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Journal Name ARTICLE Composed in the f-block: solution structure and function of kinetically inert lanthanide(III) complexes Received 00th January 20xx, Accepted 00th January 20xx DOI: 10.1039/x0xx00000x www.rsc.org/

Lea G. Nielsen, Anne Kathrine R. Junker and Thomas Just Sørensen* It has been more than 15 years since the last authoritative report on the solution structure of lanthanide complexes made from cylcen derived polydentate ligands. The field has progressed, diversified, and tools have been developed that should enable a step-change in the field in the imminent future. This will only happen if the tools are used, and the results communicated in a form that is consistent within the field and readily accesible to scientists outside the field. In this perspective, the fundamental tools for designing and investigating kinetically inert lanthanide complexes in solution will be covered. The fundamentals of this type of complexes will be laid out. The conformations of lanthanide complexes from cyclen derived ligands and the rate of exchange between conformations will be linked to their 1H NMR and luminescence spectra. The information rich ligand- and metal centred emisison spectra will be discussed, and the time-resolved luminescence decay lifetimes are shown to be directly related to the solution structure. The aim is to provide the reader with the information needed to become excited by lanthanide coordination chemistry.

Introduction f-block chemistry is often referred to as "boring", since the elements initially were found to exhibit similar chemistry, dominated by the lanthanide contraction and the 3+ oxidation 1, 2 state. The fuller picture of the chemistry of the lanthanide ions in solid state has shown this to be wrong, and it is far from the truth in solution. Here, strongly coordinated solvates and complexes undergo rapid ligand exchange changing the constitution and the conformation around the lanthanide(III) ions. Consequently, the chemical and physicochemical properties of the complexes change as expressed by e.g. their NMR and luminescence spectra. The chemistry is similar to that of other elements in the periodic table that form large, highly charged ions unable to partake in covalent interactions. But in contrast to e.g. calcium, the lanthanide(III) ions have physicochemical properties that are useful in technology and for diagnostic applications. As the rare earth elements are found in mixtures, the many industrial uses require that we develop chemistries that allow efficient rare earth separation. Thus, the motivation and the tools are available for the study of lanthanide solution chemistry: society needs a reliable 3 supply of rare earths, the lanthanide(III) ions give rise to distinct spectroscopic signatures, and a chemistry dominated by size, steric effects, and non-covalent interactions that yet has to be fully described.

a.

Nano-Science Center & Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 København Ø, Denmark. [email protected] Electronic Supplementary Information (ESI) available: trivial, systematic and abbreviated names for all ligands are included in the ESI. See DOI: 10.1039/x0xx00000x

To harness the speciation of lanthanide(III) ions for diagnostic applications, rapid ligand exchange must be negated. Therefore, macrocyclic polyaminocarboxylate chelators have been developed to form lanthanide(III) ion complexes, see scheme 1. Where linear ligands such as EDTA, DTPA and 4-6 picolinates form complexes with rapid de-complexation, macrocyclic ligands are able to form kinetically inert complexes 7-10 with the lanthanide(III) ions. The first kinetically inert lanthanide complex was [Ln.DOTA] , based on cyclen. Since, 11-14 ligands based on TACN with picolinates, and linear and macrocyclic IAM and HOPO based ligands have been developed as chelators that form kinetically inert lanthanide 15-17 complexes. While the thermodynamic stabilities of these are well documented, the kinetic parameters are less well studied. This is equally true for the established linear HOPO 18 and IAM systems, the PCTA and pcatcn ligands, and a host of 19 DOTA-like ligands. Some of these ligands are able to form kinetically inert complexes of lanthanide(III) ions. Unfortunately, the data available in the literature on the structure and properties of these complexes are not consistent. This is not a new issue in the field of f-element 20 coordination chemistry, even the stability constant for [Ln.DOTA] complexes are reported as different as five orders 21, 22 of magnitude. Conditionally stability constants are a step 9 on the way, but to compare between laboratories and between reports we need NMR spectra, stability constants, luminescent and relaxometric properties determined using standardized methods. Small variations in pH, ionic strength, instrument correction factors etc. can give rise to very 23-25 different results. With enough comparable data in the literature, we can attempt to generalise and bring forth new knowledge. Here, we try to do so for cyclen derived

This journal is © The Royal Society of Chemistry 20xx

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polyaminocarboxylate ligands. We attempt to show the connection between the solution structure, luminescence 1 spectra and the observed resonances in the H NMR spectra. Based on the solution structure, we propose a set of design guidelines when making ligands for lanthanide(III) ions that form complexes which give rise to an optical response proportional to the concentration of specific analytes. This perspective builds on the knowledge communicated in reviews 8, 26-31 by Parker, Caravan, Bünzli, and others.

Fundamentals of lanthanide chemistry Basic chemistry The elements in the f block have 4f and 5f orbitals progressively populated. The general electron configuration of n 2 the lanthanide ions is [Xe]4f 6s , with the exception of La, Ce,

n-1

1

2

Gd and Lu who all display an [Xe]4f 5d 6s configuration. For La, Ce and Gd it is a consequence of the lower energy of the 5d subshell, if no electrons are filled into the 4f subshell or when it is exactly half filled. For Lu the 4f subshell is full and the 5d subshell becomes the next available shell. The 4f elements— the lanthanide ions—are assumed to have similar chemistry due to the similar electronic configuration. The trivalent lanthanide ions have 4f valence electrons that are contained inside the xenon core. Thus, the 4f orbitals are shielded by the 5s and 5p orbitals and cannot be involved in bonding. Therefore, all interactions between lanthanide(III) ions and ligands are assumed to be purely electrostatic. Furthermore, the spectroscopic and magnetic properties of lanthanide(III) ions are assumed to be determined by ligand symmetry and 2, 29, 32-34 independent of ligand bonding.

Scheme 1. Selected thermodynamically stable lanthanide complexes. Derivatives with phosphonate, picolinate and carboxamide pendant arms have been reported for the macrocyclic ligands. Name and abbreviations can be found in the supporting information.

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Figure 1. Top: square antiprism (SAP, coordination number 8), and tricapped trigonal prism (TTP, coordination number 9) and capped square antiprismatic (cSAP) geometries of lanthanide complexes in solution. Bottom: The four conformers corresponding to the diastereoisomers of [Ln.DOTA} -.

