Chirality Induced Crystal Structural Difference in Metal Halide Composites

Abstract

hybrid perovskites (HOIPs) with noticeable circular dichroism (CD) in 2017. [7] (2). It opens up new possibilities to advance our materials functionalities. For example, the chirality transfer from organic ligands to inorganic structures provides a synthetic design paradigm toward Rashba-Dresselhaus spin-polarization for spintronics. [8] In conventional cases, the incorporation of (S-or R-) chiral organic ligands will not affect the resulting metal halide composite structure as compared with the incorporation of racemic (mixed equal ratio of S-and R-) organic ligands because of indistinguishable composition, similar chemical bonding and similar tethering group packing characteristics between enantiomers of chiral materials. This is widely demonstrated by nearidentical X-ray diffraction (XRD) patterns and photo luminescence (PL) spectra observed for chiral and racemic materials. [9][10][11][12][13][14][15] However, Zhao and his co-workers observed different photoluminescent behaviors between chiral and racemic metal halide perovskites. The optical difference was ascribed to the distinction of weak interactions existing in the perovskite crystal structure such as the hydrogen bonding and van der Waals force. [16] Moreover, recent experimental results by Mitzi and co-workers also demonstrated that the asymmetric hydrogen bonding in the chiral organic ligand (1-(1-naphthyl) ethylammonium) can induce more distorted PbBr 6 octahedra than the racemic one (without asymmetric hydrogen bonding), resulting in a difference in the corresponding perovskite XRD patterns. [8,17] These findings point out a new possibility that incorporating chiral ligands in metal halide composites can change the resulting structure, an effect though not been demonstrated previously.In the present work, by introducing MBA (methylbenzylamine) into manganous bromide frameworks, we discover a significant difference in the crystal structure between chiral and racemic metal halide composites. The XRD patterns indicate that the crystal structure is switched from octahedron of one-dimensional (chain-like) in racemic composites to tetrahedron of one-dimensional (chain-like) in chiral composites. Consistently, significantly different PL results are also observed in these composites. Specifically, the chiral composites exhibit bright green emissions while the racemic composite shows bright red emissions in low-humidity conditions. In addition, the green emission in chiral composite turns red with increasing humidity, suggesting the moisture induced crystal structure transformation. In contrast, the racemic composite shows no moisture response. The different moisture response might result from the difference in hydrogen bonding in these Incorporating chiral organic compounds into metal halide frames is a common and useful method to introduce chirality in metal halide composites. The structures of resulting racemic and chiral composites are usually considered to be nearly identical owing to similar chemical bonding. In this work, by incorporating chiral MBAB...

Dynamic CPL switching realized in chiral Mn-based metal halides with reversible thermochromism

“…The Mn–Mn distance is greatly reduced, which significantly affects the d–d transition rule and transition energy so that the octahedral coordination of AMnX 3 shows an orange-to-red emission. 14 However, our observations are significantly different from those reported above. A ( R -/ S -Br-MBA) 3 MnBr 5 single crystal displays orange emission at room temperature.…”

“…It is worth noting that, unlike most Pb-based organic–inorganic hybrid perovskites, the absorption and CD signal of the ( R -/ S -Br-MBA) 3 MnBr 5 single crystal appear before 300 nm, which is similar to the extinction spectrum of similar crystal structures. 14 The CD spectra (Fig. S3, ESI†) of the chiral ammonium salt ( R -/ S -Br-MBA)Br have been conducted, which is obviously different from that of ( R -/ S -Br-MBA) 3 MnBr 5 , indicating that the chirality of R -/ S -Br-MBA has been successfully imparted to the whole crystal.…”

“…The surrounding space of [MnBr 4 ] 2À is filled with R-Br-MBA + cations, forming a unique 0D structure, which is similar to that previously reported. 13,14 Each (R-Br-MBA) 3 MnBr 5 molecule consists of three R-Br-MBA + cations, one [MnBr 4 ] 2À tetrahedron, and one isolated Br À anion. In particular, two of the three chiral amines coordinated with the tetrahedron appear disordered.…”

“…13 Gao et al introduced chiral MBA into the manganese bromide framework to prepare ( R -/ S -MBA) 2 MnBr 4 and (rac-MBA)[Mn 2 Br 5 (EtOH)], respectively, showing significantly different fluorescence emission. 14 Mao et al successfully synthesized four chiral hybrid manganese bromide materials by using different chiral ammonium alkoxide cations. 15 Chiral Mn-based functional materials with CPL have attracted increasing attention due to their excellent luminescence properties and extensive application potential in LED devices.…”

Water‐Stable 0D Hybrid Manganese Halides with Adjustable Crystal Structure and Emission Color

“…Specifically, the weak crystal field is associated with higher-energy green light emission, and strong crystal field gives rise to lower-energy red light emission. [53][54][55][56] Based on the T-S energy level diagram, the absorption bands at 224 (44 642 cm −1 ), 312 (32 051 cm −1 ), 360 (27 777 cm −1 ), 433 (23 059 cm −1 ), and 448 nm (22 321 cm −1 ) can be defined as electron transitions of 6 A 1 ( 6 S)→ 4 T 1 ( 4 P), 6 A 1 ( 6 S)→ 4 E( 4 D), 6 A 1 ( 6 S)→ 4 T 2 ( 4 D), 6 A 1 ( 6 S)→ 4 E( 4 G), 4 A 1 ( 4 G), and 6 A 1 ( 6 S)→ 4 T 2 ( 4 G), respectively, in the [MnCl 4 ] 2− tetrahedron of [H 2 TMDAP]Mn 0.63 Zn 0.37 Cl 4 (Figure 4b). Similarly, all the absorption peaks of [H 2 TMDAP] 3 [MnCl 4 ] 2 [Mn 2 Cl 6 ] can be successively assigned as the d-d transition from excited states to ground level as illustrated in Figure 4c.…”