EPR and Optical Absorption Spectra of Cr<sup>3+</sup> Ions in Lithium Sulphate Single Crystals

Alybakov, A. A.; Bujko, V. M.; Sharsheev, K.

doi:10.1002/crat.19790140816

Cryst Res and Technol

1979

DOI: 10.1002/crat.19790140816

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EPR and Optical Absorption Spectra of Cr³⁺ Ions in Lithium Sulphate Single Crystals

A. A. Alybakov

V. M. Bujko

K. Sharsheev

Abstract: Optical absorption and EPR spectra of Li,SO, H,O crystals doped with Cr3+ are studied at liquid nitrogen temperature. The bands are found in absorption spectra with maxima about 17 000, 23 800 and 37 200 cm-I, assigned to the "A, -. 4T,, "A, -. "TI and 4A, -c 4T1 ("P) transitions, respectively. The crystal field theory parametem were determined and appeared to be as follows: Dq = 1700 cm-', B = 667 cm-', C = 3002 cm-I.The lines resulting from Cr3+ ions are found in EPR spectra. All lines are doublets, which is… Show more

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“…H,O, LiKSO, and LiNaSO, crystals doped with Cr3+ (ALYBAKOV et al 1979(ALYBAKOV et al , 1982 and the change of spectra of chromium-doped lithium and lithium-potassium sulphates under the X-irradiation (ALYBAKOV et al 1980(ALYBAKOV et al , 1983. It was shown, that X-irradiation results in weakening of Cr3+ ion absorption bands; at the same time a new band appears at about 350 nm in Li,SO, : Cr and about 355 nni in LiKSO, : Cr.…”

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Irradiation‐induced change of valence of Cr³⁺ ions doped in alkali sulphates

Alybakov

Gubanova

Kudabaev

et al. 1984

Cryst. Res. Technol.

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It is shown by rneaiis of investigation of both optical absorption spectra and Roentgen Kal-lines of chroiiiiuni doped in LiKSO,, LiNaSO,, and Li,SO,. H,O crystals, t h a t Xirradiation results in change of the impurity charge state in a following way : Cr3+ + h+Cr4, Cr4+ + h + Cr5+.Earlier we have studied the EYR and optical absorption spectra of LizSO,. H,O, LiKSO, and LiNaSO, crystals doped with Cr3+ (ALYBAKOV et al. 1979(ALYBAKOV et al. , 1982 and the change of spectra of chromium-doped lithium and lithium-potassium sulphates under the X-irradiation (ALYBAKOV et al. 1980(ALYBAKOV et al. , 1983. It was shown, that X-irradiation results in weakening of Cr3+ ion absorption bands; at the same time a new band appears at about 350 nm in Li,SO, : Cr and about 355 nni in LiKSO, : Cr. A new group of lines appears also in a highfield side of EPR spectrum of the irradiated crystal; spectrum is described by spin-Hamiltonian with 8 = 1/2. This spectrum is absent in irradiated undoped crystals, therefore its appearance was supposed to be connected with a chromium valence change. The spectruin is stable a t a room temperature, consequently, it may not be due t o either divalent or tetravalent chromium. We supposed, that Cr3+ converts in Cr+ by means of a successive capture of two electrons, Cr+ being in a low-spin state (X = l / 2 ) in the assumption of a strong crystalline field.A subsequent investigation has shown, that the intensity of a irradiation-induced absorption band in anhydrous sulphates increases when heating and becomes maximal after the annealing a t 200 'C; at LNT this band has a clearly pronounced fine structure (Fig. 1). The separation between the fine structure components is -830 cm-' in LiKSO, : Cr spectrum and -806 cm-l in LiNaSO, : Cr spectrum. It is difficult t o explain the appearance of a fine structure, if one connects the irradiation-induced absorption band with Cr+. On the other hand, absorption bands in the region of 350 t o 360nm with a fine structure were observed earlier in the crystals, containing Cr5+ ions in the oxygen environment (BAKKS et al.; SIMO et al.); the fine structure was interpreted, as electronic-vibrational one due t o interaction with a v,-mode of chromate ion.I n principle, during the irradiation chroniium ions may trap either electrons or holes. To elucidate a question about a valent state of chromium in the irradiated crystals of alkali sulphates, we have studied Roentgen K,>-lines of chromium in these crystals. Such an investigation is a direct way of studying of a valence change, as the displacement of K,,-lime maximum is completely caused by the change of the number of valent electrons. Figure 2 shows Kal-lines of chroinium in different valent states. The positions of chromium lines in standard samples were used t o construct the dependence of a line

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mentioning

confidence: 97%

Irradiation‐induced change of valence of Cr³⁺ ions doped in alkali sulphates

Alybakov

Gubanova

Kudabaev

et al. 1984

Cryst. Res. Technol.

