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Complexes of Cu(ii) with studied ligands show very short NMR longitudinal relaxation times T1 of 19F nuclei and good T2*/T1 ratio. Thus, Cu(ii) can be considered as a suitable metal ion for the design of efficient 19F MRI/NMR relaxation agents.

The synthesis and photophysical evaluation of a series of hydrophilic sulphonated and pH responsive luminescent europium(III) probes are reported. The Eu emission intensities and lifetimes increase very significantly on lowering pH, leading to a ‘switching on’ of Eu luminescence in more acidic media. By varying the nature of the substituents at an integral aniline nitrogen atom located in the sensitising chromophore, the pKa value of the complex can be tuned to between 4.3 and 6.3 for a set of five Eu(III) complexes. These systems are designed to allow conjugation to targeting vectors permitting, for example, the monitoring of receptor internalisation in cells. This approach can be used to tag proteins selectively and allows the monitoring of uptake into acidic organelles, enabling the creation of time-resolved internalisation assays to follow pH change in real time, both in vitro and in cellulo.

Progress in the selective binding and detection of magnesium ions has been slower than other biologically important divalent metal ions like calcium and zinc. The most widely used ligands for Mg2+ are by no means optimal, as they are not selective for it. Nevertheless, Mg2+ is a major cation in all cells, with physiologically critical functions. There is a need for improved sensors for Mg2+. In this review, we consider how an appreciation of fundamental coordination chemistry principles may inform the development of new ligands for Mg2+. A number of representative examples of ligands of differing denticity are discussed in this context. Low-denticity ligands such as β-keto acids offer the best selectivities, but speciation is an issue as other polydentate ligands such as pyrophosphate may complete the coordination sphere. High-denticity ligands based on aminocarboxylates such as APTRA typically offer the highest stability constants, but they bind Ca2+ and Zn2+ more strongly than Mg2+. We highlight recent examples featuring related aminophosphinates, where the longer bonds and smaller bite angles favour selectivity towards Mg2+. Macrocyclic receptors for magnesium are not discussed explicitly.

A series of four emissive europium complexes has been evaluated for the binding of glyphosate in various aqueous media, including river water and grain extracts. Binding selectivity toward inorganic phosphate and bicarbonate was enhanced by measuring samples at pH 5.9, above the pKa of glyphosate itself. The highest affinity was shown with [Eu·L1], which creates an exocyclic tripicolylamine moiety when one pyridine group dissociates from Eu. Glyphosate was bound selectively over dihydrogenphosphate, glycinate, aminomethylphosphonate and the related herbicide glufosinate. The complex was used to measure glyphosate over the range 5 to 50 μM, in river water and grain extracts.

Ytterbium and yttrium complexes of octadentate ligands based on 1,4,7,10-tetraazacyclododecane with a coordinated pyridyl group and either tricarboxylate (L1) or triphosphinate (L2) donors form twisted-square-antiprismatic structures. The former crystallizes in the centrosymmetric group P21/c, with the two molecules related by an inversion center, whereas the latter was found as an unusual kryptoracemate in the chiral space group P21. Pure shift NMR and EXSY spectroscopy allowed the dynamic exchange between the (RRR)-Δ-(δδδδ) and (RRR)-Λ-(λλλλ) TSAP diastereomers of the [Y.L2] complex to be detected. The rate-limiting step in the exchange between Δ and Λ isomers involves cooperative ligand arm rotation, which is much faster for [Ln.L1] than for [Ln.L2]. Detailed analysis of NOESY, COSY, HSQC, and HMBC spectra confirms that the major conformer in solution is (RRR)-Λ-(λλλλ), consistent with crystal structure analysis and DFT calculations. The magnetic susceptibility tensors for [Yb.L1] and [Yb.L2], obtained from a full pseudocontact chemical shift analysis, are very different, in agreement with a CASSCF calculation. The remarkably different pseudocontact shift behavior is explained by the change in the orientation of the pseudocontact shift field, as defined by the Euler angles of the susceptibility tensor.

Knowledge of the crystal structure of a monometallic inorganic molecule is often sufficient to calculate its electronic structure and interpret its magnetic properties. Here we show that for a series of nine-coordinate lanthanide complexes based on the 1,4,7-tris[(6-carboxypyridin-2-yl)methyl]-1,4,7-triazacyclononane ligand, the electronic structure is hypersensitive to geometric structure and to the presence of non-coordinated lattice solvent, which renders the magnetic and spectroscopic properties very difficult to interpret. We explore possible explanations for the peculiar electron paramagnetic resonance (EPR) spectra and conclude that a number of entangled factors are at play across the samples, and hence that great care should be taken in the interpretation of EPR spectra for systems with small magnetic anisotropy, even when the molecular structure is known.

