Influence of organic cation planarity on structural templating in hybrid metal-halides

Weak, Broken, but Working-Intramolecular Hydrogen Bond in 2,2'-bipyridine

From an academic and practical point of view, it is desirable to be able to assess the possibility of the proton exchange of a given molecular system just by knowing the positions of the proton acceptor and the proton donor. This study addresses the difference between intramolecular hydrogen bonds in 2,2'-bipyridinium and 1,10-phenanthrolinium. Solid-state ¹⁵N NMR and model calculations show that these hydrogen bonds are weak; their energies are 25 kJ/mol and 15 kJ/mol, respectively. Neither these hydrogen bonds nor N-H stretches can be responsible for the fast reversible proton transfer observed for 2,2'-bipyridinium in a polar solvent down to 115 K. This process must have been caused by an external force, which was a fluctuating electric field present in the solution. However, these hydrogen bonds are the grain that tips the scales precisely because they are an integral part of a large system of interactions, including both intramolecular interactions and environmental influence.

Influence of interaction between organic cation and inorganic unit in bi-based hybrid perovskites for photoelectronic properties

With the increase of the passion on lead-free perovskites, more and more endeavor focused on halobismuthates. Here, we have introduced the p-iodoaniline and p-phenylenediamine into Bi-based hybrid materials, and two photoactive iodobismuthate named p-phenylenediamine iodobismuthate (PDABI) and p-iodoaniline iodobismuthate (PIDBI) were prepared. Their single structures, band gaps, thermostability and other properties were explored. The structure results revealed that they all have 1D BiI₄ ^- anion chains with edge-shared BiI₆ octahedron. The DFT result revealed that PIDBI had an inherent interaction between the I substituent in p-iodoaniline cation and the Bi atom in inorganic BiI₄ ^- anion chains. The photodetector assembled by PDABI and PIDBI revealed that the interaction provided by symmetric p-phenylenediamine has a positive effect on PIDBI's optoelectronic properties compared to the role of asymmetric p-iodoaniline in PDABI.

Expanding Bismuth Trihalide Coordination Chemistry with Trimethyltriazacyclohexane and Trimethyltriazacyclononane

1,3,5-Trimethyltriazacyclohexane, Me₃tach, readily adds to bismuth triiodide to form a variety of new coordination compounds depending on the stoichiometry, solvent, and crystallization conditions. X-ray crystallographic evidence has been obtained for both 2:1 and 1:1 Me₃tach:Bi complexes with formulas of [(Me₃tach)₂BiI₂][(Me₃tach)BiI₄], [(Me₃tach)₂BiI₂]₃[Bi₂I₉][I][HMe₃tach]·THF, and (Me₃tach)BiI₃(py)₂. The related chloride structure (Me₃tach)BiCl₃(py)₂ forms from BiCl₃. The structure of (Me₃tacn)BiI₃ with the larger chelate, 1,4,7-trimethyltriazacyclononane, Me₃tacn, was obtained for comparison, and the polymeric structure of BiI₃ in THF was defined as [BiI(THF)(μ-I)₂]_n.

Influence of Aromatic Cations on the Structural Arrangement of Hg(II) Halides

Understanding the structure and arrangement of hybrid metal halides and their contribution to the optoelectronic properties is, thus far, a challenging topic. In particular, new materials composed of d¹⁰ metal halides and pyridinium cations are still largely unexplored. Therefore, we report the synthesis and characterization of six Hg(II) salts built up from (Hg₂Cl₆)^2- or (HgX₄)^2- anions (X = Cl, Br, I) and 2,2'-bipyridium (2,2'-Hbipy)⁺, 2,2'-bipyridine-1,1'-diium (2,2'-H₂bipy)²⁺, or 1,10-phenantrolinium (1,10-Hphen)⁺ cations, using the same experimental conditions. All of them have been characterized by PXRD, EA, FTIR-ATR, and ¹H NMR spectroscopies; single-crystal X-ray diffraction; and TG/DTA determinations. The study of their packing via Hirshfeld surface analysis and 3D deformation density mapping revealed the contributions of the intermolecular interactions to the structural arrangement, notably, the effect of the cation planarity on them. Successively, periodic DFT calculations showed that (i) the valence and conducting bands are mainly composed of the p orbitals of the halide and the organic cation, respectively, and (ii) the corresponding band gap depends mainly on the halide.

Anisotropic Photoconductivity and Long-Lived Charge Carriers in Bismuth-Based One-Dimensional Perovskite with Type-IIa Band Alignment

Bismuth-based perovskites are attracting intense scientific interest due to low toxicity and excellent moisture stability compared to lead-based analogues. However, high exciton binding energy, poor charge carrier separation, and transport efficiencies lower their optoelectronic performances. To address these issues, we have integrated an electronically active organic cation, naphthalimide ethylammonium, between the [BiI₅^2-]_n chains via crystal engineering to form a novel perovskite-like material (naphthalimide ethylammonium)₂BiI₅ (NBI). Single crystal analysis revealed a one-dimensional quantum-well structure for NBI in which inter-inorganic well electronic coupling is screened by organic layers. It exhibited anisotropic photoconductivity and long-lived charge carriers with milliseconds lifetime, which is higher than that of CH₃NH₃PbI₃. Density functional theory calculations confirmed type-IIa band alignment between organic cations and inorganic chains, allowing the former to electronically contribute to the overall charge transport properties of the material.