ARTICLE IN PRESS
8
2
P.S. Berdonosov et al. / Journal of Solid State Chemistry 182 (2009) 77–82
Since the asymmetric coordination of selenium atoms is often
associated with the lone pair influence, we have performed a
topological analysis of electron localization function (ELF) for the
sharing their common faces form infinite layers. These layers are
connected by [CoO Cl ] octahedra into a 3D framework with
channels where Se atoms are situated.
4
2
Sr
tool for locating such features.
An isosurface of ELF at
¼ 0.91 for the SrSeO
shown in Fig. 5. As may be seen from the figure, at high
the first features to arise are the electron basins near the selenium
atoms, evidently representing its 4s electron pairs. The shape of
the basins is quite typical for the lone pairs that are considered
stereochemically active. These lone pairs are pointed away from
the Se–O bonds and into the channels in the structure. They are
mostly located in the ab plane, however, being slightly tilted with
respect to the c axis and not quite parallel to the ab plane. Further
3
(SeO
3
)
2
Cl
2
structure. The ELF analysis has proven to be a useful
As it was expected, the presence of Se(IV) in the structure leads
to the open 3D framework formation for all the investigated
compounds. However, all the compounds have centrosymmetric
structures regardless of the strontium substitution by d-metal
atoms. It is known from literature that selenite chloride with
Z
3
Cl
2
unit cell is
values
Z
composition Cu
crystal structures of Cu
3
(SeO
3
)
2
Cl
2
exist in two forms [19,20]. But the
Cl are different from the struc-
3
(SeO
3
)
2
2
tures of the compounds described in the presented work. From
this point of view it would be interesting to obtain a compound
2
+
containing both Sr and Cu at the same time, which is the subject
of our ongoing investigations.
analysis of
after that the lowering of
shells of Sr, O, and Cl, which is not accompanied by any changes in
Z
(r) down to
Z
¼ 0.88 reveals no extra features, and
leads to the appearance of atomic
Z
Acknowledgments
the topology of 4s-pairs of selenium that remains constant from
Z
¼ 0.91 downwards. This result is in good agreement with our
earlier assumption that the lone pairs of Se(IV) are pointed inside
the channels in the Sr (SeO Cl structure.
As follows from our experimental results, one Sr atom in the
(SeO Cl crystal structure may be substituted by d-metal.
Dr. T.B. Shatalova and Mrs. I.V. Kolesnik are gratefully acknowl-
edged for assistance in thermal and IR analysis data collection.
Presented work was supported by RFBR Grant 06-03-32134.
3
3
)
2
2
Sr
3
3
)
2
2
References
Such substitution leads to a symmetry change (Table 1) but main
structural features still remain the same.
[
[
1] C.N.R. Rao, J.N. Behera, M. Dan, Chem. Soc. Rev. 35 (2006) 375–387.
2] P.S. Halasyamani, K.R. Poeppelmeier, Chem. Mater. 10 (1998) 2753–2769.
The Sr
2
M(SeO
3
)
2
Cl
2
(M ¼ Co,Ni) phases are isostructural. In
both structures Sr atoms are surrounded by six oxygen atoms and
three chlorine atoms. The BVS calculations for such coordination
utilizing data given in Table 3 and constants from [16] give values
[3] M.S. Wickleder, Handbook on the Physics and Chemistry of Rare Earths 35
2005) 45–105.
(
[4] R. Becker, M. Prester, H. Berger, P.H. Lin, M. Johnsson, D. Drobac, I. Zivkovic,
J. Solid State Chem. 180 (2007) 1051–1059.
1
.93 for the Co compound and 1.94 for the Ni one. Cobalt and
[5] Y.-L. Shen, J.-G. Mao, H.-L. Jiang, J. Solid State Chem. 178 (2005) 2942–2946.
[6] P. Millet, B. Bastide, V. Pashchenko, S. Gnatchenko, V. Gapon, Y. Ksari,
A. Stepanov, J. Mater. Chem. 11 (2001) 1152–1157.
nickel are surrounded by octahedra formed by four oxygen atoms
at the equatorial plane and two chlorine atoms in apical positions
with the distances typical for M–O and M–Cl bonds (Table 3). Sr
polyhedra are connected by common edges in ab plane. d-Metal
atoms connect these layers into a 3D framework. Selenium atoms
are situated at the corners of the channels of the framework. They
[7] R. Becker, M. Johnsson, Solid State Sci. 7 (2005) 375–380.
[8] O.A. Dityatiev, P. Lightfoot, P.S. Berdonosov, V.A. Dolgikh, Acta Cryst. E 63
2007) i149–i150.
9] H.-L. Jiang, J.-G. Mao, J. Solid State Chem. 181 (2008) 345–354.
(
[
[
11] G.M. Sheldrick, Acta Cryst. A 64 (2008) 112–122.
12] C. Pisani, R. Dovesi, C. Roetti, HF ab-initio treatment of crystalline systems.
Lecture notes in Chemistry, vol. 48; Springer, Berlin, 1988;
[
[
are surrounded by oxygen atoms having SeO
coordination (Fig. 6).
3
E tetrahedral
The IR spectra of the new selenite chlorides presented in Fig. 1
show the usual absorption bands in ranges 884–856 and
V.R. Saunders, R. Dovesi, C. Roetti, M. Causa, N.M. Harrison, R. Orlando,
C.M. Zicovich-Wilson, CRYSTAL98, University of Torino, Torino, 1998.
[13] M.P. Habas, R. Dovesi, A. Lichanot, J. Phys. Cond. Matter 10 (1998) 6897–6909.
14] C. Gatti, TOPOND98 User’s Manual, CNR-CSRSRC, Milano, 1999.
ꢂ1
7
52–760 cm
that can be assigned to the
n
(Se–O) vibrations;
(Se–O–Sr) vibra-
M(SeO Cl are
[
ꢂ1
bands in range 679–715 cm originate from
n
2
[15] L. Laaksonen, J. Mol. Graphics 10 (1992) 33;
tions [9]. It may be noted that the spectra of Sr
more complex than Sr (SeO Cl
The substitution of strontium by barium atoms in the structure
of Sr Co(SeO Cl leads to more symmetrical phase Ba Co(SeO
Cl
[18] (space group P/nnm, a ¼ 6.7635(4), b ¼ 12.6454(7), c ¼
.3866(3) A). The principle of construction of this phase is the
same as for compounds under investigation. [BaO Cl ] polyhedra
3
)
2
2
D.L. Bergman, L. Laaksonen, A. Laaksonen, J. Mol. Graphics Modelling 15
(1997) 301.
3
3
)
2
2
.
[
17] Y. Porter, P.S. Halasyamani, Inorg. Chem. 40 (2001) 2640–2641.
18] M.G. Johnston, W.T.A. Harrison, Acta Cryst. E 58 (2002) i49–i51.
19] P. Millet, B. Bastide, M. Johnsson, Solid State Commun. 113 (2000) 719–723.
2
3
)
2
2
2
3 2
)
[
[
[
2
˚
5
7
3
[20] R. Becker, H. Berger, M. Johnsson, Acta Cryst. C 63 (2007) i4–i6.
Berdonosov, Peter S.
