Synthesis, characterization and photophysical properties of new cyclometallated platinum(II) complexes with pyrazolonate ancillary ligand

New cyclometalated platinum(II) complexes with pyrazolonate ancillary ligand (ppy)Pt(pmip) (1) and (dfppy)Pt(pmip) (2) (ppy = 2-phenylpyridine, dfppy = (4,6-difluorophenyl)pyridine, Hpmip = 1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone) were synthesized and structurally characterized. Both compounds revealed square-planar geometry. The crystal cell of 1 was found to contain the monomer molecules of platinum compound whereas dimer molecules of 2 with short Pt⋯Pt contacts of 3.2217(3) A were observed in the crystal cell of 2. Photophysical properties of 1 and 2 were investigated in detail. The highly resolved photoluminesence spectra of the platinum complexes in solution contain emission bands in the region of 470–550 nm attributed to monomer compounds 1 and 2. The triplet-state energies of 1 and 2 obtained from DFT calculations agree very well with the experimental data. In the crystalline state complex 2 revealed excimer emission as a structureless broad band at ca. 584 nm related to dimer molecules of platinum compound presented in the crystals.