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Heterohexanuclear (Cu 3 Fe 3 ) Complexes of Substituted Hexaazatrinaphthylene (HATN) Ligands: Twofold BF 4 − Association in the Solid and Stepwise Oxidation (3e) or Reduction (2e) to Spectroelectrochemically Characterized Species
Author(s) -
Roy Sayak,
Sarkar Biprajit,
Duboc Carole,
Fiedler Jan,
Sarper Orkan,
Lissner Falk,
Mobin Shaikh M.,
Lahiri Goutam Kumar,
Kaim Wolfgang
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200802655
Subject(s) - electron paramagnetic resonance , chemistry , crystallography , tetrafluoroborate , pyrazine , yield (engineering) , ferrocene , hyperfine structure , electrochemistry , stereochemistry , materials science , nuclear magnetic resonance , electrode , biochemistry , ionic liquid , physics , quantum mechanics , metallurgy , catalysis
New tris(ferrocenylcopper) compounds [(μ 3 ‐dqp){Cu(dppf)} 3 ][X] 3 (dppf=1,1′‐bis(diphenylphosphinoferrocene), dqp=hexamethyl‐, hexachloro‐ or un‐substituted diquinoxalino[2,3‐ a :2′,3′‐ c ]phenazine=hexaazatrinaphthylene (HATN), X − =BF 4 − or PF 6 − ) undergo at least two different, reversible one‐electron reductions and three very closely spaced one‐electron oxidations. While the latter are attributed to the stepwise ferrocene→ferrocenium conversions, the first electron addition occurs in the ligand bridge to yield EPR detectable radical complexes. X‐band EPR measurements at 9.5 GHz showed a partially resolved hyperfine structure, while high‐frequency EPR measurements at 95 or 115 GHz revealed a small but variable axial g tensor anisotropy. All reversible steps were investigated by optically transparent thin‐layer electrode (OTTLE) spectroelectrochemistry (UV/Vis/NIR regions), revealing very low energy transitions for the reduced forms in agreement with the frontier MO arrangement. A crystal structure of the compound with unsubstituted dqp shows notable deviation from the trigonal symmetry and the close association of two tetrafluoroborate anions with the complex trication along the quasi‐trigonal axis to yield [(μ 3 ‐dqp){Cu(dppf)} 3 (BF 4 ) 2 ]BF 4 .