Muriel Hissler

Linear organic π-conjugated systems featuring the heavy Group 14 and 15 elements

Abstract An overview of the synthesis and properties of linear organic π-conjugated systems featuring Group 14 and 15 moieties is presented and comparisons made with their better-known hydrocarbon, and nitrogen- and sulfur-containing analogues. The major focus of this review is π-conjugated systems based on heteroles. The unique electronic structure and nature of siloles and phospholes is examined, highlighting the influence of both the ring substituents and the character of the heteroatom on their photophysical properties. The synthesis of a variety of Group 14 and 15 heterole building blocks suitable for the construction of π-conjugated systems is presented. The preparation and physical properties of poly- and oligo-(1,1-silole)s and -(2,5-silole)s, oligo-(2,5-phosphole)s and co-oligomers of silole and phosphole blocks with other electron-rich monomer units, all with extended π-conjugation, are discussed. A brief resume of linear π-conjugated materials that possess heavy Group 15 elements in the polymer backbone is also presented.

Phosphole‐Containing π‐Conjugated Systems: From Model Molecules to Polymer Films on Electrodes

Two series of 2,5-dipyridyl- and 2,5-dithienylphosphole derivatives containing sigma3- or sigma4-P atoms were prepared, and their optical (UV/Vis absorption, fluorescence spectra) and electrochemical properties were systematically evaluated. These physical properties depend mainly on the natures of the 2,5-substituents and of the phosphorus moiety, and they revealed that these compounds contain extended pi-conjugated systems. Structure-property relationships were established on the basis of these experimental data and ab initio calculations on the parent molecules. The limited aromatic character and low-lying LUMO of the phosphole ring appear to be crucial for achieving a highly delocalised pi system. Electrooxidation of 2,5-dithienylphosphole derivatives affords electroactive films with low optical band gaps. As observed for the corresponding monomers, the optical and electrochemical properties of the polymers can be varied over a wide range by modifying the nature of the phosphorus moiety.

Dibenzophosphapentaphenes: Exploiting P Chemistry for Gap Fine-Tuning and Coordination-Driven Assembly of Planar Polycyclic Aromatic Hydrocarbons

A synthetic route to planar P-modified polycylic aromatic hydrocarbons (PAHs) is described. The presence of a reactive σ(3),λ(3)-P moiety within the sp(2)-carbon scaffold allows the preparation of a new family of PAHs displaying tunable optical and redox properties. Their frontier molecular orbitals (MOs) are derived from the corresponding phosphole MOs and show extended conjugation with the entire π framework. The coordination ability of the P center allows the coordination-driven assembly of two molecular PAHs onto a Au(I) ion.

Organophosphorus derivatives for electronic devices

This review presents the main class of organophosphorus compounds (triaryl phosphines, phosphazenes, phospholes, phosphetes and diphosphacyclobutanes), which have been used in electronic devices (organic light-emitting diodes (OLEDs), organic photovoltaic cells (OPV cells), dye-sensitized solar cells (DSSCs), organic field-effect transistors (OFETs), and electrochromic cells).

Ligand trans-effect: using an old concept as a novel approach to bis(dipolar) NLO-phores

In plane parallel arrangement and enhancement of NLO-activity are observed upon coordination of heteroditopic dipoles containing a phosphole ring on square-planar d8-palladium centre.

Synthesis, electronic properties and electropolymerisation of EDOT-capped σ3-phospholes

EDOT-capped sigma3-phosphole self-rigidifies due to an unprecedented P-O interaction and can be electropolymerised affording functionalizable polymers.

2,2′‐Biphospholes: Building Blocks for Tuning the HOMO–LUMO Gap of π‐Systems Using Covalent Bonding and Metal Coordination

new angle: The insertion of a 2,2′-biphosphole subunit into π-conjugated systems offers a new way to control the HOMO-LUMO gap. Tuning of the dihedral angle (θ) between the two phosphorous heterocycles, either by metal coordination or covalent bonding through the P substitution can lead to control of the band gap. These new π-conjugated systems can be used as emitting materials in white organic light-emitting devices (WOLEDs).

An aromatic-antiaromatic switch in P-heteroles. A small change in delocalisation makes a big reactivity difference.

The low aromaticity of phosphole can be switched to low antiaromaticity by oxidizing the phosphorus atom. This subtle change in the mode of delocalisation alters substantially the chemical behaviour of these heteroles.

Phosphole-based π-conjugated electroluminescent materials for OLEDs

Novel mixed phosphole–fluorene π-conjugated systems have been prepared using the Fagan–Nugent route. Their optical (UV-visible absorption, fluorescence spectra) and electrochemical properties have been systematically evaluated. The variation of the substitution pattern of phosphole derivatives and chemical modification of their P atoms afford thermally stable derivatives which are photoluminescent. The use of these derivatives as emitters in OLEDs strongly depends on the substituent linked on the P-atom. The gold complexes are not stable electroluminescent materials since they decompose rapidly when the devices are operating. In contrast, the thiooxophospholes are stable electroluminescent materials, and the OLEDs incorporating these derivatives as emitters display very high performances.

Functional phosphorus-based π-conjugated systems: Structural diversity without multistep synthesis

The synthesis and properties of linear π-conjugated systems incorporating phosphole rings are described. Their supramolecular organization in the solid state can be controlled either by chemical modifications or coordination to transition metals of the phosphorus atom. Furthermore, chemical transformations of the phosphole ring allow organizing these P-chromophores in 3D assemblies exhibiting σ-π conjugation or in organometallic ferrocene-like derivatives. Phosphole-pyridine-containing π-conjugated chromophores act as P,N-chelates toward transition-metal ions, giving rise to mono- and di-nuclear complexes. The specific properties of these complexes make them valuable materials for organic light-emitting diodes (OLEDs) and interesting building blocks for the tailoring of π-conjugated systems.