The hypersensitive 2F5/2 to 2F7/2 transition of Yb3+ can be used to monitor perturbations of the coordination sphere in ytterbium(iii) complexes. An envelope of Stark components gives rise to a relatively broad and asymmetric emission band, whilst changes in their relative intensity and energy enable a ratiometric response. We report a new ytterbium complex with a sulphonamide arm that binds reversibly to Yb3+ as a function of pH, giving rise to significant pH dependent changes in the Yb emission spectrum.

Paramagnetic metal ions with anisotropic magnetic susceptibilities can shift the proton NMR signals of chelating ligands beyond the diamagnetic range of endogenous proton resonances. Such large shifts, along with enhanced longitudinal relaxation rates, allow paramagnetic complexes to be exploited as molecular imaging probes for MRI. Paramagnetically-shifted imaging probes are detected directly against zero background, as opposed to the indirect induced relaxation enhancement of surrounding water molecules, and are reviewed herein. The development of ‘smart’ probes that are sensitive to their surrounding environment is also being developed, and some of the challenges faced for in vivo imaging are discussed, including issues of sensitivity and dose, biodistribution and clearance. Several examples of lanthanide complexes have been investigated, and more recently certain paramagnetic transition metal complexes are being considered as potential imaging agents.

Funding from ERC (266804), EPSRC (EP/R013705/1, EP/M508214/1), Carnegie Trust (RIG007510), Wellcome Trust for a Multi-User Equipment Grant (099149/Z/12/Z), and the Royal Society for a University Research Fellowship to JEL. The design, synthesis, and application of a nine-coordinate gadolinium(III)-containing spin label, [Gd.sTPATCN]-SL, for use in nanometer-distance measurement experiments by EPR spectroscopy is presented. The spin label links to cysteines via a short thioether tether and has a narrow central transition indicative of small zero-field splitting (ZFS). A protein homodimer, TRIM25cc, was selectively labeled with [Gd.sTPATCN]-SL (70%) and a nitroxide (30%) under mild conditions and measured using the double electron electron resonance (DEER) technique with both commercial Q-band and home-built W-band spectrometers. The label shows great promise for increasing the sensitivity of DEER measurements through both its favorable relaxation parameters and the large DEER modulation depth at both Q- and W-band for the inter-Gd(III) DEER measurement which, at 9%, is the largest recorded under these conditions. Postprint

In three structurally related series of nine-coordinate lanthanide(iii) complexes (Ln = Tb, Dy, Ho, Er, Tm and Yb) based on triazacyclononane, solution NMR studies and DFT/CASSCF calculations have provided key information on the magnetic susceptibility anisotropy. Both experimental and computational approaches have revealed a poor correlation to Bleaney's theory of magnetic anisotropy. CASSCF calculations suggested that the magnetic susceptibility is very sensitive to small geometric variations within the first coordination sphere, whereas DFT analyses indicate that it is the thermal accessibility of low energy vibrational modes that may lead to distortion. Parallel NMRD and EPR studies on the three Gd(iii) complexes revealed good correspondence in estimating the electronic relaxation time. The Gd(iii) tris-pyridinecarboxylate complex possesses a very long electronic relaxation time making it a promising starting point for responsive gadolinium EPR probe design.

o-Aminophenol-N,N,O-triacetate, known as APTRA, is one of the most well-established ligands for targeting magnesium ions but, like other aminocarboxylate ligands, it binds Ca2+ much more strongly than Mg2+. The synthesis of an O-phosphinate analogue of APTRA is reported here, namely o-aminophenol-N,N-diacetate-O-methylene-methylphosphinate, referred to as APDAP. Metal binding studies monitored using UV-visible spectroscopy show that the affinity of APDAP for Ca2+ is reduced by over two orders of magnitude compared to APTRA, and for Zn2+ by over three orders of magnitude, whereas the affinity for Mg2+ is attenuated to a much lesser extent, by a factor of only about 7. The selectivity towards Mg2+ is thus substantially improved. DFT calculations support the notion that longer P–O and P–C bonds in APDAP (compared to corresponding C–O and C–C bonds in APTRA) favour a larger angle at the metal, an effect that is less unfavourable for smaller ions like Mg2+ than for larger ions such as Ca2+. Derivatives of APDAP can be anticipated that will offer improved sensing of Mg2+ in the presence of Ca2+, in the physiologically important millimolar concentration range.

