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Four new chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl: Syntheses, crystal structures and optical properties
Author's Accepted Manuscript
Four new chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl: syntheses, crystal Structures and optical properties Chao Li, Kai Feng, Heng Tu, Jiyong Yao, Yicheng Wu
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S0022-4596(15)00100-0 http://dx.doi.org/10.1016/j.jssc.2015.03.013 YJSSC18829
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Journal of Solid State Chemistry
Received date: 10 January 2015 Revised date: 12 March 2015 Accepted date: 15 March 2015 Cite this article as: Chao Li, Kai Feng, Heng Tu, Jiyong Yao, Yicheng Wu, Four new chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl: syntheses, crystal Structures and optical properties, Journal of Solid State Chemistry, http://dx.doi.org/10.1016/j.jssc.2015.03.013 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Title: Four
New Chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl,
KBa2SnS4Br and CsBa2SnS4Cl: Syntheses, Crystal Structures and Optical Properties Authors: Chao Lia, b, c, Kai Fenga, b, c, Heng Tua, b, c, Jiyong Yaoa, b∗ , Yicheng Wua, b Affiliation:
a
Center for Crystal Research and Development, Technical Institute of
Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China b
Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of
Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China c
University of the Chinese Academy of Sciences, Beijing 100049, China
*Corresponding author: Jiyong Yao Key Laboratory of Functional Crystals and Laser Technology Technical Institute of Physics and Chemistry, CAS Beijing 100190, P.R. China Tel: 86-10-82543725; Fax: 86-10-82543725. E-mail: [email protected]
∗
To whom correspondence should be addressed. Email: [email protected]
ABSTRACT Four new chalcohalides, namely NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl, have been synthesized by the conventional high temperature solid-state reactions. They crystallize in three different space groups: space group I4/mcm for NaBa2SnS4Cl and KBa2SnS4Cl, Pnma for KBa2SnS4Br, and P21/c for CsBa2SnS4Cl. In all four compounds, the X– halide anions are only connected to six alkali metal or Ba cations, and the Sn atoms are only tetrahedrally enjoined to four S atoms. However, the M-X-Ba pseudo layers and the SnS4 tetrahedra are arranged in different ways in the three structural types, which demonstrates the interesting effect of ionic radii on the crystal structures. UV-vis-NIR spectroscopy measurements indicate that NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl have band gaps of 2.28, 2.30, 1.95, and 2.06 eV, respectively.
Keywords: Chalcohalide; Synthesis; Crystal structure; Optical property
1. Introduction The mixed-anion compounds have been intensively investigated for their unique bonding characteristics and fascinating physical properties. For example, the LnFeOPn (Ln = rare-earth; Pn = P, As) [1-3] oxypnictides are the first Fe-based high temperature superconductors and tremendous research has been carried out to increase the Tc or to elucidate the superconducting mechanism. [(Bi4Te4Br2)(Al2Cl6–xBrx)]Cl2 [4], synthesized from Lewis acidic organic ionic liquids, contains an unusual framework with n-type semiconducting behavior. BiCuOSe [5, 6] possesses two-dimensional layer structure and large conductivity of ı = 3.3 S•cm–1. Hg3Q2Bi2Cl8(Q = S, Se) [7] may have application in X-ray and Ȗ-ray detection owing to their high specific densities, high atomic numbers and wide band gaps. Ba3AGa5Se10Cl (A = Cs, Rb, K) [8] have an interesting open-framework and strong IR second harmonic generation (SHG) effect. In a previous work, we reported the syntheses, structures, and physical properties of six new chalcohalides, i.e. Ba3GaS4X (X = Cl, Br), Ba3MSe4Cl (M = Ga, In), Ba7In2Se6F8, and NaBa4Ge3S10Cl [9, 10]. Ba3GaQ4X (Q = S, X = Cl, Br; Q = Se, X = Cl) possess zigzag BaX pseudo-layers and isolated GaQ4 tetrahedra. Ba3InSe4Cl is comprised of alternating Ba-In-Se pseudo-layer and Ba-Cl pseudo-layer. Ba7In2Se6F8 contains one-dimensional ∞1[InSe 3 ]3− chains and unique [Ba 7 F8 ]6+ chains. Interestingly, NaBa4Ge3S10Cl is built of pseudo-layers of [Ge3S9] rings with Ba, Cl, and S atoms in the inter-spaces, leading to a large band gap and moderate SHG response.
In this paper, we extend our exploration to the M-Ba-Sn-S-X (M = alkali metal, X = halogen) system, hoping that the different charge/size combination of alkali metal/alkaline-earth metal mixed cations may have different influence on the packing of the anionic structural units, which in turn will increase the chance to isolate new phases with interesting stoichiometries, structures, and properties. Our efforts have led to the discovery of four new compounds, namely NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl, which adopt three different structural types. In this paper, we report their syntheses, crystal structures, and optical properties.
2. Experimental 2.1 Single–crystal growth The following reagents were all used as obtained from Sinopharm Chemical Reagent Co., Ltd.: Ba (99.9%), Sn (99.99%), S (99.999%), NaCl (99.999%), KCl (99%), CsCl (99%), and KBr (99%). BaS and SnS2 were synthesized by high temperature reaction of elements in sealed silica tubes evacuated to 10–3 Pa. Mixtures of BaS, SnS2, and MX (M = Na, K, Cs; X= Cl, Br) in the molar ratio of 1:1:1 were ground and loaded into fused-silica tubes under an Ar atmosphere in a glove-box, which were sealed under 10–3 Pa atmosphere and then placed in a computer-controlled furnace. The samples were heated to 1123 K in 20 h and kept at that temperature for 48 h, then cooled at a slow rate of 4 K/h to 673 K, and finally cooled to room temperature. The resultant dark red crystals were manually selected
for structure characterization. Analyses of the crystals with an EDX-equipped Hitachi S-4800 SEM (Table 1) showed the presence of M:Ba:Sn:S:X in the approximate molar ratio of 1:2:1:4:1.
2.2 Solid–state synthesis Polycrystalline samples of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl were synthesized by solid–state reaction technique. Mixtures of BaS, SnS2, and MX according to the stoichiometric ratio were ground and loaded into fused silica tubes under an Ar atmosphere in a glovebox, which were sealed under 10–3 Pa atmosphere and then placed in a computer-controlled furnace. The samples were heated to 1173 K in 20 h, kept at that temperature for 48 h, and then the furnace was turned off. X-ray powder diffraction analyses of the powder samples were performed at room temperature in the angular range of 2ș = 10–70º with a scan step width of 0.05º and a fixed counting time of 0.2 s/step using an automated Bruker D8 X-ray diffractometer equipped with a diffracted monochromator set for Cu KĮ (Ȝ = 1.5418 Å) radiation. Fig. 1 shows XRD patterns of the polycrystalline samples of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl along with the calculated ones on the basis of the single crystal crystallographic data. The experimental patterns for KBa2SnS4Br and CsBa2SnS4Cl are in good agreement with the calculated ones, while some minor SnS impurity exist in the NaBa2SnS4Cl and KBa2SnS4Cl product. Numerous attempts have been tried to get rid of this impurity, but failed.
