Editing Polypyridine complex (section)

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

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<sup>II</sup> 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)<sub>3</sub>]<sup>2+</sup>. 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>