Hypoxia-targeting copper bis(selenosemicarbazone) complexes: Comparison with their sulfur analogues

Castle, Thomas C. and Maurer, Richard I. and Sowrey, Frank E. and Went, Michael J. and Reynolds, Christopher A. and McInnes, Eric J. L. and Dilworth, Jonathan R. and Blower, Philip J. (2003) Hypoxia-targeting copper bis(selenosemicarbazone) complexes: Comparison with their sulfur analogues. Journal of the American Chemical Society, 125 (33). pp. 10040-10049. ISSN 0002-7863. (The full text of this publication is not available from this repository)

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Official URL
http://dx.doi.org/10.1021/ja035737d

Abstract

The first copper bis(selenosemicarbazone) complexes have been synthesized, using the ligands glyoxal bis(selenosemicarbazone), pyruvaldehyde bis(selenosemicarbazone), and 2,3-butanedione bis(selenosemicarbazone). Their spectroscopic properties indicate that they are structurally analogous to their well-known square-planar sulfur-containing counterparts, the copper bis(thiosemicarbazone) complexes. Spectroscopic comparison of the sulfur- and selenium-containing complexes provides insight into their electronic structure. The effects on spectroscopic and redox properties of replacing sulfur with selenium, and of successive addition of methyl groups to the ligand backbone, are rationalized in terms of their electronic structure using spin-unrestricted density functional calculations. These suggest that, like the sulfur analogues, the complexes have a very low-lying empty ligand-based pi-orbital immediately above the LUMO, while the LUMO itself has d(x2-y2) character (i.e., is the spin partner of the HOMO). Replacement of S by Se shifts the oxidation potentials much more than the reduction potentials, whereas alkylation of the ligand backbone shifts the reduction potentials more than the oxidation potentials. This suggests that oxidation and reduction involve spatially different orbitals, with the additional electron in the reduced species occupying the ligand-based pi-orbital rather than d(x2-y2). Density functional calculations on the putative singlet Cu(I)reduced species suggest that this ligand pi-character could be brought about by distortion away from planarity during reduction, allowing the low-lying ligand pi-LUMO to mix into the d(x2-y2)-based HOMO. The analogy in the structure and reduction behavior between the sulfur- and selenium-containing complexes suggests that labeled with positron emitting isotopes of copper (Cu-60, Cu-62, Cu-64), the complexes warrant biological evaluation as radiopharmaceuticals for imaging of tissue perfusion and hypoxia.

Item Type: Article
Additional information: Article 712CM 0002-7863 (Print) Cited References Count:56 Comparative Study English Times Cited:6 Journal Article Research Support, Non-U.S. Gov't
Uncontrolled keywords: Copper/*chemistry Electrochemistry Electron Spin Resonance Spectroscopy Magnetic Resonance Spectroscopy Models, Molecular Organometallic Compounds/chemical synthesis/*chemistry Semicarbazones/chemical synthesis/*chemistry Spectrophotometry, Ultraviolet Sulfur Compounds/*chemistry
Subjects: Q Science > QD Chemistry
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences > Functional Materials Group
Depositing User: Michael J Went
Date Deposited: 03 Sep 2008 13:17
Last Modified: 28 Apr 2014 14:45
Resource URI: http://kar.kent.ac.uk/id/eprint/3758 (The current URI for this page, for reference purposes)
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