Electro-Inductive Effects Are Additive

The electro-inductive effect has recently emerged as a potential alternative to traditional functional groups for modulating the chemical properties of molecules. By covalently attaching a reactive molecule to an electrode surface and applying positive or negative voltage, electrons can be withdrawn from or injected into the immobilized molecule, mimicking the inductive effect of electron-withdrawing or electron-donating functional groups. To explore whether the magnitude of the electro-inductive effect changes when molecules are attached to the electrode via multiple linkers or at different molecular positions, four derivatives of mercaptobenzonitrile—3,4-dimercaptobenzonitrile, 4- mercaptobenzonitrile, 3,5-dimercaptobenzonitrile, and 3-mercaptobenzonitrile—were self-assembled into monolayers on a gold electrode surface. The electro-inductive effect was quantified by measuring the vibrational stretching frequencies of the nitrile group using surface-enhanced Raman spectroscopy. Our findings suggest that the electro-inductive effect exhibits additive and positional characteristics similar to those of conventional functional groups. The para position is significantly more effective than the meta position, and linking the molecule to the electrode through two anchors is more effective than using a single anchor.