2.3 Structure determination Single-crystal X-ray diffraction data were collected with the use of graphite–monochromatized Mo KĮ (Ȝ = 0.71073 Å) radiation at 293 K on a Rigaku AFC10 diffractometer equipped with a Saturn CCD detector. The collection of the intensity data, cell refinement and data reduction were carried out with the use of the program CrystalClear [11]. Face-indexed absorption corrections were performed numerically with the use of the program XPREP [12]. The structures were solved with the direct methods program SHELXS and refined with the least–squares program SHELXL of the SHELXTL.PC suite of programs [12]. When elements next to each other in the periodic table are involved, the atomic assignment was based on the bonding characteristics and bond valence sums calculations. In mixed anions compounds, there exists a bonding propensity that a highly electronegative element (e.g., O, F, Cl) tends to form strong ionic bonding with a highly electropositive element (e.g., alkali metal, alkaline-earth metal and rare-earth metals),whereas a less electronegative element (e.g., P, As, S, Se, Te) tends to form a stable covalent bonding with a less electropositive element (e.g., transition metal, or p-block
element).
Thus
in
NaBa2SnS4Cl,
KBa2SnS4Cl,
KBa2SnS4Br,
and
CsBa2SnS4Cl, all atoms connected to the Sn atoms were assigned as S atoms and the one connected to Ba (M) only was assigned as Cl atoms. The assortment of Cs and Ba in CsBa2SnS4Cl was based on the obviously longer Cs–S/Cl bond lengths than Ba–S/Cl ones. Besides, this assignment gives BVS of 1.059 for Cs and 1.867 for Ba, while switching the assignment will result in BVS of 0.760 for Cs and 2.588 for Ba,
which further prove the validity of the current atom assignment. The final refinement included an anisotropic displacement parameters and a secondary extinction correction. Additional experimental details are given in Table 2 and selected metrical data are given in Table 3, Table 4, and Table 5. Further information may be found in Supplementary Material.
2.4 Diffuse reflectance spectroscopy A Cary 5000 UV–vis–NIR spectrophotometer with a diffuse reflectance accessory was used to measure the spectra of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl in the range of 400 nm (3.10 eV) to 1500 nm (0.83 eV).
3. Results and discussion 3.1 Crystal structure of NaBa2SnS4Cl and KBa2SnS4Cl NaBa2SnS4Cl (Fig. 2A) and KBa2SnS4Cl are both isostructural to our previously reported Ba3InSe4Cl [9] and belong to the Cs3CoCl5 structure type in the centrosymmetric tetragonal space group I4/mcm [13]. So, only the structure of NaBa2SnS4Cl is
discussed
here.
In
the
asymmetric
unit,
there
is
one
crystallographically independent Ba atom, one Sn atom, one S atom, one Cl atom, and another metal site occupied by Ba and Na atom simultaneously with occupancy of 50% for each. As there are no metal–metal or S–S bonds in the structure, the
oxidation states of 1+, 2+, 4+, 2–, and 1– can be attributed to Na, Ba, Sn, S and Cl, respectively. Here, the more electronegative Cl atom is connected to the highly electropositive Ba and Ba/M atoms only and the less electropositive Sn is only connected to the less electronegative S element. Fig. 2B describes the coordination environments of all cations. Sn atom is surrounded by four S atoms in perfect tetrahedral geometry with identical Sn–S bond length of 2.365(3) Å, resembling those of Ba7Sn5S15 (2.361(1)–2.407(1) Å) [14]. Ba1 atom is enjoined by eight S atoms and two capping Cl atoms to form a bicapped square anti-prism. The identical Ba1–S bond length is 3.432(2) Å, similar to those of Ba3PrInS6 (3.171(1)–3.335(1) Å) [15], and the Ba1–Cl length is 3.576(1) Å, longer than that of BaCl2 (3.159(1)–3.197(1) Å) [16]. Ba2/Na2 atom is coordinated to six S and two capping Cl atoms in a bicapped trigonal prism with Ba2/Na2–S bond length of 3.066(3)–3.277(3) Å and Ba2/Na2–Cl bond length of 3.135(2) Å, comparable to those of Ba3GaS4Cl (Ba–S: 3.029(1)–3.612(1) Å) [9] and Ba–Cl (3.134(1)–3.406(1) Å) [16]. The SnS4 tetrahedra and Ba atoms may be viewed as arranged in the plane perpendicular to the c–axis and Ba/Na and Cl atoms are arranged in another plane. These two kinds of planes are stacked alternately to build up the complete structure.
3.2 Crystal structure of KBa2SnS4Br Resembling our previously reported Ba3GaS4Cl [9], KBa2SnS4Br belongs to the Ba3FeS5 structure type [17] in centrosymmetric orthorhombic space group Pnma (Fig. 3A). In the asymmetric unit, there is one crystallographically independent Ba1 atom, one Sn atom, three S atoms, one Br atom, and one independent site occupied by Ba2 and K2 atom simultaneously with occupancy of 50% for each. The oxidation states of 1+, 2+, 4+, 2–, and 1– can be attributed to K, Ba, Sn, S, and Br, respectively and charge balance is achieved. Similar to NaBa2SnS4Cl [10], the more electronegative Br atom is only connected to Ba and Ba/K atoms while the less electropositive Sn atom is only enjoined to the S atoms here. Sn atom is surrounded by four S atoms to generate a tetrahedron with Sn–S inter-atomic distances of 2.346(2)–2.362(3)Å, comparable to those in BaSn2S5 (2.421(4)–2.596(3) Å) [14]. Ba1 and Ba2/K2 atoms are both only coordinated to six S atoms and two Br atoms with Ba1–S bond length of 3.086(2)–3.262(2) Å, Ba2/K2–S distances of 3.275(2)–3.697(2)Å and Ba–Br bond distances of 3.306(1)–3.594(1) Å (Fig. 3B), similar in those of BaCeSn2S6 (Ba–S: 3.042(5)–3.305(5) Å)) [18] and BaBr2 (2.580–3.649 Å) [16].
In addition, KBa2SnS4Br may be viewed as originating
from our previously reported Ba3GaS4Cl [9] compound with the Ga3+ and half Ba22+ cations in Ba3GaS4Cl occupied by Sn4+ and K+ cations respectively. As reported in Ba3GaS4Cl, the structure of KBa2SnS4Br can be presented as K2/Ba2-Br-Ba1 zigzag pseudo
layers stacked along a direction with SnS4 tetrahedra in the interspaces.
3.3 Crystal structure of CsBa2SnS4Cl CsBa3SnS4Cl crystallizes in centrosymmetric monoclinic space group P21/c (Fig. 4A). There are two crystallographically independent Ba atoms, one Cs atom, one Sn atom, four S atoms and one Cl atom in the asymmetric unit. All atoms are at general Wyckoff sites 4e.The oxidation states of 1+, 2+, 4+ 2– and 1– can be readily attributed to Cs, Ba, Sn, S and Cl, respectively. As presented in Fig. 4B, Sn atom is in tetrahedral geometry with Sn–S distances of 2.354(2) to 2.389(2) Å, comparable to those of Sn atoms with similar coordination in Ba7Sn5S15 (2.361(1)–2.407(1) Å) [14] and Sr2SnS4(2.371(1)–2.409(1) Å) [19]. Ba1 and Ba2 atoms are both connected to six S atoms and two Cl atoms with Ba–S bond length of 3.186(2)–3.358(2) Å and the Ba–Cl distances of 3.200(2)–3.253(2) Å.
