Near-IR luminescent lanthanide complexes with 1, 8-diaminoanthraquinone-based chromophoric ligands. Issue 15 (14th March 2016) - Stacey, Oliver J.
Abstract : 1, 8-Anthraquinone derivatives can act as low energy, visible light sensitizers for near-IR emitting lanthanides. Abstract : Three new chromophoric anthraquinone-based multidentate ligands have been synthesised in a step-wise manner from 1, 8-dichloroanthraquinone. The ligands each comprise two dipicolyl amine units and react with trivalent lanthanide ions to form monometallic complexes of the form [Ln(L)](OTf)3 as indicated by MS studies and elemental analyses. Supporting DFT studies show that the monometallic species are highly favoured (>1000 kJ mol −1 ) over the formation of a 2 : 2 dimetallic congener. Both ligands and complexes absorb light efficiently ( ε ∼ 10 4 M −1 cm −1 ) in the visible part of the spectrum, with λ abs ca. 535–550 nm through an intramolecular charge transfer (ICT) transition localised on the substituted anthraquinone unit. In all cases the complexes show a fluorescence band at ca. 675 nm due to the ICT emitting state. The corresponding Nd(iii ), Yb(iii ) and Er(iii ) complexes also reveal sensitised near-IR emission characteristic of each ion following excitation of the ICT visible absorption band at 535 nm.