Fragmentation reactions of singly and doubly protonated thiourea- and sugar-substituted cyclams and their transition-metal complexes
✍ Scribed by Thorsten Felder; Anika Röhrich; Holger Stephan; Christoph A. Schalley
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 307 KB
- Volume
- 43
- Category
- Article
- ISSN
- 1076-5174
- DOI
- 10.1002/jms.1365
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✦ Synopsis
Abstract
Cyclam macrocycles tetrasubstituted with amino‐, thiourea‐, and sugar‐terminated side chains are ionized by electrospray ionization mass spectrometry (ESI‐MS) as singly or doubly protonated species or as transition‐metal complexes. Their fragmentation behavior is examined in a Fourier‐transform ion‐cyclotron‐resonance (FT‐ICR) mass spectrometer by collision‐induced dissociation (CID) experiments. Typically, fragmentation occurs within the side chains through a number of different 1,2‐elimination reactions irrespective of the absence or presence of a transition metal ion such as Co^2+^, Ni^2+^, or Zn^2+^. A remarkable exception is Cu^2+^, which induces ring cleavage reactions. This is traced back to an electron transfer from the cyclam nitrogen atoms to the Cu^2+^ ion. The electron transfer creates a cation‐radical within the macrocycle, which induces typical fragmentation reactions such as α‐cleavages that lead to fragmentation within the macrocycle. This interpretation is in line with fragmentation experiments on unsubstituted cyclam and its complexes. Copyright © 2008 John Wiley & Sons, Ltd.