachain exchange interaction of 2J/k B = +7.0 ± 1.0 K. The interchain exchange interaction zJ‘/k B was estimated to be −1.5 ± 0.2 K, where z is the number of interchain bonds per spin. On the other hand, 3 and 5 behave as 1D nonalternating and alternating Heisenberg antiferromagnets with an exchange interaction of 2J/k B = −11.6 K and 2J 1/k B = −113 K (alternation parameter α = J 2/J 1 = 0.4), respectively. The susceptibility of 4 follows the Curie−Weiss law with a negative Weiss constant of −18 K above 100 K. Below 100 K, 4 showed anomalous magnetic behavior that cannot be explained by a simple model. The magnetic properties of 2−4 are discussed based on the results obtained by crystal structure analyses.

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“…Let us consider to this end the structure of the initial complex, e.g., ZnRz, in greater detail. The construction of possible molecular diagrams of this complex with allowance for R radical structure [23] shows that due to steric hindrances created by phenyl groups, the zinc ion cannot come sufficiently near the radical on the side of the unshared electron pair of N2 or N4, lying in the xy plane of the heterocycle. (The normal Zn-N bond length in zinc complexes is 2.05 ?…”

Section: Determination Of Parameters Appearing In Marcus Equationsmentioning

confidence: 99%

Kinetics and mechanism of electron transfer via bridge metal‐ion

Maletin¹

1986

Int J of Chemical Kinetics

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The kinetics and mechanism of electron transfer between stable verdazyl radicals via bridge Mn(II), Co(II), Ni(II), Cu(I), and Zn ions have been studied in the range 280-330 K using the stopped-flow technique. It was found that the kinetic features of the reactions could be described in terms of the Marcus theory. The reorganization energy of the inner coordination sphere (ICS) of intermediate complexes was estimated from the reported data on the energy of release of various ligands from the ICS of similar complexes. The rest of the kinetic parameters (solvent reorganization energy, transmission coefficients, enthalpy, and entropy of activation) were determined from Marcus equations and from plots of rate constant versus temperature, "standard free energy, and polarity of the medium. It was also found that the reactions under consideration are nonadiabatic and the transmission coefficient value depends on the mean lifetimes of ligands in the ICS.

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Structure of 3,4-dihydro-2,4,6-triphenyl-s-tetrazin-1(2H)-yl free radical by crystal-packing analysis and x-ray diffraction

Cited by 38 publications

References 1 publication

Ultrafast primary processes of the stable neutral organic radical, 1,3,5-triphenylverdazyl, in liquid solution

Ultrafast primary processes of the stable neutral organic radical, 1,3,5-triphenylverdazyl, in liquid solution

Magnetic Properties and Crystal Structures of 1,5-Diphenylverdazyls with Electron Acceptor Groups in the 3-Position

Kinetics and mechanism of electron transfer via bridge metal‐ion

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