The
Ba–S bond lengths are similar to those of Ba2AgInS4 (3.128(2)–3.314(2) Å) [20], Ba3PrInS6 (3.171(1)–3.335(1) Å) [15], while the Ba–Cl distances are a little longer than those of BaCl2 (3.159(1)–3.197(1) Å) [16]. Cs atom is surrounded by seven S atoms and two Cl atoms with Cs–S distances of 3.491(2)–3.952(2)Å and Cs–Cl length of 3.688(2)–3.770(2) Å, comparable to those of Cs2PS5 (3.461(1)–4.038(1) Å) [21] and CsPbCl3 (3.570(1)–3.674(1) Å) [22]. The structure may also be viewed as Cs-Cl-Ba zigzag pseudo–layers stacked along a direction with SnS4 tetrahedra in the interspaces.
3.4 Structural comparison In these four compounds, all the halide X– anions are only connected to alkali metal and alkaline earth metal atoms, and Sn atoms are only enjoined to S atoms. Such bonding characteristics can be explained empirically in view of the difference in the electronegativity, or alternatively by the qualitative HASB (hard and soft acids and bases) principle [23-25], which states that hard acids prefer to bind with hard bases and soft acids prefer to bind with soft bases. Here, Ba2+ and M+ cations are harder than Sn4+cations and S2– anion is softer than X– anions. As a result, X– anions are only linked to Ba2+ and M+ cations, while Sn4+ cations are only surrounded by S2–anions NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl all contain alkali metal and alkaline-earth metal atoms simultaneously. However, in NaBa2SnS4Cl, KBa2SnS4Cl and KBa2SnS4Br, the alkali metal and half of the alkaline-earth metal atoms are located in the same site, while in CsBa2SnS4Cl, they occupy different sites. This may result from the difference of the ionic radii. In addition
In NaBa2SnS4Cl,
and KBa2SnS4Br, Ba/M and Ba layers are stacked in the sequence of Ba/M Ba Ba/M Ba. While in CsBa2SnS4Cl, the sequence is Cs Ba2 Ba1 Ba2 Cs Ba2 Ba1 Ba2. Besides the framework of KBa2SnS4Br and CsBa2SnS4Cl have similar configuration, but that of NaBa2SnS4Cl is more orderly.
3.5. Experimental band gaps Fig. 5 shows the diffuse reflectance spectra of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl. With the use of straightforward extrapolation method [26], the band gaps of 2.28, 2.30, 1.95 and 2.06 eV are deduced for NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl respectively, which are consistent with their colors. For KBa2SnS4Cl, there are two step rises in the spectrum, but the band gap obtained from the first step rise did not agree with the color of crystal. Thus, the origin of this step rise is unclear currently
4. Conclusion Four new chalcohalides namely NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl, have been obtained. Although with the same stoichiometric ratio, they present three different space groups: NaBa2SnS4Cl and KBa2SnS4Cl in space group I4/mcm, KBa2SnS4Br in Pnma and CsBa2SnS4Cl in space group P21/c. the arrangement of M-X-Ba pseudo layers and the SnS4 tetrahedra is different in the three structure types as a result of the different radii. UV-vis-NIR spectroscopy measurements
indicate
that
NaBa2SnS4Cl,
KBa2SnS4Cl,
KBa2SnS4Br
and
CsBa2SnS4Cl have band gaps of 2.28, 2.30, 1.95 and 2.06 eV, respectively.
Acknowledgments This research was supported by National Natural Science Foundation of China (No. 91122034, No.51132008, No. 21271178).
Supplementary material The Crystallographic data for KBa2SnS4Br, KBa2SnS4Cl, NaBa2SnS4Cl, and CsBa2SnS4Cl have been deposited with FIZ Karlsruhe with the CSD numbers ranging from 429010 to 429013. These data may be obtained free of charge by contacting FIZ Karlsruheat +497247808666 (fax) or [email protected] (e-mail).
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[13] H.M. Powell, A.F. Wells, J. Chem. Soc., 1935, 359-362. [14] Z. Luo, C. Lin, W. Cheng, H. Zhang, W. Zhang, Z. He, Inorg. Chem., 52 (2013), 273-279. [15] K. Feng, Y. Shi, W. Yin, W. Wang, J. Yao, Y. Wu, Inorg. Chem., 51 (2012), 11144-11149. [16] J.M. Leger, J. Haines, A. Atouf, J. Appl. Crystallogr., 28 (1995), 416-423. [17] J.T. Lemley, J.M. Jenks, J.T. Hoggins, Z. Eliezer, H. Steinfink, J. Solid State Chem., 16 (1976), 117-128. [18] K. Feng, X. Zhang, W. Yin, Y. Shi, J. Yao, Y. Wu, Inorg. Chem., 53 (2014), 2248-2253. [19] R. Pocha, M. Tampier, R.D. Hoffmann, B.D. Mosel, R. Pottgen, D. Johrendt, Z. Anorg. Allg. Chem., 629 (2003), 1379-1384. [20] W. Yin, K. Feng, D. Mei, J. Yao, P. Fu, Y. Wu, Dalton Transactions, 41 (2012), 2272-2276. [21] J.A. Aitken, C. Canlas, D.P. Weliky, M.G. Kanatzidis, Inorg. Chem., 40 (2001), 6496-6498. [22] S. Hirotsu, T. Suzuki, Ferroelectrics, 20 (1978), 179-180. [23] R.G. Pearson, J. Chem. Educ., 45 (1968), 581. [24] R.G. Pearson, J. Chem. Educ., 45 (1968), 643. [25] P.K. Chattaraj, H. Lee, R.G. Parr, J. Am. Chem. Soc., 113 (1991), 1855-1856. [26] O. Schevciw, W.B. White, Materials Research Bulletin, 18 (1983), 1059-1068.
Figure Captions Fig. 1. Experimental (red) and simulated (black) X–ray powder diffraction data of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl. The star marked lines belong to SnS. Fig. 2. Crystal structure of NaBa2SnS4Cl viewed down [010] direction (A), coordination environments of all cations (B). Fig. 3.Crystal structure of KBa2SnS4Br viewed down [001] direction (A), the coordination environments of all cations (B). Fig. 4. Crystal structure of CsBa2SnS4Cl viewed down [100] direction (A), the coordination environments of all cations (B) Fig. 5. Diffuse reflectance spectra ofNaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl.
