A stable and true-blue emissive hexacoordinate Si(IV) N-heterocyclic carbene complex and its use in organic light-emitting diodes

A neutral hexacoordinate Si(IV) complex containing two tridentate N-heterocyclic carbene ligands is synthesised and characterized by X-ray crystallography, optical spectroscopy, electrochemistry and computational methods. The stable compound exhibits remarkable deep-blue photoluminescence particularly in the solid state, which enables its use as an electroluminescent material in organic light-emitting diodes.

Open for Bismuth: Main Group Metal-to-Ligand Charge Transfer

The synthesis, characterization, and photophysical properties of 4- and 6-coordinate Bi³⁺ coordination complexes are reported. Bi(bzq)₃ (1) and [Bi(bzq)₂]Br (2) (bzq = benzo[h]quinoline) are synthesized by reaction of 9-Li-bzq with BiCl₃ and BiBr₃, respectively. Absorption spectroscopy, electrochemistry, and DFT studies suggest that 1 has 42% Bi 6s character in its highest-occupied molecular orbital (HOMO) as a result of six σ* interactions with the bzq ligands. Excitation of 1 at 450 nm results in a broad emission feature at 520 nm, which is rationalized as a metal-to-ligand charge transfer (MLCT) and phosphorescent emission resulting from bismuth-mediated intersystem crossing (ISC) to a triplet excited state. This excited state revealed a 35 μs lifetime and was quenched in the presence of oxygen. These results demonstrate that useful optoelectronic properties of Bi³⁺ can be accessed through hypercoordination with covalent organobismuth interactions that mimic the electronic structure of lead perovskites.

Synthesis, structures and photophysical properties of hexacoordinated organosilicon compounds with 2-(2-pyridyl)phenyl groups

We synthesised novel hexacoordinated organosilicon compounds with two 2-(2-pyridyl)phenyl groups. Single-crystal X-ray structure analyses indicated that Lewis acid-base interactions exist between the silicon atom and two nitrogen atoms of the pyridine rings, and that hexacoordinated organosilicon compounds have slightly distorted octahedral structures in the solid state. The hexacoordinated organosilicon compounds are stable in air, water, heat, acids, and bases. The fluorescent quantum yield increased dramatically and a significant red-shift of the maximum fluorescence wavelength was observed with the introduction of amino groups on the 2-(2-pyridyl)phenyl aromatic rings. The fluorescence colours of a hexacoordinated organosilicon compound with two amino groups can be switched by protonation and deprotonation (neutralisation) of the amino groups.

Influence of monomer deformation on the competition between two types of σ-holes in tetrel bonds

Competition between two competing sites on a tetrel atom is explained by balance between structural deformation and σ-hole intensity.

2,2′-Disilylazobenzenes featuring double intramolecular nitrogen⋯silicon coordination: a photoisomerizable fluorophore

Fluorescent (E)-4,4′-dimethyl-2,2′-bis(trimethylsilyl)azobenzene was synthesized.

Integration of benzo[h]quinoline and π-extended dibenzo[b,f]silepins on pentacoordinate silicon

We investigated the relationship between the chemical structure involving the pentacoordinate silicon and the electronic properties of the molecules.