Tin(II)-Induced Large Birefringence Enhancement in Metal Phosphates

Abstract

Two alkali tin­(II) phosphates, namely, Rb­[SnF­(HPO4)] and Rb­(Sn3O)2(PO4)3, were synthesized through mild hydrothermal methods. They belong to the orthorhombic Pnma and Pbcn space groups, respectively. Rb­[SnF­(HPO4)] features a layered structure based on 1D [SnF­(HPO4)]∞ chains interconnected by hydrogen bonds, with Rb+ cations located at the interlayer space. For Rb­(Sn3O)2(PO4)3, each pair of [Sn3O]4+ clusters is bridged by a pair of [P(1)­O4]3– tetrahedra to build a 1D [Sn–P–O]∞ chain. These 1D [Sn–P–O]∞ chains are further cross-linked though [P(2)­O4]3– tetrahedra to construct a 3D network with 7- and 10-membered-ring channels. The tin­(II) ions in Rb­[SnF­(HPO4)] and Rb­(Sn3O)2(PO4)3 with stereochemically active lone pairs (SCALPs) significantly enhance the birefringences of metal phosphates: Δn = 0.147@1064 nm for Rb­[SnF­(HPO4)] and 0.082@1064 nm for Rb­(Sn3O)2(PO4)3.

[C(NH2)3]BiCl2SO4: an excellent birefringent material obtained by multifunctional group synergy

“…Traditionally, for the purpose of ensuring transparency in the UV region, alkali/alkaline earth metal cations are selected to design and synthesize UV optical crystals, which will eliminate the contribution of cationic polyhedra on the birefringence. [30][31][32][33][34][35][36][37][38][39] Herein, in addition to the Bi 3+ ions with stereochemically active lone pairs, a planar triangle π-conjugated [C(NH 2 ) 3 ] + group with a similar structural geometry to the [BO 3 ] 3− group was selected to substitute for traditional alkali/alkaline earth metal cations. This [C(NH 2 ) 3 ] + group possesses broad UV transparency and strong optical polarization anisotropy, which is beneficial to generate a large birefringence.…”

Pb2Cl2(HPO3)(H2O) and Pb3Br2(HPO3)2: Two Phosphite Halides with 3D Structural Networks and Enlarged Birefringence

“…Many attractive birefringent crystals activated by cations with stereochemically active lone pairs (SCALP) have been seen more in recent research. In addition to the mentioned Sn 2 PO 4 I (0.664 @546 nm) and SbB 3 O 6 (0.290 @546 nm), crystals of Sn 2 B 5 O 9 Br (0.439 @546 nm), K 2 Sb­(P 2 O 7 )F (0.157 @546 nm), α-NaSb 3 P 2 O 10 (0.121 @1064 nm), and Rb­[SnF­(HPO 4 )] (0.147 @1064 nm) also exhibit large birefringence . Usually, compounds constructed by tetrahedral units exhibit relatively small birefringence due to their poor anisotropy. , However, the compounds constructed by tetrahedral units are diverse, which form acentric structures and make contributions to many physical performances such as nonlinear optics .…”

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

“…[13,83] On the whole, the birefringence increases gradually from Sn The series of crystals, X[SnF(HPO 4 )] (X = Rb, Na, NH 4 ) also show ideal optical anisotropy. [84] Rb[SnF(HPO 4 )] was obtained by Mao, et al, [84] while Gorbunova, et al reported the synthesis and crystal structure of M[SnF(HPO 4 )](M = NH 4 , Na). [85] Owing to the cation size effect, different from Na[SnF(HPO 4 )], Rb[SnF(HPO 4 )] is isomorphic with [NH 4 ]-[SnF(HPO 4 )] and crystallizes in Pnma space group.…”

“…The repulsion of the lone pair in combination with the smaller d Sn-Sn value induced the stereochemically active lone pairs in Rb[SnF(HPO 4 )] to align along the a axis, which is more conducive to producing a large birefringence in comparison with Na[SnF(HPO 4 )] (0.123@1064 nm). [84] Another Sn-based phosphate, P � 1-Sn 2 P 2 O 7 owns a large birefringence of 0.146@1064 nm. [13] The structural investigation of Sn 2 P 2 O 7 was carried out for the first time by Shpanchenko, et al using single crystal and powder X-ray diffraction.…”