Enhanced Raman spectroscopic study of the coordination chemistry of malononitrile on copper surfaces - Removal of nu(C=N) degeneracy through pi-coordination

Surface-enhanced Raman spectroscopy has been used to study the molecular interactions of malononitrile with copper electrode surfaces. The doubly degenerate CN stretching frequency at 2263/cm is removed when malononitrile adsorbs on copper. Two nu(CN) bands are observed at 2096 and 2204/cm at -0.6 V(SCE). The result shows that only one CN group is pi-coordinated with Cu, which contributes to the observed large shift (-167/cm) in nu(CN). The other CN group is not coordinated to the metal surface.