Real-world applications The important applications for lanthanide solution chemistry are magnetic resonance imaging (MRI), high content screening, 3, 8, 35, 36 and rare earth separation. Magnetic resonance imaging. The high magnetic anisotropy of the 4f ions is used to generate a high contrast in MRI. The role of the lanthanide coordination chemist is to design complexes 8, 9 that are robust and will be excreted at an appropriate rate. Several grams of lanthanide(III) ions may be administered to the patient. For this to be safe, the lanthanide coordination chemistry must be just right to maintain the constitution of the lanthanide complex from it is formulated to it has left the 37 patient. The development of safe MRI contrast agents has been one of the main driving forces of lanthanide coordination chemistry. Thus, our understanding of kinetically inert lanthanide(III) complexes comes from this huge research effort. The safer MRI contrast agents are based on cyclen derived polydentate ligands. Assay. The relatively intense long-lived lanthanide centred 15, luminescence has been used to make highly sensitive assays.

While the coordination chemistry is important to achieve the sensitivity, a dynamic competition between ligands may be used, and the constitution of the lanthanide complex varies. Indeed, some assays rely on dissociation and re-assembly of lanthanide complexes to enhance the sensitivity. Two types of assays are commercially available. Both rely on the antenna principle to achieve efficient 30, 31, 50 population of lanthanide centred excited states. Direct excitation into the 4f excited levels is very inefficient. Therefore, an alternative strategy is used: a good light harvesting antenna is placed in the proximity of the luminescent ion. This allows excited state energy migration from the organic chromophore to the lanthanide(III) ion, which 34, 51-54 either emits luminescence or act as an energy donor. The energy transfer can occur through different mechanisms e.g. Förster, Dexter or sequential electron transfers. The common denominator is that for efficient energy transfer to the lanthanide centre to occur the distance between 32, chromophore and lanthanide(III) ion must be short (< 10 Å). 51, 53 For the process to be efficient, coordination of the antenna to the lanthanide(III) ion must be possible. Mining. For lanthanide separation, the small differences between neighbouring elements are exploited, where redox chemistry or selective crystallisation do not allow for easier 55-57 separation. While ion exchange chromatographic separation is possible, the bulk of lanthanides are separated 58 using solvent extraction. A better understanding of which experimental conditions that allow for differentiation of related lanthanide(III) ions would revolutionize rare earth separation and purification. Understanding the speciation in the complex solvent extraction media and designing selective ligands for extraction from highly acidic media with high nitrate concentrations is a daunting task. Therefore, we suggest that we start simpler. Reducing complexity The three applications outlined above all require control of lanthanide coordination chemistry in solution. With ill-defined electrostatic bonding and rapid ligand exchange this is a difficult task. In ligands that form kinetically inert lanthanide complexes there can be up to two (rather than nine) exchangeable ligands and the first coordination sphere of the lanthanide(III) ion is partially locked. Thus, the speciation is 26, 59 much simpler. This allows us to determine the hydration state, measure resolved luminescence spectra, and determine 1 distinct resonances in H NMR spectra of kinetically inert lanthanide complexes. Hence, we are able to determine the solution structure of lanthanide complexes based on ligands that form kinetically inert complexes with lanthanide(III) ions, and in that way rationalise the physicochemical properties of single compounds, or at least, properties of the weighted 19, 60 average of a limited set of compounds. Compounds are here used to signify a single constitutional and conformational isomer or a set of enantiomers. That is a compound is associated with a single set of physicochemical properties. Common for all chemistry is that to understand the properties of a compound, the structure has to be known. We will argue


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that this is possible for kinetically inert lanthanide complexes in the slow ligand exchange (days) limit, and for solvates of lanthanide(III) ions with non-coordinating counter ions in the fast exchange (nanoseconds) limit. 100%

Ln.EDTA Ln.DOTA Ln.DOTAM Ln.NOTA

[Ln.L]

75% 50% 25% 0% 0

3

6

9

12

15

time / hours Figure 2. Dissociation of lanthanide complexes at pH 6 in the presence of an irreversible scavenger i.e. all dissociation event leads to loss of the lanthanide(III) ion.

Fundamental lanthanide coordination chemistry The large size of the trivalent lanthanide ions requires a high 2, 33, 61, 62 coordination number in solution (CN ≥ 7). The coordination number is often nine for the earlier lanthanide(III) ions—lanthanum(III) through europium(III), and eight for the later lanthanide(III) ions—dysprosium(III) through 2, 62 lutetium(III). The common denominator for all the ligands in scheme 1 that are capable of forming kinetically inert complexes with lanthanide(III) ions is that: i) they are at least heptadentate, ii) they have a macrocyclic backbone, and iii) release of the metal ion is sterically hindered. A list of abbreviated ligand names, ligand structures, and full ligand names can be found as Electronic Supplementary Information. 63 Lanthanide(III) ions are notoriously labile in solution, and will exchange the ligands if competitive ligands such as water or methanol are present. Due to the electrostatic nature of the metal-ligand interaction, there is no directionality, and the coordination geometry is exclusively determined by ligand structure and steric effects. Combined with fast ligand exchange, it is difficult to predict the constitution and conformation of a lanthanide complex, especially when applied in biologically relevant settings where many competitive ligands are present. Yet we can rely on geometric considerations which dictates that nine-coordinated metal ions must be either capped square antiprism cSAP, dodecahedra, 28 or tricapped trigonal prims TTP. While structures on the continuum from square antiprisms to tricapped trigonal prims 28 are common, the high symmetry of the dodecahedron makes it rare. Good ligands for trivalent lanthanide ions must be able to host a sphere with a 1 Å radius within seven to nine hard donor atoms arranged in a TTP or cSAP geometry, see figure 1. The high charge state and weak polarizability of the trivalent lanthanide ions dictate that highly electronegative and anionic 2, 32-34, 50, 62 donor atoms are preferred. Stoichiometry and stability The equilibrium stoichiometry of all complexes in scheme 1 is one-to-one, with one lanthanide(III) ion coordinated to a single ligand. Here, we will focus on cyclen derived ligands with

