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 tri- nuclear metallorods and X-shaped pen- tanuclear metallostars has been pre- pared by the reaction of metal com- plexes bearing pendant phenolic func- tionalities 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 sub- stituents 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 spe- cies. The energy transfer from rutheni- um to osmium in these complexes has been investigated in detail and the effi- ciency of transfer shown to be highly temperature dependent; the energy transfer is highly efficient at low tem- perature, whereas at room temperature nonradiative and nontransfer deactiva- tion of the excited {Ru(tpy)2}* domains is most significant.