New Rhenium(I) Complexes: Synthesis, Photophysics, Cytotoxicity, and Functionalization of Gold Nanoparticles for Sensing of Esterase

A series of the luminescent Re(I) complexes, [Re(bpy-(CH2OH)2)(CO)3(L1)], [Re(bpy-(CH2OH)2)(CO)3(L2)]+, [Re(bpy-(CH2OH)2)(CO)3(L3)]+, and [Re(bpy-(CH2OH)2)(CO)3(L4)] ((bpy-(CH2OH)2 = 4,4′-bis(hydroxymethyl)-2,2′-bipyridine; L1 = 4-pyridylmethyl lipoate; L2 = [1,2]dithiolane-3-pentyl 4-pyrindylacetate; L3 = 4-pyridinyl-methanol; L4 = 4-pyridinylmethyl pentanoate), were synthesized and characterized. The photophysical properties and cytotoxicity of the complexes and the sensing of esterase based on the gold nanoparticles (Au-NPs) modified with the complexes were also studied. The intense luminescence of the Re(I) complexes was quenched efficiently by Au-NPs due to the energy and electron transfer between the Re(I) fluorophores and Au-NPs. Upon addition of esterase to the mixture, the emission of the Re(I) complexes 1 and 2 system was enhanced significantly by the release of the Re(I) complexes from the surface of the Au-NPs.