Table 1. EDX test results in at% for NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl. Compounds
Elements Na
Ba
Sn
S
Cl
10.6
23.9
11.7
43.9
9.9
K
Ba
Sn
S
Cl
11.2
22.7
11.4
43.5
11.2
K
Ba
Sn
S
Br
13.2
21.7
11.2
43.1
10.9
Cs
Ba
Sn
S
Cl
13.8
22.0
10.7
42.8
10.7
NaBa2SnS4Cl
KBa2SnS4Cl
KBa2SnS4Br
CsBa2SnS4Cl
Table 2. Crystal data and structure refinements for NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl.
a
NaBa2SnS4Cl
KBa2SnS4Cl
KBa2SnS4Br
CsBa2SnS4Cl
Fw
580.05
596.16
640.62
689.98
a(Å)
8.21620(10)
8.3552(7)
12.5124(4)
9.946(2)
b(Å)
8.21620(10)
8.3552(7)
9.8275(2)
8.793(2)
c(Å)
14.3022(5)
14.454(2)
8.8142(3)
12.532(3)
ȕ(°)
90
90
90
90.75(3)
Space group
I4/mcm
I4/mcm
Pnma
P21/c
V(Å3)
965.48(4)
1009.1(2)
1083.84(6)
1095.8(4)
Z
4
4
4
4
T(K)
293(2)
293(2)
293(2)
293(2)
Ȝ (Å)
0.71073
0.71073
0.71073
0.71073
ȡc(g/cm3)
3.991
3.924
3.926
4.182
µ(cm–1)
11.738
11.601
14.241
13.578
R(F) a
0.0345
0.0236
0.0277
0.0389
RW(Fo2) b
0.0811
0.0594
0.0664
0.0885
R(F) =
Fo –
Fc
/
Fo forFo2 > 2ı(Fo2). bRw(Fo2) = { [w(Fo2–Fc2)2]
/ wFo4}½ for all data. w–1 =ı2(Fo2) + (zP)2, where P = (Max(Fo2, 0) + 2 Fc2)/3.
Table 3. Selected bond lengths (Å) for NaBa2SnS4Cl. Sn1–S1×4
2.365(3)
Ba2/Na2–S1×2
3.066(3)
Ba1–S1×8
3.432(2)
Ba2/Na2–Cl5×2
3.135(1)
Ba1–Cl×2
3.576(1)
Ba2/Na2–S1×4
3.277(3)
Table 4. Selected bond lengths (Å) for KBa2SnS4Br. Ba1–S1×2
3.086(2)
Ba2–Br
3.473(1)
Ba1–S3
3.117(3)
Ba2–S1
3.627(2)
Ba1–S1×2
3.262(2)
Ba2–S3
3.697(2)
Ba1–S2
3.226(3)
Ba2–S2
3.275(2)
Ba1–Br
3.306(1)
Ba2–S3
3.294(2)
Ba1–Br
3.594(1)
Sn–S1×2
2.346(2)
Ba2–S1
3.405(2)
Sn–S3
2.356(3)
Ba2–Br
3.474(1)
Sn–S2
2.362(3)
Ba2–S2
3.449(2)
Table 5. Selected bond lengths (Å) of CsBa2SnS4Cl. Cs–S1
3.491(2)
Ba1–S3
3.322(2)
Cs–S4
3.519(2)
Ba1–S2
3.358(2)
Cs–S1
3.602(2)
Ba2–S3
3.129(2)
Cs–S2
3.665(2)
Ba2–S1
3.149(2)
Cs–Cl
3.688(2)
Ba2–S2
3.163(2)
Cs–S4
3.757(2)
Ba2–S4
3.192(2)
Cs–Cl
3.770(2)
Ba2–Cl
3.200(2)
Cs–S2
3.799(2)
Ba2–S3
3.211(2)
Cs–S1
3.952(2)
Ba2–S1
3.247(2)
Ba1–S2
3.186(2)
Sn–S3
2.354(2)
Ba1–S4
3.196(2)
Sn–S1
2.356(2)
Ba1–Cl
3.202(2)
Sn–S4
2.373(2)
Ba1–Cl
3.253(2)
Sn–S2
2.389(2)
Ba1–S4
3.263(2)
Table 6. Positional coordinates and equivalent isotropic displacement parameters for NaBa2SnS4Cl, 1, and KBa2SnS4Cl, 2, KBa2SnS4Br, 3, and CsBa2SnS4Cl, 4.
1/4 1/2 1/2 1/4 0.1461(2) 1/2
Ueq [Å2] 0.0251(6) 0.0235(8) 0.0235(8) 0.0134(6) 0.0256(9) 0.0307(15)
Occupancy 1 0.500(8) 0.500(8) 1 1 1
0.34613(6) 0.34613(6) 0 1/2 0.15721(13) 0
1/2 1/2 1/4 1/4 0.35250(12) 1/2
0.0187(4) 0.0187(4) 0.0264(4) 0.0132(4) 0.0230(5) 0.0292(9)
0.505(5) 0.495(5) 1 1 1 1
0.47266(4) 0.33130(5) 0.33130(5) 0.10471(5) 0.06530(16) 0.0021(2) 0.2892(2) 0.23172(8)
1/4 0.02464(6) 0.02464(6) 1/4 0.05481(15) 1/4 1/4 1/4
0.60209(5) 0.09275(8) 0.09275(8) 0.30933(7) 0.1668(2) 0.5343(3) 0.3628(3) 0.82401(12)
0.01506(18) 1 0.0244(3) 0.499(3) 0.0244(3) 0.501(3) 0.01128(19) 1 0.0280(5) 1 0.0251(6) 1 0.0403(8) 1 0.0290(3) 1
0.47862(4) 1.02035(4) 0.74770(4) 0.75762(4) 0.44040(16) 0.78135(17) 1.05352(16) 0.78256(16) 1.21635(16)
0.08422(5) 0.09215(5) 0.10195(4) -0.18859(5) 0.17493(19) -0.12781(19) 0.1598(2) 0.03865(18) -0.17179(19)
0.17173(3) 0.17760(3) 0.47663(3) 0.09958(3) 0.44084(13) 0.28468(13) 0.43737(14) -0.00030(12) 0.27403(13)
0.01479(10) 1 0.01052(9) 1 0.00974(9) 1 0.00967(10) 1 0.0109(3) 1 0.0109(3) 1 0.0127(3) 1 0.0098(3) 1 0.0136(3) 1
Atom Ba1 Ba2 Na Sn S Cl
Wyckoff 4a 8h 8h 4b 16l 4c
0 0.35141(16) 0.35141(16) 1/2 0.3416(3) 0
0 0.14859(16) 0.14859(16) 0 0.1584(3) 0
2
Ba1 K Ba2 Sn S Cl
8h 8h 4a 4b 16l 4c
0.15387(6) 0.15387(6) 0 0 0.34279(13) 0
3
Ba1 Ba2 K2 Sn S1 S2 S3 Br
4c 8d 8d 4c 8d 4c 4c 4c
4
Cs Ba1 Ba2 Sn S1 S2 S3 S4 Cl1
4e 4e 4e 4e 4e 4e 4e 4e 4e
1
x/a
y/b
z/c
Fig. 1 Experimental (red) and simulated (black) x–ray powder diffraction data of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl. The star marked lines belong to SnS.
Fig. 2 Crystal structure of NaBa2SnS4Clviewed down [010] direction (A), coordination environments of all cations (B).
Fig. 3 Crystal structure of KBa2SnS4Br viewed down [001] direction (A), the coordination environments of all cations (B).
