Electrochemical Multiplexing: Control over Surface Functionalization by Combining a Redox‐Sensitive Alkyne Protection Group with “Click”‐Chemistry

Abstract

and molecular electronics, [11,12] over medical diagnostic devices [13][14][15] to applications tuning macroscopic and/or environmental features like, e.g., the wettability [16][17][18] or the biocompatibility [19][20][21] of material surfaces. In most cases, a bifunctional molecule, combining an anchor group attaching the molecular compound to the surface with an exposed subunit representing the active moiety with tailored physiochemical properties is used to tune the surface's terminal appearance. While such approaches are successfully applied for entire objects and surfaces of considerable dimensions and macroscopic separations, there are limitations as soon as spatial patterns of varying surface functionalities and microscopic separations are desired or a spatially constrained surface-access including buried microfluidic chips has to be overcome. For example, conventional wet chemical surface functionalization procedures are spatially limited to the size of the droplet deposited (and its subsequent surface interaction) and methods depositing the molecules from gas-phase in vacuum require advanced masking strategies. Challenging are devices with a variety of molecular features to be created in a parallel process and in a locally controlled manner, like, e.g., multidimensional sensing platforms where a multitude of nearby molecular receptors are screening analytes in parallel. Or microfluidic chips with constrained access to functional sites as the channels are locally enclosed and inaccessible for droplet deposition. Of great interest are devices analyzing molecular binding events electronically, due to their miniaturization potential and the analyte-selective binding without the requirement of labels. In such devices, each electrode is electrically addressable in a separated manner as they were contacted individually. Such a preexisting electrical wiring scheme is a unique feature for an immobilization strategy able to distinguish between the applied electrical potentials of each electrode and a common electrolyte. The electrochemical release of thiol-based self-assembled monolayers (SAMs) on gold electrodes has been reported. [22] This allows the disintegration of existing SAMs. The subsequent decoration of the liberated electrode with an alternative thiol-molecule, however, is handicapped by scrambling with the remaining SAMs. Electrochemical triggered constructive build-up of molecular Local functionalization of surfaces is a current technological challenge. An electrochemically addressable alkyne protection group is presented enabling the site-selective liberation of alkynes exclusively on electrified electrodes. This controlled deprotection is based on a mendione chromophore which becomes a strong enough nucleophile upon reduction to intramolecularly attack the trialkylsilane alkyne protection group. The site-selective liberation of the alkyne is demonstrated by immobilizing the protected alkyne precursor on a transparent TiO 2 electrode and subsequently immobilizing red and blue azide dyes by azide-alky...

Anthracene Diphosphate Ligands for CdSe Quantum Dots; Molecular Design for Efficient Upconversion

“…We reasoned that a multi-modal ligand scaffold based on a bidentate 1,8-anthracendiyl backbone would provide both high binding affinity for the surface and strong electronic coupling to the QD excited state. Multidentate ligands, including scaffolds made from citric acid, 15 EDTA, 16 or multidentate polymers, 17 are known to have greater surface binding affinities than monodentate carboxylate ligands. However, carboxylate ligands, such as 9-ACA do not readily displace the native octadecylphosphonic acid (ODPA) from the surface of CdSe QDs.…”

The Surface Chemistry of Colloidal Nanocrystals Capped by Organic Ligands

“…The Mattoussi group has been very successful in designing and synthesizing polymeric ligands based on carboxylic acid, catechol, thiol, phosphonic acid, etc . In the realm of small molecules, there are multidentate carboxylate ligands derived from citric acid or EDTA. , One can also classify the zwitterionic ligands for CsPbBr 3 nanocrystals as multidentate. , The bisphosphonate ligand class has been successful in stabilizing various nanocrystals in water. − In our recent work, we focused on multidentate phosphates. The first generation comprised 10-R-anthracene-1,8-diphosphoric acid (R = octyl, 2-hexyldecyl, phenyl) derivatives; see Figure A.…”

Naphthalenediimides with Cyclic Oligochalcogenides in Their Core

“…NDIs have functioned as anion‐π [5, 26–28] catalysts, [25] ion channels, [28, 29] sensors, [29] artificial photosystems, [6, 8, 30] semi‐conductors, [6, 31] G‐quartet stabilizers, [32] and self‐assembled matter in all variations, such as vesicles, [33] nanotubes, [34] mono‐ and multilayers on surfaces, [8, 30, 33] dynamic covalent libraries, knotted molecular topologies or donor‐acceptor stacks [33–36] . COC‐NDIs will be of interest to explore within this existing functional space, particularly with regard to artificial photosystems [8] .…”