Site-specific doping of silver atoms into a Au(25) nanocluster as directed by ligand binding preferences

For the first time site-specific doping of silver into a spherical Au(25) nanocluster has been achieved in [Au(19)Ag(6)(MeOPhS)(17)(PPh(3))(6)] (BF(4))(2) (Au(19)Ag(6)) through a dual-ligand coordination strategy. Single crystal X-ray structural analysis shows that the cluster has a distorted centered icosahedral Au@Au(6)Ag(6) core of D(3) symmetry, in contrast to the I(h) Au@Au(12) kernel in the well-known [Au(25)(SR)(18)](−) (R = CH(2)CH(2)Ph). An interesting feature is the coexistence of [Au(2)(SPhOMe)(3)] dimeric staples and [P–Au–SPhOMe] semi-staples in the title cluster, due to the incorporation of PPh(3). The observation of only one double-charged peak in ESI-TOF-MS confirms the ordered doping of silver atoms. Au(19)Ag(6) is a 6e system showing a distinct absorption spectrum from [Au(25)(SR)(18)](−), that is, the HOMO–LUMO transition of Au(19)Ag(6) is optically forbidden due to the P character of the superatomic frontier orbitals.