Научная статья на тему 'Investigation of tin and antimony compounds using NQR, X-Ray electron and quantum-chemical calculations'

Investigation of tin and antimony compounds using NQR, X-Ray electron and quantum-chemical calculations Текст научной статьи по специальности «Биологические науки»

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Аннотация научной статьи по биологическим наукам, автор научной работы — Poleshchuk O.Kh., Kalinina E.L., Nogaj B.

The semi-empirical PM3 method was applied for analysis of such experimental parameters as NQR frequencies, energy levels in X-ray electron and X-ray fluorescence spectra. The subjects of the study were complexes of tin and antimony. The strong correlation established between the differences in the energies in the inner energy levels of tin, antimony, chlorine atoms and the corresponding CIKa shifts. The obtained correlation dependencies can be used for the characterization of the donor ability of ligands.

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Текст научной работы на тему «Investigation of tin and antimony compounds using NQR, X-Ray electron and quantum-chemical calculations»

O.Kh. Poleshchuk, E.L. Kalinina, B. Nogaj. Investigation of tin and antimony compounds using..

The value of Wiberg bond order must be not lesser than 0.3. The donor-acceptor interactions of main-group elements such as Sb and Sn described in terms of the sp hybridization just as these interactions of transition metal elements mean sd hybridization.


This study was supported by the DAAD. Ex-cellent service was offered by the Hochschulrechenzentrum of the Philipps-Universitaet Marburg.


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YflK 541.49

O.Kh, Poleshchuk*, E.L. Kalinina*, B. Nogaj**


*Tomsk State Pedagogical University

"•Institute of Physics, Adam Mickiewicz University, Poznac, Poland

This paper is a part of the systematic studies performed by us for understanding the electronic structure of organic compounds of tin and antimony. It was shown in our previous papers that the NQR, X-Ray electron and fluorescence spectroscopies provides a simple way to characterise the electronic properties for qualitative interpretations of the structure, chemical reactivity and aspects of bonding [1-5]. In this paper we try to explain the relations between 35C1-NQR frequency and the energies of the internal levels in the tin and antimony compounds.

It is well known, from Townes-Dailey approximation [6], that the "CI-NQR frequencies are proportional to the degree of ionic character of the bonds. The latest one is dependent on the effective charge on the atoms and therefore is proportional to the energies of the internal levels.

We report analogous relations for Sn and Sb compounds with organic ligands. The calculations were performed by the NDDO method in PM3 modifica-

tion in the basis of sp valent orbitals using MOPAC program [7]. The geometry of the studied compounds optimized by quantum-chemical methods is consistent with that determined in experiment for the same compound in gas phase [8].

The calculated by Koopmans ionization potentials of the valent orbitals were compared with energy orbitals from photoelectron spectra [9]. A good correlation was found between the ionization potentials calculated by PM3 method and experimental values following from the photoelectron spectra. Analysis of this correlation leads to the following relation:

IP«p= i .06IPcal-0.88 (r=0.997, s=0.09). (1)

Table 1 presents the effective charge calculated by PM3 method, the experimental X-Ray electron spectroscopy (ESCA) levels [8] and the experimentally found [5] and calculated 35C1-NQR frequencies. The following relations between the energy of ESCA levels of CI and Sn atoms and the effective charge were derived:

Вестник ТГПУ, 2000. Выпуск 9 (25). Серия: ЕСТЕСТВЕННЫЕ НАУКИ

EC12p,p=-l 1.45(~qcl)+208.98 (r=G.986, s=0.01), (2) ESn3d5/;=18.0(-qSn)+476.82 (r=0.984, s=0.01). (3)

A good correlation was also found between the experimental and calculated 35C1-NQR frequencies: v35Cl =1.49v35Cl -29 46 (r=0.990, s—0.1). (4)

exp ca! v ' ' v 7

The obtained relations (2) and (3) indicate addi-tivity of the internal energy levels as a consequence of the interaction between different ligands. In the studied compounds the ligands complete about the electron density of the central atom. The replacement of CI by CH3 groups brings about increase in the ionic character of the Sn-Cl bond which leads to elongation of these bond and to an increase in the binding orbital energy C12p3;r The binding orbital energies in the first approximation are a linear function of the effective charge of the studied atom while the values of C12p5l, and Sn3d,;, prove to be an additive function of the number of substit-uents.

Since the 35CI-NQR frequencies are proportional to the effective charge on CI atoms, they are correlated with the ESCA energy levels: EC12p.p=0.136v35CI (r=0.996, s=0.03), (5)

ESn3d,"=0.121v35Cl (r=0.996, s=0.03). (6)

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The obtained dependencies can be applied in analysis of the electronic structure of other tin compounds, in particular SnCl4L, complexes with L being an organic ligand. For these compounds ESCA could not have been recorded so far. On the other hand their 35C1-NQR spectra are well known. Table 2 presents the 35C1-NQR frequencies and energies of the ESCA levels calculated from (4) and (5) as well as the ClKa shifts obtained from X-Ray fluorescence spectra [5].

