Polypyridine complex: Difference between revisions

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'''Polypyridine complexes''' are [[coordination complex]]es containing polypyridine ligands, such as [[2,2'-bipyridine]], 1,10-[[phenanthroline]], or 2,2';6'2"-[[terpyridine]].

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Polypyridine complexes are compounds in which a polypyridine, such as 2,2'-bipyridine, 1,10-phenanthroline, or 2,2';6'2"-terpyridine, coordinates to a metal ion. Polypyridine compounds are multidentate ligands which hane characteristic properties, such as photosensitization. The complexes are very stable to light, electricity, and heat because the bonds between the central metal ion and polypyridine ligands are usually very strong; furthermore, polypyridine itself is generally very stable. The compounds have peculiar optical, electrochemical, and magnetic properties. Some complexes exhibit a strong absorption band in the visible light region, which is called metal-to-ligand charge transfer (MLCT) or ligand-to-metal charge transfer (LMCT). The properties of the complexes can be tuned easily by introducing substituents, for example, electron-donating, electron-withdrawing, and π-conjugating groups, to the polypyridine moiety. The MLCT absorption band can be shifted, the emission wavelength can be changed, and the emission lifetime can be extended. A well-known example of a polypyridine complex is rutheniumtris(bipyridine), Ru[(bpy)₃]²⁺. This complex exhibits intense luminescence at room temperature in aquaous solution. Another example is a platinum-bipyridine-dithiolate complex, Pt(bpy)(bdt), which bdt denotes a 1,2-benzenedithiolate anion. This complex also exhibits photoluminescemce at room temperature, and its wavelength and lifetime can be tuned by substituation of either bipyridine or dithiolate moieties. Structual control is easier than for ruthenium complexes due to the square planar structure of the platinum complex.

Polypyridines are multidentate [[ligand]]s that confer characteristic properties to the metal complexes that they form. Some complexes strongly absorb light via a process called metal-to-ligand [[Intervalence charge transfer|charge transfer]] (MLCT).<ref>Balzani, V., Juris, A., "Photochemistry and photophysics of Ru(II)-polypyridine complexes in the Bologna group. From early studies to recent developments", Coord. Chem. Rev. 2001, 211, 97. {{doi|10.1016/S0010-8545(00)00274-5}}.</ref> The properties of these complexes can be tuned by changes in substituents. For example, electron donation, electron withdrawal, and π-conjugating groups, to the polypyridine [[Moiety (chemistry)|moiety]]. The MLCT absorption band can be shifted, the emission wavelength can be changed, and the emission lifetime can be extended.<ref>Hammarstroem, L., Johansson, O., "Expanded bite angles in tridentate ligands. Improving the photophysical properties in bistridentate Ru^II polypyridine complexes", Coord. Chem. Rev. 2010, 254, 2546. {{doi|10.1016/j.ccr.2010.01.006}}</ref>

[[File:Tris(bipyridine)ruthenium(II) chloride.png|thumb|right|224px|[[Tris(bipyridine)ruthenium(II) chloride|Tris(bipyridine)ruthenium(II)]] is the preeminent example of a polypyridine complex.]]

A well-known example of a polypyridine complex is the tris(bipyridine) derivative of ruthenium(II), [Ru(bpy)₃]²⁺. This complex exhibits intense [[luminescence]] at room temperature in aqueous solution. Another example is a platinum-bipyridine-dithiolate complex, Pt(bpy)(bdt), in which bdt denotes a 1,2-benzenedithiolate [[ion|anion]]. This complex also exhibits [[Fluorescence|photoluminescence]] at room temperature, and its wavelength and lifetime can be tuned by substitution of either bipyridine or dithiolate moieties. Structural control is easier than for [[ruthenium]] complexes due to the square planar structure of the [[platinum]] complex.

Some other areas of investigation involves immobilizing these complexes on electrodes.<ref>Zhong, Y.-W., Yao, C.-J., Nie, H.-J., "Electropolymerized films of vinyl-substituted polypyridine complexes: Synthesis, characterization, and applications", Coord. Chem. Rev. 2013, 257, 1357. {{doi|10.1016/j.ccr.2013.01.001}}</ref> Some polypyridyl complexes intercalate into [[DNA]] and show promise as drugs.<ref>Komor, Alexis C.; Barton, Jacqueline K. "The path for metal complexes to a DNA target" Chemical Communications 2013, vol. 49, 3617-3630. {{doi|10.1039/c3cc00177f}}</ref>

==See also==

* [[Transition metal complexes of 2,2'-bipyridine]]

==References==

<references />

{{DEFAULTSORT:Polypyridine Complex}}

[[Category:Bipyridines]]