Sensors for cations

In a variation on this approach, Wong [19] reported a mono-aza crown ether covalently appended via alkyle linkers to triacetic acid derivatives of cyclen and cyclam, giving 

Acyclic derivatives based upon the DTP A ligand core have been reported by Nagano and utilised for targeting and imaging intracellular zinc [22]. The design rationale for such a 

An attractive photophysical attribute of the emissive trivalent lanthanide ion is the large dependency of emission lifetime upon variation in the hydration/solvation of the ion in 

Therefore, the incorporation of a long wavelength sensitising antenna into an analyte receptor site enables visible light sensitisation of near-IR emitting lanthanide ions such as Nd and Yb, and the potential for single molecule bimodal luminescent/MR agents [38]. 

For example, 1-amidoanthraquinone and 8-amidoquinoline derivatives (Fig. 6.11) each possess exeitation wavelengths of 400-430 nm and promote emission from Nd (ca. 880, 1055 and 1340nm) and Yb (ca. 980 nm). Assessment of the luminescence of Yb eomplexes in the presence of Cu, Zn, Cd and Hg revealed that quenched emission, 

---

Valeur B., Leray I., Design principles of fluorescent molecular sensors for cation recognition, Coord. Chem. Rev. 2000 205 3. 

Similarly, an anionic chromophore HC can also be used for designing optical sensors for cations, in this case, no extra anionic site (R ) is needed to maintain charge neutrality during the sensing. 

PET fluorescent sensors for cations have been highly developed (Bissell et al., 1993). The principle is the same as for PET pH indicators, described in Section 10.2.2.5. 

Most PET fluorescent sensors for cations are based on the principle displayed in Figure 10.7, but other photoinduced electron transfer mechanisms can take place with transition metal ions (Fabbrizzi et al., 1996 Bergonzi et al., 1998). In fact, 3d metals exhibit redox activity and electron transfer can occur from the fluorophore... 

Anions play key roles in chemical and biological processes. Many anions act as nucleophiles, bases, redox agents or phase transfer catalysts. Most enzymes bind anions as either substrates or cofactors. The chloride ion is of special interest because it is crucial in several phases of human biology and in disease regulation. Moreover, it is of great interest to detect anionic pollutants such as nitrates and phosphates in ground water. Design of selective anion molecular sensors with optical or electrochemical detection is thus of major interest, however it has received much less attention than molecular sensors for cations. 

Valeur B. and Leray I. (2001) PCT (Photo-induced Charge Transfer) Fluorescent Molecular Sensors for Cation Recognition, in Valeur B. and Brochon J. C. (Eds),... 

In Chapter 10, fluorescent pH indicators and fluorescent molecular sensors for cations, anions and neutral molecules are described, with an emphasis on design principles in regard to selectivity. 

Ruzicka, et al. (11) increased the oil solubility gf phosphate ester anions to increase the sensitivity of the Ca electrode. Gavach, et al. (12) and Birch, et al. (13) made detergent sensors for cations and anions. 

Valeur, B. Leray, I. Design Principles of Fluorescent Molecular Sensors for Cation Recognition. Coord. Chem. Rev. 2000, 205, 3—40... 

Pt acetylenes can also function as fluoresecent sensors for cations. Receptor 45 incorporates two 4-ethynylbenzo-15-crown-5 moieties with luminescent dimino Pt(ii) complexes.In acetonitrile solution, complex 45 is weakly emissive (excitation at 405 nm, Amax = 635, 0= 1.1 x 10 ). However, on addition of significant increase in the emission intensity and a blue shift in A ax to 555 nm were observed. At 40equiv. of Mg or Zn, the measured enhancement was 1,035- and 870-fold, respectively. Other cations, namely, K, Na, and Gd, resulted in a less than 10-fold emission enhancement. The binding stoichiometry was found to be 1 2 receptor cation, and the overall stability constants calculated for Na, Mg, and Zn were [3 = 7.9 x 10, 5.3 x 10, and 9.3 x 10 respectively. 

Figure 1. Diagrammatic representation of the design logic of fluorescent PET sensors for cations.

Figure 18 Examples of PET-based fluorescent sensors for cations. (Reproduced from Ref. 196. Royal Society of Chanistry, 1986.)...

Scheme 6.5 Tb-based cyclam (left) and cyclen (right) derived sensors for cationic alkali...

---