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1.
Phys Chem Chem Phys ; 22(5): 3073-3088, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-31965122

RESUMO

For the compounds promising for use as n-type semiconductors in organic electronics and energy storage devices, hexaazatrinaphthylene (HATNA) and its derivative hexamethoxy-hexaazatrinaphthylene (HMHATA), the monomolecular processes occurring under the exposure of molecules to low-energy (0-15 eV) free electrons were studied by means of resonant electron capture negative ion mass spectrometry. Resonant electron attachment results in the formation of eminently long-lived molecular negative ions (MNIs) in an abnormally wide range of incident electron energy (Ee) from 0 to 5-7 eV. For both compounds, this observation serves as an indication of the strong electron-accepting properties and high stability of MNIs against electron autodetachment. A weak yield of the only fragment NIs, dehydrogenated anions, was detected for HATNA at Ee > 6 eV. MNIs of HMHATA are less stable to dissociative decay because of the presence of weakly bound terminal substituents. This is evidenced by the mass spectral observation of intense fragmentation occurring above Ee≈ 1 eV and leading to a loss of up to 3 methyl groups as the Ee increases. A series of metastable NI peaks observed in the mass spectra testify to the delayed and sequential nature of fragmentation. Based on the principles of statistical Rice-Ramsperger-Kassel-Marcus (RRKM) theory, the theoretical model of dissociative decay of NIs was developed and then adopted to quantify the rates of ground-state anion decay via electron autodetachment. The experimentally measured electron autodetachment lifetimes and fragmentation rates were best reproduced by the model at molecular adiabatic electron affinities preset to 2.15 eV for HATNA and 1.88 eV for HMHATA, in reasonable agreement with the quantum chemical DFT PBE/3ζ predictions.

2.
J Chem Phys ; 137(6): 064308, 2012 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-22897274

RESUMO

High-spin organic molecules with dominant spin-orbit contribution to magnetic anisotropy are reported. Quintet 4-azido-3,5-dibromopyridyl-2,6-dinitrene (Q-1), quintet 2-azido-3,5-dibromopyridyl-4,6-dinitrene (Q-2), and septet 3,5-dibromopyridyl-2,4,6-trinitrene (S-1) were generated in solid argon matrices by ultraviolet irradiation of 2,4,6-triazido-3,5-dibromopyridine. The zero-field splitting (ZFS) parameters, derived from electron spin resonance spectra, show unprecedentedly large magnitudes of the parameters D: ∣D(Q1)∣ = 0.289, ∣D(Q2)∣ = 0.373, and ∣D(S1)∣ = 0.297 cm(-1). The experimental ZFS parameters were successfully reproduced by density functional theory calculations, confirming that magnetic anisotropy of high-spin organic molecules can considerably be enhanced by the "heavy atom effect." In bromine-containing high-spin nitrenes, the spin-orbit term is dominant and governs both the magnitude and the sign of magnetic anisotropy. The largest negative value of D among septet trinitrenes is predicted for 1,3,5-trinitrenobenzene bearing three heavy atoms (Br) in positions 2, 4, and 6 of the benzene ring.

3.
Nanoscale Res Lett ; 7(1): 206, 2012 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-22471942

RESUMO

We have investigated the electroluminescence spectra of the electroluminescent devices based on the new zinc complexes of amino-substituted benzothiazoles and quinolines containing the C-N-M-N chains in their chelate cycles. The spectra exhibit strong exciplex bands in the green to yellow region 540 to 590 nm due to interaction of the excited states of zinc complexes and triaryl molecules of the hole-transporting layer. For some devices, the intrinsic luminescence band of 460 nm in the blue region is also observed along with the exciplex band giving rise to an almost white color of the device emission. The exciplex band can be eliminated if the material of the hole-transporting layer is not a triarylamine derivative. We have also found the exciplex emission in the photoluminescence spectra of the films containing blends of zinc complex and triphenylamine material.

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