Abstract
Surface enhanced Raman scattering (SERS) spectra of heterometal extended metal atom chain (EMAC) complexes diruthenium nickel dipyridylamide [Ru2Ni(dpa)4Cl2]0,1+ display Ru-Ru stretching band at 312 cm-1. However, these bands obtained in solid form are at 327 and 333 cm-1 for the neutral and oxidized complexes, respectively. In these EMACs, moiety ruthenium dimer has charge [Ru2]+5 and nickel has charge Ni+1 and Ni+2, respectively. Hence, their Ru-Ru stretching wavenumbers are similar. When the thiol molecule 3-mercaptopropionic acid was used to cover the surface of nanoparticle the band positions are blue shifted to those in solid form. The hot electron was proposed to be produced when the surface plasmon band of nanoparticle is excited. The electron configuration of moiety [Ru2]+5 is (σ)2(π)4(δ)2(δ*)1(π*)2 thus the bond order is 2.5. When reduction occurs, one extra electron fills in the antibonding orbital weakening the Ru-Ru bonding. For both EMAC complexes ruthenium is reduced to [Ru2]+4 and the Ru-Ru stretching is about 321 cm-1. When oxidation occurs, one electron removed from antibonding orbital strengthen the Ru-Ru bonding. For both EMAC complexes ruthenium is oxidation to [Ru2]+6 and the Ru-Ru stretching is about 337 cm-1. So we can identified the valence of transition metal in the heterometal extended metal atom chain (EMAC) complexes diruthenium nickel dipyridylamide.