Cyanide ions are shown to interact with lanthanide complexes of phenacylDO3A derivatives in aqueous solution, giving rise to changes in the luminescence and NMR spectra. These changes are the consequence of cyanohydrin formation, which is favored by the coordination of the phenacyl carbonyl group to the lanthanide center. These complexes display minimal affinity for fluoride and can detect cyanide at concentrations less than 1 μm.
View Article and Find Full Text PDFAngew Chem Weinheim Bergstr Ger
September 2015
Yb⋅DTMA forms a ternary complex with fluoride in aqueous solution by displacement of a bound solvent molecule from the lanthanide ion. [Yb⋅DTMA⋅F] and [Yb⋅DTMA⋅OH] are in slow exchange on the relevant NMR timescale (<2000 s), and profound differences are observed in their respective NMR and EPR spectra of these species. The observed differences can be explained by drastic modification of the ligand field states due to the fluoride binding.
View Article and Find Full Text PDFLanthanide complexes of tetrapicolyl cyclen displayed remarkably high affinities for fluoride (log K≈5) in water, and were shown to form 1:1 complexes. The behaviour of these systems can be rationalised by changes to the magnitude of the crystal-field parameter, B20 . However, such changes are not invariably accompanied by a change in sign of this parameter: for early lanthanides, the N8 donor set with a coordinated axial water molecule ensures that the magnetic anisotropy has the opposite sense to that observed in the analogous dehydrated lanthanide complexes.
View Article and Find Full Text PDFA europium complex derived from NP-(DO3A)2 exhibits pH-dependent europium-centred luminescence following excitation of the nitrophenolate chromophore. Such behaviour is not observed with an analogous mononuclear complex, suggesting coordination of both lanthanide ions to the phenolate oxygen in the emissive species.
View Article and Find Full Text PDFThe importance of the directional dependence of magnetic susceptibility in magnetic resonance and of electric susceptibility in the optical spectroscopy of lanthanide coordination complexes is assessed. A body of more reliable shift, relaxation and optical emission data is emerging for well-defined isostructural series of complexes, allowing detailed comparative analyses to be undertaken. Such work is highlighting the limitations of the current NMR shift and relaxation theories, as well as emphasising the absence of a compelling theoretical framework to explain optical emission phenomena.
View Article and Find Full Text PDFFluoride binding by a series of europium and ytterbium complexes of DOTA-tetraamide ligands derived from primary, secondary and tertiary amides has been studied by NMR and luminescence spectroscopies. In all the systems studied, fluoride binding results in a change in the nature of the magnetic anisotropy at the metal centre from an easy axis, to an easy plane anisotropy. This results in reversal of the peaks in the NMR spectra, and in changes to the fine structure of the luminescence spectra.
View Article and Find Full Text PDFYb⋅DTMA forms a ternary complex with fluoride in aqueous solution by displacement of a bound solvent molecule from the lanthanide ion. [Yb⋅DTMA⋅F](2+) and [Yb⋅DTMA⋅OH2 ](3+) are in slow exchange on the relevant NMR timescale (<2000 s(-1) ), and profound differences are observed in their respective NMR and EPR spectra of these species. The observed differences can be explained by drastic modification of the ligand field states due to the fluoride binding.
View Article and Find Full Text PDFAddition of fluoride to aqueous solutions of lanthanide complexes of DTMA results in the formation of ternary complexes of the form [F·Ln·DTMA](2+) in which an axial solvent molecule is displaced by fluoride. [F·Ln·DTMA](2+) and [H2O·Ln·DTMA](3+) are in exchange on a timescale of around 1 s. Dramatic changes are observed in both the NMR and luminescence spectra of the complexes: these are consistent with a change in the nature of the magnetic anisotropy at the paramagnetic lanthanide centre, itself arising from a change in the local crystal field.
View Article and Find Full Text PDFStrong bidentate ligation between a fluorinated isophthalate and binuclear lanthanide-DO3A species yields a new class of (19)F NMR agent with very high nuclear relaxation rates at physiologically-relevant pH.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
October 2014
The first anion-templated synthesis of a lanthanide-containing interlocked molecule is demonstrated by utilizing a nitrite anion to template initial pseudorotaxane formation. Subsequent stoppering of the interpenetrated assembly allows for the preparation of a lanthanide-functionalized [2]rotaxane in high yield. Following removal of the nitrite anion template, the europium [2]rotaxane host is demonstrated to recognize and sense fluoride selectively.
View Article and Find Full Text PDFA study of the anion-binding properties of three structurally related lanthanide complexes, which all contain chemically identical anion-binding motifs, has revealed dramatic differences in their anion affinity. These arise as a consequence of changes in the substitution pattern on the periphery of the molecule, at a substantial distance from the binding pocket. Herein, we explore these remote substituent effects and explain the observed behaviour through discussion of the way in which remote substituents can influence and control the global structure of a molecule through their demands upon conformational space.