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Quantum‐theoretical calculation of activation parameters for mass transfer and mass transport processes on ionic crystals (V)

Winzer

1980

Cryst Res and Technol

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A report is given on the calculation of activation parameters for mass transfer and mass transport processes for ionic crystals on a quantum-theoretical basis. Einstein's model for calculating the internal energy of ionic crystals and the specific heat was extended and applied to the problems of mass transfer and transport, the frequency of the optical phonons and the characteristic oscillation frequencies of the crystals (Einstein frequency, Debye-frequency) being employed for the calculation. The experimentally determined activation energies of the mass transfer and transport processes were compared with the values calculated on a quantum theoretical basis which resulted in good agreement.Es wird uber die Berechnung von Aktivierungsparametern fur Stoffubergangs-und Stofftransportvorgknge fur Ionenkristalle auf quantentheoretischer Grundlage berichtet. Das Einstein-Model1 zur Berechnung der inneren Energie von Ionenkristallen sowie der spezifischen WIrme wurde erweitert und auf die Problematik der Stoffubergangs-und Transportprozesse angewendet, wobei die Frequenz der optischen Phononen bzw. die charakteristische Schwingungsfrequenz der Kristalle (Einstein-Frequenz, Debye-Frequenz) zur Berechnung herangezogen wurde. Die experimentell ermittelten Aktivierungsenergien fur die Stoffubergangs-und Stofftransportprozesse werden mit den auf quantentheoretischer Grundlage berechneten Werten verglichen, wobei gute Ubereinstimmung gefunden wurde.

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Synthesis, Structure−Activity Relationships, and Molecular Modeling Studies of N-(Indol-3-ylglyoxylyl)benzylamine Derivatives Acting at the Benzodiazepine Receptor^,

et al. 1996

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A number of N-(indol-3-ylglyoxylyl)benzylamine derivatives were synthesized and tested for [3H]flunitrazepam displacing activity in bovine brain membranes. Some of these derivatives (9, 12, 14, 15, 17, 27, 34, 35, 38, 41, and 45) exhibited high affinity for the benzodiazepine receptor (BzR) with Ki values ranging from 67 to 11 nM. The GABA ratio and [35S]-tert-butylbicyclophosphorothionate binding data, determined for the most active compounds, showed that they elicit an efficacy profile at the BzR which depends on the kind of substituent present on the phenyl ring of the benzylamine moiety. Moreover, lengthening (propylamine derivatives 1-3) and shortening (aniline derivatives 46-54) of the distance between the phenyl ring and the amide group of the side chain gave compounds with a drastically lower binding potency. The biological results are discussed in the light of a recently proposed pharmacophore model and compared, by molecular modeling studies, with those obtained from effective BzR ligands.

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EPR and Optical Absorption Spectra of Cr³⁺ Ions in Lithium Sulphate Single Crystals

Cited by 3 publications

References 5 publications

Irradiation‐induced change of valence of Cr³⁺ ions doped in alkali sulphates

Irradiation‐induced change of valence of Cr³⁺ ions doped in alkali sulphates

Quantum‐theoretical calculation of activation parameters for mass transfer and mass transport processes on ionic crystals (V)

Synthesis, Structure−Activity Relationships, and Molecular Modeling Studies of N-(Indol-3-ylglyoxylyl)benzylamine Derivatives Acting at the Benzodiazepine Receptor^,

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EPR and Optical Absorption Spectra of Cr3+ Ions in Lithium Sulphate Single Crystals

Cited by 3 publications

References 5 publications

Irradiation‐induced change of valence of Cr3+ ions doped in alkali sulphates

Irradiation‐induced change of valence of Cr3+ ions doped in alkali sulphates

Quantum‐theoretical calculation of activation parameters for mass transfer and mass transport processes on ionic crystals (V)

Synthesis, Structure−Activity Relationships, and Molecular Modeling Studies of N-(Indol-3-ylglyoxylyl)benzylamine Derivatives Acting at the Benzodiazepine Receptor,

Contact Info

Product

Resources

About

EPR and Optical Absorption Spectra of Cr³⁺ Ions in Lithium Sulphate Single Crystals

Irradiation‐induced change of valence of Cr³⁺ ions doped in alkali sulphates

Irradiation‐induced change of valence of Cr³⁺ ions doped in alkali sulphates

Synthesis, Structure−Activity Relationships, and Molecular Modeling Studies of N-(Indol-3-ylglyoxylyl)benzylamine Derivatives Acting at the Benzodiazepine Receptor^,