A series of luminescent dinuclear platinum(II) complexes incorporating diphenylpyrazine-based bridging ligands (L n ) have been prepared. Both 2,5-diphenylpyrazine (n = 2) and 2,3-diphenylpyrazine (n = 3) are able to undergo cyclometallation of the two phenyl rings, with each metal ion binding to the two nitrogen atoms of the central heterocycle, giving, after treatment with the anion of dipivaloyl methane (dpm), complexes of the formula {Pt(dpm)} 2 L n . These compounds are isomers of the analogous complex of 4,6-diphenylpyrimidine (n = 1). Related complexes of dibenzo(f,h)quinoxaline (n = 4), 2,3-diphenyl-quinoxaline (n = 5) and dibenzo[3,2-a:2',3'-c]phenazine (n = 6) have also been prepared, allowing the effects of strapping together the phenyl rings (n = 4 and 6) and/or extension of the conjugation from pyrazine to quinoxaline (n = 5 and 6) to be investigated. In all cases, the corresponding mononuclear complexes, Pt(dpm)L n H, have been isolated too. All 12 complexes are phosphorescent in solution at ambient temperature. The emission spectra of the dinuclear complexes are consistently red-shifted compared to their mononuclear analogues, as are the lowest-energy absorption bands. Electrochemical data and TD-DFT calculations suggest that this effect arises primarily from a stabilisation of the LUMO. The introduction of the second metal ion also has the effect of substantially increasing extinction coefficients in absorption, and -in most cases -the radiative rate constants. Meanwhile, the extension of conjugation in the heterocycle of L 5 and L 6 , and planarisation of the aromatic system favoured by interannular bond formation in L 4 and L 6 , leads to further red shifts of the absorption and emission spectra to wavelengths that are unusually long for cyclometallated platinum(II) complexes. The results may offer a versatile design strategy for tuning and optimizing the optical properties of d-block metal complexes for contemporary applications. † Northumbria University.

A new family of bridged cyclometallating ligands is reported, which incorporate two terdentate N(∧)C(∧)N-coordinating binding sites linked via pyrazine, pyrimidine or pyridazine units. Dinuclear Ir(III) complexes of one ligand have been prepared and crystallographically characterised; they display intense red phosphorescence.

In this work we present synthesis and an in-depth photophysical analysis of a di-Pt(II) complex with a ditopic bis-N^C^N ligand. The complex exhibits a dual luminescent behaviour by emitting simultaneously...

The design, synthesis, photophysical properties, and the ion-binding properties of cyclometallated platinum(II) complexes containing pyridyl-appended alkynyl ligands are described. When the pyridyl group is incorporated into an azamacrocycle, a specific response towards lead(II) cations involves a change in the nature of the excited charge transfer state, resulting in the appearance of a low-energy absorption band and a partial quenching of luminescence.