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Lanthanide complexes of azidophenacyl DO3A are effective substrates for click reactions with ethyne derivatives, giving rise to aryl triazole appended lanthanide complexes, in which the aryl triazole acts as an effective sensitising chromophore for lanthanide luminescence. They also undergo click chemistry with propargylDO3A derivatives, giving rise to heterometallic complexes., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Polyoxometalates (POMs) with heterodinuclear lanthanoid cores, TBA8H4[{Ln(μ2-OH)2Ln'}(γ-SiW10O36)2] (LnLn'; Ln = Gd, Dy; Ln' = Eu, Yb, Lu; TBA = tetra-n-butylammonium), were successfully synthesized through the stepwise incorporation of two types of lanthanoid cations into the vacant sites of lacunary [γ-SiW10O36](8-) units without the use of templating cations. The incorporation of a Ln(3+) ion into the vacant site between two [γ-SiW10O36](8-) units afforded mononuclear Ln(3+)-containing sandwich-type POMs with vacant sites (Ln1; TBA8H5[{Ln(H2O)4}(γ-SiW10O36)2]; Ln = Dy, Gd, La). The vacant sites in Ln1 were surrounded by coordinating W-O and Ln-O oxygen atoms. On the addition of one equivalent of [Ln'(acac)3] to solutions of Dy1 or Gd1 in 1,2-dichloroethane (DCE), heterodinuclear lanthanoid cores with bis(μ2-OH) bridging ligands, [Dy(μ2-OH)2Ln'](4+), were selectively synthesized (LnLn'; Ln = Dy, Gd; Ln' = Eu, Yb, Lu). On the other hand, La1, which contained the largest lanthanoid cation, could not accommodate a second Ln'(3+) ion. DyLn' showed single-molecule magnet behavior and their energy barriers for magnetization reversal (ΔE/kB) could be manipulated by adjusting the coordination geometry and anisotropy of the Dy(3+) ion by tuning the adjacent Ln'(3+) ion in the heterodinuclear [Dy(μ2-OH)2Ln'](4+) cores. The energy barriers increased in the order: DyLu (ΔE/kB = 48 K) < DyYb (53 K) < DyDy (66 K) < DyEu (73 K), with an increase in the ionic radii of Ln'(3+); DyEu showed the highest energy barrier., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

LnDOTA-tetraamide chelates (DOTA=1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) have received considerable recent attention as a result of their potential to act as PARACEST contrast agents for magnetic resonance imaging (MRI). Although PARACEST agents afford several advantages over conventional contrast agents they suffer from substantially higher detection limits; thus, improving the effectiveness of LnDOTA-tetraamide chelates is an important goal. In this study we investigate the potential to extend conformational control of LnDOTA-type ligands to those applicable to PARACEST. Furthermore, the question of whether δ- rather than α-substitution of the pendant arms could be used to control the chelate coordination geometry is addressed. Although δ-substitution does influence coordination geometry it does not afford control. However, it can play an important role in governing the conformation of the amide substituent relative to the chelate in such as way that suggests a PARACEST agent could be designed that has detection limits at least as low as a conventional MRI contrast agent., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A family of linear Dy(3) and Tb(3) clusters have been facilely synthesized from the reactions of DyCl(3), the polydentate 3-methyloxysalicylaldoxime (MeOsaloxH(2) ) ligand with auxiliary monoanionic ligands, such as trichloroacetate, NO(3)(-), OH(-), and Cl(-). Complexes 1-5 contain a nearly linear Ln(3) core, with similar Ln···Ln distances (3.6901(4)-3.7304(3) Å for the Dy(3) species, and 3.7273(3)-3.7485(5) Å for the Tb(3) species) and Ln···Ln···Ln angles of 157.036(8)-159.026(15)° for the Dy(3) species and 157.156(8)-160.926(15)° for the Tb(3) species. All three Ln centers are bridged by the two doubly-deprotonated [MeOsalox](2-) ligands and two of the four [MeOsaloxH](-) ligands through the N,O-η(2)-oximato groups and the phenoxo oxygen atoms (Dy-O-Dy angles=102.28(16)-106.85(13)°; Tb-O-Tb angles=102.00(11)-106.62(11)°). The remaining two [MeOsaloxH](-) ligands each chelate an outer Ln(III) center through their phenoxo oxygen and oxime nitrogen atoms. Magnetic studies reveal that both Dy(3) and Tb(3) clusters exhibit significant ferromagnetic interactions and that the Dy(3) species behave as single-molecule magnets, expanding upon the recent reports of the pure 4f type SMMs., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A lanthanide-complex-based ratiometric luminescence probe specific for peroxynitrite (ONOO(-)), 4'-(2,4-dimethoxyphenyl)-2,2':6',2''-terpyridine-6,6''-diyl]bis(methylenenitrilo)tetrakis(acetate)-Eu(3+)/Tb(3+) ([Eu(3+)/Tb(3+)(DTTA)]), has been designed and synthesized. Both [Eu(3+)(DTTA)] and [Tb(3+)(DTTA)] are highly water soluble with large stability constants at approximately 10(20), and strongly luminescent with luminescence quantum yields of 10.0 and 9.9%, respectively, and long luminescence lifetimes of 1.38 and 0.26 ms, respectively. It was found that the luminescence of [Tb(3+)(DTTA)] could be quenched by ONOO(-) rapidly and specifically in aqueous buffers, while that of [Eu(3+)(DTTA)] did not respond to the addition of ONOO(-). Thus, by simply mixing [Eu(3+)(DTTA)] and [Tb(3+)(DTTA)] in an aqueous buffer, a ratiometric luminescence probe specific for time-gated luminescence detection of ONOO(-) was obtained. The performance of [Tb(3+)(DTTA)] and [Eu(3+)/Tb(3+)(DTTA)] as the probes for luminescence imaging detection of ONOO(-) in living cells was investigated. The results demonstrated the efficacy and advantages of the new ratiometric luminescence probe for highly sensitive luminescence bioimaging application.

Metal complexes possess unique tunable properties, such as radioactivity, cytotoxicity or photophysical features, enabling them to act as diagnostic tracers or therapeutic agents. In applying them in biological systems, it is often necessary to enhance their solubility and biocompatibility. To achieve such goals, like the targeting of binding domains, transport systems and enzyme activities, the attachment of carbohydrate moieties appears to be suitable. Sugar-substitution in the periphery of metal complexes has therefore become a strongly growing field of research. Outlined herein is a selection of recent examples.

A lanthanide complex, named CLaNP (caged lanthanide NMR probe) has been developed for the characterisation of proteins by paramagnetic NMR spectroscopy. The probe consists of a lanthanide chelated by a derivative of DTPA (diethylenetriaminepentaacetic acid) with two thiol reactive functional groups. The CLaNP molecule is attached to a protein by two engineered, surface-exposed, Cys residues in a bidentate manner. This drastically limits the dynamics of the metal relative to the protein and enables measurements of pseudocontact shifts. NMR spectroscopy experiments on a diamagnetic control and the crystal structure of the probe-protein complex demonstrate that the protein structure is not affected by probe attachment. The probe is able to induce pseudocontact shifts to at least 40 A from the metal and causes residual dipolar couplings due to alignment at a high magnetic field. The molecule exists in several isomeric forms with different paramagnetic tensors; this provides a fast way to obtain long-range distance restraints.