Hyperfine and quadrupole coupling constants of deuterium nuclei in the phosphorescent triplet states of quinoline and quinoxaline

doi:10.1016/0009-2614(75)85523-0

Chemical Physics Letters

Volume 30, Issue 1, 1 January 1975, Pages 160-164

https://doi.org/10.1016/0009-2614(75)85523-0 Get rights and content

Abstract

Results are presented of an ENDOR study on deuterium hyperfine and quadrupole interactions in the phosphorescent triplet state of two aza-aromatic molecules. Although the hamiltonian for a nucleus with spin I = 1 is more complicated than for a proton with I = $12$ it is shown that in the case of deuterons one can obtain the hf and quadrupole interaction parameters and their orientational dependence with considerable precision.

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C.A. Hutchison
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Cited by (16)

Structure and magnetic properties of aza-aromatic triplet states. the case of quinoxaline
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Citation Excerpt :
This Letter reports the results of a first exploratory study of the structure and the hcc's of triplet states of aza-aromatics by DFT methods. To this end we have chosen quinoxaline, for which a number of discrepancies were found when linking experimental hyperfine couplings with theoretical spin densities by application of different semi-empirical procedures [14–19]. No further progress was made during the last twenty years in spite of the increasing importance of magnetic resonance triplet state measurements on large aza-aromatic molecules such as the porphyrins in relation to the studies on the early stages of the photosynthetic process [11,20,21].
A recently developed quantum mechanical approach devoted to the study of structural and magnetic properties of organic free radicals was applied to the lowest triplet state of quinoxaline. From a quantitative point of view, hybrid Hartree–Fock/Kohn–Sham methods (here B3LYP) confirm their reliability, whereas the Hartree–Fock method gives disappointing magnetic results. From an interpretative point of view, spin polarization effects are well represented by the semi-empirical McConnel relation between spin densities and isotropic hyperfine couplings.
Measurement of the <sup>14</sup>N nuclear quadrupole couplings in the lowest (nπ<sup>*</sup>) excited triplet state of pyrazine by ODMR
1983, Chemical Physics
High-resolution optically detected magnetic resonance (ODMR) and optically detected electron—electron double resonance (ODEEDOR) have been performed on the lowest excited triplet states of pyrazine-h₄ and pyrazine-d₄, as dilute guests in polycrystalline benzene and cyclohexane host matrices. Computer simulated spectra have been fitted to those experimentally observed, using a spin hamiltonian which takes into account the ¹⁴N and ¹H (or ²D) nuclei of the pyrazine guest molecule. Good agreement is obtained when one ¹⁴N nuclear quadrupole energy difference, |ε_y^N - ε_z^N| ⩽ 1.3 MHz, and the remaining component, |ε_x^N| = 0.6 ± 0.2 MHz for pyrazine-d₄ in benzene-d₆.
Radicals in solution studied by endor and triple resonance spectroscopy
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High-resolution ODMR- and ODNQR spectroscopy of acridine-d<inf>9</inf> in its lowest excited triplet state
1981, Chemical Physics
High-resolution ODMR- and ODNQR spectroscopy have been performed on acridine-d₉ in its photoexcited triplet state. The nuclear quadrupole constants e²qQ/h = −4.36(3) MHz and η = 0.22(1) have been measured for the ¹⁴N nucleus, where the sign of e²qQ/h is determined relative to the signs of the fine structure parameters, D and E. The ¹⁴N ODNQR spectrum, with linewidths as low as 60 kHz, exhibits a satellite structure attributable to the ²D nucleus located at the meso-position in the molecule. For this nucleus |e²qQ/h| = 180(30) kHz may be estimated. The intensity behaviour of the ODNQR transitions as a function of the NMR rf power level leads to a coarse determination of the in-plane components of the ¹⁴N hyperfine tensor with |A_yy^N| ⩽ 0.2 MHz and |A _yy^N| ⩽ 4.7 MHz. Owing to accidental overlap of two transitions in the 2E-ODMR spectrum of acridine, the ODNQR technique had to be extended to a five-pulse sequence.
The phosphorescent triplet state of aniline in a p-xylene host crystal: a study of spin-spin and spin-lattice relaxation
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Hyperfine and quadrupole coupling constants of deuterium nuclei in the phosphorescent triplet states of quinoline and quinoxaline

Abstract

J. Chem. Phys.