Impact of Skeletal Isomerization of Ultrasmall Gold Clusters on Electrochemical Properties: Voltammetric Profiles of Nonspoked Octanuclear Clusters.

Electronic properties of ultrasmall gold clusters with defined nuclearity and geometrical structures have been a recent subject of interest not only with respect to the concept of molecularity but also because of their potential applicability as nanomaterials and catalysts. In this work, the electrochemical properties of dppp-protected octagold clusters ([Au8L4]n+ (L = dppp, n = 2 (1) and 4 (2), dppp = Ph2P(CH2)3PPh2) with charge-dependent geometrical structures were investigated. Unlike conventional spherelike centered clusters held by multiple spokes, the nonspoked Au8 clusters displayed irreversible electrochemical profiles for the two-electron redox interconversion between 1 and 2, exhibiting a wide energy gap between the redox couples. This electrochemical irreversibility could be attributed to the significant alteration of electronic structures associated with the redox-coupled isomerization of the nonspoked cluster structures. In addition, we show that the coordinative interaction of Cl– anions with the Au8 clusters notably affects both reduction and oxidation courses, providing an example of coordination-coupled electron transfer events.