Clarifying the Electronic Structure of Anion-Templated Silver Nanoclusters by Optical Absorption Spectroscopy and Theoretical Calculation.

Electronic structures of anion-templated silver nanoclusters (Ag NCs) are not well understood compared to conventional, template-free Ag NCs. In this study, we synthesized three new anion-templated Ag NCs, namely [S@Ag(S-4CBM)(PPh)], [S@Ag(S-4CBM)(PPh)], and [Cl@Ag(S-4CBM)(PPh)][PPh], where S-4CBM = 4-chlorobenzene methanethiolate, and single-crystal X-ray crystallography revealed that they have S@Ag, S@Ag, and Cl@Ag cores, respectively. Investigation of their electronic structures by optical spectroscopy and theoretical calculations elucidated the following unique features: (1) their electronic structures are different from those of template-free Ag NCs described by the superatomic concept; (2) optical absorption in the range of 550-400 nm for S-templated Ag NCs is attributed to the charge transitions from S-templated Ag-cage orbitals to the s-shaped orbital in the S moiety; (3) the Cl-templated Ag NCs can be viewed as [Cl@Ag(S-4CBM)(PPh)][PPh] rather than the ion pair [Cl@Ag(S-4CBM)(PPh)][PPh]; and (4) singlet-coupled singly occupied orbitals are involved in the optical absorption of the Cl-templated Ag NC.