Intracation and Interanion–Cation Charge-Transfer Properties of Tetrathiafulvalene-Bismuth-Halide Hybrids

Abstract

Tetrathiafulvalene (TTF) derivatives as promising hole transport materials in assembling hybrid halide perovskite solar cells have attracted great attention; however, electron transfer or charge-transfer (CT) between TTF and metal halides has been studied with less detail at the molecular level. Using molecular models, we herein report four new TTF-bismuth-halides assembled by methylated or protonated bis(4'-pyridyl)-tetrathiafulvalene cations, (MePy)TTF or (HPy)TTF, and bismuth-halide anions. Single crystal analysis showed that the cations are stacked to form a TTF column, and the bismuth-halide anions are inlaid between the TTF columns with anion-cation interactions. In these compounds, the main contribution to CT is the intracation CT, namely intramolecular CT (IMCT) from TTF moiety to pyridinium group. However, the anion to cation CT (ACCT) has a significant effect on the IMCT and physical properties. The different anion-cation interaction modes result in different synergistic effects of IMCT and ACCT, which modified the band gaps and photocurrent properties of the hybrids. The research gives a clear image of structure-property relationship and provides a perspective on the design of new perovskite materials at the molecular level.

Assembling Polyiodides and Iodobismuthates Using a Template Effect of a Cyclic Diammonium Cation and Formation of a Low-Gap Hybrid Iodobismuthate with High Thermal Stability

“…At the same time, the majority of these compounds have rather wide band gaps exceeding 2 eV, which makes them poor light harvesters. However, recent literature provides several examples of hybrid iodobismuthates with low band gaps, ranging from 1.59 to 1.80 eV [ 32 , 33 , 34 , 35 , 36 ]. These compounds contain various organic cations and, more importantly, have different dimensionality of the anionic substructure, ranging from isolated anions to vertex-sharing BiI 5 chains to edge-sharing BiI 4 – chains.…”

“…Namely, they are multifold weak interactions that include hydrogen bonds (mainly (N)H•••I) as well as interanionic I•••I interactions [36][37][38][39][40][41][42]. DFT calculations reveal that weak non-covalent bonds are capable of promoting charge mobility along the direction of spreading such bonds in the crystal structure [34][35][36][37][38][39].…”

Hybrid Charge-Transfer Semiconductors: (C7H7)SbI4, (C7H7)BiI4, and Their Halide Congeners

“…Such templating may give rise to properties from the cooperative behavior (e.g., electrical transport) not found in simple packings of the molecules, 16 and spatial charge separation within the bulk of the material (e.g., (Pb2I6)•(H2DPNDI)•(H2O)•(NMP)). 17 A great diversity of compounds appears in the tetrathiofulvalene (TTF) based charge-transfer salts (e.g., TTF3SnCl6, (TTF)BiI4, (TTF)Pb2I5), [18][19][20][21] in which the inorganic rarely shows spatial connectivity. A recent study has shown that the connectivity of the inorganic subunit can be modified in the compounds (TMP) that structural modification can be achieved, although the organic cation is not optoelectronically active.…”

Advanced X-ray Shielding Materials Enabled by the Coordination of Well-Dispersed High Atomic Number Elements in Natural Leather

“…Equilibrium speciation of bismuth­(III) at different pHs was calculated by Visual MINTEQ 3.1 using experimental ion concentrations as initial parameters. The optimized molecular geometries and energies of the system were obtained by density functional theory (DFT) calculations using Gaussian 09, where H, C, N, and O atoms were performed using the B3LYP/6–311G­(d,p) basis set, and Bi and I atoms using the LanL2DZ basis set . Additional basis set superposition error (BSSE) corrections were carried out for the interactions between amino acids (fragment A) and high-Z element ions (fragment B), and the changes in the system energy during noncovalent binding are given by eq : …”