Alkynyl Gold(I) Phosphine Complexes: Evaluation of Structure–Activity Relationships for the Alkynyl Ligands on Luminescence and Cytotoxicity

A series of gold (I) phoshpine complexes with diverse alkynyl ligands [Au(C≡CR)(PTA)] (R=C 6 H 11 OH, 1 ; C 5 H 9 OH, 2 ; C 15 H 11 OH, 3 ; C 19 H 27 O 2 , 4 ; C 18 H 23 O 2 , 5 ; C 9 H 12 N, 6 ; CH 2 OCH 2 C 6 H 5 , 7 ; C 6 H 4 OCH 3 , 8 ; PTA=1,3,5‐Triaza‐7‐phosphaadamantane) have been synthesized and characterized using a range of spectroscopic techniques. Complex 1 and 3 show an infinite one–dimensional S–type and zigzag aurophilic chain, respectively, whereas complex 2 containing 1‐ethynyl‐1‐cyclohexanol gives an approximate linear two–dimensional aurophilic chain, through intra/intermolecular Au(I)⋯Au(I) interactions as well as hydrogen bonding interactions between hydroxy groups of alkynyl ligands and PTA. Solid complexes 1 – 8 display strongly room/low–temperature emissive of 477–613 nm with the emission lifetime of 0.40–14.0 μs. All the complexes display higher cytotoxicities against MCF‐7, with the cytotoxicity decreasing in the following order 4 > 8 > 5 > 3 > 7 > 6 > 2 > 1 . Complex 4 and 5 stand out for the highest selectivity towards MCF–7 (IC 50 =0.63–0.78 μM) compared with normal human embryonic lung fibroblasts (helf) (IC 50 =14.85–18.13 μM), which makes those complexes attractive for breast cancer therapy.