Highly Sensitive Sensory Materials for Fluoride Ions Based on the Dithieno[3,2-b:2‘,3‘-d]phosphole System

Abstract

[structure: see text]. The newly developed functionalization of an unsubstituted dithieno[3,2-b:2',3'-d]phosphole at the 5,5'-positions gives access to bis(pinacoleboryl) species that can be utilized as sensory materials for fluoride ions. The fluoride-triggered response of the air- and moisture-stable boryl-functionalized dithienophosphole oxide manifests itself in the generation of a new fluorescence emission that can be detected at very low analyte concentrations (ppm) or even with the naked eye upon irradiation with UV light (366 nm).

Dendrimeric Oligo(phenylenevinylene)‐Extended Dithieno[3,2‐b:2′,3′‐d]phospholes—Synthesis, Self‐Organization, and Optical Properties

“…: d = 17.0(AE3) ppm), and also relate to the model compound 5 (d = 18.6 ppm). [16,17] The different shifts observed furthermore reflect the electronic impact of the terminal end-groups on the conjugated system. 1 H NMR data also support the formation of the desired dendrimers 9 a-c with trans-configured stilbene units ( 3 JA C H T U N G T R E N N U N G (H,H) = 16.0 Hz).…”

“…To improve the acceptor properties of the central phosphorus atom, [16,17] as well as to obtain a suitable photophysical reference material for the targeted dendrimers (vide infra), we oxidized the phosphorus atom of the phenyl-A C H T U N G T R E N N U N G vinylene extended compound 4 a in our typical protocol using hydrogen peroxide in dichloromethane at room temperature. [16] Complete conversion of the trivalent phosphorus center to the phosphole oxide can be monitored by 31 P NMR spectroscopy, showing a distinct lowfield shift for the product 5 at d = 18.6 ppm that is typical for these compounds; 1 H and 13 C NMR spectra also show consistent data.…”

“…Another indication of the successful transformation of 5 is the fluorescence emission at l em = 551 nm that is red-shifted by about Dl em = 44 nm from that of the non-oxidized starting material; oxidation of the phosphorus center in dithienophospholes in general affords a red-shift of 40-50 nm due to a lowered LUMO level. [16,17] Synthesis and properties of dendrimeric dithienophospholes: Having verified the general accessibility of phenylene-A C H T U N G T R E N N U N G vinylene-extended dithienophospholes through the "zerogeneration" model compounds, corresponding "first-generation" materials were synthesized in a similar Wittig-Horner protocol. Appropriate benzyl phosphonates 8 a-c were obtained in a modified procedure from the one reported by Marder et al, [22a] using benzylic alcohols 7 a-c (accessible from the corresponding carboxylic acids 6 a-c [24] by reduction with LiAlH 4 , Scheme 3), instead of the generally applied benzyl halides.…”

“…[16] Our building block, which conjoins two thiophene subunits with a central phosphole moiety through annelation, allows for the selective and efficient tuning of the (opto)electronic properties of the materials by functionalization of phosphorus atom or the main scaffold. [16,17] The materials obtained in the context of our studies, display highly advantageous, unprecedented photophysical properties with respect to emission wavelengths, intensity, and tunability. Since then, the groups of Yamaguchi [18] and Matano, [19] among others, were able to further solidify the benefits of phosphole units within p-conjugated assemblies, reporting materials with remarkable optoelectronic properties.…”

Metalated heterocycles in organic synthesis: Recent applications

“…229 This type of thienylboronates have also been prepared using palladium-catalysis, 230 as well as by lithiation of the thiophene system and further reaction with 2-isopropoxy(pinacole)borane. 231 These heteroaromatic pinacolboranes have been used in cross-coupling processes, 230,232 …”