Infrared multiple photon dissociation spectroscopy of group I and group II metal complexes with Boc-hydroxylamine
Article first published online: 9 JUL 2013
Copyright © 2013 John Wiley & Sons, Ltd.
Rapid Communications in Mass Spectrometry
Volume 27, Issue 16, pages 1867–1872, 30 August 2013
How to Cite
Dain, R. P., Gresham, G., Groenewold, G. S., Steill, J. D., Oomens, J. and Van Stipdonk, M. J. (2013), Infrared multiple photon dissociation spectroscopy of group I and group II metal complexes with Boc-hydroxylamine. Rapid Commun. Mass Spectrom., 27: 1867–1872. doi: 10.1002/rcm.6640
- Issue published online: 9 JUL 2013
- Article first published online: 9 JUL 2013
- Manuscript Accepted: 19 MAY 2013
- Manuscript Revised: 17 MAY 2013
- Manuscript Received: 25 MAR 2013
- U.S. National Science Foundation. Grant Number: CAREER-0239800
- National High Field FT-ICR Facility. Grant Number: CHE-9909502
Hydroxamates are essential growth factors for some microbes, acting primarily as siderophores that solubilize iron for transport into a cell. Here we determined the intrinsic structure of 1:1 complexes between Boc-protected hydroxylamine and group I ([M(L)]+) and group II ([M(L-H)]+) cations, where M and L are the cation and ligand, respectively, which are convenient models for the functional unit of hydroxamate siderphores.
The relevant complex ions were generated by electrospray ionization (ESI) and isolated and stored in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Infrared spectra of the isolated complexes were collected by monitoring (infrared) photodissociation yield as a function of photon energy. Experimental spectra were then compared to those predicted by density functional theory (DFT) calculations.
The infrared multiple photon dissociation (IRMPD) spectra collected are in good agreement with those predicted to be lowest-energy by DFT. The spectra for the group I complexes contain six resolved absorptions that can be attributed to amide I and II type and hydroxylamine N-OH vibrations. Similar absorptions are observed for the group II cation complexes, with shifts of the amide I and amide II vibrations due to the change in structure with deprotonation of the hydroxylamine group.
IRMPD spectroscopy unequivocally shows that the intrinsic binding mode for the group I cations involves the O atoms of the amide carbonyl and hydroxylamine groups of Boc-hydroxylamine. A similar binding mode is preferred for the group II cations, except that in this case the metal ion is coordinated by the O atom of the deprotonated hydroxylamine group. Copyright © 2013 John Wiley & Sons, Ltd.