Iridium luminescent, applications

In the following sections, luminescent organometallic rhenium(I) and iridium(III) polypyridine complexes relying on the labelling or binding strategies mentioned above will be described. We focus on the molecular structures, spectroscopic and photophysical properties of the complexes, and the emissive behaviour and potential applications of the labelled bioconjugates. 

Complexes of the lower members of the group with terpy have attracted little attention. A number of salts of the [Rh(terpy)2] cation have been characterized, as have the complexes [Rh(terpy)X3] (X = Cl, Br, or I) (55, 224, 328). In each case, the compounds are thought to possess a distorted octahedral geometry. The luminescent 1 1 chelate formed between irid-ium(III) and terpy has been studied, and may be of some application in the determination of iridium (197,198,328). 

Ruthenium complexes used to lead research in photochemistry of metal compounds, but rhodium complexes have recently overtaken them as the key target compounds due to their applications in OLEDs. This is a lively and ever-changing field for example, over 90% of luminescent iridum(III) complexes have been reported only in the six years to the beginning of 2009. With their luminescence tuneable through ligand choice, iridium complexes are firm candidates for optical display applications. 

Abstract Considerable studies have been made on iridium complexes during the past 10 years, due to their high quantum efficiency, color tenability, and potential applications in various areas. In this chapter, we review the synthesis, structure, and photophysical properties of luminescent Ir complexes, as well as their applications in organic light-emitting diodes (OLEDs), biological labeling, sensitizers of luminescence, and chemosensors. 

Iridium metal compounds have shown some remarkable effects recently for luminescent properties such as very high photoluminescent quantum yields [27, 29, 44] and high stability [46]. Two reviews [2, 4] have recently reported on phosphorescent heavy-metal complexes (Re, Ru, Os, Ir, and Rh) as bioimaging probes, including their photophysical properties, cytotoxicity, and cellular uptake mechanisms [2], and on transition metals (Ir, Re, Ru) in fluorescent cell imaging applications such as uptake and toxicity [4], respectively. 

In this field of luminescent organometallic probes, rhenium and iridium complexes have played so far the major role, thus explaining their predominance in this chapter. The lower number of platinum, rhodium, and gold fluorescent complexes could be explained by demanding synthesis, low luminescence efficiency, poor operational stability, unsuitability for biological applications, or even simply by the lack of systematic studies. 

Two mechanisms are conceivable. The first is a luminescence resonance energy transfer (LRET) from the UCNPs to nearby molecules of the iridium (or other) probe for oxygen. Alternatively (or in addition), the UCNPs may act as nanolamps whose blue emission leads to the photoexcitation of the iridium complex. The applicability and full reversibility was demonstrated on alternately exposing the sensor film to argon and oxygen, which resulted in a fully reversible increase and decrease of the emission of the iridium(III) complex, respectively, as shown in Fig. 9... 

Research in the chemistry of rhodium and iridium Af-heterocyclic carbene (NHC) complexes has extraordinarily evolved since 2000. A quick search for rhodiimi-NHC and iridiimi-NHC complexes in the SCl-expanded database, with a 2005-2013 timespan, results in more than 360 hits for rhodium, and more than 340 for iridiiun, which gives a good idea on the interest that rhodium and iridium NHC-based chemistry have achieved in the last few years. It is important to note that a nimiber of reviews and book chapters specifically concerning the chemistry of NHC-based compounds of rhodium and iridiiun have recently appeared [1]. This chapter will deal with all new aspects of the NHC-M (M = Rh, Ir) chemistry not reviewed before, and therefore is mainly restricted to the last 4-5 years. The chapter is classified into two main sections, the first of which deals with relevant structural and electronic features of Rh-NHC and Ir-NHC complexes, and the second with the catalytic applications of these compounds. While not pretending to be completely comprehensive, we have tried to describe the most relevant examples assigned to each section. Some other relevant applications of these complexes have not been considered, such as the emerging biochemical applications, mostly referred to Rh-NHC complexes [2], and the luminescent properties of some Ir-NHC complexes, mostly used for the fabrication of electro-optical devices [3]. 

Polysilanes are also applicable as matrix materials in phosphorescent OLEDs. Mixtures of polysilanes and triplet emitters are sufficient to effect an energy transfer from polysilane triplet states to emitter triplet states, thus amplifying the luminescence of the device. It has been shown that if polysilanes have electrophosphorescent side chains consisting of triplet emitters, the energy transfer from polysilane to emitter is most effective [124]. Thus the beneficial electronic properties of polysilanes are perfectly combined with the spectroscopic properties of transition metal based triplet emitters. The compounds described are derivatives of polymethylphenylsi-lanes, (Fig. 24) which are covalently attached to triplet emitters with iridium as metal centre. The polymers were applied in OLEDs with an ITO/active layer/Ca/Ag layer sequence. The active layer contained a fraction of 70% by weight of the... 

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