The photophysical processes have been investigated in first, second and third generation dendrimers with poly-(phenylenevinylene) branches and a ruthenium tris-bipyridine core, RuDn (n=1-3). These dendrimers show very efficient forward singlet-singlet energy transfer from the branches to the ruthenium core upon UV irradiation, with efficiencies of 0.99 for RuD1 and 0.88 for RuD2 and RuD3 in CH2Cl2. The RuDn dendrimers show a bi-exponential emission decay in CH2Cl2, when excited with a 460 nm light with short lifetimes, however, the emission decay lifetimes become mono-exponential in 10% Triton X-100 aqueous solution (tau = 840 ns for RuD1, 890 ns for RuD2 and 1120 ns for RuD3). (c) 2008 Elsevier B.V. All rights reserved.