Fig. 4 Crystal structure of CsBa2SnS4Cl viewed down [100] direction (A), the coordination environments of all cations (B).
Fig. 5 Diffuse reflectance spectra of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl.
Highlights ! Four new chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and
CsBa2SnS4Cl were obtained. They adopt three different structures owing to different ionic radii and elemental electronegativity. NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl have band gaps of 2.28, 2.30 1.95, and 2.06 eV, respectively.
*Graphical Abstract (TOC Figure)
*Graphical Abstract Legend (TOC Figure)
A new series of chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl have been obtained. They present three different space groups: NaBa2SnS4Cl and KBa2SnS4Cl in space group I4/mcm, KBa2SnS4Br in Pnma and CsBa2SnS4Cl in space group P21/c. UV-vis-NIR spectroscopy measurements indicate that NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl have band gaps of 2.28, 2.30 1.95, and 2.06 eV, respectively.
Four new chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl: syntheses, crystal Structures and optical properties Chao Li, Kai Feng, Heng Tu, Jiyong Yao, Yicheng Wu
www.elsevier.com/locate/jssc
PII: DOI: Reference:
S0022-4596(15)00100-0 http://dx.doi.org/10.1016/j.jssc.2015.03.013 YJSSC18829
To appear in:
Journal of Solid State Chemistry
Received date: 10 January 2015 Revised date: 12 March 2015 Accepted date: 15 March 2015 Cite this article as: Chao Li, Kai Feng, Heng Tu, Jiyong Yao, Yicheng Wu, Four new chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl: syntheses, crystal Structures and optical properties, Journal of Solid State Chemistry, http://dx.doi.org/10.1016/j.jssc.2015.03.013 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Title: Four
New Chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl,
KBa2SnS4Br and CsBa2SnS4Cl: Syntheses, Crystal Structures and Optical Properties Authors: Chao Lia, b, c, Kai Fenga, b, c, Heng Tua, b, c, Jiyong Yaoa, b∗ , Yicheng Wua, b Affiliation:
a
Center for Crystal Research and Development, Technical Institute of
Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P.R. China b
Key Laboratory of Functional Crystals and Laser Technology, Technical Institute of
Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China c
University of the Chinese Academy of Sciences, Beijing 100049, China
*Corresponding author: Jiyong Yao Key Laboratory of Functional Crystals and Laser Technology Technical Institute of Physics and Chemistry, CAS Beijing 100190, P.R. China Tel: 86-10-82543725; Fax: 86-10-82543725. E-mail: [email protected]
∗
To whom correspondence should be addressed. Email: [email protected]
ABSTRACT Four new chalcohalides, namely NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl, have been synthesized by the conventional high temperature solid-state reactions. They crystallize in three different space groups: space group I4/mcm for NaBa2SnS4Cl and KBa2SnS4Cl, Pnma for KBa2SnS4Br, and P21/c for CsBa2SnS4Cl. In all four compounds, the X– halide anions are only connected to six alkali metal or Ba cations, and the Sn atoms are only tetrahedrally enjoined to four S atoms. However, the M-X-Ba pseudo layers and the SnS4 tetrahedra are arranged in different ways in the three structural types, which demonstrates the interesting effect of ionic radii on the crystal structures. UV-vis-NIR spectroscopy measurements indicate that NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl have band gaps of 2.28, 2.30, 1.95, and 2.06 eV, respectively.
Keywords: Chalcohalide; Synthesis; Crystal structure; Optical property
1. Introduction The mixed-anion compounds have been intensively investigated for their unique bonding characteristics and fascinating physical properties. For example, the LnFeOPn (Ln = rare-earth; Pn = P, As) [1-3] oxypnictides are the first Fe-based high temperature superconductors and tremendous research has been carried out to increase the Tc or to elucidate the superconducting mechanism. [(Bi4Te4Br2)(Al2Cl6–xBrx)]Cl2 [4], synthesized from Lewis acidic organic ionic liquids, contains an unusual framework with n-type semiconducting behavior. BiCuOSe [5, 6] possesses two-dimensional layer structure and large conductivity of ı = 3.3 S•cm–1. Hg3Q2Bi2Cl8(Q = S, Se) [7] may have application in X-ray and Ȗ-ray detection owing to their high specific densities, high atomic numbers and wide band gaps. Ba3AGa5Se10Cl (A = Cs, Rb, K) [8] have an interesting open-framework and strong IR second harmonic generation (SHG) effect. In a previous work, we reported the syntheses, structures, and physical properties of six new chalcohalides, i.e. Ba3GaS4X (X = Cl, Br), Ba3MSe4Cl (M = Ga, In), Ba7In2Se6F8, and NaBa4Ge3S10Cl [9, 10]. Ba3GaQ4X (Q = S, X = Cl, Br; Q = Se, X = Cl) possess zigzag BaX pseudo-layers and isolated GaQ4 tetrahedra. Ba3InSe4Cl is comprised of alternating Ba-In-Se pseudo-layer and Ba-Cl pseudo-layer. Ba7In2Se6F8 contains one-dimensional ∞1[InSe 3 ]3− chains and unique [Ba 7 F8 ]6+ chains. Interestingly, NaBa4Ge3S10Cl is built of pseudo-layers of [Ge3S9] rings with Ba, Cl, and S atoms in the inter-spaces, leading to a large band gap and moderate SHG response.
In this paper, we extend our exploration to the M-Ba-Sn-S-X (M = alkali metal, X = halogen) system, hoping that the different charge/size combination of alkali metal/alkaline-earth metal mixed cations may have different influence on the packing of the anionic structural units, which in turn will increase the chance to isolate new phases with interesting stoichiometries, structures, and properties. Our efforts have led to the discovery of four new compounds, namely NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl, which adopt three different structural types. In this paper, we report their syntheses, crystal structures, and optical properties.
2. Experimental 2.1 Single–crystal growth The following reagents were all used as obtained from Sinopharm Chemical Reagent Co., Ltd.: Ba (99.9%), Sn (99.99%), S (99.999%), NaCl (99.999%), KCl (99%), CsCl (99%), and KBr (99%). BaS and SnS2 were synthesized by high temperature reaction of elements in sealed silica tubes evacuated to 10–3 Pa. Mixtures of BaS, SnS2, and MX (M = Na, K, Cs; X= Cl, Br) in the molar ratio of 1:1:1 were ground and loaded into fused-silica tubes under an Ar atmosphere in a glove-box, which were sealed under 10–3 Pa atmosphere and then placed in a computer-controlled furnace. The samples were heated to 1123 K in 20 h and kept at that temperature for 48 h, then cooled at a slow rate of 4 K/h to 673 K, and finally cooled to room temperature. The resultant dark red crystals were manually selected
for structure characterization. Analyses of the crystals with an EDX-equipped Hitachi S-4800 SEM (Table 1) showed the presence of M:Ba:Sn:S:X in the approximate molar ratio of 1:2:1:4:1.