carboxylate and carboxamide pendant arms, as these dominate the literature. For [Ln.DOTA] , the association and 64-67 dissociation mechanism has been studied in detail, and for [Ln.DOTA] , Ln.DO3A, Ln.DOTA-monoamides, and [Ln.DOTA3+ tetraamides] the association constants K and dissociation kinetics kobs has been scrutinised. A collection of literature values is presented in table 1. The binding constants vary from 13 -1 27 -1 10 M to 10 M , but that is to some extent not important, as these values are exceedingly large and corresponds to equilibria where no or very little free lanthanide(III) ion is 68 present. The key parameter is the kinetic stability, here represented by the rate constant of dissociation kobs in pure water at pH 1. The data in table 1 reveals, when plotted as done in figure 2, that macrocyclic complexes bar Ln.NOTA are kinetically inert in water at pH 6 on a timescale of hours. Of note is that the phosphonate derivatives of [Ln.DOTA] are particularly stable, and that the charged carboxamide complexes are kinetically inert despite a significantly lower binding constant. Recent studies report on kinetic inertness in 19, 20, 69-76 a variety of ways, therefore it should be a priority to establish a common method for determining K, k0 and k1. There can be no doubt that Ln.PCTA, [Ln.DOTA] , [Ln.DOTA3+ tetraamides] and derivatives of [Ln.DOTA] , Ln.DO3A and Ln.DOTA-monamides form kinetically inert lanthanide complexes, but there is a need to compare data and thereby the robustness of one ligand to that of another. Table 1. Thermodynamic and kinetic stabilities of selected lanthanide complexes. The table report the rate constants of dissociation kobs = k0 + k1[H+], the stability constant K = [Ln.L]/[L][Ln(III)], and the observed rate constant for dissociation at pH = 1.

Compound [Gd.DOTA]- a [Eu. DOTAM-Me]3+ c [Eu.DOTAM-Gly]3+ a [Gd.HPDO3A]- d Gd.Gadobutrol c [Ce.DOTAM-Me]3+ f [Gd.DO2A2P(1,7)]2- e Ce.NOTAg Ce.DO3Ah Gd.NOTAf Gd.PCTAf Yb.NOTA f [Gd.DTPA]2[Eu.DTPA]2a

kobs(pH 1) /s-1 5 x 10-5 5.8 x 10-6 8.2 x 10-5 2.6 x 10-3 2.8 x 10-4 2.7 x 10-4 1.9 x 10-3 0.43 11 0.23 5.1 x 10-3 1.6 x 10-2 1.2 x 10-3 h -

k0 /s-1 10'000 M cm rather than ~1 M cm . Following excitation there are multiple pathways for the energy absorbed by the antenna to migrate to the lanthanide centre. It is commonly accepted that the dominating energy 31 transfer cascade is the following: a photon absorbed by the antenna chromophore promotes the chromophore from the ground state S0 to the first excited singlet state S 1. The excitation is then followed by rapid intersystem crossing (facilitated by the lanthanide(III) ion) to an accessible triplet excited state T1. From the triplet state T1 the energy is then transferred to an isoenergetic lanthanide centred excited 32, 52, 54 state. For the energy transfer to be efficient it is important that the triplet excited state of the antenna matches the energy level of the accepting lanthanide centred state. This is a delicate balance as the excited state must not be too high in energy, as this will result in poor overlap of the lanthanide centred state and the energy transfer will be ineffective. In such complexes the antenna fluorescence will dominate. On the other hand, if the triplet energy is too close in energy to that of the lanthanide excited state it will result in back energy transfer, 51, 53, 54 and a low quantum yield of lanthanide luminescence. Efficient sensitisation has been shown to require an antenna triplet-lanthanide excited state energy gap of approximately -1 2’000 cm to avoid back energy transfer while maintaining a 2, 32, 34, 51, 52, 54, 148 good overlap of the excited states. Energy transfer can also occur through the singlet excited S1 state, but energy transfer from the triplet excited state T1 is still generally seen as the most common mechanism due to the 52 much longer T1 lifetime. An efficient antenna unit has a triplet energy of more than -1 20’000 cm , and can thus sensitize most of the luminescent 2, 50-52 lanthanide(III) ions. Furthermore, efficient sensitisation requires that the antenna and lanthanide centre are close if not in direct contact. Thus, the most efficient antenna chromophores are directly coordinated to the lanthanide(III) 11, 60, 149 ion. In figure 10 some common antenna units are shown, all of these are derived from organic fluorophores and have photophysical properties favourable for sensitisation of 54, 128, 150-154 lanthanide(III) ions.


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Figure 10. Selection of antenna chromophores that has been incorporated in kinetically 128, 150-154 inert lanthanide complexes shown with their key photophysical properties.

General design of luminescence lanthanide complexes Luminescent lanthanide complexes are multicomponent systems, with three components: the lanthanide(III) ion, the chelator, and the antenna chromophore. All organised in a supramolecular structure. The choice of each component is important to optimize the efficiency of the responsive complex. When creating a new lanthanide luminescence based probe, there are several important design considerations:  Solubility – the probe should be water soluble  Stability I – the complex should have high thermodynamic and kinetic stability in serum  Reading I – the probe must have strong absorption above 330 nm to minimize detrimental effects in biological material  Reading II – the probe should have efficient sensitisation of lanthanide centred emission with long luminescence lifetime  Stability II – the probe should be highly photostable  Future perspective – the ideal probe can be addressed by blue lasers opening for a wider scope of applications Thus, in optimising the design of a luminescent lanthanide probe there are several factors to consider, all relating to the choice of lanthanide(III) ion, chelator, and antenna chromophore. The lanthanide(III) ion. The choice of lanthanide(III) ion determines the luminescence intensity, the emission wavelength and the excited state lifetime. The luminescence intensity of the ion is influenced by the competing process of 50, 54 radiative versus non-radiative deactivation. To favour the radiative decay, the energy gap law dictates that the energy gap between the emitting excited state and the highest ground state of the lanthanide(III) ion must be as large as possible. Thus, gadolinium(III) is the most luminescent of the lanthanide(III) ions, however, it emits in the UV (310 nm) and 54 is not useful for optical applications. Europium(III) and terbium(III) ions are the most studied luminescent lanthanide(III) ions. They display significantly higher emission intensity than erbium(III), holmium(III), samarium(III) and dysprosium(III). All these ions display luminescence in the

