Researchers Achieve Selective Formation and 2D Crystallization of Radialene Molecules on Gold Surface
Scientists have demonstrated a highly selective chemical reaction on a gold surface that produces tetraaza[4]radialene molecules — a rare class of conjugated carbon ring — with precise control over their chemical and spatial structure. The process uses isocyanide molecules that first coordinate with gold atoms at room temperature, then undergo stepwise covalent bond formation upon heating to form four-membered rings that self-assemble into ordered 2D crystals. The findings advance understanding of how to engineer chiral molecular crystals on surfaces, with potential implications for organic functional materials and nanotechnology.
A research team has reported a [1+1+1+1] cycloaddition reaction on the Au(111) gold surface that selectively generates tetraaza[4]radialenes — conjugated four-membered carbon ring structures — with high chemo- and stereoselectivity. Using a progressive annealing approach, the researchers found that isocyanide molecules first react with gold adatoms at room temperature to form two-fold symmetric coordination complexes, and that gradually raising the temperature drives these complexes to undergo stepwise C-C bond formation, yielding stereospecific homotactic products. The resulting tetraaza[4]radialenes then self-assemble into long-range-ordered 2D homochiral molecular crystals through enantioselective molecular recognition, mediated by multiple C-H···Cl hydrogen-bonding interactions. Scanning tunneling microscopy and spectroscopy, combined with non-contact atomic force microscopy, confirmed that the four-membered ring adopts a planar geometry and possesses a localized lowest unoccupied molecular orbital. Density functional theory calculations attribute the high selectivity of the cycloaddition to spatial steric hindrance during stepwise bond formation. The work provides new mechanistic insights into surface-confined conjugated ring synthesis and offers a strategy for constructing 2D homochiral molecular architectures relevant to organic electronics and chiral materials engineering.
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As a preprint, this work has not yet undergone peer review, so the results and interpretations have not been independently validated.
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- arXiv physicsCenter
Steering Selective Formation and 2D Crystallization of [4]Radialenes on Au(111) via [1+1+1+1] Cycloaddition of Isocyanides and Enantioselective Molecular Recognition
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