Noncovalent Chalcogen Bonds and Disulfide Conformational Change in the Cystamine‐Based Hybrid Perovskite [H₃N(CH₂)₂SS(CH₂)₂NH₃]Pb^III₄

Abstract

International audienceThe cystamine-based hybrid perovskite, α-[NH3(CH2)2S-S(CH2)2NH3]PbI4 (1a), can be transformed into its polymorph, β-[NH3(CH2)2S-S(CH2)2NH3]PbI4 (1b), by heat activation (T = 150 °C). The crystal structures have been characterised by single-crystal X-ray diffraction, whereas the phase transition was followed by both solid-state 1H,13C cross-polarisation magic-angle spinning (CPMAS) NMR spectroscopy and thermodiffractometry techniques. At 150 °C, compound 1a is transformed into 1b, and, remarkably, the β phase (1b) can be nearly retained down to room temperature, which means that both polymorphs 1a and 1b can coexist over a large temperature range. The structure of 1b has been solved, and it was found that cystamine molecules are disordered over two positions: the two related components with opposite helical conformations. Solid-state 1H,13C CPMAS NMR spectroscopic measurements show a significant broadening of the NMR spectroscopic line associated with two disordered carbon atoms when cooling 1b from 160 to 50 °C, thereby revealing the presence of exchange between these related atoms, and this favours a molecular dynamical disorder. Disulfide bridges of cystamine molecules are engaged in weak interactions with neighbours, either another cystamine molecule in 1a (SS***SS interactions), or iodine atoms in 1b (SS***I interactions). To evaluate the donating and accepting abilities of the disulfide bridge, and their impact on such weak interactions, a detailed partition of the interaction energy of ten dimer models has been calculated and revealed that the main contribution to the intermolecular bonding comes from the dispersion forces

Postsynthetic Crystalline Transformation in Two-Dimensional Perovskites via Organothiol-Based Chemistry

“…The structures of (MEA) 2 PbI 4 and (PDSBA)PbI 4 are firstly reported in this study (Figure 2a, S1, and S3). As for (DSBA)PbI , Louvain et al reported two polymorphs 22 and in this study we only synthesized the one with α-conformation which is believed to be more stable at room temperature. We noticed that the use of the reductant hypophosphorous acid (H 3 PO 2 ) is the key to the synthesis of (MEA) 2 PbI 4 to avoid the undesired, spontaneous oxidation of MEA (see Experimental Section).…”

Structural chemistry of layered lead halide perovskites containing single octahedral layers

“…Despite the difference apparent in unit-cell metrics and space group compared with the chloride, the resulting layer topology is actually very similar: this time the tilt mode is disallowed, rather than just very small. In contrast, the iodide exists in two polymorphs which co-exist over a wide temperature range (Louvain et al, 2014). The high-temperature -phase has the common a À a À c, P2 1 /a structure (724583) with disordered cystamine moieties, whereas the ambient-temperaturephase has a more complex supercell discussed in Section 3.3.…”

“…Note that there is a significant change in the inorganic layer from to , with a change of rotation mode from c to (Àc), in addition to the changes in the conformation and positioning of the cystamine. Although the tilt system and layer shift in thephase result in a similar overall structure to that of the chloride and bromide, the expanded superlattice is caused by ordering of two distinct enantiomeric forms of the cystamine: all these interesting features are discussed in more detail by Louvain et al (2014) For n-butylamine a more diverse range of phases has been reported, which are discussed in Section 4.2.…”

Supramolecular self-assembly of three-dimensional polyaniline and polypyrrole crystals

“…2 Therefore, the preparation of 3D semiconductor crystals is fundamental and is being intensively researched. [3][4][5] Inspired by 3D supramolecular assembly 6 of biological molecules such as DNA, peptides and nacre in solution system, 7,8 supramolecular assembly technology extends to the preparation of 3D inorganic/organic semiconductor crystals. 9,10 However, the 3D assembly of p-conjugated polymer crystals is still a challenge because 3D fantastic self-assembly requires coded nanocrystals 11 with a sufficiently monodisperse distribution of size and shape first, then these nanocrystals repeat the ''bottomup'' self-assembly into 3D crystal structure along the optimal dynamic path, these configurations may be affected by a considerable number of energy contributions (for example, p-p stacking interaction, van der Waals, electrostatic, and dipolar), as well.…”