Ag+ labeling: A convenient new tool for the characterization of hydrogen-bonded supramolecular assemblies by MALDI-TOF mass spectrometry

Herein we describe our results on the characterization of a wide variety of different hydrogen-bonded assemblies by means of a never matrix-assisted l aser desorption ionization time-of-flight mass spectrometry (MAL-DI-TOF MS) technique with Ag+ labeling. The labeling technique with Ag+ ions is extre mely mild and provides a nondestructive way to generate charged assemblies that can be detected by mass spectrometry, Up to now more than 25 different single (1(3).2(3)), double (3(3).2(6)), and tetrarosettes (4(3).2(12)) hav e been successfully characterized by the use of this method. The success of the method entirely depends on the presence of a suitable binding site for the Ag+ ion. A variety of functionalities has been identified that provide strong binding sites for Ag+, either acting in a cooperative way (pi -aren e and pi -alkene donor functionalities) or individually (cyano and crown et her functionalities). The method works well for assemblies with molecular w eights between 2000 and 8000 Da, and most likely far beyond this limit.