The coordination chemistry of fluorescent pyridinyl– and quinolinyl–phthalimideligands with the {AuI–PPh3} cationic unit

Abstract

The new mono-dentate ligands, 2-(2-aminoethyl)-N-phthalimido-pyridine (L⁴4) and 8-amino-N-phthalimido-quinoline (L⁶6), were synthesised using a solvent-free melt method. These ligands together with L^1–3,51–3,5 (3-amino-N-phthalimido-pyridine; 3-aminomethyl-N-phthalimido-pyridine; 4-aminomethyl-N-phthalimido-pyridine; 3-amino-N-phthalimido-quinoline) were then used to access six luminescent Au^I complexes of the generic type {Ph₃P–Au–Lⁿ}(OTf). X-Ray crystallography has been used to structurally characterise three of the complexes showing that in the cases of L¹1 and L³3 the complexes adopt an approximately linear P–Au–N coordination geometry. However, in the case of the sterically demanding L⁶6 the structure shows distortions within the ligand and deviations from a linear coordination geometry. Solution state ¹H and ³¹P{¹H} NMR confirmed that the proposed formulations and coordination modes exist in solution. At room temperature the photophysical studies showed that the emission from each of the six complexes was in the visible region (395–475 nm) and assigned to a ligand-centred fluorescence (τ < 10 ns) in each case.