The difference between the energies of CI and Sn atoms as well as the ClKa shifts characterises the donor properties of the ligands. The following correlation was found between A(Sn3ds/,~C12p3/,) and ClKa values:

A(Sn3d5„ C12p3/J)= -1.45(-ACfKa)+288.6 (r=0.959, s=0.02). (7)

On the other hand we found that the analogous correlation between Mussbauer chemical shifts and energy of the Sn3d5/2 levels for SnCl4L2 and

SnBr4L, (experimental data were taken from the reference [6]):

8=-0.54ESn3ds/2+262.3 (r=0.959, s=0.02) (8) and between Moessbauer chemical shifts and AClKa:

8=1.7(-AC'lKa)+0.212 (r=0.970, s=0.02). - (9)

On the basis of these above-mentioned equations we found the correlation dependence between ESn3d5 2 and AClKa:

ESn3ds;,=-3.2(-AClKa)+486.5. (10)

Which is very similar to those (7) obtained for the SnCl JL,.

4 Z

The analogous correlation dependencies we obtained for the SbClsL complexes. We have also found good correlations between the AE [11] and n 35C1 as well as between AClKa and inner levels from photo-electron spectra. The dependence between the AE and v 35C1 is described by the equation:

AE(Sb3d5/2-C12p3/,)=-0.427 v35Cl+333.58 (r=0,948, s=0.03)," (11)

what means that the AE decrease with v35Cl increasing and ionicity of the Sb-Cl bond decreasing.

The dependence between the AE and AClKa was described by the equation:

AE(Sb3d5/2-C12p3„)= 12.1 (-AClKa)+320.9 (r=0.926, s=0.O4),~ (12)

what means that qSb increase with the DN ligand properties increase. If the ligand gives more and more the electron density to the central atom, than more and more the electron density from central atom is transferred. The dependencies (7) and (12) are completely different for SbCl5L and SnCl4L2 complexes. It could be explain by the difference between Sn and Sb atoms. It is well known [12], that the change of the trans-shorting of the central atom - ligand bond length to trans-influence of ligand upon exchange from Sn to Sb can be observed.

These relations order the ligand in the following sequence with respect to their donor properties. This sequence is in the agreement with the ordering given by Gutitun [13]:

PhN02<MeCN<PhCN<0(CH,)40<Me0H<Me2S0< <Me2NC0H<Py<(Me,N)3P0~

Table t

The energies of ESCA levels for Sn(IV) compounds studied

Compound ECI2p3/J [eV| „ PM3 ~4a [el ESn3ds„ [eVI qs/M3 [e| vanp [MHz] va" [MHz]

SnCl4 206.19 0.253 494.92 1.011 24.10 36.22

MeSnCl3 205.52 0.294 494.06 0.957 20.24 32.77

Me2SnCl2 204.96 0.340 493.21 ■ 0.901 15.46 29.71

MejSnCl 204.49 0.400 492.27 0.843 11.73 28.08

Me4Sn - - 491.38 0.829 - -

V. P. Gladysev, S. F. Ko vale va, E.V. Kolesnicova. Concept of techogenesis dependent food chains

Table 2

The MCI-NQR frequiencies and the energies of ESCA levels calculated by (5) and (8) equations a$ well as the CIKa shifts obtained

from X-Ray fluorescence spectra for SnCI4L, complexes

L vcrP ECI2pw A(Sn3d5J-CI2p3/2) -ACIKa

[MHz] leVI ieV'i lev J leV]

(Me2N)3PO 17.91 205.32 493.61 288.29 0.215

Bz2S 18.33 205.37 493.70 288.33 0.155

(CH2)40 19.02 205.47 493.84 288.37 0.141

Me2NCOH 17.71 205.27 493.59 288.32 0.162

0(CH2)40 19.46 205.51 493.96 288.45 0.079

Py 17.73 205.27 493.59 288.32 0.165

Me2SO 18.32 205.35 493.72 288.37 0.119

MeOH 18.89 205.43 493.84 288.41 0.108

MeCN 20.12 205.60 494.10 288.50 0.075

PhCN 19.79 205.55 494.03 288.48 0.062

Table 3

The "CI-NQR frequencies and the energies of the photoelectron levels as well as the CIKa shifts obtained from X-Ray fluorescence

spectra for SbClsL complexes

I v*a AE(Sb3d5/2-C12p3/2) -ACIKa

(MHz) [eV] [eV|

(Me2N),PO 24.54 323.10 0.189

Py 25.30 322.78 0.148

Me2NCOH 24.90 322.95 0.156

0(CH2)4)0 25.65 322.63 0.133

MeCN 25.93 322.51 0.140

PhCN 26.21 322.39 0.136

PhN02 26.68 322.19 0.110


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V.P. Gladysev*, S. V. Kovaleva*, E. V. Kolesnikova**

yflK 631.416+581.192+577.4


'Tomsk State Pedagogical University •Institute of Chemical Ecology of International Academy of Creative Endeavors

At the normal conditions of life activity, the organism of a human being needs 22 biogenous elements which source is water and food of vegetal and animal origin. A state of environment is a major factor of human existence, since it is environment that determines the quality of nutritive [1].

The content of chemical elements in alive organisms is not a direct function of their abundance in nature [2]. At the same time it is known that the passage of chemical elements along a food chain can lead to both their dissipation and their accumulation, biological concentration [3].

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