visible spectrum (> 405 nm), but only europium(III) and terbium(III) ions has luminescence lifetimes of milliseconds. In contrast, samarium(III), dysprosium(III), and the near-infrared emitting neodymium(III) and ytterbium(III) have luminescence lifetimes in the microsecond or sub-microsecond range. Probes based on europium(III) gain additional advantages, as the well50-52, 54 understood emission spectrum is rich in information. The chelator. The chelating part of the lanthanide luminescent probe has three main purposes. It serves to prevent the release of the toxic lanthanide ions into i.e. a biological environment, it protects the lanthanide from quenching by OH oscillators of solvent molecules, and it carries the antenna 51, 54 chromophore. For the linear ligands the scaffold is usually made up of four or more acetate groups, which are covalently bound to a polyamine backbone e.g. EDTA and DTPA. EDTA has a unique historical place in lanthanide chemistry, and a vast amount of research has gone into the development of substituted DTPA ligands for use as MRI contrast agents. In aqueous media, EDTA and DTPA form thermodynamically stable yet kinetically labile complexes, see figure 2 and table 1. Thus the polyaminocarboxylate chelator should be a macrocyclic ligand, 8, 50, thereby ensuring both thermodynamic and kinetic stability. 54 As complexes of macrocyclic ligands often are kinetically inert, see above, it is ensured that they remain intact in biological systems. Coordination of solvent molecules like water, that is increasing q, shortens the emissive lifetime of the lanthanide(III) ion through non-radiative vibrational energy transfer to high frequency O-H oscillations. For applications other than MRI contrast agents, the number of solvent molecules able to 32, 34, coordinate to the lanthanide centre should be minimized. 50-52, 54 The degree of shielding by the ligand largely depends on the length, flexibility, number and nature of donor atoms, and in the case of macrocyclic ligands the preorganization of the 50, 54, 99, 100, 108 ligand is also important. As the ligands that form kinetically inert complexes are hepta- or octadentate and present a steric barrier for lanthanide(III) ion release, they efficiently shield the lanthanide(III) ion from most solvent X-H oscillators. That is highly luminescent, low q complexes follow directly from the need to make stable probes. To invoke the antenna principle, the chelator must contain an antenna chromophore. This can be as an addition to the main 8, 109, 129, 150, 155 chelator structure as demonstrated for DO3A, or as part of the ligand backbone e.g. the extended tpatcn 11, 12, 93 ligands. The antenna chromophore. The requirements of the antenna chromophore are of a photophysical nature as these determine the luminescence of the resulting lanthanide based probe. The most efficient antenna units will be those designed to take part in the coordination of the lanthanide(III) ion. In general, an antenna can be any aromatic or heteroaromatic highly π-conjugated system. What characterizes a good antenna unit is that it has a high molar absorption coefficient (ε) for the S0 to S1 transition. The ideal excitation wavelength should be > 340 nm and preferably higher, as this minimizes the interference from excitation of other chromophores in

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biological media (i.e. tryptophan). Finally, the antenna should 32, 50-52, have highly efficient intersystem crossing from S1 to T1. 54 For a chromophore to act as an efficient sensitizer, the energy of the triplet excited state T1 should be between 2'000 -1 and 3'500 cm above the lowest emitting levels of the chosen lanthanide(III) ion. Thereby back energy transfer and thermal 50-52 deactivation can be prevented. To ensure that rapid energy transfer from the antenna chromophore to the lanthanide(III) ion occur, a short distance between the antenna and the lanthanide(III) ion is required. Although it is not a prerequisite, the best results are observed when the antenna 50-52, 54 is part of the chelator. Engineering a response Responsive luminescent lanthanide probes are used to sense biological analytes or changes to the chemical microenvironments through alterations in their photophysical 54 behaviour. Other probes operate as dosimeters, where an 156-158 irreversible change occurs and induces a response. Here, only reversible responses are considered. The response of the probes can be detected either as a modulation of the luminescence intensity, spectral shape, excited-state lifetime or emission profile. The luminescent signal of the emissive lanthanide complexes can be modulated in different ways. The two most common consist of modulation of the bound water molecule and 34, 52, 54 altering the excited state of the antenna. Modulation of the number of bound water molecules q by association to an analyte is useful as it influences emission intensity, luminescent lifetime and the spectral form that all are means of detection. The first two results from a decrease 32, 54 in non-radiative deactivation, while the latter is a result of a change in solution structure. The modulation of q efficiently 147 monitor changes in pH, and is efficient in the sensing of 34, 52, 54 anions in solution. Modulating antenna chromophore photophysics can be achieved by incorporating a receptor unit in the chromophore 52, 159 design. When the analyte binds to the receptor unit, it changes the photophysical properties of the antenna. This change can have different consequences for the lanthanide centre. If the binding event changes the triplet excited state T1 of the antenna, the energy transfer cascade is altered, which incurs a change in the intensity of the lanthanide luminescence. A third way of designing responsive lanthanide(III) complexes rely on modulating photo-induced electron transfer PET processes in the antenna chromophore. Several cation sensing complexes work this way, where the binding of the cation will suppress the PET process, increasing the lanthanide emission. 159

When making a responsive molecular probe based on lanthanide luminescence it is crucial to document that the observed modulation by the analyte is due to expected interaction, and not to secondary effects due to other changes 24 in the medium. There are two approaches to do so. One is performing numerous control experiments. The other is mapping the solution structure using other techniques.

Summary The chemistry of lanthanide(III) ions in solution is complicated and diverse. To meet the demand for lanthanidesin technology, to fulfil the potential that the physicochemical properties of the lanthanide(III) ion promises, and to unravel the fundamentals of lanthanide chemistry in solution we need to develop and standardize common experimental methods. The hunt for safe and efficient MRI contrast agents have resulted in a good understanding of DOTA and DOTA-like 1 lanthanide complexes. Thus, we can rationalise the H NMR spectra of this class of lanthanide complexes. The distinct features of lanthanide(III) luminescence provide additional structural information through band shapes and intensities. Further, the modified Horrocks’ equation, an empirical relationship relating luminescence lifetime and q, counts the number of solvent molecules i.e. q directly coordinated to the lanthanide(III) ion. These tools have shown that even the most stable lanthanide complexes exist as mixtures of exchanging conformers. Even as mixtures of exchanging conformers, kinetically inert lanthanide(III) complexes are potent MRI contrast agents, optical reporters, and hold a great potential as responsive probes.

Conflicts of interest There are no conflicts to declare.

Acknowledgements We thank the Villum Foundation (#14922) and the University of Copenhagen.

Notes and references 1. 2. 3. 4.

5. 6. 7. 8. 9. 10. 11.

