Synthesis, structures, and photoluminescence properties of lanthanide dicyanoaurates containing dimeric aurophilic interactions

Abstract The synthesis of a series of lanthanide dicyanoaurates containing the ancillary ligand 2,2′:6′,2″-terpyridine (terpy) have been carried out by reaction of Ln 3+ nitrate salts with terpy and potassium dicyanoaurate. The resultant compounds, [ Ln (C 15 H 11 N 3 )(H 2 O)(NO 3 ) 2 Au(CN) 2 ] ( Ln  = Eu, Tb, Dy, Ho, Er, Yb), form an isostructural series as established by single-crystal X-ray diffraction studies. These studies reveal the existence of two important non-covalent interactions in these compounds. Dimeric aurophilic interactions and terpyridine π-stacking are both present with distances of ∼3.5 A for each. Photoluminescence measurements illustrate that the Eu 3+ and Tb 3+ compounds display enhanced Ln -based emission due to intramolecular energy transfer from the coordinated terpy ligands. Additionally, a [Au(CN) 2 − ] 2 dimeric excimer produces a broad, green emission band in this class of compounds, albeit reduced in intensity in several of the compounds where a reasonable energy match exists with Ln 3+ excitation bands.