title: Near-IR luminescent lanthanide complexes with 1,8-diaminoanthraquinone-based chromophoric ligands.
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 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.
authors.affiliation: School of Chemistry, Main Building. and Cardiff University, Cardiff CF10 3AT, UK. popesj@cardiff.ac.uk.
authors.forename: Oliver J
authors.initials: OJ
authors.lastname: Stacey
authors.affiliation: School of Chemistry, Main Building. and Cardiff University, Cardiff CF10 3AT, UK. popesj@cardiff.ac.uk.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Ward
authors.affiliation: School of Chemistry, Main Building. and Cardiff University, Cardiff CF10 3AT, UK. popesj@cardiff.ac.uk.
authors.forename: Angelo J
authors.initials: AJ
authors.lastname: Amoroso
authors.affiliation: School of Chemistry, Main Building. and Cardiff University, Cardiff CF10 3AT, UK. popesj@cardiff.ac.uk.
authors.forename: Simon J A
authors.initials: SJ
authors.lastname: Pope