2.2 Solid–state synthesis Polycrystalline samples of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl were synthesized by solid–state reaction technique. Mixtures of BaS, SnS2, and MX according to the stoichiometric ratio were ground and loaded into fused silica tubes under an Ar atmosphere in a glovebox, which were sealed under 10–3 Pa atmosphere and then placed in a computer-controlled furnace. The samples were heated to 1173 K in 20 h, kept at that temperature for 48 h, and then the furnace was turned off. X-ray powder diffraction analyses of the powder samples were performed at room temperature in the angular range of 2ș = 10–70º with a scan step width of 0.05º and a fixed counting time of 0.2 s/step using an automated Bruker D8 X-ray diffractometer equipped with a diffracted monochromator set for Cu KĮ (Ȝ = 1.5418 Å) radiation. Fig. 1 shows XRD patterns of the polycrystalline samples of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl along with the calculated ones on the basis of the single crystal crystallographic data. The experimental patterns for KBa2SnS4Br and CsBa2SnS4Cl are in good agreement with the calculated ones, while some minor SnS impurity exist in the NaBa2SnS4Cl and KBa2SnS4Cl product. Numerous attempts have been tried to get rid of this impurity, but failed.
2.3 Structure determination Single-crystal X-ray diffraction data were collected with the use of graphite–monochromatized Mo KĮ (Ȝ = 0.71073 Å) radiation at 293 K on a Rigaku AFC10 diffractometer equipped with a Saturn CCD detector. The collection of the intensity data, cell refinement and data reduction were carried out with the use of the program CrystalClear [11]. Face-indexed absorption corrections were performed numerically with the use of the program XPREP [12]. The structures were solved with the direct methods program SHELXS and refined with the least–squares program SHELXL of the SHELXTL.PC suite of programs [12]. When elements next to each other in the periodic table are involved, the atomic assignment was based on the bonding characteristics and bond valence sums calculations. In mixed anions compounds, there exists a bonding propensity that a highly electronegative element (e.g., O, F, Cl) tends to form strong ionic bonding with a highly electropositive element (e.g., alkali metal, alkaline-earth metal and rare-earth metals),whereas a less electronegative element (e.g., P, As, S, Se, Te) tends to form a stable covalent bonding with a less electropositive element (e.g., transition metal, or p-block
element).
Thus
in
NaBa2SnS4Cl,
KBa2SnS4Cl,
KBa2SnS4Br,
and
CsBa2SnS4Cl, all atoms connected to the Sn atoms were assigned as S atoms and the one connected to Ba (M) only was assigned as Cl atoms. The assortment of Cs and Ba in CsBa2SnS4Cl was based on the obviously longer Cs–S/Cl bond lengths than Ba–S/Cl ones. Besides, this assignment gives BVS of 1.059 for Cs and 1.867 for Ba, while switching the assignment will result in BVS of 0.760 for Cs and 2.588 for Ba,
which further prove the validity of the current atom assignment. The final refinement included an anisotropic displacement parameters and a secondary extinction correction. Additional experimental details are given in Table 2 and selected metrical data are given in Table 3, Table 4, and Table 5. Further information may be found in Supplementary Material.
2.4 Diffuse reflectance spectroscopy A Cary 5000 UV–vis–NIR spectrophotometer with a diffuse reflectance accessory was used to measure the spectra of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl in the range of 400 nm (3.10 eV) to 1500 nm (0.83 eV).
3. Results and discussion 3.1 Crystal structure of NaBa2SnS4Cl and KBa2SnS4Cl NaBa2SnS4Cl (Fig. 2A) and KBa2SnS4Cl are both isostructural to our previously reported Ba3InSe4Cl [9] and belong to the Cs3CoCl5 structure type in the centrosymmetric tetragonal space group I4/mcm [13]. So, only the structure of NaBa2SnS4Cl is
discussed
here.
In
the
asymmetric
unit,
there
is
one
crystallographically independent Ba atom, one Sn atom, one S atom, one Cl atom, and another metal site occupied by Ba and Na atom simultaneously with occupancy of 50% for each. As there are no metal–metal or S–S bonds in the structure, the
oxidation states of 1+, 2+, 4+, 2–, and 1– can be attributed to Na, Ba, Sn, S and Cl, respectively. Here, the more electronegative Cl atom is connected to the highly electropositive Ba and Ba/M atoms only and the less electropositive Sn is only connected to the less electronegative S element. Fig. 2B describes the coordination environments of all cations. Sn atom is surrounded by four S atoms in perfect tetrahedral geometry with identical Sn–S bond length of 2.365(3) Å, resembling those of Ba7Sn5S15 (2.361(1)–2.407(1) Å) [14]. Ba1 atom is enjoined by eight S atoms and two capping Cl atoms to form a bicapped square anti-prism. The identical Ba1–S bond length is 3.432(2) Å, similar to those of Ba3PrInS6 (3.171(1)–3.335(1) Å) [15], and the Ba1–Cl length is 3.576(1) Å, longer than that of BaCl2 (3.159(1)–3.197(1) Å) [16]. Ba2/Na2 atom is coordinated to six S and two capping Cl atoms in a bicapped trigonal prism with Ba2/Na2–S bond length of 3.066(3)–3.277(3) Å and Ba2/Na2–Cl bond length of 3.135(2) Å, comparable to those of Ba3GaS4Cl (Ba–S: 3.029(1)–3.612(1) Å) [9] and Ba–Cl (3.134(1)–3.406(1) Å) [16]. The SnS4 tetrahedra and Ba atoms may be viewed as arranged in the plane perpendicular to the c–axis and Ba/Na and Cl atoms are arranged in another plane. These two kinds of planes are stacked alternately to build up the complete structure.
3.2 Crystal structure of KBa2SnS4Br Resembling our previously reported Ba3GaS4Cl [9], KBa2SnS4Br belongs to the Ba3FeS5 structure type [17] in centrosymmetric orthorhombic space group Pnma (Fig. 3A). In the asymmetric unit, there is one crystallographically independent Ba1 atom, one Sn atom, three S atoms, one Br atom, and one independent site occupied by Ba2 and K2 atom simultaneously with occupancy of 50% for each. The oxidation states of 1+, 2+, 4+, 2–, and 1– can be attributed to K, Ba, Sn, S, and Br, respectively and charge balance is achieved. Similar to NaBa2SnS4Cl [10], the more electronegative Br atom is only connected to Ba and Ba/K atoms while the less electropositive Sn atom is only enjoined to the S atoms here. Sn atom is surrounded by four S atoms to generate a tetrahedron with Sn–S inter-atomic distances of 2.346(2)–2.362(3)Å, comparable to those in BaSn2S5 (2.421(4)–2.596(3) Å) [14]. Ba1 and Ba2/K2 atoms are both only coordinated to six S atoms and two Br atoms with Ba1–S bond length of 3.086(2)–3.262(2) Å, Ba2/K2–S distances of 3.275(2)–3.697(2)Å and Ba–Br bond distances of 3.306(1)–3.594(1) Å (Fig. 3B), similar in those of BaCeSn2S6 (Ba–S: 3.042(5)–3.305(5) Å)) [18] and BaBr2 (2.580–3.649 Å) [16].
In addition, KBa2SnS4Br may be viewed as originating
from our previously reported Ba3GaS4Cl [9] compound with the Ga3+ and half Ba22+ cations in Ba3GaS4Cl occupied by Sn4+ and K+ cations respectively. As reported in Ba3GaS4Cl, the structure of KBa2SnS4Br can be presented as K2/Ba2-Br-Ba1 zigzag pseudo
layers stacked along a direction with SnS4 tetrahedra in the interspaces.
