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

[Image: see text] 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(17)(S-4CBM)(15)(PPh(3))(5)](0), [S@Ag(18)(S-4CBM)(16)(PPh(3))(8)](0), and [Cl@Ag(18)(S-4CBM)(16)(PPh(3))(8)][PPh(4)], where S-4CBM = 4-chlorobenzene methanethiolate, and single-crystal X-ray crystallography revealed that they have S@Ag(6), S@Ag(10), and Cl@Ag(10) 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(2–)-templated Ag NCs is attributed to the charge transitions from S(2–)-templated Ag-cage orbitals to the s-shaped orbital in the S(2–) moiety; (3) the Cl(–)-templated Ag NCs can be viewed as [Cl@Ag(18)(S-4CBM)(16)(PPh(3))(8)](0)[PPh(4)](0) rather than the ion pair [Cl@Ag(18)(S-4CBM)(16)(PPh(3))(8)](−)[PPh(4)](+); and (4) singlet-coupled singly occupied orbitals are involved in the optical absorption of the Cl(–)-templated Ag NC.