12H-Quinoxalino[2,3-b]phenoxazinium complexes with CoII and ZnII hexafluoroacetylacetonates: synthesis, structure, and properties

Abstract

Reactions of 12H-quinoxaline[2,3-b]phenoxazine (QOPO) derivatives with the Co^II and Zn^II hexafluoroacetylacetonates accompanied by protonation of the starting bases result in stable complexes [QOPOH]⁺[M(hfac)₃]⁻ whose structure was determined by X-ray diffraction and by ¹H and ¹⁵N NMR spectroscopy. The complexes are characterized by long-wavelength absorption (560–664 nm) and fluorescence in the red region (λ_fl = 674–805 nm). The relative energies of the protonated tautomers N(14)—H and N(7)—H were determined using the results of B3LYP–D3BJ/6-311G++(d,p) density functional calculations with inclusion of D3BJ dispersion correction. A SQUID magnetometry study of the static and dynamic magnetic properties of the Co^II complex revealed that it behaves as a field-induced single-ion magnet.