Abstract
AbstractFive Pt(II) complexes are described in which the metal ion is bound to anionic ‐coordinating ligands. The central, deprotonated N atom is derived from an imide Ar−C(=O)−NH−C(=O)−Ar {PtL1–2Cl; Ar=pyridine or pyrimidine}, an amide py−C(=O)−NH−CH2−py {PtL3Cl}, or a hydrazide py−C(=O)−NH−N=CH−py {PtL4Cl}. The imide complexes PtL1–2Cl show no significant emission in solution but are modestly bright green/yellow phosphors in the solid state. PtL3Cl is weakly phosphorescent. PtL4Cl is formed as a mixture of isomers, bound through either the amido or imino nitrogen, the latter converting to the former upon absorption of light. Remarkably, the imino form displays fluorescence in solution, λ0,0=535 nm, whereas the amido shows phosphorescence, λ0,0=624 nm, τ=440 ns. It is highly unusual for two isomeric compounds to display emission from states of different spin multiplicity. The amido‐bound PtL4Cl can act as a bidentate ‐coordinating ligand, demonstrated by the formation of bimetallic complexes with iridium(III) or ruthenium(II).
Highlights
M(ECE) unit, coupled with the lability of the M X bond for some metals like Ni(II) and Pd(II), underpins much of the success of pincer complexes in homogeneous catalysis.[3]In the field of inorganic photochemistry and photophysics, square-planar platinum(II) complexes continue to offer much interest to researchers.[4]
We describe the synthesis of four such ligands and their Pt(II) complexes, together with their luminescence properties
The ease of synthesis and lack of requirement for expensive organometallic reagents or palladium catalysts contrasts with routes typically used to prepare related cyclometallating pincer ligands – featuring a central carbon in place of nitrogen – such as 1,3-dipyridylbenzene and its derivatives.[14]
Summary
M(ECE) unit, coupled with the lability of the M X bond for some metals like Ni(II) and Pd(II), underpins much of the success of pincer complexes in homogeneous catalysis.[3]. Pt(II) complexes of 1,3-di(2-pyridyl) benzene (dpybH) and its derivatives, such as Pt(dpyb)Cl (Figure 1b), are intensely luminescent in solution at room temperature.[11] They are readily amenable to colour tuning and form strongly emissive excimers: they have shown promise as OLED emitters in the visible and NIR,[12] and as long-lived probes for bioimaging.[13] Despite this promise, there are some drawbacks to systems based on such N^ C ^ N-coordinating ligands. One of the complexes has the potential to bind a second metal ion as an N^ O-bidentate ligand, as evidenced by the formation of two heterometallic dinuclear compounds with Ru(II) and Ir(III) units
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