Mercedes Crego Calama

Characterization of Hydrogen‐Bonded Supramolecular Assemblies by MALDI‐TOF Mass Spectrometry after Ag+ Labeling

The high affinity of Ag+ ions for aromatic π donors and cyano groups is exploited in a novel MALDI-TOF mass spectrometric method for the identification of hydrogen-bonded assemblies. The interaction with the Ag+ ions-which, for example, can be complexed by two phenyl groups in a sandwich-type manner (see drawing on the right)-provides positively charged assemblies in a nondestructive way.

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 novel matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) technique with Ag+ labeling. The labeling technique with Ag+ ions is extremely 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)) have 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-arene and pi-alkene donor functionalities) or individually (cyano and crown ether functionalities). The method works well for assemblies with molecular weights between 2,000 and 8,000 Da, and most likely far beyond this limit.

Charakterisierung von supramolekularen Wasserstoffbrücken-Aggregaten durch MALDI-TOF-Massenspektrometrie nach Markierung mit Ag+

Die hohe Affinitat von Ag+-Ionen fur aromatische π-Donoren und Cyangruppen wird bei einer neuen MALDI-TOF-MS-Methode zur Identifizierung von H-Brucken-Aggregaten genutzt (MALDI-TOF-MS=Matrix-unterstutzte Laser-Desorptions-Ionisierungs-Flugzeit-Massenspektrometrie): Durch das Ag+-Ion, das z. B. sandwichartig von zwei Phenylgruppen komplexiert werden kann (siehe rechts), lassen sich die Aggregate - ohne Zersetzung - mit einer positiven Ladung versehen.

Growth of individual hydrogen-bonded nanostructures on gold monolayers

The growth of individual nanometer-sized (3.4 +/- 1.4 nm) hydrogen bonded assemblies 1(2) x (DEB)6 on gold monolayers was achieved through an exchange reaction between single isolated calix[4]arene dimelamine 2 (1.1 +/- 0.2 nm) embedded in hexanethiol monolayers and double rosette hydrogen bonded assembly 1(3) x (DEB)6 in solution. The growth process was monitored by tapping mode atomic force microscopy (TM-AFM).