Gold Nanoparticles Stabilized by Acetylene‐Functionalized Multidentate Thioether Ligands: Building Blocks for Nanoparticle Superstructures

Abstract

Aiming at the formation of inorganic/organic hybrid gold nanoparticle superstructures, the design and synthesis of acetylene‐monofunctionalized multidentate thioether ligands and their ability to stabilize gold nanoparticles are presented. Rather monodisperse gold particles with diameters of about 1 nm are obtained, which are coated by a small number of ligands, each comprising a silyl‐protected acetylene. The acetylene is attached at the end of a rigid ethynylene‐phenylene unit of variable length, leading to functionalized gold nanoparticles carrying acetylenes at different distances from the nanoparticle surface. These particles are interlinked by diacetylene formation and are investigated by transmission electron microscopy and UV/vis spectroscopy, revealing the formation of nanoparticle aggregates and small superstructures such as dimers or trimers while the nanoparticles themselves retain their integrity. The interparticle distance in small nanoparticle superstructures reflects the ethynylene‐phenylene spacer length corroborating the wet chemical interlinking as the origin of these organic/inorganic hybrid structures.

Covalently linked multimers of gold nanoclusters Au102(p-MBA)44and Au∼250(p-MBA)n

“…Similar changes in the UV-vis spectrum has been reported before for diacetylene linked 1.1 nm AuNPs. 17 The crude synthesis product was further analyzed by PAGE, where the sample separated to several distinct bands (see Fig. 1, and ESI, Fig.…”

“…12 However, for several applications, it would be desirable to have a controlled, wet-chemistry synthesis of superstructures. Successful wet-chemistry approaches based on self-assembly has been demonstrated, for example, with DNA-templating 13 and with several different molecular linkers [14][15][16][17][18] .…”

A Phenyl‐Ethynyl‐Macrocycle: A Model Compound for “Geländer” Oligomers Comprising Reactive Conjugated Banisters

“…[28][29][30] Initially, classical Glaser-Hay conditions (CuCl, TMEDA, O 2 ) [31,32] were applied for the macro-cyclization by intramolecular oxidative acetylene coupling. [28][29][30] Initially, classical Glaser-Hay conditions (CuCl, TMEDA, O 2 ) [31,32] were applied for the macro-cyclization by intramolecular oxidative acetylene coupling.…”

Size Matters: Influence of Gold‐to‐Ligand Ratio and Sulfur‐Sulfur Distance of Linear Thioether Heptamers on the Size of Gold Nanoparticles

“…Inspired by this concept, we explored various multidentate macromolecules like linear oligomers, and dendritic systems for the stabilization of small NPs. The low integer number of molecules per NPs decorated with a masked ethynyl moieties allowed mono‐ or bifunctionalized NPs to create supramolecular dumbbell, trikes and quads or linear pearl‐necklace hybrid materials via mild acetylene homo‐coupling or acetylene/azide‐click reactions. What is strikingly conspicuous however is the fact that all these macromolecule‐coated NPs feature almost the same sizes around 1 – 1.3 nm with barely noticeable SPR‐bands (UV/VIS), and have thus limited potential for optical sensing applications.…”

“…Even when comparing the dendritic ligands with a fairly prior determined cage‐like form, and the linear ligands with no further predetermined curvature, the resulted NPs featured almost the same size. Also the spacing between the thioether sulfur atoms in the oligomeric ligand seems to have only a minor influence on the dimension of the stabilized nanoparticle, as demonstrated by the very comparable dimensions of nanoparticles stabilized by linear heptamers based either on a m ‐xylene‐based motive and the more bulky tetraphenylmethane‐based ligand with an increased spacing between the sulfur atoms. While the AuNPs showed promising stability features for both octadentate ligands, the major difference was the heptamer/NP ratio required, as two ligands of the xylene‐derivative coated one NP while a single tetraphenylmethane‐based ligand was able to enwrap an entire NP.…”