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 pi-pi* 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 pi-pi*(C[triple bond]Cphen) transition, which means that the hybrid architecture constructed with Ru(ii) polypyridyl and metal bis-acetylide units converts a blue-green metal perturbed pi-pi* 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)](PF(6))(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 pi-conjugated phenanthroline under photo-excitation in this photoactive supramolecular system.