Diphenylethylene (DPE) is a monomer which has attracted significant interest from both academia and industry. DPE can undergo (co)polymerization by living anionic polymerization but is incapable of forming a homopolymer due to steric hindrance. Herein the copolymerization of DPE and 1,1-bis(4-tert-butyldimethylsiloxyphenyl)ethylene (DPE-OSi) with styrene or butadiene is described in order to produce (functional) copolymers with controlled comonomer sequences—either alternating or telechelic. The copolymer sequences are inherently controlled by relative reactivity ratios, which in turn can be tuned by both monomer structure and the polarity of the polymerization solvent. The compositions of the copolymers prepared in this study were analyzed by 1H NMR spectroscopy and MALDI ToF mass spectrometry, the latter offering a unique opportunity to demonstrate perfect alternating sequences and insight into other sequences such as telechelic polymers.

The design principles, mechanism of action and performance of europium(III) complexes that serve as strongly emissive and responsive molecular probes in water are critically discussed. Examples of systems designed to assess pH, selected metal ions and anions, including chiral species, as well as selected small molecules and biopolymers are considered, and prospects evaluated for improved performance in more complex biological media such as in bio-fluids and within living cells. Modulation of the emission spectral form, lifetime and degree of circular polarisation can be used to quantify the spectral response and permit calibration.

The development of 68Ge/68Ga generators has made the positron-emitting 68Ga isotope widely accessible and raised interest in new chelate complexes of Ga3+. The hexadentate 1,4-di(acetate)-6-methyl[amino(methyl)acetate]perhydro-1,4-diazepane (DATAm) ligand and its bifunctional analogue, 1,4-di(acetate)-6-pentanoic acid[amino(methyl)acetate]perhydro-1,4-diazepane (DATA5m), rapidly form complexes with 68Ga in high radiochemical yield. The stability constants of DATAm and DATA5m complexes formed with Ga3+, Zn2+, Cu2+, Mn2+ and Ca2+ have been determined by using pH potentiometry, spectrophotometry (Cu2+) and 1H and 71Ga NMR spectroscopy (Ga3+). The stability constants of Ga(DATAm) and Ga(DATA5m) complexes are slightly higher than those of Ga(AAZTA). The species distribution calculations indicated the predominance of Ga(L)OH mixed-hydroxo complexes at physiological pH. The 1H and 71Ga NMR spectroscopy studies provided information about the coordinated functional groups of ligands and on the kinetics of exchange between the Ga(L) and Ga(L)OH complexes. The transmetalation reactions between the Ga(L) complexes and Cu2+ citrate (6

Two bright, europium(III) complexes based on an achiral heptadentate triazacyclononane ligand bearing two strongly absorbing chromophores have been evaluated for the selective emission and CPL signalling of various chiral O-phosphono-anions. Binding of O-phosphono-Ser and Thr gives rise to a strong induced CPL signature and a favoured Δ complex configuration is adopted. A similarly large induced CPL signal arises when [Eu·L1]2+ binds to lysophosphatidic acid (LPA), where the strong binding (log K 5.25 (295 K)) in methanol allowed its detection over the range 5 to 40 μM. Strong and chemoselective binding to the phosphorylated amino-acid residues was also observed with a set of four structurally related hexapeptides: in one case, the sign of the gem value in the ΔJ = 1 transition allowed differentiation between the binding to O-P-Ser and O-P-Tyr residues.

The 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.

A series of Eu and Tb complexes of four different chiral ligands incorporating an azaxanthone sensitiser has been evaluated as probes for the bicarbonate anion. Their binding affinities were assessed at ambient pH with bicarbonate, lactate, citrate, phosphate and serum albumin. Binding was signalled by modulation of circularly polarised luminescence and apparent affinity constants were measured by examining changes in emission intensity ratios. Competition experiments show that with these species and ATP present at normal physiological values, bicarbonate can be determined selectively over the concentration range 10 to 35 mM. Bicarbonate levels are also reported by using a mixture of Eu and Tb complexes of a common ligand, examining the ratio of red/green emitted light. These methods have been adapted for the determination of bicarbonate in human serum and used for the assessment of mitochondrial levels of bicarbonate in several different cell types with confocal microscopy.

Paramagnetic magnetic resonance chemical shift probes containing a proximal CF(3) group have been characterised. Different systems have been created that report reversible changes in calcium ion concentrations in the millimolar regime, signal the presence of citrate selectively in competitive aqueous media and allow the monitoring of remote ester/amide hydrolysis in relayed, irreversible transformations. Chemical shift non-equivalence is amplified by the presence of the proximate lanthanide ion, with a mean separation between the CF(3) group and the metal ion of 6.4 Å found for a thulium complex, in an X-ray structure of the metal complex aqua adduct. The enhanced rate of longitudinal relaxation of the (19)F nucleus allows faster data acquisition.

For the first time a series of anionic surfactant ionic liquids (SAILs) has been synthesized based on organic surfactant anions and 1-butyl-3-methyl-imidazolium cations. These compounds are more environmentally friendly and chemically tunable as compared to other common ionic liquids. A detailed investigation of physicochemical properties highlights potential applications from battery design to reaction control, and studies into aqueous aggregation behavior, as well as structuring in pure ILs, point to possible uses in electrochemistry.

