From Cc to P6₃mc: Structural Variation in La₃S₂Cl₂[SbS₃] and La₃OSCl₂[SbS₃] Induced by the Isovalent Anion Substitution

Abstract

The first antimony oxychloride sulfide, namely, La3OSCl2[SbS3], has been designed by isovalent anion substitution strategy. It belongs to the polar hexagonal space group P63 mc (No. 186) with a = 9.327(5) Å, c = 7.075(5) Å, V = 533.0(5) Å3, and Z = 2. It is composed of three-dimensional (3D) cationic [La3OSCl2]3+ networks hosting covalent [SbS3] molecular anions. The 3D cationic [La3OSCl2]3+ are formed by the one-dimensional (1D) hexagonal columns of corner-shared [(Cl/S)­La3] polyhedra propagating along the 63 axis situated in (0,0,z) and [OLa3] trigonal pyramids via corner-sharing. Moreover, the alternating [SbS3] and [OLa3] trigonal pyramids are arranged along the 3-fold axis located at (1/3, 2/3, z), generating a dipole moment component along the c-direction. Another remarkable structural motif is the occurrence of the empty octahedra formed by the disordered Cl/S anions, which further share the face to form 1D chains extending along the 63 axis located at (0,0,z). Interestingly, the occurrence of the isolated [La3SbOS3]4+ cubane-like clusters instead of the “chains of [La3SbOS3]4+” make the title compound distinct from the related La4OCl2S4 featuring common chains of [La4OS3]4+. The preliminary nonlinear optical (NLO) measurement indicates a moderate second-harmonic-generation (SHG) signal (ca. 0.7 × AgGaS2) at 2050 nm laser. Moreover, calculated birefringence for La3OSCl2[SbS3] is ∼0.269 at 2050 nm. In addition, the optical energy gap of 2.5 eV for La3OSCl2[SbS3] was derived, which can be assigned to the charge transition from the highest value of valence band derived dominantly from the of S 3p states to the lowest value of conduction band mainly made up of the Sb 5p and of La 5d states.

Visualizing the alignment of lone pair electrons in La3AsS5Br2 and La5As2S9Cl3 to form an acentric or centrosymmetric structure

“…9), which belongs to the known La 3 AsS 5 Cl 2 structure type. 52 Other isostructural compounds Pr 3 AsS 5 Cl 2 , 53 La 3 SbS 5 Cl 2 , 54 and Ce 3 SbS 5 Cl 2 55 were also reported. Selected crystal data and parameters are listed in Tables 1, S1 and S2 †.…”

“…9), which belongs to the known La 3 AsS 5 Cl 2 structure type. 52 Other isostructural compounds Pr 3 AsS 5 Cl 2 , 53 La 3 SbS 5 Cl 2 , 54 The La-S interactions within La 3 AsS 5 Br 2 fall into the range of 2.87(1)-3.15 (1) Å, which are comparable to the La-S interactions within La 5 As 2 S 9 Cl 3 of 2.81(7)-3.14 (4) Å and many lanthanum sulfide compounds such as La 4 Ge 3 S 12 (2.864-3.245 Å), 25 La 6 Pd 0.96 Si 2 S 14 (2.817-3.164 Å), 56 La 5 Sb 2 S 9 -Cl 3 (2.841-3.106 Å), 55 La 3 SbS 5 Cl 2 (2.833-3.117 Å), 55 La 3 LiSnS 7 (2.848-3.297 Å), 57 etc. The La-Br interactions within La 3 AsS 5 -Br 2 of 3.04 (3)-3.44(3) Å are longer than the La-Cl interactions within La 5 As 2 S 9 Cl 3 of 2.83(1)-2.97(1) Å, which is expected due to the larger ionic size of Br − than Cl − .…”

A unique [Sb6O2S13]12−finite chain in oxychalcogenide Ba6Sb6O2S13leading to ultra-low thermal conductivity and giant birefringence

“…The Sb–O and Sb–S distances are 2.023–2.085 and 2.393–2.858 Å (Table S1†), respectively, which are comparable to those in the reported Sb-based chalcogenides. 12 The heteroanionic [Sb1OS 2 ] and [Sb3OS 3 ] BBUs adopt O-sharing and S4-sharing to form [Sb 2 S 4 O] 4− groups, which are further connected by isolated [SbS 4 ] units resulting in a unique finite [Sb 6 O 2 S 13 ] 12− chain (Fig. 1b).…”

An overview of Mg-based IR nonlinear optical materials

“…Among these, the most commonly used method for obtaining non-centrosymmetric structures is the introduction of various asymmetric building units (ABUs) into one structure. The common ABUs for IR-NLO materials are as follows: (i) distorted [MQ 4 ] tetrahedra (M = main-group elements; Q = chalcogen); 44–52 (ii) [MQ n ] polyhedra (M = transition-metal elements; n = 2, 3, and 4); 53–57 (iii) distorted [REQ n ] polyhedra (RE = rare-earth-metal elements); 58–61 (iv) lone-pair-cation-based [MQ n ] polyhedra (M = As( iii ), Sb( iii ), Bi( iii ), Pb( ii ), and Sn( ii )); 62–71 and (v) mixed-anion [MO x Q y ] polyhedra. 72–81…”