Energy Transfer Dynamics in Multichromophoric Arrays Engineered from Phosphorescent PtII/RuII/OsII Centers Linked to a Central Truxene Platform

A rigid star-shaped tetrachromophoric trimetallic complex engineered from a 5,5′,10,10′,15,15′-hexabutyltruxene platform functionalized in the 2,7,12 positions with three different metal centers, namely, a terpyridine-Pt(II) ethynylene unit and Ru(II) and Os (II) bipyridine centers, was synthesized in a controlled fashion and characterized by 1H NMR and mass spectrometry. The protocol was devised in such a way that key mono and dinuclear model complexes and two reference truxene ligands could also be prepared. Room temperature (RT) optical absorption and RT and 77 K luminescence studies were performed on the truxene ligands, the trimetallic species, the various mono- and binuclear complexes and precursors lacking the truxene fragment; RT nanosecond transient absorption measurements were also carried out in particular cases. The electronic properties of the Ru and Os subunits in the arrays were found to be unaffected by the presence of the truxene core whereas direct linking of the Pt subunit to the truxen...