The physicochemical basis of probe design for 19F MRS and MRI applications is reviewed. Complexes that give a single major resonance in solution are described, in which the Ln3+ ion is about 6 A from the 19F label. Sensitivity improvements of 15-fold are reported in both imaging and spectroscopy based on longitudinal relaxation enhancement. The pseudocontact shift allows an amplification of chemical shift non-equivalence in responsive 19F probes, e.g. for monitoring pH in the range between 5 and 8.

The synthesis and spectral properties are reported of a set of four europium(III) complexes containing between one and four 3-azaxanthone sensitising chromophores. Each complex is based on a macrocyclic cyclen core. The emission and aqueous solution 1 H NMR spectral properties are compared, revealing information about the local complex symmetry on the experimental timescale. A C 2 -symmetric mono-cationic complex shows an overall emission quantum yield of 10 % in HEPES buffer and exhibits the best relative stability profile in the presence of a million-fold excess of added metal salts or EDTA, as indicated by the time-dependence of overall europium emission, following indirect excitation of the 3-azaxanthone chromophore.

A series of seven emissive europium(III) and terbium(III) complexes was prepared, incorporating a 3-pyridyl-4-azaxanthone or 3-pyrazolyl-4-azaxanthone sensitising moiety within a polydentate macrocyclic ligand. High overall emission quantum yields in aqueous media are attenuated in the presence of protein or certain oxy anions due to displacement of the N,N′-chelated sensitiser. Nevertheless, these complexes are taken into cells and tend to localise over the first few hours in mitochondria before being trafficked to endosomal compartments. Cell uptake studies, in the presence of competitive inhibitors or promoters of well-defined uptake pathways, reveal a common uptake mechanism involving macropinocytosis.

New Cu II and Ni II complexes of potentially tridentate N 2 O Schiff base ligands 1 and 2 have been synthesised and characterised. [Cu( 2 )(OH 2 )] + possesses a square planar geometry in the solid state whereas [Ni( 1 ) 2 ] possesses a distorted octahedral geometry in which the amine donors of 1 coordinate weakly to the Ni II centre. EPR spectroscopy demonstrates that the N 2 O 2 coordination sphere of [Cu( 2) (OH 2 )] + is retained in CH 2 Cl 2 solution. [Cu( 2) (OH 2 )] + exhibits a reversible one electron oxidation at E 1/2 = 0.54 V versus [Fc] + /[Fc], the product of which has been characterised by UV–Vis absorption and EPR spectroscopies. The spectroscopic signature of the oxidised product is consistent with the formation of a stable phenoxyl radical ligand bound to a Cu II centre. [Ni( 1 ) 2 ] possesses a reversible metal-based oxidation process at E 1/2 = 0.03 V versus [Fc] + /[Fc] and a further oxidation, attributed to the generation of a phenoxyl radical centre, at E p a = 0.44 V versus [Fc] + /[Fc]. UV–Vis absorption and EPR spectroscopic studies indicate that the lower potential process is a formal Ni III/II couple. In contrast, the pro-ligands 1H and 2H exhibit chemically irreversible oxidation processes at E p a = 0.42 and 0.40 V versus Fc + /Fc, respectively, and do not support the formation of stable phenoxyl radical species.

Using recognition moieties that bind to the inner co-ordination sphere of a monomeric DO3A-type di-aqua complex, dimeric poly(aminocarboxylate) gadolinium(III) compounds can be formed with greatly enhanced relaxivities, arising from optimized contributions of inner- and second spheres of hydration.

We study the melt rheology of randomly branched polymers in the hyperbranched polymer (HBP) class which are formed by the co-condensation of AB and AB2 type monomers. Specifically, we study the effect of branch length Mx on the entanglement transition in the HBP class. To this end, two series of HBPs were prepared using AB2 mole fractions of 10% and 1% respectively. This allowed us to vary Mx from just below to just above Me, the entanglement molecular weight for linear chains of the same chemistry. For the 10% branched samples (Mx Me), there is a clear entanglement plateau for the higher molecular weight samples and we were able to quantitatively model the rheology around the entanglement plateau region using the tube model. Our data demonstrate conclusively that the entanglement transition for randomly branched polymers in the HBP clas...

The development of the brightest luminescent europium(III) complexes is traced, including analysis of the C3-symmetric core complex based on a functionalized triazacyclononane and identification of the most suitable strongly absorbing chromophore. Strategies for the synthesis of the complexes, including enantiopure analogues, are outlined and opportunities for applications in time-resolved microscopy and spectral imaging emphasised. Practicable examples are introduced, including selective organelle staining for cellular optical imaging at 65 nm resolution and the development of new bioassays using time-resolved FRET methods.

