Multichromophoric systems from Pt-ethynyl terpyridine and Ru- and Os- bipyridine centers linked to a truxene platform: syntheses and photophysical properties

Multichromophoric architectures based on metallic complexes are of large interest for energy conversion applications. Pt(II) terpyridyl acetylides complexes have been object of an extensive investigation in the recent years,1 since the presence of the acetylide ligand in the fourth coordination position accounts for favourable luminescence properties, and their 3MLCT excited state has an energy content higher than those of several other metallic species, such as Ru(II)- and Os(II)- bipyridine complexes. The assembly of square planar Pt(II) acetylide chromophores with octahedral Ru(II)- and Os(II)- bipyridine centers is thus a synthetic challenge opening new perspectives for the construction of photoactive supramolecular arrays.2 Here we report on the synthesis and the photophysical characterization of a series of arrays where the Pt(II), Ru(II) and Os(II) centers are arranged around a truxene scaffold, such as a triad Pt-Ru-Os and two dyads, Pt-Os and Ru-Os. Truxene derivatives have been recently recognized as potential photoactive cores for supramolecular multichromophoric systems.3 The photoinduced processes that occur in the triad Pt-Ru-Os and in the dyads Pt-Os and Ru-Os have been characterized by studying and comparing their spectroscopic properties with those of precursor mononuclear species. The role of the "non-innocent" truxene ligand on the excited state dynamics of the arrays has also been analysed and details will be presented.