View Article and Find Full Text PDFWe report the preparation of [2]rotaxanes containing an electrochemically and optically active osmium(II) bipyridyl macrocyclic component mechanically bonded with cationic pyridinium axles. Such interlocked host systems are demonstrated to recognise and sense anionic guest species as shown by (1)H NMR, luminescence and electrochemical studies. The rotaxanes can be surface assembled on to gold electrodes through anion templation under click copper(I)-catalysed Huisgen cycloaddition conditions to form rotaxane molecular films, which, after template removal, respond electrochemically and selectively to chloride.
View Article and Find Full Text PDFThe self-assembly of higher order structures in water is realised by using the association of 1,3-biscarboxylates to binuclear meta-xylyl bridged DO3A complexes. Two dinicotinate binding sites are placed at a right-angle in a rhenium complex, which is shown to form a 1 : 2 complex with α,α'-bis(Eu·DO3A)-5-amino-m-xylene.
View Article and Find Full Text PDFThe first lanthanide cation-templated synthesis of an interlocked structure is demonstrated through an interpenetrated assembly between a pyridine N-oxide threading component coordinating to a lanthanide cation complexed within a macrocycle. Stoppering of the pseudo-rotaxane assembly allows for preparation of the [2]rotaxane.
View Article and Find Full Text PDFA heterotrimetallic tetranuclear lanthanide complex containing two dysprosium ions, a terbium ion and a europium ion has been prepared by coupling three kinetically stable complexes together using the Ugi reaction. The covalently linked trimetallic system exhibits luminescence from all the different lanthanide centres.
View Article and Find Full Text PDFBinuclear lanthanide complexes consisting of two lanthanide binding domains in kinetically stable DO3A binding pockets linked by a 3-functionalized meta-xylyl bridge form stable 1:1 adducts with isophthalate and dinicotinate in water. The influence of buffer, pH and ligand structure on the binding of dinicotinate has been investigated.
View Article and Find Full Text PDFPhys Chem Chem Phys
October 2012
Thulium salts and complexes are shown to be emissive from three states in the excited state manifold of Tm(3+). Formation of the (1)D(2) state can result in luminescence, or in energy transfer to the lower energy (1)G(4) and (3)H(4) emissive states. Where chromophores are present in the ligand structure, emission is restricted to thulium centred emissive states that are lower in energy than the chromophore centred donor state.
View Article and Find Full Text PDFA large series of complexes has been synthesized with two chelating, Schiff base azobenzene derivatives connected linearly by coordination to a central nickel(II) or palladium(II) ion. These compounds have the general formulas M(II)(OC(6)H(3)-2-CHNR-4-N═NC(6)H(4)-4-CO(2)Et)(2) [M = Ni; R = n-Bu (3c), n-C(6)H(13) (3d), n-C(8)H(17) (3e), n-C(12)H(25) (3f), Ph (3g), OH (3h), C(6)H(4)-4-CO(2)Et (3i). M = Pd; R = i-Pr (4a), t-Bu (4b), n-Bu (4c), n-C(6)H(13) (4d), n-C(8)H(17) (4e), n-C(12)H(25) (4f), Ph (4g)], M(II)[OC(6)H(3)-2-CHN(n-C(8)H(17))-4-N═NC(6)H(4)-4-CO(2)(n-C(8)H(17))](2) [M = Ni (9), Pd (10)], M(II)[OC(6)H(3)-2-CHN(n-C(8)H(17))-4-N═NC(6)H(4)-4-C(6)H(4)-4-O(n-C(7)H(15))](2) [M = Ni (14), Pd (15)], and M(II)[OC(6)H(3)-2-CHN(CMe(2))-4-N═NC(6)H(4)-4-CO(2)Et](2) [M = Ni (17), Pd (18); the CMe(2) groups are connected].
View Article and Find Full Text PDFThe complete molecule of the title compound, C(20)H(32)N(2)O(6), is generated by crystallographic inversion symmetry. The two mutually trans nitro substituents are hence in fully eclipsed conformation and also twisted by 43.2 (2)° with respect to the phenyl ring plane.
View Article and Find Full Text PDF1,3-Bis(1-pyrazolyl)-5-methyl-benzene, HL(2), undergoes cyclometalation at the C(2) position upon reaction with K(2)PtCl(4), to generate an N=C=N-coordinated complex, PtL(2)Cl. This compound is luminescent in degassed solution at 298 K, emitting in the blue region of the spectrum on the microsecond time scale (lambda(max) = 453 nm, tau = 4.0 micros, Phi(lum) = 0.
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