Self-organizing layers from complex molecular anions

Abstract

The formation of traditional ionic materials occurs principally via joint accumulation of both anions and cations. Herein, we describe a previously unreported phenomenon by which macroscopic liquid-like thin layers with tunable self-organization properties form through accumulation of stable complex ions of one polarity on surfaces. Using a series of highly stable molecular anions we demonstrate a strong influence of the internal charge distribution of the molecular ions, which is usually shielded by counterions, on the properties of the layers. Detailed characterization reveals that the intrinsically unstable layers of anions on surfaces are stabilized by simultaneous accumulation of neutral molecules from the background environment. Different phases, self-organization mechanisms and optical properties are observed depending on the molecular properties of the deposited anions, the underlying surface and the coadsorbed neutral molecules. This demonstrates rational control of the macroscopic properties (morphology and size of the formed structures) of the newly discovered anion-based layers.

Rational design of an argon-binding superelectrophilic anion

“…A cation should not compete with the noble gas for the positive binding site within the electrophilic anion (cations are usually electrophiles themselves). Gaseous ion deposition on surfaces (ion soft landing) has recently been shown to generate condensed-phase material layers from mass selected anions (40) The mass spectrometry of [B 12 (CN) 11 Ar] − and infrared photodissociation (IRPD) spectroscopy, to determine the stretching vibration of CO bound to the electrophilic binding site, were studied using the Leipzig cryogenic ion trap triple mass spectrometer described in detail elsewhere (43,44). In brief (for more details, see SI Appendix, section S7.1) [B 12 (CN) 11 ] − anions were produced via skimmer collision-induced dissociation (sCID) from precursor ions formed using a nanospray ion source with a 0.5 mmol/L solution of [B 12 (CN) 12-n (OH) n ][N(C 4 H 9 ) 4 ] 2 (n = 0-5) in CH 3 OH/H 2 O (2:1, vol/vol).…”

Top-down synthesis of polyoxometalate-like sub-nanometer molybdenum-oxo clusters as high-performance electrocatalysts

“…27 Pioneering studies have started to address these challenges by developing new deposition routes: Laskin and colleagues have recently used a mass spectrometry-based ion so landing technology to deposit mass-selected, electroactive POM anions from the gas phase directly onto electrode surfaces. 28,29 In addition, Newton and colleagues have demonstrated that internal integration of POMs into conductive carbon nanotubes leads to remarkable improvement and stabilization of their electrochemical performance. 30 Here, we propose an unprecedented top-down approach for the deposition of polyoxometalate-like metal oxo clusters on high-porosity carbon electrodes.…”

From Isolated Ions to Multilayer Functional Materials Using Ion Soft Landing

“…Characterization of these layers showed that hydrocarbons (primarily phthalates) from the instrument background accumulated together with the deposited anions, which helped stabilize the layers. These layers with a high coverage of anions exhibited remarkable properties as interfaces for supercapacitors or self‐organizing layers, as will be discussed in the following sections. Based on the high density of anions that must be present in such multilayer materials we propose that the layer is not electrostatically stabilized by the image charges alone.…”

“…In contrast to cations that readily lose their charge on conducting surfaces, the high‐coverage deposition of stable anions generates layers containing charged species that readily attract neutral molecules from the gas phase. A recent study showed that these previously unreported ion‐based layers stabilized by coadsorption of gas‐phase molecules can exhibit self‐organization processes known as “dewetting” after exposure to ambient conditions . The strong influence of the properties of the deposited anions on the self‐organization process was systematically investigated using a series of highly stable and structurally similar dianions: [B 12 X 12 ] 2− (X=F, Cl, Br, I).…”