Anion‐Dependent Hydrogen‐Bond Polarity Switching in Ethylene‐bridged Urea Oligomers

The reversible coordination of anions to an N,N’‐disubstituted 3,5‐bis(trifluoromethyl)phenylurea located at a terminus of a linear chain of ethylene‐bridged hydrogen‐bonded ureas triggers a cascade of conformational changes. A series of hydrogen‐bond polarity reversals propagates along the oligomer, leading to a global switch of its hydrogen‐bond directionality. The induced polarity switch, transmitted through four reversible urea groups, results in a change in emission and excitation wavelengths of a fluorophore located at the opposite terminus of the oligomer. The molecule thus behaves as a chemical sensor with a relayed remote spectroscopic response to variations in anion concentration. The polarity switch induced by anion concentration constitutes an artificial communication mechanism for conveying information through oligomeric structures.