A New Family of Luminescent Sensors for Alkaline Earth Metal Ions

Abstract

Abstract:The effects on the photophysical properties of three crown ethers (1 a ± c) containing the 1,8-dioxyxanthone residue caused by the complexation with Ba 2 , Sr 2 , and Ca 2 metal ions are reported. The strong enhancement of the fluorescence, the appearance of a long-lived delayed fluorescence, and a good selectivity towards Ba 2 ions prove that 1 c is an efficient fluorescent chemosensor for this ion. In addition, the range of selectivities shown by this family of crown ethers towards the alkaline earth metal ions together with their favorable photophysical properties, make them suitable for the construction of (multi)sensory devices. The differences in the photophysical properties between the uncomplexed and complexed crown ethers can be accounted for by the stabilization of a different ground state conformer of the dioxyxanthone moiety by the metal ion within the cavity of the crown ether.

Synthesis, characterisation and metal ion binding properties of crown ethers incorporating 4,5-dioxyxanthones

“…Decolourised 4,5-dihydroxyxanthone, 5 (0.200 g, 0.88 mmol), acetic anhydride (10 ml) and pyridine (1 ml) were refluxed for 5 h. Evaporation under vacuum yielded crystals which were collected by filtration, rinsed with ethanol and dried under vacuum (160 mg, 58%); mp 262-270 ЊC (lit. (13), 228 (100), 171 (5%); (ϩCI) 330 (30), 313 (100), 285 (5), 29 (7), 228 (9%).…”

“…Reaction of decolourised 4,5-dihydroxyxanthone, 5 (0.3 g, 1.3 × 10 Ϫ3 mol), anhydrous potassium carbonate (0.6 g, 4.3 × 10 Ϫ3 mol), DMF (60 ml) and 1,14-dibromo-3,6,9,12tetraoxatetradecane (0.72 g, 1.97 × 10 Ϫ3 mol) as described above yielded a crude product (0.3 g, 53%) which was purified by column chromatography (basic alumina, tetrahydrofuran) to yield an off-white solid which was washed with ether and dried in air (0. (M ϩ , 16), 386 (3), 342 (6), 298 (8), 255 (27), 254 (100), 253 (18), 228 (36), 226 (18), 225 (40%); (ϩCI/NH 3 ) 448 (100), 431 (16), 430 (3), 404 (6), 360 (8), 343 (7), 330 (33), 299 (10%).…”

“…b) By spectrofluorimetry. Emission spectra were run for solutions of the crown ethers in methanol (3.0 ml of 1 × 10 Ϫ4 M § IUPAC name : 8,9,11,12,14,15,17,18,20,21,23,4,7,10,13,16,19,22]octaoxacyclotetraicosa [2,3,4,5,6-defg]xanthen-23-one. at 25 ЊC), by excitation of the solution at an isosbestic point.…”

“…The 1,8-dioxyxanthone-based crowns were not strongly fluorescent themselves, but showed strong fluorescence enhancement and appearance of a long lived delayed fluorescence upon binding to alkaline earth cations, especially Ba 2ϩ , which make them suitable for construction of multi-sensory devices. 7 In this series, the ketonic oxygen of the xanthone residue lies within the macrocycle, and has near ideal placement and polarity for involvement in metal ion complexation (Fig. 2), and its close association with a bound metal ion is clearly a factor in the desirable photophysical behaviour of these crowns.…”

Polarization-Based Sensing with a Self-Referenced Sample

“…[1][2][3][4][5] Numerous new sensing fluorophores have been developed that provide responses to specific analytes, especially to cations and anions. [6][7][8][9][10] A significant problem in fluorescence sensing is the difficulty of performing intensity measurements in a real-world situation. Intensity measurements are typically unreliable or require frequent recalibration because of a variety of chemical and instrumental factors.…”