Influence of π-Iodide Intermolecular Interactions on Electronic Properties of Tin(IV) Iodide Semiconducting Complexes

Abstract

Coordination compounds with a tin center surrounded by both organic and inorganic ligands ([SnI4{(C6H5)3PO}2], [SnI4{(C6H5)2SO}2], and [SnI4(C5H5NO)2]) acting as molecular semiconductors are in the spotlight of this article. This is a new class of hybrid semiconducting materials where optoelectronic properties of inorganic core (SnI4) were tuned by organic ligands. The valence band is located at the inorganic portion of the molecule while the conduction band is made of carbon-based orbitals. This suggests the great importance of hydrogen bonds where iodine atoms play the role of an acceptor. Weak intermolecular interactions between iodine atoms and aromatic rings are essential in a band structure formation. These materials form orange-red crystals soluble in most of organic solvents. Their semiconducting properties are addressed experimentally via photovoltage measurements, as well as theoretically, using DFT and semiempirical approaches.

Triiodide Organic Salts: Photoelectrochemistry at the Border between Insulators and Semiconductors

“…Described method and fitting parameters are presented in Figure S5 in the Supplementary Information. These values are comparable with other iodide‐containing semiconductors, like lead halide perovskites and organotin complexes …”

“…Hydrogen bonds, depending on their nature, are known to cause either bathochromic or hypsochromic shifts in the electronic spectra, however in some cases they exert no visible spectral effects . Stronger influence of the C−H⋅⋅⋅I type interaction has been shown in previous studied case on tin iodide complexes, in which interactions between iodide ligands and aromatic moieties were responsible for semiconducting properties …”

“…[30] Stronger influence of the CÀH···I type interaction has been shown in previous studied case on tin iodide complexes, in which interactions between iodide ligands and aromatic moieties were responsible for semiconducting properties. [14] Optical band gaps for studied materials were determined using the Tauc plots. [31] The diffuse reflectance spectra were converted using Kubelka-Munk function.…”

“…These values are comparable with other iodide-containing semiconductors, like lead halide perovskites [34] and organotin complexes. [14]…”

“…We demonstrate that the semiconducting character of these compounds is the result of the electronic interactions between triiodide anions. In our previous report [14] we have demonstrated that combination of weak interactions between aromatic substituents and iodide ligands is the series of [SnI 4 L 2 ] complexes (L = diphenylsulfoxide, triphenylphosphine oxide, pyridine N-oxide) results in semiconducting character despite the lack of strong intermolecular interaction. Therefore, we were searching for compounds with analogous structural features: pnictogen or pnictogen oxide center with three aromatic substituents.…”