title: High-frequency EPR study of reduced diruthenium and dirhenium polypyridine complexes based on the 1,2,4,5-tetrazine radical bridge.
abstract: 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.
authors.affiliation: Institut für Anorganische Chemie, Universität Stuttgart, Germany.
authors.forename: Biprajit
authors.initials: B
authors.lastname: Sarkar
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Frantz
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kaim
authors.forename: Carole
authors.initials: C
authors.lastname: Duboc