title: Chirality and electronic structure of the thiolate-protected Au38 nanocluster.
abstract: Structural, electronic, and optical properties of the thiolate-protected Au(38)(SR)(24) cluster are studied by density-functional theory computations (R = CH(3) and R = C(6)H(13)) and by powder X-ray crystallography (R = C(12)H(25)). A low-energy structure which can be written as Au(23)@(Au(SR)(2))(3)(Au(2)(SR)(3))(6) having a bi-icosahedral core and a chiral arrangement of the protecting gold-thiolate Au(x)(SR)(y) units yields an excellent match between the computed (for R = C(6)H(13)) and measured (for R = C(12)H(25)) powder X-ray diffraction function. We interpret in detail the electronic structure of the Au(23) core by using a particle-in-a-cylinder model. Although the alkane thiolate ligands are achiral, the chiral structure of the ligand layer yields strong circular dichroism (CD) in the excitations below 2.2 eV for Au(38)(SCH(3))(24). Our calculated CD spectrum is in quantitative agreement with the previously measured low-energy CD signal of glutathione-protected Au(38)(SG)(24). Our study demonstrates a new mechanism for the strong chiral response of thiolate-protected gold clusters with achiral metal cores and ligands.
authors.affiliation: Department of Physics, Nanoscience Center, University of Jyväskylä, FI-40014 Jyväskylä, Finland.
authors.forename: Olga
authors.initials: O
authors.lastname: Lopez-Acevedo
authors.forename: Hironori
authors.initials: H
authors.lastname: Tsunoyama
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Tsukuda
authors.forename: Hannu
authors.initials: H
authors.lastname: Häkkinen
authors.forename: Christine M
authors.initials: CM
authors.lastname: Aikens
mesh_terms: D000042:Absorption; D002942:Circular Dichroism; D004583:Electrons; D006046:Gold / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry*; D055620:Optical Phenomena; D011789:Quantum Theory; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D013438:Sulfhydryl Compounds; D006046:Gold