Syntheses and luminescent properties of 3,5-diphenylpyrazolato-bridged heteropolynuclear platinum complexes. The influence of chloride ligands on the emission energy revealed by the systematic replacement of chloride ligands by 3,5-dimethylpyrazolate.

Heteropolynuclear Pt(II) complexes with 3,5-diphenylpyrazolate [Pt(2)Ag(4)(μ-Cl)(2)(μ-Ph(2)pz)(6)] (3), [Pt(2)Ag(2)Cl(2)(μ-Ph(2)pz)(4)(Ph(2)pzH)(2)] (4), [Pt(2)Cu(2)Cl(2)(μ-Ph(2)pz)(4)(Ph(2)pzH)(2)] (5), [Pt(2)Ag(4)(μ-Cl)(μ-Me(2)pz)(μ-Ph(2)pz)(6)] (7), and [Pt(2)Ag(4)(μ-Me(2)pz)(2)(μ-Ph(2)pz)(6)] (8) have been prepared and structurally characterized. These complexes are luminescent except for 5 in the solid state at an ambient temperature with emissions of red-orange (3), orange (4), yellow-orange (7), and green (8) light, respectively. Systematic red shift of the emission energies with the number of chloride ligands was observed for 3, 7, and 8. DFT calculations indicate that the highest occupied molecular orbital (HOMO) as well as HOMO-1 of the heterohexanuclear complexes, 3, 7, and 8, having Pt(2)Ag(4) core, mainly consist of dδ orbital of Pt(II) and π orbitals of Ph(2)pz ligands, while the lowest unoccupied molecular orbital (LUMO) of these complexes mainly consists of in-phase combination of 6p of two Pt(II) centers and 5p of four Ag(I) centers. It is likely that the emissions of 3, 7, and 8 are attributed to emissive states derived from the Pt(2)(d)/π → Pt(2)Ag(4) transitions, the emission energy of which depends on the ratio of chloride ligands to pyrazolate ligands.