Redox-Activated NO Release in Monolayer Regime

Development of platforms capable of guarantee a controlled NO release at a specific target is highly promising yet challenging. Herein, we present the synthesis and characterization of cis-[Ru(bpy)₂(1,4-dt)(NO)](PF₆)₃ (RuNO), where 1,4-dt = 1,4-dithiane and bpy = 2,2’-bipyridine, which was adsorbed on gold through the sulfur atom of 1,4-dt. This complex was thoroughly characterized by electrochemistry, nuclear magnetic resonance, and vibrational and electronic spectroscopies whose assignments were corroborated by theoretical data. The formation of the self-assembled monolayer (SAM) of RuNO on gold was monitored by surface plasmon resonance giving a coverage density of 2.1 × 10–¹⁰ mol cm^–2. Taking advantage of the NO lability upon reduction, electrochemical scanning microscopy (SECM) was used to both trigger the NO release from the SAM of RuNO on the gold substrate and detection at the SECM tip. Accordingly, upon reduction, the generated NO⁰ species was detected at the SECM TIP, where it was oxidized back to NO⁺.

Keywords:
nitric oxide; ruthenium; nitrosyl complex; self-assembled monolayer; NO release; SECM