F. A. Cotton, G. Wilkinson and P. L. Gaus, Basic Inorganic Chemistry, John Wiley & Sons, New York, 3rd edn., 1995. S. Cotton, Lanthanide and Actinide Chemistry, Wiley, Chichester, 2006. K. Binnemans, P. T. Jones, T. Müller and L. Yurramendi, Journal of Sustainable Metallurgy, 2018, 4, 126-146. R. H. Betts, O. F. Dahlinger and D. M. Munro, Radioisotopes in Scientific Research, Pergamon Press, Oxford 1958. K. R. Williams and G. R. Choppin, J. Inorg. Nucl. Chem., 1974, 36, 1849-1853. W. D'Olieslager, G. R. Choppin and K. R. Williams, J. Inorg. Nucl. Chem., 1970, 32, 3605-3610. J. F. Desreux, Inorganic chemistry, 1980, 19, 1319-1324. P. Caravan, J. J. Ellison, T. J. McMurry and R. B. Lauffer, Chemical Reviews, 1999, 99, 2293-2352. A. D. Sherry, P. Caravan and R. E. Lenkinski, Journal of Magnetic Resonance Imaging, 2009, 30, 1240-1248. A. Boltjes, A. Shrinidhi, K. van de Kolk, E. Herdtweck and A. Domling, Chemistry, 2016, 22, 7352-7356. A. D’Aléo, A. Picot, A. Beeby, J. A. Gareth Williams, B. Le Guennic, C. Andraud and O. Maury, Inorganic chemistry, 2008, 47, 10258-10268.


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24. 25.

26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36.

Journal Name A. D'Aleo, A. Bourdolle, S. Brustlein, T. Fauquier, A. Grichine, A. Duperray, P. L. Baldeck, C. Andraud, S. Brasselet and O. Maury, Angewandte Chemie, 2012, 51, 6622-6625. C. Gateau, M. Mazzanti, J. Pecaut, F. A. Dunand and L. Helm, Dalton transactions, 2003, DOI: 10.1039/B303079B, 2428-2433. G. Nocton, A. Nonat, C. Gateau and M. Mazzanti, Helvetica Chimica Acta, 2009, 92, 2257-2273. E. G. Moore, A. P. Samuel and K. N. Raymond, Acc Chem Res, 2009, 42, 542-552. A. Datta and K. N. Raymond, Acc Chem Res, 2009, 42, 938947. L. J. Daumann, P. Werther, M. J. Ziegler and K. N. Raymond, Journal of Inorganic Biochemistry, 2016, 162, 263-273. S. Aime, M. Botta, S. G. Crich, G. B. Giovenzana, G. Jommi, R. Pagliarin and M. Sisti, Journal of the Chemical Society, Chemical Communications, 1995, DOI: 10.1039/c39950001885, 1885. L. Dai, C. M. Jones, W. T. K. Chan, T. A. Pham, X. Ling, E. M. Gale, N. J. Rotile, W. C.-S. Tai, C. J. Anderson, P. Caravan and G.-L. Law, Nature Communications, 2018, 9, 857. M. Polasek and P. Caravan, Inorganic chemistry, 2013, 52, 4084-4096. W. P. Cacheris, S. K. Nickle and A. D. Sherry, Inorganic chemistry, 1987, 26, 958-960. M. F. Loncin, J. F. Desreux and E. Merciny, Inorganic chemistry, 1986, 25, 2646-2648. T. J. Sørensen, L. R. Hill, J. A. Tilney, O. A. Blackburn, M. W. Jones, M. Tropiano and S. Faulkner, European Journal of Inorganic Chemistry, 2014, 2014, 2520-2528. T. J. Sørensen, L. R. Hill and S. Faulkner, ChemistryOpen, 2015, 4, 509 – 515. S. A. Bogh, M. Simmermacher, M. Westberg, M. Bregnhøj, M. Rosenberg, L. De Vico, M. Veiga, B. W. Laursen, P. R. Ogilby, S. P. A. Sauer and T. J. Sørensen, ACS Omega, 2017, 2, 193-203. D. Parker, R. S. Dickins, H. Puschmann, C. Crossland and J. A. K. Howard, Chem. Rev., 2002, 102, 1977-2010. J.-C. G. Bünzli, Journal of Coordination Chemistry, 2014, DOI: 10.1080/00958972.2014.957201, 1-45. M. G. B. DREW, Coordination Chemistry Reviews, 1977, 24 179-275. D. G. Karraker, Journal of Chemical Education, 1970, 47, 424. J. C. G. Bunzli, Coordination Chemistry Reviews, 2015, 293, 19-47. M. C. Heffern, L. M. Matosziuk and T. J. Meade, Chem Rev, 2014, 114, 4496-4539. P. Hänninen and H. Härmä, Lanthanide Luminescence, Springer, Heidelberg, 2011. C. E. Housecroft and A. G. Sharpe, Inorganic Chemistry, Pearson, Essex, UK, 2 edn., 2005. J.-C. G. Bünzli and C. Piguet, Chemical Society reviews, 2005, 34, 1048-1077. P. R. Selvin, Annu Rev Biophys Biomol Struct, 2002, 31, 275-302. J. M. Zwier and N. Hildebrandt, in Reviews in Fluorescence 2016, ed. C. D. Geddes, Springer, 2017, DOI: 10.1007/9783-319-48260-6_3, pp. 17-43.

37.

38. 39.

40. 41. 42. 43. 44. 45.

46.

47.

48.

49.

50.

51. 52. 53. 54. 55. 56.

57.

58. 59. 60. 61.

62.

