Highly Sensitive and Selective Molecular Probes for Chromo‐Fluorogenic Sensing of Carbon Monoxide in Air, Aqueous Solution and Cells

Abstract

Optical sensing offers a low‐cost and effective means to sense carbon monoxide in air and in solution. This contribution reports the synthesis of a new series of vinyl complexes [Ru(CH=CHR)Cl(CO)(TBTD)(PPh3)2] (R=aryl, TBTD=5‐(3‐thienyl)‐2,1,3‐benzothiadiazole) and shows them to be highly sensitive and selective probes for carbon monoxide in both solution and air. Depending on the vinyl substituent, chromogenic and fluorogenic responses signalled the presence of this invisible, odourless, tasteless and toxic gas. Adsorbing the complexes on silica produced colorimetric probes for the ′naked eye′ detection of CO in the gas phase with a limit of detection as low as 8 ppm in some cases, while the release of the TBTD fluorophore allowed detection at much lower concentrations through the fluorescence response. Structural data were obtained by single‐crystal X‐ray diffraction techniques, while the photophysical behaviour was explored computationally using TD‐DFT experiments. The systems were also shown to be selective for CO over all other gases tested, including water vapour and common organic solvents. By introducing a poly(ethylene)glycol chain to the vinyl functionality, water compatibility was achieved and these non‐cytotoxic complexes were employed in the sensing of CO in HeLa cells, offering a simple and rapid system for sensing this gasotransmitter in this challenging medium.

Simultaneous Detection of Carbon Monoxide and Viscosity Changes in Cells

“…[14b,c, 18] Our previous work on CO detection resulted in a new approach using divalent ruthenium vinyl complexes to deliver combined chromogenic and fluorogenic responses. [19] Reaction of these compounds with CO results in bright, turn-on emission of a conjugated fluorophore, providing high selectivity and sensitivity towards CO, as demonstrated in an in vivo model of inflammation. [20] The probe design described herein incorporates a BODIPY-based molecular rotor, which not only detects the binding of CO, but also enables the use of FLIM for viscosity monitoring.…”

“…The BTD ligand binds trans to the vinyl moiety and resists displacement by other species (even high concentrations of MeCN and DMSO). [19,20] However, on exposure to CO, the BTD ligand is rapidly substituted to yield 4•CO, 5•CO (structurally characterised, Figure 1) and 6•CO, which display significant fluorescence enhancement ( Figures S4-2 to S4-6). The brightest emission (F f = 0.77) was measured for 4•CO, which displayed a 16-fold revival ( Figure S4-3) of the BODIPY fluorescence in pH 7.4, 25 mm phosphate-buffered saline (PBS)-DMSO (9:1 v/v) solution.…”

Synthesis and Application of Ruthenium(II) Alkenyl Complexes with Perylene Fluorophores for the Detection of Toxic Vapours and Gases

“…This provides ample demonstration of the reactivity at the metal centre, however, the installation of the vinyl ligand through facile reaction with terminal alkynes (also internal alkynes under more forcing conditions) allows the incorporation of further functionality that can be influenced by the metal centre . Our recent work has demonstrated the potential of this approach through the selective detection of very low concentrations of carbon monoxide both in air and in cells, following work by others in the area –. Among other features, this contribution provides an illustration of the versatility of such ruthenium vinyl complexes to install a fluorophore either through coordination to the metal centre or as the substituent of the vinyl itself.…”

“…This allows detection of an analyte through two different emission responses. Previously, we have used the 5‐(3‐thienyl)‐2,1,3‐benzothiadiazole (TBTD) fluorophore ( λ exc =355 nm, λ em =500 nm) to detect carbon monoxide in cells and in a mouse model of inflammation . This fluorophore could also be excited under two‐photon conditions at 715 nm to allow detection of endogenous CO at extremely low probe concentrations.…”

Organic Thin-Film Transistors as Gas Sensors: A Review

“…It is worth noticing that there are several methods available for gas detection exhibiting selectivity and sensitivity, including gas chromatography (GC), mass spectrometry (MS) and optical chemical sensing [144][145][146][147][148][149][150][151][152]. Nonetheless, they are based on robust and costly equipment, which are hardly implemented at remote locations, and therefore, do not allow for on-site monitoring.…”