Correlation between biological activity and energies of electronic transitions in benzodiazepines. Negative ion mass spectrometry and ultraviolet absorption spectroscopy study of some derivatives

Khvostenko, O. G.; Yarullina, Zemfira Sh.; Шишлов, Н. М.; Rusin, Valentine E.

doi:10.1002/(sici)1097-0231(19990630)13:12<1091::aid-rcm616>3.0.co;2-o

Cited by 14 publications

(4 citation statements)

References 10 publications

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“…In 1987 it was found in CS 2 and, further, it was shown to be of widespread occurrence in a variety of compounds . Our papers, as well as our other data (unpublished), indicate conclusively that ISRs are formed in any compounds, apart from their chemical class, in the REC energy range which is the same that presents molecular singlet electronic excitation that is observed mainly by UV absorption spectroscopy. Existence of ISRs can be seen, for instance, from a minor example depicted in Fig.…”

Section: Resultssupporting

confidence: 72%

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Anomalously long‐lived molecular negative ions of duroquinone

Khvostenko

Lukin

Tseplin

2012

Rapid Comm Mass Spectrometry

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The problem under investigation here is establishment of mechanisms of the resonant electron capture by molecules, using the example of duroquinone (2,3,5,6-tetramethyl-1,4-benzoquinone). A solution is important because it will provide new insights into the fundamental physical laws and widespread applications in various fields like molecular nanoelectronics, touched upon herein too. Resonant electron capture (REC) in duroquinone was studied with negative ion mass spectrometry of the REC as the main method, and UV absorption and the photoelectron spectroscopy as the auxiliary ones. The latter were used to study the electronic structures of the various neutral molecular states that are the parent ones for the negative molecular ions formed by electron attachment to the molecules. B3LYP/6-311 + G(d,p) calculations were widely used throughout the study. As a result, an intensive peak of the negative molecular ions with anomalously high lifetime (200 microseconds) was registered at the attached electron energy of 1.8 eV. The ions were determined to be quartets delaying the electron autodetachment because of spin prohibition and appearing via inter-system crossing from the negative molecular ion doublets produced in the core-excited Feshbach resonances. Finally, the pattern of the REC in duroquinone was obtained for the energy region of 1-4 eV which is presented by shape resonances, core-excited Feshbach resonances and by mechanisms little-known for molecules of inter-shell resonances and the formation of ion quartets. The latter were proposed to be related to the negative differential resistance in molecular nanoelectronics.

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Section: Resultssupporting

confidence: 72%

“…Many studies have been performed applying the gas‐phase REC principles to elucidate biological problems, like the report where a destructive action of slow electrons on DNA was shown . We also have examined the issue with respect to biological applications that can be also mentioned . Molecular electronics is another field of similar applications.…”

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Anomalously long‐lived molecular negative ions of duroquinone

Khvostenko

Lukin

Tseplin

2012

Rapid Comm Mass Spectrometry

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“…The electronic configuration of the M − ions at each resonance peak depends on the molecular orbitals (MOs) involved in the given resonant process as well as on the electron capture mechanism. Four such mechanisms are known: vibrationally excited Feshbach resonance (VEFR) with attachment of an additional electron onto a vacant MO having a negative energy (E el ≈ 0);5 shape resonance (SR) (E el > 0) with electron capture onto a positive energy vacant MO;6 electron‐excited Feshbach resonance (EEFR) (E el > 0), where two paired electrons are placed on the same vacant MO;7 inter‐shell resonance (ISR) (E el > 0) forming M − ions with multiplicity ( M ) of 2, but with two unpaired electrons on two different vacant MOs 8, 9…”

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confidence: 99%

“…This opinion was based on a thesis that one electron, placed on a lower UMO, shields the electron placed on a higher UMO from the positive charge of the nuclear frame; because of that the second electron (with the higher energy) cannot be in a bound state, and only the electron‐excited M − ions formed by EEFRs can exist, since they have two paired electrons on the same UMO. Some time ago, however, the IRs were found as a dominant mechanism of resonant electron capture in the energy region of the singlet electronic excitation of neutral molecules 8, 9. At IRs the corresponding M − ions have two unpaired electrons on two different UMOs.…”

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Doublet–quartet conversion in negative ions as a possible mechanism of the electron autodetachment delay

Khvostenko

Tuimedov

2006

Rapid Comm Mass Spectrometry

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Molecular negative ions with abnormally high lifetimes (20 micros) relative to electron autodetachment were registered at 1.65 eV electron energy in pyromellitic acid imide by means of negative ion mass spectrometry with resonant electron capture. Using quantum-chemical calculations, it was shown that the delay of the electron autodetachment may be caused by the conversion of an originally generated molecular ion-doublet into a molecular ion-quartet, as a result of intersystem crossing of the potential energy surfaces of these ions. It was noticed that the ion-quartet cannot decay rapidly into the molecule of the ground state because of the prohibition of the spin flip, which is similar to that for phosphorescence. It can also not decay into the parent triplets, because these triplets are higher in energy than the ion. As a whole, both prohibitions provide the observed effect of the high lifetime of the ions.

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Frozen shell approximation violation in negative ion formation from halogenated benzenes via dissociative attachment

Asfandiarov

Fokin

et al. 2000

Rapid Commun. Mass Spectrom.

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A series of benzene derivatives (R(1)C(6)H(4)R(2)) has been studied by means of electron capture negative ion mass spectrometry (ECNI-MS), and PM3 quantum chemical calculations. The dissociation channel M(-.) --> Hal(-) + (M - Hal). is analysed from the point of view of symmetry conservation. Generally, a symmetry ban on dissociation may be avoided in at least two ways: (i) out-of-plane vibrations of the halogen atom in the molecular negative ion (MNI), mixing pi- and sigma-states of the anion; (ii) symmetrical in-plane vibration of the C-Hal bond, changing the order of the empty levels in the MNI with subsequent radiationless conversion into a sigma-state. Our analysis shows that neither of them provides a satisfactory explanation of the ECNI mass spectra for chlorobenzene, if one retains the usual assumption that an additional electron goes into the LUMO of the neutral molecule. Thus, it may be concluded that in this case electron capture causes a significant perturbation of the energy ordering of vacant orbitals, thus making the frozen shell approximation inapplicable. Copyright 2000 John Wiley & Sons, Ltd.

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Correlation between biological activity and energies of electronic transitions in benzodiazepines. Negative ion mass spectrometry and ultraviolet absorption spectroscopy study of some derivatives

Cited by 14 publications

References 10 publications

Anomalously long‐lived molecular negative ions of duroquinone

Anomalously long‐lived molecular negative ions of duroquinone

Doublet–quartet conversion in negative ions as a possible mechanism of the electron autodetachment delay

Frozen shell approximation violation in negative ion formation from halogenated benzenes via dissociative attachment

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