Synthesis, spectral and reactivity studies of rutheniumcomplexes with 2,6-bis(benzimidazol-2-yl)pyridine complexes with 2,6-bis(benzimidazol-2-yl)pyridine

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Ruthenium(II) polypyridyl complexes have been the subject matter of considerable attention over the last few decades and perhaps, have been investigated in greater detail than any other class of luminescent metal complexes.1,2 In this direction, a considerable number of compounds have been prepared to study their utility in photophysics, electrochemistry, solar cells, biosensors, modified electrodes, displays, etc.3 The enormous popularity of this class of compounds and also, of the related osmium, rhodium and iridium compounds has been driven by their wide range of applications. Investigation into this chemistry of ruthenium has started in earnest in the late 1950Ds with the report of the dinuclear complex [(NH3)5Ru2pz]2+ (pz = pyrazine) by Creutz and Taube2 and the first report of luminescence of the paradigm complex [Ru(bpy)3]2+ (bpy = 2,2/- bipyridine) by Paris and Brandt.4 However, the study of ruthenium polypyridyl complexes really exploded in the next decade with the realization that the combination of excited state and electrochemical properties of [Ru(bpy)3]2+ would enable it to split water into hydrogen and oxygen.5 Although the initial expectations of photochemical water splitting were not easily achieved, the physical properties of these compounds were sufficiently promising to encourage the search for potential applications in other areas.6 The interest in mimicking the photo-induced charge separation occurring in natural photosynthesis has guided many research groups in the design of synthetic analogues. This has led to the development of multicomponent systems containing donor and/or acceptor units attached to the photo sensitizer, creating long-lived charge separated states in which solar energy is stored as chemical energy.7-9 The photoactive transition metal complexes, especially the polypyridines of ruthenium(II) and osmium(II), have played a major role due to their favorable photophysical behavior.1,10-13 Both ruthenium(II)bis(terpyridine), [Ru(trpy)2]2+ and ruthenium(II)tris(bipyridine), [Ru(bpy)3]2+ have been widely used as sensitizers, where the [Ru(trpy)2]2+ unit offers the...
Supervisor: Biplob Mandal