On the selection and design of proteins and peptide derivatives for the production of photoluminescent, red-emitting gold quantum clusters

Novel pathways of the synthesis of photoluminescent gold quantum clusters (AuQCs) using biomolecules as reactants provide biocompatible products for biological imaging techniques. In order to rationalize the rules for the preparation of red-emitting AuQCs in aqueous phase using proteins or peptides, the role of different organic structural units was investigated. Three systems were studied: proteins, peptides, and amino acid mixtures, respectively. We have found that cysteine and tyrosine are indispensable residues. The SH/S-S ratio in a single molecule is not a critical factor in the synthesis, but on the other hand, the stoichiometry of cysteine residues and the gold precursor is crucial. These observations indicate the importance of proper chemical behavior of all species in a wide size range extending from the atomic distances (in the AuI-S semi ring) to nanometer distances covering the larger sizes of proteins assuring the hierarchical structure of the whole self-assembled system

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]^<i>n</i>+ (L = dppp, <i>n</i> = 2 (<b>1</b>) and 4 (<b>2</b>), 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 <b>1</b> and <b>2</b>, 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

Phosphine-Coordinated Pure-Gold Clusters: Diverse Geometrical Structures and Unique Optical Properties/Responses

Synthetic techniques, geometrical structures, and electronic absorption spectra of phosphine-coordinated pure-gold molecular clusters (PGCs) accumulated over 40 years are comprehensively collected especially for those with unambiguous X-ray crystal structures available. Inspection of the electronic absorption spectra from geometrical aspects reveals that their optical properties are highly dependent on the cluster geometries rather than the nuclearity. Recent examples of unusual clusters that show unique color/photoluminescence properties and their utilization for stimuli-responsive modules are also presented

Charge Redistribution Effects on the UV-VIS Spectra of Small Ligated Gold Clusters: a Computational Study

peer reviewe