Abstract
Redox reaction was photoinduced on metal nanoparticle (NP) with diruthenium complexes absorbing on the surface. Surface enhanced Raman scattering (SERS) was employed to detect the vibrational wavenumber of the Ru-Ru stretching mode ν Ru-Ru,str . During reaction, the local environment remains roughly unaltered; the variation of bonding strength of Ru-Ru related to its valence state can be measured. The heterometal extended metal atom chain (EMAC) complexes diruthenium nickel dipyridylamide [Ru 2 Ni(dpa) 4 Cl 2 ] 0,1+ (dpa = dipyridylamide) display the Raman ν Ru-Ru,str at 327 (broad) and 333 cm -1 in solid form for the neutral and oxidized complexes, respectively, but red-shift to 312 cm -1 on gold NP substrate and to 328 cm -1 on AgNP. According to the oxidation potentials from voltammogram, and the Raman shifts obtained for the model complex Ru 2 (OAc) 4 Cl we assign the diruthenium core with charge +5/+4 and +6, respectively for the neutral and oxidized diruthenium nickel dipyridylamide in solid form. On substrate AuNP the hot electrons produced to fill in the antibonding orbital, the Ru 2 4+ π∗ 4 core with weak Ru-Ru bonding was formed and on AgNP the oxidized complex was reduced to neutral form. For pentanuclear EMAC [Ni-Ru 2 -Ni 2 (tpda) 4 (NCS) 2 ] (tpda = tripyridyldiamide) ν Ru-Ru,str is at 337 cm -1 and SERS band peaked at 328 cm -1 . We assign the Ru 2 6+ core in solid and reduction by NPs to form Ru 2 5+ .