The binding of a series of phosphate anions to coordinatively unsaturated macrocyclic complexes of Yb, Tm, and Eu was studied by 1H-NMR, emission and circularly polarized luminescence (CPL) spectroscopy. Each ternary adduct was distinguished by its spectral profile. With O-phosphorylated amino acids and peptides, chemoselective ligation of the phosphate moiety was favored by Eu over chelation involving the terminal amino group, which was competitive for Tm and Yb. A preference for binding O-phosphono-L-tyrosine sites was found with various Eu complexes, and was signalled by ratiometric changes in metal-based emission and CPL spectra.

A detailed investigation of the nature of the binding of each of the 20 common alpha-amino acids and various selected dipeptides to a chiral, diaqua-ytterbium complex in aqueous solution has been carried out. Analysis of the dipolar 1H NMR paramagnetic shifts suggests that the alpha-amino acids form a common chelated structure within a nine-coordinate mono-capped square antiprismatic coordination environment, with the amine N axially disposed. Crystal structures of nine chelated YbL1-amino acid adducts (Gly, Ala, Ser, Thr, Met) confirm this. The ternary complexes with dipeptides (e.g. Gly-Ala, Gly-Ser, Gly-Met, Gly-Asp, Gly-Asn, Gly-His, Ser-Met, Asp-Phe, His-Gly) also favour the terminal amine as the axial donor with the proximate amide group binding to generate a five-ring chelate. Evidence for chelation through side-chain functionality was found only in the case of N-terminal Asp. The chiral environment about the ytterbium ion upon amino acid binding has also been probed using near-IR circular dichroism spectroscopy.

The structures of 10 isomorphous lanthanide (Ln) complexes of a chiral DOTA tetra-amide ligand (L(1)), [LnL(1)(H(2)O)](CF(3)SO(3))(3).3H(2)O, crystallizing in space group P2(1), have been studied by single-crystal X-ray diffraction. The Ln coordination is a O(4)N(4) square antiprism, the O(4) base of which is capped by an aqua ligand. The sterically demanding position of the latter results in the lengthening of the Ln-OH(2) distance along the Pr to Lu series by 0.06 A (after allowing for the lanthanide contraction). In parallel, the distance between the bound water oxygen and the second-sphere water oxygen is reduced from 3.17 A (Pr) to 3.04 A (Lu), consistent with the enhanced hydrogen bond acceptor ability of the coordinated water oxygen across the series. A Cambridge Structural Database survey of [Ln(H(2)O)(9)](CF(3)SO(3))(3) salts (space group P6(3)/m) and of six reported isostructural complexes of DOTA [L(2)] revealed a similar trend. The implications of the resultant destabilization of the ground state structure for the water interchange process are discussed.

The 1 H and 1 7 O NMR relaxometric properties of two cationic complexes formed by Gd I I I with a macrocyclic heptadentate triamide ligand, L 1 , and its N-methylated analogue, L 2 , have been investigated in aqueous media as a function of pH, temperature and magnetic field strength. The complexes possess two water molecules in their inner coordination sphere for which the rate of exchange has been found to be sensibly faster for the N-methylated derivative and explained in terms of electronic effects (decrease of the charge density at the metal center) and perturbation of the network of hydrogen-bonded water molecules in the outer hydration sphere. The proton relaxivity shows a marked dependence from pH and decreases of about six units in the pH range 6.5 to 9.0. This has been accounted for by the displacement of the two water molecules by dissolved carbonate which acts as a chelating anion. The formation of ternary complexes with lactate, malonate, citrate, acetate, fluoride and hydrogenphosphate has been monitored by 1 H NMR relaxometric titrations at 20 MHz and pH 6.3 and the value of the affinity constant, K, and of the relaxivity of the adducts could be obtained. Lactate, malonate and citrate interact strongly with the complexes (log K ≥ 3.7) and coordinate in a biden-date mode by displacing both water molecules. Larger affinity constants have been measured for GdL 2 . Acetate, fluoride and hydrogenphosphate form monoaqua ternary complexes which were investigated in detail with regard to their relaxometric properties. The NMR dispersion (NMRD) profiles indicate a large contribution to the relaxivity of the adducts from water molecules belonging to the second hydration shell of the complexes and hydrogen-bonded to the anion. A VT 1 7 O NMR study has shown a marked increase of the rate of water exchange upon binding which is explained by coordination of the anion in an equatorial site, thus leaving the water molecule in an apical position, more accessible for interactions with the solvent molecules of the second hydration shell which facilitate the exchange process.

