High-frequency EPR study of reduced diruthenium and dirhenium polypyridine complexes based on the 1,2,4,5-tetrazine radical bridge

The radical complexes [(micro-L)[Ru(bpy)(2)](2)]*(3+), [(micro-bmtz)[Ru(cym)Cl](2)]*(+) and [(micro-L)[Re(CO)(3)Cl](2)]*(-), where L are 3,6-disubstituted 1,2,4,5-tetrazines such as 3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine (bmtz) and cym =p-cymene, were studied by X-band EPR in fluid solution and by 2...

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Published in:Dalton transactions : an international journal of inorganic chemistry 2004-11 (21), p.3727-3731
Main Authors: Sarkar, Biprajit, Frantz, Stéphanie, Kaim, Wolfgang, Duboc, Carole
Format: Article
Language:English
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Summary:The radical complexes [(micro-L)[Ru(bpy)(2)](2)]*(3+), [(micro-bmtz)[Ru(cym)Cl](2)]*(+) and [(micro-L)[Re(CO)(3)Cl](2)]*(-), where L are 3,6-disubstituted 1,2,4,5-tetrazines such as 3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine (bmtz) and cym =p-cymene, were studied by X-band EPR in fluid solution and by 285 GHz EPR in glassy frozen solution. A comparison with other transition metal complexes (Cu, Rh, Os, Ir, Pt) involving tetrazine radical ligands reveals that the g anisotropy reflects (i) the pi acceptor effect of the tetrazine substituents, (ii) the competition from ancillary pi acceptor ligands for back donation from the metal, and (iii) the spin-orbit coupling contributions from the transition metal.
ISSN:1477-9226
1477-9234
DOI:10.1039/b407611g