Efficient fluorescent chemosensing of iodide based on a cationic meso-tetraarylporphyrin in pure water

Recent Advances in Luminescent Recognition and Chemosensing of Iodide in Water

“…These two sensing approaches include 1) Cation displacement assays where transition-metal-complexes of Hg 2 + , Ag + and Cu + 2 , with a modest emission, irreversibly react with I À ions to form its corresponding salts (MI n ) along with release a luminescent ligand. This displacement reaction is an indirect measure of binding and generates a fluorescence "Turn-on" response ( Figure 1 Among these strategies two approaches that are specifically good for I À include (a) the use of luminescent complexes of Hg 2 + and Pt 2 + due to the strong affinity of the anion for these metals [46][47][48]59] and (b) chemosensors based on organic receptors containing ionic H-bond donors [66][67][68][69][70] of the kind (CÀ H) + or halogen donors (CÀ I) [80][81][83][84] in combination with hydrophobic moieties because these fragments can generate a binding site with a low degree of hydration which favors the formation of the supramolecular complex. The lower hydration enthalpy of I À can also make it easier the binding with the organic receptor compared to oxoanions and lighter halides which are better hydrogen bond acceptors but with higher hydration energies ( Table 1).…”

“…Notable examples that operate in 100% water include fluorescent receptors containing an arrays of hydrogen bond donors such as NÀ H, [62][63][64][65] CÀ H, [66][67][68][69][70] and boronic acids (BÀ OH) [71] able to bind iodide through (DÀ H … I À ) ionic interactions.…”

“…[65] Of note, recent works have include other non-common Hbond donors such as sp 3 or sp 2 -hybridized CÀ H groups [75] or boronic acids B(OH) 2 [71] (Figure 7). Dorazco and coworkers reported the cationic porphyrin 23 is able to detect iodide in pure water at pH = 7.4 [66] with a rapid, direct analytical response and a detection limit of 180 nM. The Dipod 24 bearing two pyrenyl tethered benzimidazolium moieties displays emission bands at 395 and 475 nm due to the monomer and excimer of pyrene groups.…”

“…This enhancement of emission intensity upon iodide binding is particularly notable because it is more common to observe quenching behaviour of emissive organic anion receptors and transition-metal-based receptors. [59,[66][67][73][74][75][76]…”

A pyrenyl-appended C-symmetric hexahomotrioxacalix[3]arene for selective fluorescence sensing of iodide

“…Particularly, fluorescence methodology has been widely used as a great tool for detection of ion species due to its operational simplicity, high sensitivity and selectivity [16][17][18]. In recent years a number of selective fluorescent sensors have been developed for the detection of iodide ion by the change in photophysical or colorimetric properties of the receptor without substantial interferences from other anions [19][20][21][22][23]. Homooxacalix [3]arenes are related to both calixarenes and crown ethers, and possess a three-dimensional cavity with a C 3v symmetric structure.…”