Single-molecule electrical spectroscopy of organocatalysis

Abstract

•Universal single-molecule electrical spectroscopy to monitor complex reactions •Novel reaction dynamics and new intermediates discovered by correlation analysis •New thermodynamic/kinetic model offering quantitative analysis on a molecular basis Conventional mechanistic studies based on detection of species concentration reveal the basic laws of matter conversion, but inherently display ensemble averages. Single-molecule detection provides a solution and direct visualization of reaction pathway rather than only detection of species. Here, we establish an in situ label-free electrical detection platform and report universal single-molecule electrical spectroscopy (SMES) of organocatalysis to decipher the intrinsic mechanism of a benzoin reaction. This SMES is capable of monitoring each event in a simple (homo-condensation) or complex (cross-condensation) system. Both experimental and theoretical results consistently revealed accuracy of the spectroscopic attribution and proved its reliability. Furthermore, the correlation of adjacent events in the spectroscopy indicated the local repeated interaction between a catalyst and a substrate. Through a new thermodynamic and kinetic model, the inventory of substrates around the single-molecule catalyst can be reversely deduced, which enables quantitative analysis of the target single molecule. Conventional mechanistic studies based on detection of species concentration reveal the basic laws of matter conversion, but inherently display ensemble averages. Single-molecule detection provides a solution and direct visualization of reaction pathway rather than only detection of species. Here, we establish an in situ label-free electrical detection platform and report universal single-molecule electrical spectroscopy (SMES) of organocatalysis to decipher the intrinsic mechanism of a benzoin reaction. This SMES is capable of monitoring each event in a simple (homo-condensation) or complex (cross-condensation) system. Both experimental and theoretical results consistently revealed accuracy of the spectroscopic attribution and proved its reliability. Furthermore, the correlation of adjacent events in the spectroscopy indicated the local repeated interaction between a catalyst and a substrate. Through a new thermodynamic and kinetic model, the inventory of substrates around the single-molecule catalyst can be reversely deduced, which enables quantitative analysis of the target single molecule.