E. M. Gale, P. Caravan, A. G. Rao, R. J. McDonald, M. Winfeld, R. J. Fleck and M. S. Gee, Pediatric Radiology, 2017, 47, 507-521. E. Soini and I. Hemmila, Clin Chem, 1979, 25, 353-361. K. Pettersson, H. Siitari, I. Hemmila, E. Soini, T. Lovgren, V. Hanninen, P. Tanner and U. H. Stenman, Clin Chem, 1983, 29, 60-64. H. Siitari, I. Hemmilä, E. Soini, T. Lövgren and V. Koistinen, Nature, 1983, 301, 258-260. E. SolnI and H. Kojola, CLIN.CHEM., 1983, 29, 65-68. I. Hemmilä, S. Dakubu, V.-M. Mukkala, H. Siitari and T. Lövgren, Analytical Biochemistry, 1984, 137, 335-343. I. Hemmilá and V.-M. Mukkala, Critical Reviews in Clinical Laboratory Sciences, 2008, 38, 441-519. H. B. Beverloo, A. v. Schadewijk, S. v. Gelderen-Boele and H. J. Tanke, Cytometry, 1990, 11, 784-792. M. Delbianco, V. Sadovnikova, E. Bourrier, G. Mathis, L. Lamarque, J. M. Zwier and D. Parker, Angewandte Chemie, 2014, 53, 10718-10722. J. M. Zwier, T. Roux, M. Cottet, T. Durroux, S. Douzon, S. Bdioui, N. Gregor, E. Bourrier, N. Oueslati, L. Nicolas, N. Tinel, C. Boisseau, P. Yverneau, F. Charrier-Savournin, M. Fink and E. Trinquet, Journal of Biomolecular Screening, 2010, 15, 1248-1259. H. N. Barnhill, S. Claudel-Gillet, R. Ziessel, L. J. Charbonniere and Q. Wang, Journal of the American Chemical Society, 2007, 129, 7799-7806. L. J. Charbonniere, N. Hildebrandt, R. F. Ziessel and H. G. Lohmannsroben, Journal of the American Chemical Society, 2006, 128, 12800-12809. P. R. Selvin and J. E. Hearst, Proceedings of the National Academy of Sciences of the United States of America, 1994, 91, 10024-10028. L. Armelao, S. Quici, F. Barigelletti, G. Accorsi, G. Bottaro, M. Cavazzini and E. Tondello, Coordination Chemistry Reviews, 2010, 254, 487-505. J. C. Bunzli, Chem Rev., 2010, 110, 2729-2755. S. V. Eliseeva and J.-C. G. Bünzli, Chemical Society reviews, 2009, 39, 189-227. J. Lehr, P. D. Beer, S. Faulkner and J. J. Davis, Chem Commun 2014, 50, 5678-5687. M. C. Heffen, L. M. Matosziuk and T. J. Meade, Chem Rev., 2014, 114, 4496-4539. J. A. Bogart, C. A. Lippincott, P. J. Carroll and E. J. Schelter, Angewandte Chemie, 2015, 54, 8222-8225. H. Fang, B. E. Cole, Y. Qiao, J. A. Bogart, T. Cheisson, B. C. Manor, P. J. Carroll and E. J. Schelter, Angewandte Chemie, 2017, 56, 13450-13454. X. Yin, Y. Wang, X. Bai, Y. Wang, L. Chen, C. Xiao, J. Diwu, S. Du, Z. Chai, T. E. Albrecht-Schmitt and S. Wang, Nat Commun, 2017, 8, 14438. P. Frohlich, T. Lorenz, G. Martin, B. Brett and M. Bertau, Angewandte Chemie, 2017, 56, 2544-2580. D. Parker, Chemical Society reviews, 2004, 33, 156-165. A. K. R. Junker, L. R. Hill, A. L. Thompson, S. Faulkner and T. J. Sørensen, Dalton transactions, 2018, 47, 4794-4803. F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, Interscience Publishers, New York, USA, 3 edn., 1972. J. C. Bunzli, Journal of Coordination Chemistry, 2014, 67, 1-45.

14 | J. Name., 2012, 00, 1-3




Journal Name 63. 64.

65. 66.

67.

68.

69.

70.

71.

72.

73.

74.

75.

76. 77. 78. 79. 80.

81.

82. 83. 84. 85.

ARTICLE

L. Helm and A. E. Merbach, Chem Rev, 2005, 105, 19231959. M. Audras, L. Berthon, C. Berthon, D. Guillaumont, T. Dumas, M.-C. Illy, N. Martin, I. Zilbermann, Y. Moiseev, Y. Ben-Eliyahu, A. Bettelheim, S. Cammelli, C. Hennig and P. Moisy, Inorganic chemistry, 2017, 56, 12248-12259. E. Toth, E. Brucher, I. Lazar and I. Toth, Inorganic chemistry, 1994, 33, 4070-4076. S. Aime, M. Botta, M. Fasano, M. P. M. Marques, C. F. G. C. Geraldes, D. Pubanz and A. E. Merbach, Inorganic chemistry, 1997, 36, 2059-2068. Z. Baranyai, I. Bányai, E. Brücher, R. Király and E. Terreno, European Journal of Inorganic Chemistry, 2007, 2007, 3639-3645. M. F. TWEEDLE, J. J. HAGAN, K. KUMAR, S. MANTHA and C. A. CHANG, Magnem Resonance Imaging, 1991, 9, 409415. G. Tircso, M. Regueiro-Figueroa, V. Nagy, Z. Garda, T. Garai, F. K. Kalman, D. Esteban-Gomez, E. Toth and C. Platas-Iglesias, Chemistry, 2016, 22, 896-901. F. K. Kalman, A. Vegh, M. Regueiro-Figueroa, E. Toth, C. Platas-Iglesias and G. Tircso, Inorganic chemistry, 2015, 54, 2345-2356. A. Rodriguez-Rodriguez, D. Esteban-Gomez, R. Tripier, G. Tircso, Z. Garda, I. Toth, A. de Blas, T. Rodriguez-Blas and C. Platas-Iglesias, Journal of the American Chemical Society, 2014, 136, 17954-17957. Z. Baranyai, M. Botta, M. Fekete, G. B. Giovenzana, R. Negri, L. Tei and C. Platas-Iglesias, Chem Eur J, 2012, 18, 7680-7685. N. N. Katia, A. Lecointre, M. Regueiro-Figueroa, C. PlatasIglesias and L. J. Charbonniere, Inorganic chemistry, 2011, 50, 1689-1697. C. Vanasschen, E. Molnar, G. Tircso, F. K. Kalman, E. Toth, M. Brandt, H. H. Coenen and B. Neumaier, Inorganic chemistry, 2017, 56, 7746-7760. A. Vagner, E. Gianolio, S. Aime, A. Maiocchi, I. Toth, Z. Baranyai and L. Tei, Chem Commun (Camb), 2016, 52, 11235-11238. J. Wahsner and M. Seitz, Inorganic chemistry, 2015, 54, 9681-9683. G. Anderegg, F. Arnaud-Neu, R. Delgado, J. Felcman and K. Popov, Pure and Applied Chemistry, 2005, 77, 1445-1495. A. Pasha, G. Tircso, E. T. Benyo, E. Brucher and A. D. Sherry, Eur J Inorg Chem, 2007, 2007, 4340-4349. É. Tóth, R. Király, J. Platzek, B. Radüchel and E. Brücher, Inorganica Chimica Acta, 1996, 249, 191-199. F. K. Kálmán, Z. Baranyai, I. Tóth, I. Bányai, R. Király, E. Brücher, S. Aime, X. Sun, A. D. Sherry and Z. Kovács, Inorganic chemistry, 2008, 47, 3851-3862. A. Pasha, M. Lin, G. Tircsó, C. L. Rostollan, M. Woods, G. E. Kiefer, A. D. Sherry and X. Sun, JBIC Journal of Biological Inorganic Chemistry, 2008, 14, 421-438. G. Tircsó, Z. Kovács and A. D. Sherry, Inorganic chemistry, 2006, 45, 9269-9280. A. C. Muscatello, G. R. Choppin and W. D'Olieslager, Inorg. Chem., 1989, 28, 993-997. S. Faulkner and S. J. A. Pope, J. Am. Chem. Soc., 2003, 125, 10526-10527. M. P. Placidi, A. J. L. Villaraza, L. S. Natrajan, D. Sykes, A. M. Kenwright and S. Faulkner, Journal of the American Chemical Society, 2009, 131, 9916-9917.