In Bleaney's theory of magnetic anisotropy, the second-order crystal field coefficient, Bo2, is predicted to determine the dipolar NMR shift of paramagnetic lanthanide complexes in solution. This parameter has been measured directly, by analysing the europium emission spectra for a series of eight- and nine-coordinate axially symmetric complexes based on cyclen including aza-carboxylate ligands (e.g. DOTA), phosphonates (DOTP), phosphinates and several carboxamides (e.g. DOTAM). For both Yb and Eu complexes with a common coordination number and geometry (square antiprism (SAP) or twisted square antiprism (TSAP)), the dipolar NMR shift correlates very well with this parameter, which also determines the sign and magnitude of a major CD band in the near-IR CD spectra of a series of enantiopure Yb complexes. Measurements of the free energy change associated with axial ligand exchange in a cationic europium tetraamide complex, [Eu(DOTAMPh)](CF3SO3)3 supported by a simple electrostatic perturbation model, have been interpreted in terms of a predominant donor atom polarisation model which affords a simple assessment of Ln ion donor atom preference and ranks the axial second-order ligand field coefficient.

We study the melt rheology and molecular weight distribution of four short chain branched hyperbranched polyesters with different molecular weights and containing branched monomers of various alkyl chain lengths n (2 → 4; n is the number of CH2 groups in the alkyl chain). We find that the molecular weight distribution for all our samples obeys the static scaling form n(M) ∼ M- τexp(−M/Mchar) where n(M) is the number density of hyperbranched polymers with mass M, Mchar is the largest characteristic molecular weight, and τ is the polydispersity exponent. The values of τ for all our samples (either 1.35 or 1.55) are close to but not the same as the mean field value of τ = 1.5, a consequence of the fact that our polymers were synthesized under non-mean-field polycondensation conditions. For all our samples, we found that the rheology at low and intermediate frequencies could be modeled accurately using a dynamic scaling theory based on the Rouse model. This confirms that these hyperbranched polymers behave as...

Macrocyclic polystyrene (PS) was synthesized by initiation of styrene by naphthalide anion or benzylic dianions in the presence of Li or K ions followed by reaction of the resulting PS dianions with dibromomethane (DBM) or 1,4-bis(bromomethylbenzene) (DBX) in THF at −78 °C under high dilution conditions. MALDI and NMR studies of the DBM cycles showed the presence of 1,2-diphenyl linkages. Fluorescence studies on the DBM cycles show strongly enhanced and anomalous structured emission bands between 300 and 320 nm attributable to linear chains containing styrenic chain end impurities. This indicates rapid metal bromine exchange to give chain end benzyl bromides that eliminate with polystyryl anion to give small (

Emission from a bright europium(III) complex, based on a 1,4,7-triazacyclononane ring bearing an alkyliminodiacetate group, is modulated only when in the presence of zinc(II) ions and a carboxylate anion and was characterised by ratiometric luminescence analysis at pH 7.4. No change in emission spectral form was observed when either the metal ion or oxy-anion was added separately. Amongst the diamagnetic systems examined, the strongest binding was observed for zinc and citrate (log K = 3.9, pH 7.4) and anion selectivity was observed in the order citrate > lactate/acetate/bicarbonate. No changes in the Eu spectral characteristics were found in the presence of added Ca2+ or Mg2+ ions, consistent with the much lower affinity of these cations for the iminodiacetate binding site.

The configuration of the remote amide chiral moiety determines the helicity of the metal complex in Ln(III) complexes of nonadentate N6O3 ligands based on triazacyclononane. Solution NMR studies revealed the presence of a dominant isomer whose proportion varies from 9 : 1 to 4 : 1 from Ce to Yb and X-ray crystallographic studies at 120 K of the Yb and two enantiomeric Eu complexes confirmed the configuration as S-Δ-λ in the major isomer. Global minimisation methods allowed magnetic susceptibility and electronic relaxation times of the lanthanide ions to be estimated by analysis of variable field longitudinal relaxation rate (R1) data sets. A set of four europium complexes, containing different para-substituted pyridinyl-aryl groups, exist as one major isomer (15 : 1), and absorb light strongly via an ICT transition in the range 320 to 355 nm (ε = 55 to 65,000 M(-1) cm(-1)). The two examples absorbing light at 332 nm, possess overall emission quantum yields of 35 and 37% in aerated water, making these systems as bright as any Eu complex in solution.

