Significance: Strong electrophilicity usually goes hand in hand with positive charge. In contrast, most negative ions behave like nucleophiles. Here we challenge this conventional wisdom by introducing an apparently counterintuitive idea that anions can, under well-defined circumstances, behave as superelectrophiles and even show superior binding strength and kinetic product stabilization in comparison with typical superelectrophilic cations. Emanating from the most stable gas-phase dianion [B₁₂(CN)₁₂]²⁻, synthesized here, we generate its superelectrophilic fragment anion [B₁₂(CN)₁₁]⁻, which binds Ar covalently at room temperature. This opens up additional directions for activation of inert compounds and elements.

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.

A neon containing molecular anion is observed and analyzed.