86.

87.

88. 89.

90. 91.

92. 93. 94. 95. 96.

97. 98. 99.

100.

101. 102.

103. 104.

105. 106. 107. 108.

109.

M. Tropiano, N. L. Kilah, M. Morten, H. Rahman, J. J. Davis, P. D. Beer and S. Faulkner, J. Am. Chem. Soc., 2011, 133, 11847-11849. R. Uppal, K. L. Ciesienski, D. B. Chonde, G. S. Loving and P. Caravan, Journal of the American Chemical Society, 2012, 134, 10799-10802. A. M. Nonat, C. Allain, S. Faulkner and T. Gunnlaugsson, Inorganic chemistry, 2010, 49, 8449-8456. T. Koullourou, L. S. Natrajan, H. Bhavsar, Pope, J. Feng, J. Narvainen, R. Shaw, E. Scales, R. Kauppinen, A. M. Kenwright and S. Faulkner, Journal of the American Chemical Society, 2008, 130, 2178-2179. M. S. Tremblay and D. Sames, Chemical Communications, 2006, 0, 4116-4118. O. A. Blackburn and S. Faulkner, in The Chemistry of Molecular Imaging, eds. N. J. Long and W.-T. Wong, Wiley, Online, 2014, DOI: doi:10.1002/9781118854754.ch8. S. Shuvaev, E. A. Suturina, K. Mason and D. Parker, Chemical Science, 2018, 9, 2996-3003. A. T. Frawley, Holly V. Linford, M. Starck, R. Pal and D. Parker, Chemical Science, 2018, 9, 1042-1049. S. Shuvaev, R. Pal and D. Parker, Chem Commun (Camb), 2017, 53, 6724-6727. S. Aime, M. Botta and G. Ermondi, Inorg. Chem, 1992, 31, 4291-4299. K. J. Miller, A. A. Saherwala, B. C. Webber, Y. Wu, A. D. Sherry and M. Woods, Inorganic chemistry, 2010, 49, 8662-8664. D. Delli Castelli, M. C. Caligara, M. Botta, E. Terreno and S. Aime, Inorganic chemistry, 2013, 52, 7130-7138. A. Barge, M. Botta, D. Parker and H. Puschmann, Chemical Communications, 2003, DOI: 10.1039/b302211k, 1386. M. Tropiano, O. A. Blackburn, J. A. Tilney, L. R. Hill, M. P. Placidi, R. J. Aarons, D. Sykes, M. W. Jones, A. M. Kenwright, J. S. Snaith, T. J. Sørensen and S. Faulkner, Chem Eur J, 2013, 19, 16566-16571. S. Aime, M. Botta, M. Fasano, M. P. M. Marques, C. F. G. C. Geraldes, D. Pubanz and A. E. Merbach, Inorg Chem, 1997, 36, 2059-2068. T. LAMMERS, S. AIME, W. E. HENNINK, G. STORM and F. KIESSLING, Accounts of Chemical Research, 2011. M. Woods, G. E. Kiefer, S. Bott, A. Castillo-Muzquiz, C. Eshelbrenner, L. Michaudet, K. McMillan, S. D. Mudigunda, D. Ogrin, G. Tircso, S. Zhang, P. Zhao and A. D. Sherry, Journal of the American Chemical Society, 2004, 126, 9248-9256. G. Tircso, B. C. Webber, B. E. Kucera, V. G. Young and M. Woods, Inorganic chemistry, 2011, 50, 7966-7979. N. Cakic, B. Tickner, M. Zaiss, D. Esteban-Gomez, C. PlatasIglesias and G. Angelovski, Inorganic chemistry, 2017, 56, 7737-7745. K. Binnemans, K. van Herck and C. Görller-Walrand, Chem. Phys. Lett., 1997, 266, 297-302. L. Di Bari and P. Salvadori, Chem Phys Chem, 2011, 12, 1490-1497. N. A. Viola, R. S. Rarig Jr., W. Ouellette and R. P. Doyle, Polyhedron, 2006, 25, 3457-3462. M. Regueiro-Figueroa, K. Djanashvili, D. Esteban-Gómez, T. Chauvin, É. Tóth, A. de Blas, T. Rodríguez-Blas and C. Platas-Iglesias, Inorganic chemistry, 2010, 49, 4212-4223. N. Cakic, S. Gündüz, R. Rengarasu and G. Angelovski, Tetradone Letters, 2015, 56, 759-765.


J. Name., 2013, 00, 1-3 | 15



ARTICLE 110.

111.

112. 113. 114.

115. 116.

117.

118.

119.

120.

121. 122.

123. 124. 125. 126. 127.

128. 129. 130.

131.

132.

133.