3.3 Crystal structure of CsBa2SnS4Cl CsBa3SnS4Cl crystallizes in centrosymmetric monoclinic space group P21/c (Fig. 4A). There are two crystallographically independent Ba atoms, one Cs atom, one Sn atom, four S atoms and one Cl atom in the asymmetric unit. All atoms are at general Wyckoff sites 4e.The oxidation states of 1+, 2+, 4+ 2– and 1– can be readily attributed to Cs, Ba, Sn, S and Cl, respectively. As presented in Fig. 4B, Sn atom is in tetrahedral geometry with Sn–S distances of 2.354(2) to 2.389(2) Å, comparable to those of Sn atoms with similar coordination in Ba7Sn5S15 (2.361(1)–2.407(1) Å) [14] and Sr2SnS4(2.371(1)–2.409(1) Å) [19]. Ba1 and Ba2 atoms are both connected to six S atoms and two Cl atoms with Ba–S bond length of 3.186(2)–3.358(2) Å and the Ba–Cl distances of 3.200(2)–3.253(2) Å.
The
Ba–S bond lengths are similar to those of Ba2AgInS4 (3.128(2)–3.314(2) Å) [20], Ba3PrInS6 (3.171(1)–3.335(1) Å) [15], while the Ba–Cl distances are a little longer than those of BaCl2 (3.159(1)–3.197(1) Å) [16]. Cs atom is surrounded by seven S atoms and two Cl atoms with Cs–S distances of 3.491(2)–3.952(2)Å and Cs–Cl length of 3.688(2)–3.770(2) Å, comparable to those of Cs2PS5 (3.461(1)–4.038(1) Å) [21] and CsPbCl3 (3.570(1)–3.674(1) Å) [22]. The structure may also be viewed as Cs-Cl-Ba zigzag pseudo–layers stacked along a direction with SnS4 tetrahedra in the interspaces.
3.4 Structural comparison In these four compounds, all the halide X– anions are only connected to alkali metal and alkaline earth metal atoms, and Sn atoms are only enjoined to S atoms. Such bonding characteristics can be explained empirically in view of the difference in the electronegativity, or alternatively by the qualitative HASB (hard and soft acids and bases) principle [23-25], which states that hard acids prefer to bind with hard bases and soft acids prefer to bind with soft bases. Here, Ba2+ and M+ cations are harder than Sn4+cations and S2– anion is softer than X– anions. As a result, X– anions are only linked to Ba2+ and M+ cations, while Sn4+ cations are only surrounded by S2–anions NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl all contain alkali metal and alkaline-earth metal atoms simultaneously. However, in NaBa2SnS4Cl, KBa2SnS4Cl and KBa2SnS4Br, the alkali metal and half of the alkaline-earth metal atoms are located in the same site, while in CsBa2SnS4Cl, they occupy different sites. This may result from the difference of the ionic radii. In addition
In NaBa2SnS4Cl,
and KBa2SnS4Br, Ba/M and Ba layers are stacked in the sequence of Ba/M Ba Ba/M Ba. While in CsBa2SnS4Cl, the sequence is Cs Ba2 Ba1 Ba2 Cs Ba2 Ba1 Ba2. Besides the framework of KBa2SnS4Br and CsBa2SnS4Cl have similar configuration, but that of NaBa2SnS4Cl is more orderly.
3.5. Experimental band gaps Fig. 5 shows the diffuse reflectance spectra of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl. With the use of straightforward extrapolation method [26], the band gaps of 2.28, 2.30, 1.95 and 2.06 eV are deduced for NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl respectively, which are consistent with their colors. For KBa2SnS4Cl, there are two step rises in the spectrum, but the band gap obtained from the first step rise did not agree with the color of crystal. Thus, the origin of this step rise is unclear currently
4. Conclusion Four new chalcohalides namely NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl, have been obtained. Although with the same stoichiometric ratio, they present three different space groups: NaBa2SnS4Cl and KBa2SnS4Cl in space group I4/mcm, KBa2SnS4Br in Pnma and CsBa2SnS4Cl in space group P21/c. the arrangement of M-X-Ba pseudo layers and the SnS4 tetrahedra is different in the three structure types as a result of the different radii. UV-vis-NIR spectroscopy measurements
indicate
that
NaBa2SnS4Cl,
KBa2SnS4Cl,
KBa2SnS4Br
and
CsBa2SnS4Cl have band gaps of 2.28, 2.30, 1.95 and 2.06 eV, respectively.
Acknowledgments This research was supported by National Natural Science Foundation of China (No. 91122034, No.51132008, No. 21271178).
Supplementary material The Crystallographic data for KBa2SnS4Br, KBa2SnS4Cl, NaBa2SnS4Cl, and CsBa2SnS4Cl have been deposited with FIZ Karlsruhe with the CSD numbers ranging from 429010 to 429013. These data may be obtained free of charge by contacting FIZ Karlsruheat +497247808666 (fax) or [email protected] (e-mail).
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Figure Captions Fig. 1. Experimental (red) and simulated (black) X–ray powder diffraction data of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl. The star marked lines belong to SnS. Fig. 2. Crystal structure of NaBa2SnS4Cl viewed down [010] direction (A), coordination environments of all cations (B). Fig. 3.Crystal structure of KBa2SnS4Br viewed down [001] direction (A), the coordination environments of all cations (B). Fig. 4. Crystal structure of CsBa2SnS4Cl viewed down [100] direction (A), the coordination environments of all cations (B) Fig. 5. Diffuse reflectance spectra ofNaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl.
Table 1. EDX test results in at% for NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl. Compounds
Elements Na
Ba
Sn
S
Cl
10.6
23.9
11.7
43.9
9.9
K
Ba
Sn
S
Cl
11.2
22.7
11.4
43.5
11.2
K
Ba
Sn
S
Br
13.2
21.7
11.2
43.1
10.9
Cs
Ba
Sn
S
Cl
13.8
22.0
10.7
42.8
10.7
NaBa2SnS4Cl
KBa2SnS4Cl
KBa2SnS4Br
CsBa2SnS4Cl
Table 2. Crystal data and structure refinements for NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br, and CsBa2SnS4Cl.
a
NaBa2SnS4Cl
KBa2SnS4Cl
KBa2SnS4Br
CsBa2SnS4Cl
Fw
580.05
596.16
640.62
689.98
a(Å)
8.21620(10)
8.3552(7)
12.5124(4)
9.946(2)
b(Å)
8.21620(10)
8.3552(7)
9.8275(2)
8.793(2)
c(Å)
14.3022(5)
14.454(2)
8.8142(3)
12.532(3)
ȕ(°)
90
90
90
90.75(3)
Space group
I4/mcm
I4/mcm
Pnma
P21/c
V(Å3)
965.48(4)
1009.1(2)
1083.84(6)
1095.8(4)
Z
4
4
4
4
T(K)
293(2)
293(2)
293(2)
293(2)
Ȝ (Å)
0.71073
0.71073
0.71073
0.71073
ȡc(g/cm3)
3.991
3.924
3.926
4.182
µ(cm–1)
11.738
11.601
14.241
13.578
R(F) a
0.0345
0.0236
0.0277
0.0389
RW(Fo2) b
0.0811
0.0594
0.0664
0.0885
R(F) =
Fo –
Fc
/
Fo forFo2 > 2ı(Fo2). bRw(Fo2) = { [w(Fo2–Fc2)2]
/ wFo4}½ for all data. w–1 =ı2(Fo2) + (zP)2, where P = (Max(Fo2, 0) + 2 Fc2)/3.
