In this article we highlight, by means of selected examples drawn from work performed in our or other laboratories, the features of some classes of fluorinated conjugated materials and their use in electronic devices such as electroluminescent diodes or field effect transistors. A variety of fluorinated conjugated systems, either molecular or polymeric, such as poly(phenylenevinylene)s, poly(phenyleneethynylene)s, polythiophenes, polyphenylenes, are dealt with. Attention is also focused on a different class of electroluminescent compounds, represented by the cyclometalated iridium complexes with various forms (mer and fac). In particular, fluorine atoms lower both the HOMO and LUMO energy levels. Consequently, the electron injection is made easier, the materials display a greater resistance against the degradative oxidation processes and organic n-type or ambipolar semiconducting materials may result. Moreover, the C–H⋯F interactions play an important role in the solid state supramolecular organization, originating a typical π-stack arrangement which enhances the charge carrier mobility.

White organic light emitting diodes (WOLEDs) are promising devices for application in low energy consumption lighting since they combine the potentialities of high efficiency and inexpensive production with the appealing features of large surfaces emitting good quality white light. However, lifetime, performances and costs still have to be optimized to make WOLEDs commercially competitive as alternative lighting sources. Development of efficient and stable emitters plays a key role in the progress of WOLED technology. This tutorial review discusses the main approaches to obtain white electroluminescence with organic and organometallic emitters. Representative examples of each method are reported highlighting the most significant achievements together with open issues and challenges to be faced by future research.

Homoleptic Ir(F_nppy)₃ and heteroleptic (F_nppy)₂Ir(acac) complexes (n = 3: F₃ppy = 2-(3′,4′,6′-trifluorophenyl)pyridine; n = 4: F₄ppy = 2-(3′,4′,5′,6′-tetrafluorophenyl)pyridine; acac = acetylacetonate) have been synthesized and their spectroscopic properties investigated. The homoleptic complexes exist as two stereoisomers, facial (fac) and meridional (mer), that have been isolated and fully characterized. Their electrochemical and photophysical properties have been studied both in solution and in the solid state and electroluminescent devices have been fabricated. The emissive layers in devices have been obtained mixing the iridium complexes with a PVK [poly(9-vinylcarbazole)] host matrix, in the presence of the electron carrier Bu-PBD [2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole]. The application of a voltage (5.0–6.5 V) between the electrodes of devices leads to electro-generated blue luminescence which has similar energy to the solution emissions. Interestingly, the stability of the devices made with the homoleptic fluorinated iridium complexes strongly depends on the stereochemistry of these phosphors and high (up to 5.5%) external quantum efficiencies for the fac complexes are measured.

Results of special interest in the field of organometallic chemistry directed towards the synthesis of conjugated oligomers and polymers are reviewed. Methodologies widely employed in the synthesis of well-defined molecules and based on the transition metal catalyzed coupling reactions of various organometallic (B, Sn, Si, Mg and Zn) reagents have been more recently extended to build up poly- or oligo-meric conjugated molecular architectures. Although the focus of the present work is on transition metal cross-coupling or homo-coupling processes, other useful organometallic routes, such as metathesis reactions and acetylene polymerization, have also been dealt with. Owing to their higher versatility with respect to the non-organometallic processes commonly used for the synthesis of these materials, the approaches presented allow the realization of more complex molecular structures, which are nowadays required in many electronic and optoelectronic applications. The use of organometallic strategies has been discussed from a synthetic organic chemist's point of view, and advantages and limitations of the different methodologies reviewed have been highlighted. Some attention has also been paid to the properties of the resulting materials and to their dependence on the procedure followed and the framework obtained.