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Quenching of Fluorescence in Bodipy‐Derived Trifluoromethyl Enaminone Ligands upon Coordination to Copper(II)

2014; Wiley; Volume: 2014; Issue: 36 Linguagem: Inglês

10.1002/ejic.201402714

1099-0682

Nicolas Chopin, Maurice Médebielle, Olivier Maury, Ghénadie Novitchi, Guillaume Pilet,

Magnetism in coordination complexes

Abstract The synthesis of two trifluoromethyl‐derived enaminone ligands, L1 H (bidentate) and L2 H 2 , (tridentate), which bear a fluorescent 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐ s ‐indacene (Bodipy) moiety, leads to the preparation and characterization of two Cu II complexes {[Cu( L1 ) 2 ] · 2(CH 2 Cl 2 ) ( A ) and [Cu 4 ( L2 ) 4 ] · 4(C 4 H 8 O 2 ) ( B )} that exhibit different architectures. The magnetic properties of the cubane‐like complex B evidence a dominant ferromagnetic behavior characterized by exchange coupling constants J 1 = +20.56(3) cm –1 and J 2 = –10.29(2) cm –1 . Indeed, whereas the luminescence properties of the Bodipy‐derived trifluoromethyl enaminones L1 H and L2 H 2 are typical of the Bodipy skeleton, the emission is totally quenched in both mononuclear ( A ) and cubane ( B ) Cu II complexes. To elucidate this quenching phenomenon, the Rehm–Weller equation has been used based on experimental cyclic voltammetry redox potential measurements. The result remains ambiguous for complexes A and B , and the origin of the quenching phenomenon, photoinduced electron transfer (PET) versus energy transfer (Förster or Dexter), cannot be deduced.