New series of salts with 12H-quinoxalino[2,3-b]phenoxazinium cation and [Ln(hfac)4]− anions

Abstract

The reaction of 12H-quinoxaline[2,3-b]phenoxazine (QOPO) with lanthanide hexafluoroacetylacetonates is accompanied by protonation of the QOPO and leads to the formation of salts of the general formula [QOPOH]+[Ln(hfac)<inf>4</inf>]− (Ln = Nd, Dy, Tb, Ho), whose structures have been determined by X-ray diffraction analysis and 1H NMR spectroscopy. The compounds are characterized by long wavelength absorption and fluorescence (λ<inf>fl</inf> = 677–740 nm). The study of the magnetic properties of the complexes has revealed that the Tb complex exhibits slow magnetic relaxation under an applied dc field, while the Dy complex behaves as single-ion magnet (SIM) even at zero field. These two compounds are the first examples of anionic complexes based on Dy and Tb ions coordinated by four hexafluoroacetylacetonates that exhibit the SIM properties under zero and applied dc fields, respectively.