Rigidly Tethered Bis‐phosphoric Acids: Generation of Tunable Chiral Fluorescent Frameworks and Unexpected Selectivity for the Detection of Ferric Ions

Abstract

We describe the straightforward synthesis of a series of bis-phosphoric acids (R,R)-1 a-d, featuring two chiral 1,1'-binaphthyl-phosphoric acid units that are tethered by rigid, π-conjugated linkers. The nature of the linker has a profound influence on the properties of the bis-phosphoric acids, such as their self-association behavior and their interaction with metal ions. This led to the identification of one preferred bis-phosphoric acid (R,R)-1 d, which shows selective fluorescence quenching in the presence of ferric ions (Fe ). Thus, (R,R)-1 d could be applied for the detection of Fe , even in the presence of a variety of other metal ions. The chiral nature of the bis-phosphoric acid enables the interaction with Fe to be followed by CD spectroscopy, providing a complementary detection mode with the same probe.

Development of Fluorescent Chemosensors for Amino‐Sugars

“…We recently reported a series of multidentate phosphoric acids ( 1 d / e / f , Figure 1 for 1 d / e / f ) that feature two or three BINOL‐based phosphoric acid diesters of the type (ArO) 2 P(O)OH. These systems were applied in organocatalysis, [13] but also for the chemosensing of metal‐ions [14] and amino acids [15] . By an acid‐catalyzed cyclization, we also generated the furane‐annelated phosphoric acid monoesters 11 d / e / f , which possess two or three binding units of the type (ArO)P(O)(OH) 2 .…”

Dual Brønsted‐acid Organocatalysis: Cooperative Asymmetric Catalysis with Combined Phosphoric and Carboxylic Acids

“…[46] Making use of the mechanical bond it is possible to impart al arge conformational flexibility,w hile generating al arge local concentration of catalyticallyactivephosphoric acid groups. [46] Making use of the mechanical bond it is possible to impart al arge conformational flexibility,w hile generating al arge local concentration of catalyticallyactivephosphoric acid groups.…”

“…Recently,o ur group has designed ac atenated bisphosphoric acid catalyst, in which am echanical bond is used to connect two binaphthyl-phosphoric acids. [46] Making use of the mechanical bond it is possible to impart al arge conformational flexibility,w hile generating al arge local concentration of catalyticallyactivephosphoric acid groups.…”

Stereoselective Sensing of l‐ and d‐Amino Acids: Development of a Fluorescence‐Array Based on Readily Available Chiral Phosphoric Acids

“…Initial investigations showed that using only the sensors 1 a – f , the fluorescence responses were negligible for most amino acids, and only for those with nitrogen‐containing side‐chains (Lys, His, Arg, Trp) considerable fluorescence quenching was observed (Supporting Information, Figure S1). Based on our previous experience with the strong interaction of the bisphosphoric acids with metal ions, we turned to using metal salts in combination with the organophosphoric acids. We envisaged an initial metal‐induced fluorescence quenching, which would improve the differential response upon addition of the amino acids.…”