Construction of a photoactive supramolecular system based on a platinum(II) bis-acetylide building block incorporated into a ruthenium(II) polypyridyl complex

A new ruthenium(II) polypyridyl-platinum(II) diethynyl triad containing 3-ethynylphenanthroline linked by platinum(II) bis-tributylphosphine organometallics, Ru(II)-Pt(II)-Ru(II), and platinum(II) bis-ethynylphenanthroline complex has been prepared. The ruthenium(II)-metal triads, Ru(II)-M-Ru(II) (M = Pt(II) and Au(I)), showed typical MLCT absorption bands and a lowest energy π-π* absorption involved with the metal perturbation in the 350-500 nm region. Broad emission bands assignable to triplet MLCT transitions were definitely observed in the triads Ru(II)-M-Ru(II), while those of platinum(II) and gold(I) bis-ethynylphenanthroline complexes displayed a phosphorescent band with vibronic progression assignable to the metal-perturbed triplet π-π*(CCphen) transition, which means that the hybrid architecture constructed with Ru(II) polypyridyl and metal bis-acetylide units converts a blue-green metal perturbed π-π* phosphorescence into an orange MLCT-based emission. The transient differential absorption spectra of ruthenium compounds showed the difference of the electron transfer process between [Ru(bipy)(phen)](PF6)2 and triads under the MLCT state. Photophysical data of the triad suggest an efficient energy transfer from the platinum bis-acetylide site to the ruthenium polypyridyl site followed by the supposed charge injection from a ruthenium center to the extended π-conjugated phenanthroline under photo-excitation in this photoactive supramolecular system