Metal Methanesulfonates with Mixed Anionic Groups with Large Band Gaps and Enhanced Birefringence

Abstract

Four new metal methanesulfonates with mixed anionic groups, Bi(SeO 3 )(CH 3 SO 3 ) (1), Bi(TeO 3 )(CH 3 SO 3 ) (2), Ba(BF 4 )(CH 3 SO 3 ) (3), and Ba 2 (BF 4 )(CH 3 SO 3 ) 3 (H 2 O) 3 (4), have been successfully synthesized. Compounds 1 and 2 are isomorphic and exhibit a two-dimensional (2D) layered structure. Stereoactive lone pairs are observed with Se 4+ , Te 4+ , and Bi 3+ . Compound 3 features a three-dimensional (3D) structure formed by connecting [Ba(CH 3 SO 3 )] + layers via BF 4 tetrahedra, whereas compound 4 features a 2D layered structure, where the BF 4 tetrahedra are positioned on both sides of the [Ba 2 (CH 3 SO 3 ) 3 ] + layers. The ultraviolet−visible−near-infrared (UV−vis-NIR) spectra indicate that compounds 1 and 2 have absorption edges at 270 and 274 nm, whereas compounds 3 and 4, with absorption edges below 200 nm, are characterized as deep-UV crystals. Calculations were performed to determine the absorption edges, and comparative analysis indicates a significant enhancement in the calculated birefringence values compared to analogous compounds.

Crystal clear: unveiling giant birefringence in organic–inorganic cocrystals

“…29 π-Conjugated groups with delocalized electrons and cations with lone pair electrons exhibit large Δ α , making them suitable birefringence-active groups. 30–34 In contrast, the nearly isotropic distribution of electronic clouds in halogens results in rigid regular tetrahedral groups such as TO 4 (T = B, Si, P, S, etc. ) having Δ α close to zero.…”

Hg16O12(NO3)6F2(H2O): A Mercury-Rich Nitrate Oxyfluoride with Diverse Triple-Coordinated Mercury-Based Units That Exhibits an Unparalleled [(Hg16O12F2(H2O))6+]∞ Cationic Framework and a Large Birefringence

“…The optical band gap of the Hg 16 O 12 (NO 3 ) 6 F 2 (H 2 O) polycrystalline powder sample was determined to be 2.5 eV using UV–vis–near-IR (NIR) diffuse-reflectance spectroscopy, which is lower than those of the nitrate halide Cs 2 Pb 2 (NO 3 ) 2 Br 2 (3.01 eV) and CsHgNO 3 Cl 2 (3.1 eV), while higher than that of Hg 3 O 2 (NO 3 )F (2.19 eV) (Figure ). ,, We can improve the band gap by introducing the alkali metal, alkaline-earth alkaline, or increasing the proportion of F atoms, as well as adjusting the proportions of F – and NO 3 – anions. − In the IR spectrum (Figure S7), the peaks at 3430, 1737, and 1563 cm –1 indicate the existence of H 2 O molecules, which contain the stretching and vibration of the O–H bonds. The intense band at 1398 cm –1 is attributable to the N–O stretching vibrations in the NO 3 triangles, and the band at 1263 cm –1 is ascribed to the nonplanar bending vibrations of the NO 3 planar groups.…”