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Luminescence Color Tuning of Pt II Complexes and a Kinetic Study of Trimer Formation in the Photoexcited State
Author(s) -
Kayano T.,
Takayasu S.,
Sato K.,
Shinozaki K.
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201403789
Subject(s) - trimer , excited state , dimer , excimer , luminescence , chemistry , monomer , dissociation (chemistry) , photochemistry , analytical chemistry (journal) , emission spectrum , crystallography , fluorescence , materials science , spectral line , atomic physics , polymer , physics , optoelectronics , organic chemistry , chromatography , astronomy , quantum mechanics
We investigated the luminescence properties and color tuning of [Pt(dpb)Cl] (dpbH=1,3‐di(2‐pyridyl)benzene) and its analogues. An almost blue emission was obtained for the complex [Pt(Fmdpb)CN] (FmdpbH=4‐fluoro‐1,3‐di(4‐methyl‐2‐pyridyl)benzene), modified by the introduction of F and CH 3 groups to the dpb ligand and the substitution of Cl by CN. As the concentration of the solution was increased, the color of the emission varied from blue to white to orange. The color change resulted from a monomer–excimer equilibrium in the excited state. A broad emission spectrum around 620 nm was clearly detected along with a structured monomer emission around 500 nm. Upon further increases in concentration, another broad peak appeared in the longer wavelength region of the spectrum. We assigned the near‐infrared band to the emission from an excited trimer generated by the reaction of the excimer with the ground‐state monomer. The emission lifetimes of the monomer, dimer, and trimer were evaluated as τ M =12.8 μs, τ D =2.13 μs, and τ T =0.68 μs, respectively, which were sufficiently long to allow association with another Pt II complex and dissociation into a lower order aggregate. Based on equilibrium constants determined from a kinetic study, the formation of the excimer and the excited trimer were concluded to be exothermic processes, with Δ G* D =−24.5 kJ mol −1 and Δ G* T =−20.4 kJ mol −1 respectively, at 300 K.