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Realised by ALMS™
developer of the AIDS-HIV Reference project
Abstract No.: MoP-200
Session: Metal Ions in Biology
Presentation date: Mon, Aug 28, 2006
Presentation time: 14:30 – 16:00

A Gas Phase Comparative Study of Organic Azides as Ligands in the Complexation of Transition Metals

M. Tereza Fernandez1,4, Narciso Couto1,4, Ana Assis1, Vitor Pinto1, Paula Rodrigues2,5, M. Teresa Barros2,5, M. Lourdes Costa3,6, M. Filomena Duarte1,4

1 Departamento Quimica e Bioquimica, Faculdade Ciencias, Universidade Lisboa, Lisboa, Portugal
2 Departamento Quimica, Faculdade Ciencias e Tecnologia, Universidade Nova Lisboa, Lisboa, Portugal
3 Departamento Fisica, Faculdade Ciencias e Tecnologia, Universidade Nova Lisboa, Lisboa, Portugal
4 CQB - Centro de Quimica e Bioquimica, Lisboa, Portugal
5 CQFB - Centro de Quimica Fina e Biotecnologia, Lisboa, Portugal
6 CEFITEC - Centro de Fisica e Investigacao Tecnologica, Lisboa, Portugal

Correspondence address: Maria Tereza Fernandez, Faculdade de Ciencias Universidade de Lisboa, Departamento de Quimica e Bioquimica, Campo Grande, Edificio C8, Lisboa, 1749-016 Portugal.

Keywords: Ionization, Electrospray; Mass Spectrometry, Ion Trap Quadrupole; MS/MS; Organometallics.

Novel aspect: Contribution to coordination chemistry of organic azides. Gas-phase transition metal study of complexes with organic azides (RN3) as ligands: Comparative study of the behaviour of different ligands.

 

Azides are used as high-energy sources in a number of industrial applications and as reagents for the preparation of semi-conductors substrates.1 They are also useful in areas such as: organic synthesis, pharmacology and biochemistry research.2 They are well known as enzymes inhibitors. For instance, 3-azido-3-deoxythymidine (AZT) was the first anti retrovirus used in AIDS treatment due to its ability to inhibit reverse transcriptase.3 Another example is inhibition, of human carbonic anhydrase,4 by coordination of azide to the protein metal centre. One of the most remarkable aspects in the reactivity of organic azides is the loss of molecular nitrogen, which can occur thermally, photochemically or catalytically by acid or transition metal. In spite of the importance of interaction of azides with metals, most of the coordination chemistry studies on azides deal with the N3 group as ligand.
In this study, the main goal is to understand the coordination of nickel (II) and cobalt (II) by different organic azides (azidoacetic acid, azidoacetone, 3-azidopropionitrile and azidoacetonitrile). In order to fulfill this aim, both the complex formation and the complexation site were investigated by Electrospray Ionization Mass Spectrometry (ESI-MS) combined with Tandem Mass Spectrometry (MS-MS) and Collision Induced Dissociation (CID) experiments.
Only singly charged complex ions were detected, with different ligands and different stoichiometries. The diversity of complex ions formed depends on the type of the azide ligand. In sequential fragmentation, of the main complex ions, reduction of the metal was observed, by an internal charge transfer reaction due to the loss of a radical.4 In these fragmentation sequences the terminal ions had similar composition for different systems. This observation led to the proposal of a general mechanism, applicable to all systems studied, allowing a correlation of the data obtained with different azides.

1. N. Hooper, L. J. Beeching, J. M. Dyke, A. Morris, J. S. Ogden, A. A. Dias, M. L. Costa, M. T. Barros, M. H. Cabral and A. M. C. Moutinho, J. Phys. Chem. 106, 9968 (2002).
2. M. F. Duarte, F. Martins, M. T. Fernandez, G. J. Langley, P. Rodrigues, M. T. Barros and M. L. Costa, Rapid Commun. Mass Spectrom. 17, 957 (2003).
3. O. Turriziani, J .D. Schuetz, C. Scagnolari, J. Sampath, M. Adachi and F. Bambacioni, Biochem. J. 368, 325 (2002).
4. B. M. Jonsson, K. Hakansson and A. Liljas, FEBS 322, 186 (1993).