Luminescence Ir complexes

Luminescent Ir complexes of diphosphine and diphosphinite calix[4]arene show emission maxima at 619 nm and 597 nm, respectively, at 77 K. The emission lifetimes are perturbed by addition of Li+, Na+, and U022+. 

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. 

The synthesis, structure, and photophysical properties of luminescent Ir complexes, as well as their applications are introduced in this chapter. 

There is also a polymerized lr(C N)2(LX)-type Ir complex in which the bis-cyclometalated fragment Ir(C N)2 is incorporated on the side chain of a polymer. The design of the entire system could have better dissolution and fllm-forming ability as that of the polymer, as well as high quantum efficiency similar to that of luminescent Ir complexes. The chemical structure of a selected polymerized lr(C N)2(LX)-type Ir complex is shown in Fig. 7 [82]. 

Photoluminescent materials in which luminescence output can be modified by interaction with a substrate are being extensively investigated for use as sensors. Luminescent Ir complexes have been used as oxygen sensors, homocysteine sensors, metal cation sensors, and volatile organic compound sensors because of their rich photophysical properties. 

From this diagram, one may notice that ca. 90% of the known luminescent Ir(III) complexes, mostly from cyclometalating ligands, have been reported in the last 6 years. One relevant reason for this trend is related to the use of the cyclometalated complexes for OLED fabrication [9-12], with those of Ir(III) exhibiting relevant advantages with respect to complexes from other metals [13]. 

Reactions of the dichloro-bridged rhodium(ni) and iridium(III) dimers with diimine ligands resulted iu the formation of the luminescent mononuclear complexes [M(N C)2(N N)]+ (M = Ir, Rh = ppy, bzq N N = bpy, phen). The electronic absorption and emission spectra of these complexes are shown in Figure 8. The rhodium(III) complexes displayed very long-lived emission in... 

The successful application of Ir(ppy)3 as a phosphorescent dopant has led to a number of synthetic modifications of the parent complex. Most of the new derivatives were prepared in order to alter the luminescent properties (color, efficiency, stability, etc.) or to further characterize the excited-state properties of these materials. Tris-cyclometal-lated Ir complexes can be prepared using two general methods, either by direct formation in a one-step reaction or with a two-step synthesis that uses a /t-dichloro-bridged dimeric complex as an isolated intermediate. The first efficient direct synthesis to be reported involved the reaction of Ir(acac)3 (acac = acetylacetonate) with an excess of... 

The first example of an Ir complex-based oxygen sensor was reported by Donckt et al. in 1994 [123]. They embedded/ac-1 in polystyrene and studied the luminescence properties of the system for use as an oxygen sensor to avoid self-quenching offac-1 at higher concentration. In 1996, DiMarco et al. [124] reported another Ir complex [Ir(ppy)2(dpt-NH2)](PF6) (where dpt-NH2 = 4-amino-3,5-di-2-pyridyl-4/f-l,2,4-triazole), immobilized in a polymerized poly-(ethyleneglycol) ethyl ether... 

Luminescence has been observed from a large number of later transition element complexes and a rich array of excited states have been observed. Related sections from CCC (1987) include Chapter 16.5 on Pt, Rh, and Ir complexes, 36.3 on Mo halide clusters, 43 on Re complexes, 45.4 on Ru polypyridyls, 46.4 on Os polypyridyls, 48.6 on Rh complexes, and sections of Chapter 52 on Pt complexes. Several recent reviews have been published on polynuclear complexes, the photophysics of gold complexes,and platinum diimine complexes. Many other more narrowly focused review articles have been published on transition metal complex luminescence a significant number are published in the journal Coordination Chemistry Reviews and some of these reviews are cited in this chapter. 

Scheme 11.7 Luminescent Ir(lll) and Rh(lll) complexes used in cell imaging (PFe counterion omitted for clarity).

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