Metal-Directed Synthesis and Photophysical Studies of Trinuclear V-Shaped and Pentanuclear X-Shaped Ruthenium and Osmium Metallorods and Metallostars Based upon 4'-(3,5-Dihydroxyphenyl)-2,2':6',2''-terpyridine Divergent Units

A new series of V-shaped trinuclear metallorods and X-shaped pentanuclear metallostars has been prepared by the reaction of metal complexes bearing pendant phenolic functionalities with complexes containing electrophilic ligands. Specifically, {M- (tpy)2} motifs (M=Ru or Os; tpy= 2,2':6',2''-terpyridine) bearing one or two pendant 3,5-dihydroxyphenyl substituents at the 4-position of the central ring of the tpy have been reacted with the complexes [Ru(tpy)(Xtpy)]2+ (X= Cl or Br) to form new ether-linked species. The energy transfer from ruthenium to osmium in these complexes has been investigated in detail and the efficiency of transfer shown to be highly temperature dependent; the energy transfer is highly efficient at low temperature, whereas at room temperature nonradiative and nontransfer deactivation of the excited {Ru(tpy)2}* domains is most significant.