A ¹¹⁹Sn Mössbauer-spectroscopic characterization of the diamagnetic birefringence material Sn₂B₅O₉Cl

Abstract

The crystal structure of diamagnetic borate chloride Sn2B5O9Cl exhibits two crystallographically independent tin sites which both show pronounced lone-pair activity of the tin atoms. This is reflected in substantial quadrupole splitting in the 119Sn Mössbauer spectrum. The isomer shifts of 3.887(8) and 4.137(7) mm s−1 clearly indicate divalent tin. In agreement with bond valence calculations, the Sn1 atoms have a lower charge and the higher isomer shift, compatible with a higher electron density at the tin nuclei.

An Exceptional Peroxide Birefringent Material Resulting from d–π Interactions

“…0.105 at 1064 nm) and Rb 3 VO(O 2 ) 2 CO 3 (calc. 0.075 at 1064 nm), as well as the recently reported Li 2 Na 2 B 2 O 5 (0.095 at 532 nm), Ca(BO 2 ) 2 (0.1355 at 546 nm), Sn 2 B 5 O 9 Cl (0.168 at 546 nm), NaCa 4 V 5 O 17 (calc. 0.1 at 1064 nm), and LiHgPO 4 (calc.…”

“…Some strategies have been developed to enhance the birefringence of a crystal: 1) Introducing second‐order Jahn–Teller distorted polyhedra with d 0 cation (V 5+ , Mo 6+ ) centers; related compounds include YVO 4 (Δ n =0.225 at 633 nm) and NaCa 4 V 5 O 17 (Δ n =0.1 at 1064 nm); 2) introduction or condensation of delocalized π‐conjugated planar groups such as BO 3 groups; for example, Pan and co‐authors recently reported two borates, Li 2 Na 2 B 2 O 5 and CaB 2 O 4 , which are composed of condensed B 2 O 5 dimers and [B 2 O 4 ] ∞ infinite chains and exhibit large birefringences of Δ n =0.095 at 532 nm and Δ n =0.1355 at 546 nm, respectively; 3) introducing highly polarizable cations such as Hg 2+ with d 10 ‐configuration or Pb 2+ , Sn 2+ , I 5+ with lone pair electrons as in LiHgPO 4 (Δ n =0.068 at 1064 nm), Pb 2 (IO 3 )(PO 4 ) (Δ n =0.060 at 1064 nm), and Sn 2 B 5 O 9 Cl (Δ n =0.168 at 546 nm) . In particular, Sn 2 B 5 O 9 Cl exhibits a remarkable enhancement of 16 times as compared with the isostructural Ba 2 B 5 O 9 Cl. It is of great importance and current interests to develop new strategies for birefringent materials.…”

Recent Development of SnII, SbIII‐based Birefringent Material: Crystal Chemistry and Investigation of Birefringence

“…In the structure, the extremely distorted SnO 7 X 2 polyhedra are connected to build a 3D framework, leading to pronounced stereochemically active, which is reflected in substantial quadrupole splitting in the 119 Sn Mössbauer spectrum. [133] The birefringence measurements on Sn 2 B 5 O 9 X and Ba 2 B 5 O 9 Cl crystals with a Nikon ECLIPSE LV100 POL polarizing microscope suggested that the birefringence is about 0.168, 0.439, and 0.010@546 nm for Sn 2 B 5 O 9 Cl, Sn 2 B 5 O 9 Br, and Ba 2 B 5 O 9 Cl, respectively, which are well matched with the calculated results. Meanwhile, the polished (010)-Ba 2 B 5 O 9 Cl crystal plate was also measured using GR-5 Gem Refractometer (0.012@589 nm).…”

“…After much effort in the Sn-B-O-X (X = Cl, Br) system, Pan's group successfully synthesized two new millimeter-sized tin(II) borate halides, Sn 2 B 5 O 9 X (X = Cl, Br) (Figure 22a). [78,132,133] The two crystals crystallize in the noncentrosymmetric space group Pnn2, which is isostructural to the hilgardite-type M 2 B 5 O 9 X (M = Ca, Sr, Ba, Pb, Eu). The FBBs are the B 5 O 12 groups, which can be described as an interconnection of two B 3 O 8 groups by sharing BO 4 .…”

Recent Development of SnII, SbIII‐based Birefringent Material: Crystal Chemistry and Investigation of Birefringence

“…In the structure, the extremely distorted SnO 7 X 2 polyhedra are connected to build a 3D framework, leading to pronounced stereochemically active, which is reflected in substantial quadrupole splitting in the 119 Sn Mössbauer spectrum. [133] The birefringence measurements on Sn 2 B 5 O 9 X and Ba 2 B 5 O 9 Cl crystals with a Nikon ECLIPSE LV100 POL polarizing microscope suggested that the birefringence is about 0.168, 0.439, and 0.010@546 nm for Sn 2 B 5 O 9 Cl, Sn 2 B 5 O 9 Br, and Ba 2 B 5 O 9 Cl, respectively, which are well matched with the calculated 22d). To demonstrate the influence of halogen on the lone pairs of Sn 2 + , the isostructural Sn 2 B 5 O 9 I is obtained through repeating structural optimizations, the calculated results especially its unbelievable birefringence (0.422@1064 nm) indicated that in Sn 2 B 5 O 9 X, from Sn 2 B 5 O 9 Cl to Sn 2 B 5 O 9 I, the stereochemically active of Sn 2 + is strengthened gradually, resulting in significant linear and NLO performance improvement (Figure 22c).…”