Near-IR luminescent lanthanide complexes with 1,8-diaminoanthraquinone-based chromophoric ligands?

Dalton Transactions Pub Date: 2016-03-14 DOI: 10.1039/C5DT04351D

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 ～ 104 M?1 cm?1) in the visible part of the spectrum, with λabsca. 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.

Graphical abstract: Near-IR luminescent lanthanide complexes with 1,8-diaminoanthraquinone-based chromophoric ligands
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