Table 3. Selected bond lengths (Å) for NaBa2SnS4Cl. Sn1–S1×4
2.365(3)
Ba2/Na2–S1×2
3.066(3)
Ba1–S1×8
3.432(2)
Ba2/Na2–Cl5×2
3.135(1)
Ba1–Cl×2
3.576(1)
Ba2/Na2–S1×4
3.277(3)
Table 4. Selected bond lengths (Å) for KBa2SnS4Br. Ba1–S1×2
3.086(2)
Ba2–Br
3.473(1)
Ba1–S3
3.117(3)
Ba2–S1
3.627(2)
Ba1–S1×2
3.262(2)
Ba2–S3
3.697(2)
Ba1–S2
3.226(3)
Ba2–S2
3.275(2)
Ba1–Br
3.306(1)
Ba2–S3
3.294(2)
Ba1–Br
3.594(1)
Sn–S1×2
2.346(2)
Ba2–S1
3.405(2)
Sn–S3
2.356(3)
Ba2–Br
3.474(1)
Sn–S2
2.362(3)
Ba2–S2
3.449(2)
Table 5. Selected bond lengths (Å) of CsBa2SnS4Cl. Cs–S1
3.491(2)
Ba1–S3
3.322(2)
Cs–S4
3.519(2)
Ba1–S2
3.358(2)
Cs–S1
3.602(2)
Ba2–S3
3.129(2)
Cs–S2
3.665(2)
Ba2–S1
3.149(2)
Cs–Cl
3.688(2)
Ba2–S2
3.163(2)
Cs–S4
3.757(2)
Ba2–S4
3.192(2)
Cs–Cl
3.770(2)
Ba2–Cl
3.200(2)
Cs–S2
3.799(2)
Ba2–S3
3.211(2)
Cs–S1
3.952(2)
Ba2–S1
3.247(2)
Ba1–S2
3.186(2)
Sn–S3
2.354(2)
Ba1–S4
3.196(2)
Sn–S1
2.356(2)
Ba1–Cl
3.202(2)
Sn–S4
2.373(2)
Ba1–Cl
3.253(2)
Sn–S2
2.389(2)
Ba1–S4
3.263(2)
Table 6. Positional coordinates and equivalent isotropic displacement parameters for NaBa2SnS4Cl, 1, and KBa2SnS4Cl, 2, KBa2SnS4Br, 3, and CsBa2SnS4Cl, 4.
1/4 1/2 1/2 1/4 0.1461(2) 1/2
Ueq [Å2] 0.0251(6) 0.0235(8) 0.0235(8) 0.0134(6) 0.0256(9) 0.0307(15)
Occupancy 1 0.500(8) 0.500(8) 1 1 1
0.34613(6) 0.34613(6) 0 1/2 0.15721(13) 0
1/2 1/2 1/4 1/4 0.35250(12) 1/2
0.0187(4) 0.0187(4) 0.0264(4) 0.0132(4) 0.0230(5) 0.0292(9)
0.505(5) 0.495(5) 1 1 1 1
0.47266(4) 0.33130(5) 0.33130(5) 0.10471(5) 0.06530(16) 0.0021(2) 0.2892(2) 0.23172(8)
1/4 0.02464(6) 0.02464(6) 1/4 0.05481(15) 1/4 1/4 1/4
0.60209(5) 0.09275(8) 0.09275(8) 0.30933(7) 0.1668(2) 0.5343(3) 0.3628(3) 0.82401(12)
0.01506(18) 1 0.0244(3) 0.499(3) 0.0244(3) 0.501(3) 0.01128(19) 1 0.0280(5) 1 0.0251(6) 1 0.0403(8) 1 0.0290(3) 1
0.47862(4) 1.02035(4) 0.74770(4) 0.75762(4) 0.44040(16) 0.78135(17) 1.05352(16) 0.78256(16) 1.21635(16)
0.08422(5) 0.09215(5) 0.10195(4) -0.18859(5) 0.17493(19) -0.12781(19) 0.1598(2) 0.03865(18) -0.17179(19)
0.17173(3) 0.17760(3) 0.47663(3) 0.09958(3) 0.44084(13) 0.28468(13) 0.43737(14) -0.00030(12) 0.27403(13)
0.01479(10) 1 0.01052(9) 1 0.00974(9) 1 0.00967(10) 1 0.0109(3) 1 0.0109(3) 1 0.0127(3) 1 0.0098(3) 1 0.0136(3) 1
Atom Ba1 Ba2 Na Sn S Cl
Wyckoff 4a 8h 8h 4b 16l 4c
0 0.35141(16) 0.35141(16) 1/2 0.3416(3) 0
0 0.14859(16) 0.14859(16) 0 0.1584(3) 0
2
Ba1 K Ba2 Sn S Cl
8h 8h 4a 4b 16l 4c
0.15387(6) 0.15387(6) 0 0 0.34279(13) 0
3
Ba1 Ba2 K2 Sn S1 S2 S3 Br
4c 8d 8d 4c 8d 4c 4c 4c
4
Cs Ba1 Ba2 Sn S1 S2 S3 S4 Cl1
4e 4e 4e 4e 4e 4e 4e 4e 4e
1
x/a
y/b
z/c
Fig. 1 Experimental (red) and simulated (black) x–ray powder diffraction data of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl. The star marked lines belong to SnS.
Fig. 2 Crystal structure of NaBa2SnS4Clviewed down [010] direction (A), coordination environments of all cations (B).
Fig. 3 Crystal structure of KBa2SnS4Br viewed down [001] direction (A), the coordination environments of all cations (B).
Fig. 4 Crystal structure of CsBa2SnS4Cl viewed down [100] direction (A), the coordination environments of all cations (B).
Fig. 5 Diffuse reflectance spectra of NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl.
Highlights ! Four new chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and
CsBa2SnS4Cl were obtained. They adopt three different structures owing to different ionic radii and elemental electronegativity. NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl have band gaps of 2.28, 2.30 1.95, and 2.06 eV, respectively.
*Graphical Abstract (TOC Figure)
*Graphical Abstract Legend (TOC Figure)
A new series of chalcohalides, NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl have been obtained. They present three different space groups: NaBa2SnS4Cl and KBa2SnS4Cl in space group I4/mcm, KBa2SnS4Br in Pnma and CsBa2SnS4Cl in space group P21/c. UV-vis-NIR spectroscopy measurements indicate that NaBa2SnS4Cl, KBa2SnS4Cl, KBa2SnS4Br and CsBa2SnS4Cl have band gaps of 2.28, 2.30 1.95, and 2.06 eV, respectively.