Metal complexes with pyridyl azolates: Design, preparation and applications

•Design and properties of the azole-containing bidentate chelates are reviewed.•Selected chelates comprise 2-pyridyl pyrrole, pyrazole, triazole and tetrazole.•Luminescent Os(II), Ir(III), Pt(II) and Cu(I) metal complexes are useful phosphors for organic light emitting diodes.•The corresponding Ru(II) and Os(II) complexes serve as sensitizers for dye sensitized solar cells upon incorporation of carboxy functionalized polypyridine anchors.

This review is aimed at updating the current advance of metal complexes bearing pyridyl azolates or relevant functionality. Of particular emphasis is the emerging metal complexes, which show bright prospect in the energy relevant issues such as organic light emitting diodes (OLEDs) and dye sensitized solar cells (DSCs). Our motive lies in the development of OLED phosphors as well as the realization of superior sensitizers in DSCs. It covers a great extension of azolates based derivatives as well as a large variety of core metal ions spanning from Re(I), Ru(II), Os(II), Ir(III), Pt(II) and to Cu(I). Their synthetic strategy, chemical/physical and photophysical properties and electroluminescence as a function of chelate or metal characteristics are systematically discussed. The potential applications are far-reaching in the wake of the previously unrecognized feature on harnessing the highly excited states, which are then realized by several new designs endowed with this unique property. Also, the interplay of the ligand design, i.e, the sameness and difference, between lighting and photovoltaic oriented metal complexes is highlighted.

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