Structural diversities in centrosymmetric La₈S₄Cl₈La₁₂S₈Cl₄[SbS₃]₈ and non-centrosymmetric Ln₁₂S₈Cl₈[SbS₃]₄ (Ln = La and Ce): syntheses, crystal and electronic structures, and optical properties

Abstract

Three thioantimonides charge compensated by Ln/S/Cl cationic layers, namely centrosymmetric La8S4Cl8La12S8Cl4[SbS3]8 and non-centrosymmetric Ln12S8Cl8[SbS3]4 (Ln = La and Ce) have been discovered for the first time.

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

“…In addition, LaCa 2 GeS 4 Cl 3 was also documented to be SHG active at a 1064 nm . Regrettably, no apparent SHG activity was observed in the La 3 S 2 Cl 2 [SbS 3 ] …”

“…Although with similar components, La 3 S 2 Cl 2 [SbS 3 ] shows a total different structure type, belonging to the monoclinic space group Cc . Its major structural motif is also the isolated [SbS 3 ] trigonal-pyramidal units arranged in the (100) plane, which are stacked with the acentric layers of [La 3 S 2 Cl 2 ] 3+ in an alternating fashion.…”

“…The diffuse reflectance spectra of La 3 OSCl 2 [SbS 3 ] displayed in Figure reveals an E g value of 2.5 eV, comparable to those for La 3 S 2 Cl 2 [SbS 3 ] (2.31 eV) and [La 2 SCl 2 ]­[La 3 S 2 Cl]­[SbS 3 ] 2 (2.6 eV) . A similar value of 2.3 eV was determined for the La 8 Sb 2 S 15 , consistent with that for binary La 2 S 3 (2.4–2.9 eV) .…”

“…However, our exploration in the La/Ga/Sb/S systems lead unexpectedly to the formation of La 2 Ga 0.33 SbS 5 instead of the “NCS La 4 GaSbS 9 ”, which adopts the centrosymmetric (CS) tetragonal space group I 4/ mcm . In our previous work, we realized that complex La/S/Cl cationic layers with different compositions and symmetry also have an interesting impact on the arrangement of the discrete [SbS 3 ] trigonal-pyramidal units in [La 2 SCl 2 ]­[La 3 S 2 Cl]­[SbS 3 ] 2 and La 3 S 2 Cl 2 [SbS 3 ] . The centric [La 2 SCl 2 ] 2+ and mirror-symmetric [La 3 S 2 Cl] 4+ in the former favor the centrosymmetric packing of the [SbS 3 ] molecular anions, while acentric [La 3 S 2 Cl 2 ] 3+ in the latter prefers in-phase alignments of such anionic units, resulting in the NCS crystal structure.…”

“…Thioantimonates have received considerable attention, because of the existence of lone-pair electrons around Sb 3+ , yielding flexible anionic [SbQ n ] groups, which are responsible for the various crystal structures with fascinating physical properties. − On the other hand, the ratios and charge of counteractions, such as alkali and alkaline-earth metals, play significant roles with regard to the microscopic arrangement of these anionic [SbQ n ] groups. Therefore, modifications can be done by a substitution of the alkali metal, as in the case of Li 3 SbS 3 crystallizing in space group Pna 2 1 and Na 3 SbS 3 adopting space group P 2 1 3. , Moreover, a partial replacement of alkali-metal Ba yielded ABaSbQ 3 that exhibited different space groups, as the result of the different radii of alkali-metal cations .…”