Cation Recognition with Fluorophore Crown Ethers

Abstract

The fluoroionophore behavior of various macrocycles with oxygen and nitrogen donors was reviewed in the present paper, and the cationic recognition of alkali and alkaline-earth metals involving different photophysical effects depending on the fluoroionophore structures was summarized. Spectrofluorometry is a very sensitive technique measuring both emission and excitation intensities of a fluorescent molecule that is influenced by the environment. The cationic recognition of fluoroionophore crown ethers which possess at least two molecular components with sites that interact with photons as well as ions is studied. Cations mostly induce the changes in triplet energy relative to the excited singlet state, S 1 f T 1 , and the ground state, T 1 f S 0 . In the presence of metal cations, the increased phosphorescence lifetime of luminescent macrocycles, in general, gave complexation-enhanced quenching fluorescence spectra that reduce the fluorescence lifetime. However, if the phosphorescence lifetime is reduced, the fluorescence life is increased and the complexation-enhanced fluorescence spectra would be observed. Optical responses originating from the different photophysical mechanisms of photoinduced charge transfer, electronic energy transfer, monomer/excimer equilibrium, and internal charge transfer were represented. The recent studies on the cation recognition of fluorophore macrocyclic ethers are exemplified and discussed in the present paper.

The synthesis of novel crown ethers, part X, 4‐propyl‐and 3‐ethyl‐4‐methylchromenone‐crown ethers

“…The products were used after vacuum drying at room temperature. The cation and cation/macrocycle solutions (1/1 molar ratio of mixtures), of 1.0 x10 -5 mol/L in AN were placed in 10-mm quartz cells in a thermostated cell compartment at 25 o C and fluorescence emission intensities were recorded at 10 nm band width [11,13], (see Table 1). …”

“…We have previously synthesised various crown ethers and podands with different chromophore moieties and reported their cation-complex formation stabilities using steady state fluorescence spectroscopy in acetonitrile [9][10][11][12][13]. The macrocyclic ether derivatives of the 3-phenyl, 4-H, 4-methyl-6,7-dihydroxy-as well as -7,8-dihydroxycoumarins synthesised recently showed selective cation binding effects with steady state fluorescence emission spectroscopy.…”

“…The reports on macrocycles containing common aromatic groups have shown the essential cation selectivity role using fluorescence spectroscopy [14][15][16]. Detailed literature and explanation of optical aspects have been given in our earlier paper [13].…”

The synthesis of chromophore ended glycoles, part IV. Bis-coumarin derivatives ended polyglycols

“…The crude product was dissolved in CHCl 3 (20 mL) and chromatographed on alumina (basic) with CHCl 3 (4x25 mL) to give the compounds, 3a-3d. The mp, yields, IR spectra, and 1 H nmr spectra of compounds, 3a-3d, are displayed in Table 3 [8,11,12].…”

“…Fluorescent supramolecules with strong polar groups are fast and practical for remote detection of cationic and molecular interactions [6][7][8]. The synthesis and the ionic recognition properties of the synthetic receptors of macrocyclic ethers and their noncyclic polyoxa initials with chromophore moieties have been our work of interest [8][9][10][11][12][13][14]. On the other hand, cation selectivity is the prime importance that very much depends on the analytical method [1][2][3].…”