Polypyridyl transition metal

Polypyridyl transition metal complexes, especially those of ruthenium(II), have been extensively apphed in light harvesting and information storage, because they exhibit a wide range of photophysical and electrochemical properties. Storrier et al. have reported the synthesis and characterization of PAMAM dendrimers functionalized with tris(bipyridyl) ruthenium(II) (dend- -[Ru(bpy)3] +) or bis (terpyridyl) ruthe-nium(II) (dend-n-[Ru(tpy)2] ) complexes (GO, 1, 2, 3, and 4 with 4, 8, 16, 32,... 

The encouraging results with photoredox catalysis sparked an explosion of additional investigations of visible-light-promoted oxidation of sp carbons. Many studies explored use of related polypyridyl transition metal based... 

Covalent hydration and pseudobase formation in transition metal polypyridyl complexes reality or myth N. Serpone, G. Ponterini, M. A. Jamieson, F. Bolletta and M. Maestri, Coord. Chem. Rev.,... 

The coordination compounds are widely used as luminescent probes for polymer-based PSP. The coordination compounds are classified into two categories. One is the transition metal polypyridyl complex. In this group, transition metals are Ru2+, Os+ and Ir3+ as shown in Fig. 10. The second group comprises the metalloporphyrins as shown in Fig. 11. Pt2+ and Pd2+ porphyrins are especially used as PSP probes. 

In the transition metal polypyridyl complex group, tris(4,7-diphenylphen-antroline) ruthenium(II) (Ru(dpp)2+) is widely used as a probe for a PSP. The luminescence lifetime of Ru(dpp)2+ is long compared with the other ruthe-nium(II) polypyridyl complexes [17]. The absorption and emission maxima of Ru(dpp)2+ are 457 and 610 nm, respectively. The luminescence lifetimes under nitrogen- and air-saturated conditions are ca. 4.0 and 2.0 ps, respec-... 

Fig. 10 Chemical structures of transition metal polypyridyl complexes...

Table 2 Transition metal polypyridyl complexes luminescence probes for PSP ...

Gillard257 has summarized many of the so-called anomalies existing for transition metal polypy-ridyl complexes in aqueous solution, and postulated covalent hydrate formation to explain these anomalies . Nord and coworkers258 have questioned the validity, and indeed the premise upon which covalent hydration in polypyridyl complexes is based. 

There is much interest in transition metal polypyridyl complexes, largely due to their numerous applications in a variety of fields (247-250). In particular, ruthenium(II) tris(2,2 -bipyridyl) has been one of the most extensively studied complexes of the last decade due to its chemical stability, redox properties, excited-state reactivity, and luminescent emission (251, 252). 

The discovery and coordination chemistry of phenanthrolines closely followed that of the bipyridines throughout the early twentieth century, much as it does today. F. Blau1 and Gerdiessen2 are credited with the earliest published syntheses of 1,10-phenanthrolines (phen, (1)) in the late nineteenth century. While the colored metal complexes of these compounds had been reported, their utility as colorimetric indicators was not discussed until 1931.3 For the next several decades, phenanthroline derivatives served primarily as colorimetric indicators for many transition metals. Throughout this period, the contributions of G. F. Smith,4-7 F. H. Case,8-10 A. A. Schilt,11 and others toward the chemistry of these complexes resulted in a wealth of synthetic routes for derivatives of (1). The flourishing studies of polypyridyl-coordinated metal complexes provided inspiration for preparing unique phenanthrolines with a wealth of pendant photo- and electro-active molecules.12-16... 

The development of probes for large biomolecules has attracted considerable attention using luminescent late transition metals, particularly Ru(II) polypyridyl... 

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. 

Reductive Electropolymerization of Polypyridyl Complexes. Good examples of transition-metal coordination complexes that could have potential use in ECDs include the [M (bipy)3l + (M = iron, ruthenium, osmium bipy = 2,2 -bipyridine) series which are respectively red, orange, and green in the M(II) redox state, due to the presence of an intense MLCT absorption band (26). Elec-trochromicity results from loss of the MLCT absorption band on switching to the M(III) redox state. 

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