Solid‐State Gas Sensors Developed from Functional Difluoroboradiazaindacene Dyes

Abstract

This article describes the synthesis and characterization of several new difluoroboradiazaindacene (BODIPY) dyes functionalized at the central 8-position by a phenyliodo, phenylheptynoate or phenylheptynoic fragment and at the 3- or 3/5-position(s) by 4-dimethylaminophenylstyryl residue(s). Single-crystal structural determinations confirm the planarity of the dyes, while the absorption and fluorescence spectroscopic properties are highly sensitive to the state of protonation (or alkylation) of the terminal anilino donor group(s). Reversible color tuning from green to blue for absorption and from colorless (i.e., near-IR region) to red for fluorescence is obtained on successive addition of acid and base. The difunctionalized derivative is especially interesting in this respect and shows two well-resolved pK(a) values of 5.10 and 3.04 in acetonitrile. Addition of the first proton causes only small spectral changes and deactivates the molecule towards addition of the second proton. It is this latter step that accommodates the large change in absorption and emission properties, due to the reversible extinction of the intramolecular charge-transfer character inherent to this type of dye. The main focus of the work is the covalent anchoring of the dyes to inert, porous polyacrylate beads so as to form a solid-state sensor suitable for analysis of gases or flowing liquids. The final material is highly stable--its performance is undiminished after more than one year--and fully reversible over many cycles. The sensitivity is such that reactions can be followed by the naked eye and the detection limit is about 600 ppb for HCl and about 80 ppb for ammonia. Trace amounts of diphosgene can be detected, as can alkylating agents. The sensing action is indiscriminate and also operates when the beads are dispersed in aqueous media.

Dihydronaphthalene‐Fused Boron–Dipyrromethene (BODIPY) Dyes: Insight into the Electronic and Conformational Tuning Modes of BODIPY Fluorophores

“…[45,46] On the other hand, the simplest way to obtain BODIPYs with emission in the red-visible or near infrared (NIR) region of the spectrum is the condensation of 4-donor-substituted benzaldehydes to the active methyl groups located at the 3,5-positions of the BODIPY core. [31,35,[47][48][49] The following rules of thumb for bathochromic displacement along this route can be derived from the data in Scheme 2 with tetramethyl-BODIPY 3 a serving as the reference for the parent dipyrrin chromophore: [50] 1) Introduction of two phenyl groups at the 3,5-positions entails a shift of approximately 50 nm (3 a!4). Alternatively, the other strategies apparent from Scheme 2 lead to the following shifts:…”

Synthesis, spectroscopic, and in vitro investigations of 2,6-diiodo-BODIPYs with PDT and bioimaging applications

“…The investigation of BODIPY (difluoro boron dipyrromethene)-based bioimaging agents has been an active area of research in recent decades, that has produced a multitude of fluorescent dyes with a variety of purposes including use as labels for biomolecules such as DNA, peptides, and lipids[1–4], as well as for applications as enzyme substrate fluorescent tags[5,6], as environmental indicators (pH and ion sensors)[7–10], and as cellular stains [11]. Despite their extensive investigation, only a few studies have evaluated BODIPYs for applications as photodynamic therapy (PDT) photosensitizers and as radioimaging agents, particularly for positron emission tomography (PET) and single photon emission computed tomography (SPECT).…”

Using a Photoacid Generator to Switch the Direction of Electronic Energy Transfer in a Molecular Triad

“…Such protocols could be developed as a means for designing rapid switching systems. We have also shown [16] that green Bodipy-based dyes can be appended to porous microspheres in such a way that reversible protonation still takes place. It is reasonable to suppose that B(DPP)G could likewise be anchored to polystyrene spheres preloaded with PAG.…”