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 PtII complexes with 3,5-diphenylpyrazolate [Pt2Ag4(μ-Cl)2(μ-Ph2pz)6] (3), [Pt2Ag2Cl2(μ-Ph2pz)4(Ph2pzH)2] (4), [Pt2Cu2Cl2(μ-Ph2pz)4(Ph2pzH)2] (5), [Pt2Ag4(μ-Cl)­(μ-Me2pz)­(μ-Ph2pz)6] (7), and [Pt2Ag4(μ-Me2pz)2(μ-Ph2pz)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 Pt2Ag4 core, mainly consist of dδ orbital of PtII and π orbitals of Ph2pz ligands, while the lowest unoccupied molecular orbital (LUMO) of these complexes mainly consists of in-phase combination of 6p of two PtII centers and 5p of four AgI centers. It is likely that the emissions of 3, 7, and 8 are attributed to emissive states derived from the Pt2(d)/π → Pt2Ag4 transitions, the emission energy of which depends on the ratio of chloride ligands to pyrazolate ligands.