High-frequency EPR and structural data as complementary information on stable radical complexes containing the semi-reduced azo function

Heterohexanuclear (Cu3Fe3) Complexes of Substituted Hexaazatrinaphthylene (HATN) Ligands: Twofold BF4− Association in the Solid and Stepwise Oxidation (3e) or Reduction (2e) to Spectroelectrochemically Characterized Species

“…The altered frontier orbital pattern as indicated above may be invoked to rationalize this reversal of g components. In general, the g 1 − g 3 =Δ g and the g iso values conform with those of copper(I)‐coordinated radical anions of N‐heterocyclic ligands 23…”

“…In general, the g 1 Àg 3 = Dg and the g iso values conform with those of copper(I)-coordinated radical anions of N-heterocyclic ligands. [23] Reduction beyond the first step only resulted in a diminished EPR response; a half-field signal as expected for a triplet formation was not observed at 110 or 4 K. Similarly, oxidation did not produce any EPR signals at 4 K, most likely due to enhanced relaxation and thus excessive linebroadening in view of three very weakly coupled ferrocenium/ferrocene redox centers.…”

“…The relatively high stability of the one‐electron reduced complexes allowed us to study these species by high‐frequency EPR at 95 or 115 GHz in the glassy, frozen solution state (Figure 3, Table 4). This technique yielded results for the g factor anisotropy, which provides useful information for metal complexes of radical ligands 23. Figure 3 and the data from Table 4 show that the symmetry of the system is reflected by the axial g component splitting, which, however, is not uniform throughout the series: for 1 2+ and 2 2+ the g ⊥ > g ∥ , whereas the reverse holds for 3 2+ .…”

An Odd‐Electron Complex [Ruk(NOm)(Qn)(terpy)]2+ with Two Prototypical Non‐Innocent Ligands

“…The present case of an isolated odd‐electron species is distinguished by offering a clearer picture through application of EPR spectroscopy at high frequency (285 GHz) and at conventional X‐band (9.5 GHz, Figure 3). The very small22a resolved g anisotropy g 1 ‐g 3 =0.0068 even at 285 GHz22b suggests little participation of the metal at the singly occupied molecular orbital (SOMO), in spite of the high spin‐orbit coupling constant of ruthenium 8a. 10a Furthermore, a partially hyperfine‐resolved signal observed at 9.5 GHz indicates a small but unresolved contribution from NO to the overall spin distribution and a diminished12, 16 14 N(imine) EPR coupling constant.…”

Das ungeradzahlig elektronenkonfigurierte Komplexion [Ruk(NOm)(Qn)(terpy)]2+ mit zwei idealtypischen “nicht‐unschuldigen” Liganden

“…Im hier vorliegenden Fall einer isolierten Spezies mit ungeradzahliger Elektronenkonfiguration erlaubt EPR‐Spektroskopie bei hoher Frequenz (285 GHz) und im konventionellen X‐Band (9.5 GHz, Abbildung 3 a,b) eine eingehendere Analyse. Die kaum22a aufgelöste g ‐Anisotropie g 1 ‐ g 3 =0.0068 selbst bei 285 GHz22b belegt einen sehr geringen Beitrag des Metalls am einfach besetzten Molekülorbital (singly occupied MO, SOMO), trotz der hohen Spin‐Bahn‐Kopplungskonstante von Ruthenium 8a. 10a Außerdem legt das nur unvollständig hyperfeinaufgelöste EPR‐Signal bei 9.5 GHz eine nur geringe Hyperfeinwechselwirkung mit NO und eine verringerte12, 16 14 N(Imin)‐Kopplungskonstante nahe.…”