The synthetic utility of europium complexes with three coordinated 4-bromopyridyl groups for chromophore elaboration has been assessed in palladium-catalysed Sonogashira coupling reactions, and in copper(i) mediated click reactions of the triazide derivative, generated in situ. The crystal structure of the Eu complex of a p-OMe-phenyl substituted triazole at 100 K is reported in which the pendant triazole sensitising moieties interdigitate in the solid-state lattice. The triazole complex can be separated into Δ and Λ enantiomers by chiral HPLC but is weakly emissive in methanol (ε 5.5 mM(-1) cm(-1); λexc 320 nm; ϕ 0.2%), contrasting with a set of four alkynyl-aryl derivatives which are one thousand times brighter and absorb strongly with broad absorption maxima in the range 332 to 360 nm. An enantiopure europium complex gives an intense CPL signal in solution that is the strongest yet reported.

Medium molecular weight glycol chitosan conjugates have been prepared, linked by an amide bond to paramagnetic Gd(III), Ho(III) and Dy(III) macrocyclic complexes in which a trifluoromethyl reporter group is located 6.5 Å from the paramagnetic centre. The faster relaxation of the observed nucleus allows modified pulse sequences to be used with shorter acquisition times. The polydisperse materials have been characterised by gel permeation chromatography, revealing an average molecular weight on the order of 13,800 (Gd), 14,600 (Dy) and 16,200 (Ho), consistent with the presence of 8.5, 9.5 and 13 complexes, respectively. The gadolinium conjugate was prepared for both a q = 1 monoamide tricarboxylate conjugate (r1p 11.2 mM(-1) s(-1), 310 K, 1.4 T) and a q = 0 triphosphinate system, and conventional contrast-enhanced proton MRI studies at 7 T were undertaken in mice bearing an HT-29 or an HCT-116 colorectal tumour xenograft (17 μmol/kg). Enhanced contrast was observed following injection in the tail vein in tumour tissue, with uptake also evident in the liver and kidney with a tumour-to-liver ratio of 2:1 at 13 min, and large amounts in the kidney and bladder consistent with predominant renal clearance. Parallel experiments observing the (19)F resonance in the holmium conjugate complex using a surface coil did not succeed owing to its high R2 value (750 Hz, 7 T). However, the fluorine signal in the dysprosium triphosphinate chitosan conjugate [R1/R2 = 0.6 and R1 = 145 Hz (7 T)] was sharper and could be observed in vivo at -65.7 ppm, following intravenous tail vein injection of a dose of 34 μmol/kg.

The molecular weight of hyperbranched polyesters, prepared by condensation polymerization of the AB2 monomer dimethyl 5-(2-hydroxyethoxy)isophthalate in the presence of either a B3 core (trimethyl 1,3,5-benzenetricarboxylate) or a B2 core (dimethyl isophthalate), was controlled by varying the core-to-monomer ratio. During polymerization polycondensation, cyclization and core-termination reactions occurred in competition. The polyester's weight-average molecular weight continued to increase even after complete consumption of the A groups by cyclization and core termination, which is postulated to result from a redistribution of polymer chains by ester−ester interchange reactions. The polymers are soluble in common organic solvents, and solutions have characteristically low intrinsic viscosities. The physical characterization of these polymers is reported.

The solution and solid-state structures of a Dy(III) complex with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetryltetramethylenetetra(benzylphosphinate) have been examined by means of circularly polarized luminescence spectroscopy and crystallographic methods. The spectroscopic measurements show that the complex occurs in solution as enantiomeric pairs that do not racemize on the luminescence time-scale. It is also demonstrated that the complex crystallizes in two different unit cells, even though no significant intramolecular differences in the arrangement of the ligand around the central Dy(III) ion were evident.

The Eu(III), Tb(III) and Y(III) complexes of an eight-coordinate ligand containing a pendant dansylamidoethyl group were synthesised. Reversible intramolecular binding of the dansylamide nitrogen was demonstrated by UV absorption and luminescence pH titration, although no sensitisation of the Eu(III) or Tb(III) luminescent emission was seen due to lack of population of the chromophore triplet state. However, sensitisation of Eu(III) was achieved by protonation of the dimethylamino group on the naphthyl ring. Deprotonation constants of the dimethylamino (p K a1 ) and dansylamido (p K a2 ) group were determined in 0.1 M NaCl. Values of p K a1 3.9 (ligand), 3.6 (Eu), 3.7 (Tb), 3.8 (Y) and p K a2 (log K MLH ) 10.8 (ligand), 5.8 (Eu), 6.0 (Tb), 6.2 (Y) were obtained.

The melt condensation polymerization of the AB2 monomer dimethyl 5-(2-hydroxyethoxy)isophthalate exhibits unusual molecular weight growth characteristics. The number-average molecular weight (Mn) reaches a plateau value after a relatively short polymerization time, whereas the weight-average molecular weight (Mw) continues to increase. The maximum in Mn is thought to be a consequence of intramolecular cyclization reactions, evidence of which is provided by MALDI-TOF MS. It is postulated that the continual increase in weight-average molecular weight, even after complete cyclization, is due to a redistribution of polymer chains by ester interchange reactions. The polymers are soluble in common organic solvents, and solutions have characteristically low intrinsic viscosities. The degree of branching, as determined by quantitative 13C NMR spectroscopy, is consistent with the theoretical value for a statistical distribution at high conversion. The physical characterization of these polymers is reported.

