Asymmetry in Platinum Acetylide Complexes: Confinement of the Triplet Exciton to the Lowest Energy Ligand (Postprint)
Abstract
As part of an ongoing investigation of structure-optical property relationships in asymmetric platinum acetylide complexes, we synthesized the compounds trans-Pt(PBu3)2(C equivalent CC6H5)(C equivalent C-C6H4-C equivalent CC6H5) (PE1-2), trans-Pt(PBu3)2-(C equivalent CC6H5)(C equivalent C-C6H4-C equivalent C-C6H4-C equivalent CC6H5) (PEl-3), and trans-Pt(PBu3)2(C equivalent C-C6H4-C equivalent CC6H5)-(C equivalent C-C6H4-C equivalent C-C6H4-C equivalent CC6H5) (PE2-3) that have different ligands on either side of the central platinum and compared their spectroscopic properties to the symmetrical compounds PEl, PE2, and PE3. We measured trends in ground state absorption, fluorescence, phosphorescence, and triplet state absorption spectra. We also performed density functional theory calculations of the triplet state geometries and energies. The ground state absorption and fluorescence spectra give evidence the singlet exciton is delocalized across the central platinum atom. In contrast, the behavior of the phosphorescence spectra suggests the triplet exciton is confined to one ligand. The phosphorescence from the asymmetric complexes comes from the lowest energy, most delocalized ligand. The triplet state geometries obtained from the density functional theory calculations show distortion on the lowest energy ligand, while the other ligand has the ground state geometry. The calculated trend in the triplet state energies agrees very well with the experimental trend. Calculations of triplet state spin density also show the triplet exciton is confined to one ligand. In the asymmetric complexes the spin density is confined to the more conjugated, lower energy ligand. The results show Kasha's rule applies to these complexes, where following excitation and intersystem crossing, the triplet exciton moves to the lowest energy ligand.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 11, 2006
- Accession Number
- ADA475099
Entities
People
- Aaron R. Burke
- Daniel G. Mclean
- Douglas M. Krein
- Jonathan E. Slagle
- Joy E. Rogers
- Thomas M Cooper
Organizations
- Air Force Research Laboratory