Europium macrocyclic complexes

The luminescence of terbium (42) and europium macrocyclic complexes have been studied and found to depend upon pH. The phenanthridine sidechain acts as a photosensitizer and (42) exhibits luminescence quenched by molecular oxygen corresponding Eu compounds exhibit halide-quenched emisssion. ... 

Holz, R. C. Allen Chang, C. Horrocks, W. De W. Jr. Spectroscopic characterization of the europium(III) complexes of a series of N.N -bislcarboxymethyl macrocyclic ether bis(lactones). Inorg. Chem. 1991, 30,3270-3275. 

Several of the complexes in Figure 2 were examined further for their resistance to dissociation. The europium complexes Eu(THED)3+ and Eu(TCMC)3+ were more difficult to study quantitatively by H NMR because of their broad H resonances. Decomposition was monitored by use of a UV-vis assay. Excess Cu2+ was added to solutions containing the lanthanide macrocycles. The Cu2+ ion served the dual purpose of trapping the free macrocycle and as an indicator to monitor the amount of macrocycle that had dissociated. All Cu(II) macrocyclic complexes gave an absorbance peak in the UV-vis spectrum that was characteristic of the Cu(II) macrocycle complex. For all macrocycles, Cu2+ was an effective trap formation of the Cu(II) macrocyclic complex went to completion in the presence of 0.10 mM La3+ or 0.10 mM Eu3+, 0.10 mM ligand and excess Cu2+ (1.0 mM). The increase in the concentration of Cu(II) macrocycle complex over time is a measure of the inertness of the lanthanide complex to dissociation. For the La(THED)3+ complex, the reaction rate (51) was independent of the concentration of Cu2+, consistent with the following mechanism ... 

The luminescence properties of macrobicyclic mixed bipyridine-bipyrazine and macrocyclic polybipyrazine europium(III) complexes were reported in Ref. 380. A noticeable enhancement in the lifetime and fluorescence quantum yield for the macrobicyclic [Eu(bpy.bpy.bpz)]3+ cation was observed in comparison with other europium(III) clathrochelates and attributed to the introduction of the bpz fragment. Among the four studied europium(III) complexes, only the macrobicyclic one is stable in dilute aqueous solution [380]. 

Amin S, Voss DA Jr, Horrocks WD Jr, Lake CH, Churchill MR, Morrow JR. Laser-induced luminescence studies and crystal structure of the europium(III) complex of 1,4,7,10-tetrakis (carbamoylmethyl)-l,4,7,10-tetraazacyclododecane. The link between phosphate diester binding and catalysis by lanthanide(III) macrocyclic complexes. Inorg Chem. 1995 34(12) 3294—3300. 

Chappell LL, Voss DA Jr, Horrocks WD Jr, Morrow JR. Effect of mixed pendent groups on the solution and catalytic properties of europium(III) macrocyclic complexes bifunctional and monofunctional amide and alcohol pendents in septadentate or octadentate ligands. Inorg Chem. 1998 37 3989-3998. 

Parker, D., Senanayake, P. K., Williams, J. A. G., Luminescent sensors for pH, p0(2), halide and hydroxide ions using phenanthridine as a photosensitiser in macrocyclic europium and terbium complexes. J. Chem. Soc., Perkin Trans. 21998, 2129-2139. 

Lowe, M. P., Parker, D., Reany, O., Aime, S., Botta, M., Castellano, G., Gianolio, E., Pagliarin, R. pH-dependent modulation of relaxivity and luminescence in macrocyclic gadolinium and europium complexes based on reversible intramolecular sulfonamide ligation, J. Am. Chem. Soc. 123 (2001), 7601... 

Calix[ ]arenes are a family of macrocycles prepared by condensation reactions between n /v/ra-substituted phenols and n formaldehyde molecules under either base or acid catalysis. Different sizes of the macrocycles can be obtained (n = 4-20) (Stewart and Gutsche, 1999) depending on the exact experimental conditions, which were mastered in the 1960 s (Gutsche, 1998), but the most common receptors are those with n =4,6,8 (macrocycles with an odd number of phenol units are more difficult to synthesize). We use here the simplified nomenclature in which the number of phenolic units is indicated between square brackets and para substituents are listed first.4 Calixarenes, which can be easily derivatized both on the para positions of the phenolic units and on the hydroxyl groups, have been primarily developed for catalytic processes and as biomimics, but it was soon realized that they can also easily encapsulate metal ions and the first complexes with d-transition metal ions were isolated in the mid-1980 s (Olmstead et al., 1985). Jack Harrowfield characterized the first lanthanide complex with a calixarene in 1987, a bimetallic europium complex with p-terf-butylcalix[8]arene (Furphy etal., 1987). 

One should also mention an interesting article [74] describing the photophysical properties of the macrocyclic DOTA-like europium complexes upon direct excitation of the emissive europium ion at 2exc = 394 nm. 

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