ARTICLE IN PRESS
Journal of Solid State Chemistry 182 (2009) 2368–2373
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
Strontium–copper selenite–chlorides: Synthesis and structural investigation
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Peter S. Berdonosov , Andrei V. Olenev, Valery A. Dolgikh
Department of Chemistry, Moscow State University, 119991 GSP-1, Leninskie Gory, 1 build. 3, Moscow, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
Two new complex selenite–chlorides of strontium and copper Sr Cu(SeO ) Cl (I) and SrCu (SeO ) Cl
2
2
3 2
2
2
3 2
Received 7 April 2009
Received in revised form
(II) were obtained and characterized by X-ray diffraction technique, DTA and IR spectroscopy. Both
˚
˚
compounds crystallize in the monoclinic system I: Sp. gr. P2
1
/n, a ¼ 5.22996(3) A, b ¼ 6.50528(4) A,
11 June 2009
˚
˚
˚
c ¼ 12.34518(7) A,
b
¼ 91.3643(2)1, Z ¼ 2; II: Sp. gr. P2
1
,
a ¼ 7.1630(14) A, b ¼ 7.2070(14) A,
Accepted 13 June 2009
Available online 21 June 2009
˚
c ¼ 8.0430(16) A,
b
¼ 95.92(3)1, Z ¼ 2. Comparison of the crystal structure of (I) with the structures
of Sr
2
M(SeO
3
)
2
Cl
2
(M ¼ Co, Ni) was performed. The substitution of strontium atom in the structure of (I)
Keywords:
2+
9
by Cu ion with a 3d Jahn–Teller distorted surrounding leads to the lowering of the structure
Selenite
symmetry and to the appearance of the noncentrosymmetric structure of (II). The noncentrosymmetric
Crystal structure
Lone electron pair
Copper compounds
character of the structure of (II) was confirmed by SHG signal (1.2 units relative to an
sample).
a-quartz powder
&
2009 Elsevier Inc. All rights reserved.
1. Introduction
important magnetic properties, such as spin ordering and spin
frustrations [13–15].
Noncentrosymmetric (NCS) compounds exhibit a number of
interesting and useful properties such as ferroelectricity, piezo-
electricity, and second-order nonlinear optical (NLO) behavior. The
asymmetric cationic coordination environment is frequently ob-
served in NCS crystals. Two families of cations are often met in
In the present study we report the synthesis and structure
characterization of two novel strontium–copper (II) seleni-
2 3 2 2 2 3 2 2
te–chlorides Sr Cu(SeO ) Cl (I) and SrCu (SeO ) Cl (II).
2+
4+
2
. Experimental section
2.1. Synthesis and structure determination
Sr Cu(SeO ) Cl was obtained as a green fine powder using the
asymmetric environments: d-metals and lone pair ions (Sn , Se
4+
,
Te , etc.). In addition, the oxyhalides of the transition-metals and
Se(IV) or Te(IV) display a number of new structure types and unusual
magnetic properties such as low-dimensional magnetism, etc. [1–3].
In our previous work [4] the new selenite chlorides of Sr and d-
metals (Co, Ni) were described. However, all just mentioned
compounds exhibit centrosymmetric crystal structures. It is well
2
3 2
2
technique described elsewhere [4]. Strontium selenite prepared
according to [16] was mixed under argon with anhydrous
CuCl2 (Merk498%) in molar ratio 2:1. The mixture was sealed
in a quartz tube and heated at 550 1C for 48 h. The bulk
powder sample contained a very small amount of green crystals.
9
known that copper (II) cations with the d electron configuration
usually provide a good example of ions with strongly distorted
surrounding due to the first order Jahn–Teller effect. From this
point of view incorporation of copper ions into a selenite
compound may increase the probability of the NCS structure
formation. However, pure copper (II) selenite–chloride exists in
two polymorphs which are centrosymmetric and crystallize in P1
The X-ray powder pattern (2
Y range 10–1201, step size 0.011,
STADI (STOE) diffractometer, transmission mode, Ge
P
curved monochromator, CuKa1 radiation, linear-PSD) from
the obtained substance showed similarity to the patterns
obtained from Sr M(SeO ) Cl (M ¼ Co, Ni) [4]. Most of the
[
5] and C2/m [6] space groups as well as most of copper (II)
selenites, oxoselenites and diselenites [7–12]. Only one poly-
morph of Cu O(SeO ) [10] crystallizes in the NCS space group
P2 3. The mixed metal selenite–chlorides may appear to be more
appropriate for NCS formation. Moreover, the Jahn–Teller distor-
2
3 2
2
reflections on the powder diffractogram were indexed in a
monoclinic system with the parameters a ¼ 5.22995(2) A˚ ,
2
3
b ¼ 6.50527(3) A˚ , c ¼ 12.34517(7) A˚ ,
b ¼ 91.3641(2)1, similar to
1
those known for Sr M(SeO ) Cl . No contradictions with the
2
3 2
2
2+
9
tion of the Cu 3d configuration may lead to the originating of
extinctions of the P2 /n (No. 14) space group were found. The
1
structure determination based on powder data was performed. As
a model for the structure refinement, coordinates of metal,
Ã
selenium and chlorine atoms were taken from the Sr
2 3 2 2
M(SeO ) Cl
structure. The refinement was carried out utilizing the JANA2000
0