Reversible anion binding in aqueous media at chiral EuIII and TbIII centers has been characterized by 1H NMR and by changes in the emission intensity and circular polarization following direct or sensitized (365 nm) excitation via an alkylphenanthridinium chromophore. Using a series of heptadentate tri-amide or polycarboxylate ligands, the affinity for CO32-/HCO3-, phosphate, lactate, citrate, acetate, and malonate at pH 7.4 was found to decrease as a function of the overall negative charge on the complex: citrate and malonate bound most strongly, and lactate and hydrogen carbonate also formed chelated ternary complexes in which displacement of both of the metal-bound water molecules occurred, which was confirmed by VT 17-O NMR measurements of the corresponding Gd complexes. The binding of carbonate was studied in particular, and 1H NMR and CPL data were obtained that were consistent with the formation of a complex with a reduced helical twist about the metal center. Monohydrogen phosphate was bound in a...

Stable lanthanide complexes have been devised in which the emission intensity or lifetime is a sensitive function of pH, pO2 or halide concentration following excitation in the range 350–380 nm. The pH-dependent systems report the pKa of the excited singlet or triplet of an integral phenanthridine chromophore. Modulation of the emission may occur via ligand or metal-centred processes: quenching of the singlet or triplet phenanthridine excited state occurs by halide and oxygen respectively; in complexes with chiral heptadentate ligands displacement of bound water molecules by lactate, phosphate and hydrogencarbonate leads to enhancements in the emission intensity and lifetime and pronounced changes in emission polarisation.

Two pentadentate tribasic ligand systems containing aniline or benzylamine nitrogens covalently linked to a proximate kinetically stable Eu or Tb complex are described. The affinity of these complexes and their non-conjugated analogues for Zn2+, Ca2+ and Mg2+ ions has been measured at ambient pH in a high salt background. Apparent binding constants for the parent ligands (L1: Zn2+ log βML 5.04, Ca2+ 3.91, Mg2+ 2.1, L3: Zn2+ 5.93, Ca2+ 5.00, Mg2+ 3.60) were slightly lowered in the aniline-based terbium conjugate [TbL4], and were the same for the benzylamine-based conjugate [LnL2], except for zinc binding for which a slightly enhanced affinity was observed. Changes in the form of ligand absorption and emission spectra and in the intensity of delayed lanthanide luminescence characterised metal ion binding. With [LnL2], a 42 and 26% increase in emission at 700 nm (Eu) and 545 nm (Tb) accompanied zinc binding in a simulated extracellular background, with an apparent dissociation constant of 0.6 μM (295 K).

The synthesis, solution complexation behaviour and solvent extraction ability of related chelating mono-and bis-(benzimidazole)phosphinate ligands 8 and 9 has been assessed. 31P NMR, fluorescence and absorption spectroscopy and electrospray mass spectrometry revealed preferential formation of 1:1 complexes with the divalent ions Zn, Co and Ni, and ML2 complex formation with the bidentate ligand. Extraction studies showed that 9 extracted Zn>CoNi with no extraction of copper(II), but avid extraction of copper(I), generated insitu, consistent with the ligand's preference for the binding of tetrahedrally-coordinating metal ions.

Four new thiophosphoryl ligands containing NNPS or CNPS connectivities have been prepared and three of them characterised by single-crystal X-ray diffraction. The complexation of these ligands with salts of CuI, CuII, NiII and ZnII has been studied by electrospray mass spectrometry and uv-visible spectrophotometry in acetonitrile and methanol solution. Evidence for 1∶1 and 2∶1 complexation is presented. Two copper(I) complexes were isolated including a mixed chloride–bromide copper(I) complex in which a dimeric structure is adopted with a 22-membered metallacycle.

The relaxivity of [GdL1]3+ in aqueous solution has been studied as a function of temperature and magnetic field strength. The complex possesses a high relaxivity at pH 6 (12.8 mmol-1 s-1) that diminishes as successive water molecules are deprotonated, leading to a complex species whose relaxivity is typical of a purely outer-sphere complex. Measurements of the luminescence lifetime of a very similar complex, [YbL2]3+, in H2O and D2O were used to confirm that the complex possesses three bound waters at pH 5.5, but above pH 11 there are no bound OH groups in the putative di-oxo-bridged dimer.

The X-ray structure is reported of a diprotonated Gd(III) tetra-aqua complex of the ligand 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane (DOTAM), a thermodynamic intermediate in metal ion association and dissociation pathways.