Highly NIR-emitting ytterbium complexes containing 2-(tosylaminobenzylidene)-N-benzoylhydrazone anions: structure in solution and use for bioimaging

Abstract

Solution behaviour in DMSO using 1D and 2D NMR spectroscopy was performed for lanthanide complexes Ln(L)(HL) and Ln(HL)₂Cl, containing non-macrocyclic 2-(tosylamino)-benzylidene-N-benzoylhydrazone (H₂L), and the structure of [Yb(L)]⁺ cation in solution was determined. Based on the NMR data, the possibility to obtain novel complexes containing [Ln(L)₂]⁻ was predicted, which was successfully synthesized, and the crystal structure of K(C₂H₅OH)₃[Yb(L)₂] was determined. Thanks to its high quantum yield of NIR luminescence (1.3 ± 0.2%), high absorption, low toxicity, and the stability of its anion against dissociation in DMSO, K(H₂O)₃[Yb(L)₂] was successfully used for bioimaging.