Cyclometalated Ir(III) complexes containing ancillary pyrazole-based ligands

Abstract

A series of neutral mononuclear cyclometalated Ir(III) complexes, [Ir(ppy)₂(Me₂pzH)Cl] (<b style="">1</b>),<b style=""> </b>[Ir(ppy)₂(MepzH)Cl] (<b style="">2</b>),<b style=""> </b>[Ir(ppy)₂(Mepz)(MepzH)] (<b style="">3</b>), [Ir(ppy)₂(Phpz)(PhpzH)] (<b style="">4</b>), [Ir(ppy)₂(NPpz)(NPpzH)] (<b style="">5</b>) and [Ir(ppy)₂(NP-2-pz)(NP-2-pzH)] (<b style="">6</b>) [where ppyH = 2-phenylpyridine; Me₂pzH = 3,5-dimethylpyrazole; MepzH = 3-methylpyrazole; PhpzH = 3-phenylpyrazole; NPpzH = 3-(1-naphthyl)pyrazole; NP-2-pzH = 3-(2-naphthyl)pyrazole) have been synthesised and structurally characterised. While (<b style="">1</b>) and (<b style="">2</b>) contain neutral pyrazole ligands which binds in a <i style="">κ¹ </i>manner, in compounds (<b style="">3</b>)<b style="">-</b>(<b style="">6</b>), one of the pyrazole ligands is anionic while the other is neutral. In the latter also the pyrazole ligands bind to the metal in a <i style="">κ¹</i> manner. Further, the two types of pyrazoles interact with each other by H-bonded interaction. The photophysical and electrochemical properties of all of these compounds have been studied which reveal that the absorption/emission behaviour of these compounds is dependent on the Ir(ppy)₂ unit of the complexes; the ancillary pyrazole ligands do not influence the photophysical behavior in any significant manner.