Journal Name M. Woods, S. Aime, M. Botta, J. A. K. Howard, J. M. Moloney, M. Navet, D. Parker, M. Port and O. Rousseaux, Journal of the American Chemical Society, 2000, 122, 9781-9792. S. Aime, M. Botta, Z. Garda, B. E. Kucera, G. Tircso, V. G. Young and M. Woods, Inorganic chemistry, 2011, 50, 7955-7965. G. Pintacuda, M. John, X.-C. Su and G. Otting, Accounts of Chemical Research, 2007, 40, 206-212. B. Bleaney, J Magn Reson, 1972, 8, 91-&. B. Bleaney, C. M. Dobson, B. A. Levine, R. B. Martin, R. J. P. Williams and A. V. Xavier, Journal of the Chemical Society, Chemical Communications, 1972, DOI: 10.1039/c3972000791b, 791b. B. BLEAnEY and K. W. H. STEVEnS, Rep Prog Phys, 1953. A. M. Funk, K. L. N. A. Finney, P. Harvey, A. M. Kenwright, E. R. Neil, N. J. Rogers, P. K. Senanayake and D. Parker, Chemical Science, 2015, 6, 1655-1662. G. Castro, M. Regueiro-Figueroa, D. Esteban-Gomez, P. Perez-Lourido, C. Platas-Iglesias and L. Valencia, Inorganic chemistry, 2016, 55, 3490-3497. O. A. Blackburn, R. M. Edkins, S. Faulkner, A. M. Kenwright, D. Parker, N. J. Rogers and S. Shuvaev, Dalton transactions, 2016, 45, 6782–6800. O. A. Blackburn, A. M. Kenwright, A. R. Jupp, J. M. Goicoechea, P. D. Beer and S. Faulkner, Chemistry – A European Journal, 2016, 22, 8929 – 8936. O. A. Blackburn, J. D. Routledge, L. B. Jennings, N. H. Rees, A. M. Kenwright, P. D. Beer and S. Faulkner, Dalton transactions, 2016, 45, 3070-3077. J. D. Rinehart and J. R. Long, Chemical Science, 2011, 2, 2078. M. E. Boulon, G. Cucinotta, J. Luzon, C. Degl'Innocenti, M. Perfetti, K. Bernot, G. Calvez, A. Caneschi and R. Sessoli, Angewandte Chemie, 2013, 52, 350-354. I. Bertini and L. Sacconi, J. Mol. Struct., 1973, 19, 371-385. C. Piguet and C. F. G. C. Geraldes, Handbook on physics and Chemistry of Rare Earths, Elsvier, 2013. S. Aime, M. Botta and G. Ermondi, Inorg Chem, 1992, 31, 4291-4299. B. Bleaney, J. Magn. Reson., 1972, 8, 91-100. S. Aime, A. Barge, J. I. Bruce, M. Botta, J. A. K. Howard, J. M. Moloney, D. Parker, A. S. de Sousa and M. Woods, Journal of the American Chemical Society, 1999, 121, 5762-5771. D. Kovacs, X. Lu, L. S. Mészáros, M. Ott, J. Andres and K. E. Borbas, J Am Chem Soc, 2017, 139, 5756-5767. J. D. Routledge, M. W. Jones, S. Faulkner and M. Tropiano, Inorg Chem, 2014, 3337-3345. T. Vitha, V. Kubicek, J. Kotek, P. Hermann, L. Vander Elst, R. N. Muller, I. Lukes and J. A. Peters, Dalton transactions, 2009, DOI: 10.1039/B820705D, 3204-3214. J. W. Walton, R. Carr, N. H. Evans, A. M. Funk, A. M. Kenwright, D. Parker, D. S. Yufit, M. Botta, S. De Pinto and K.-L. Wong, Inorganic Chemistry, 2012, 51, 8042-8056. M. Tropiano, O. A. Blackburn, J. A. Tilney, L. R. Hill, T. Just Sørensen and S. Faulkner, Journal of Luminescence, 2015, 167, 296-304. W. T. Carnall, G. L. Goodman, K. Rajnak and R. S. Rana, The Journal of chemical physics, 1989, 90, 3443-3457.

134.

135. 136.

137.

138. 139.

140.

141. 142. 143. 144. 145.

146. 147. 148.

149.

150.

151.

152.

153.

154. 155. 156.

A. de Bettencourt-Dias, Luminescence of Lanthanide Ions in Coordination Compounds and Nanomaterials, John Wiley & Sons Ltd, 2014. W. D. Horrocks and D. R. Sudnick, Journal of the American Chemical Society, 1979, 101, 334-340. A. Beeby, I. M. Clarkson, R. S. Dickins, S. Faulkner, D. Parker, L. Royle, A. S. de Sousa, J. A. G. Williams and M. Woods, Journal of the Chemical Society, Perkin Transactions 2, 1999, DOI: 10.1039/a808692c, 493-504. J. Scholten, G. A. Rosser, J. Wahsner, N. Alzakhem, C. Bischof, F. Stog, A. Beeby and M. Seitz, Journal of the American Chemical Society, 2012, 134, 13915-13917. A. Beeby and S. Faulkner, Chem Phys Lett, 1997, 266, 116122. S. Faulkner, A. Beeby, M. C. Carrie, A. Dadabhoy, A. M. Kenwright and P. G. Sammes, Inorg Chem Commun., 2001, 4, 187-190. Y. Hasegawa, K. Murakoshi, Y. Wada, S. Yanagida, J.-H. Kim, N. Nakashima and T. Yamanaka, Chem Phys Lett, 1996, 248, 8-12. W. T. Carnall, P. R. Fields and B. G. Wybourne, The Journal of chemical physics, 1965, 42, 3797. W. PRANDTL and K. SCHEINER, Zeitschrift fur anorganische und allgemeine Chemie, 1934, 220, 107-112. J. Hoogschagen and C. J. Gorter, Physica, 1948, 14, 197206. K. B. Yatsimirskii and N. K. Davidenko, Coordination Chemistry Reviews, 1979, 27, 223-273. O. A. Blackburn, M. Tropiano, T. J. Sørensen, J. Thom, A. Beeby, L. M. Bushby, D. Parker, L. S. Natrajan and S. Faulkner, Physical chemistry chemical physics : PCCP, 2012, 14, 13378-13384. M. P. Jensen and A. H. Bond, Journal of the American Chemical Society, 2002, 124, 9870-9877. D. Parker, Coordination Chemistry Reviews, 2000, 205, 109-130. M. Latva, H. Takalo, V.-M. Mukkala, C. Matachescu, J. C. Rodriguez-Ubis and J. Kankare, Journal of Luminescence, 1997, 75, 149-169. T. Lazarides, D. Sykes, S. Faulkner, A. Barbieri and M. D. Ward, Chemistry – A European Journal, 2008, 14, 93899399. P. Atkinson, K. S. Findlay, F. Kielar, R. Pal, D. Parker, R. A. Pool, H. Puschmann, S. L. Richardson, P. A. Stenson, A. L. Thompson and J. Yu, Org. Biomol. Chem., 2006, 4, 17071722. S. Quici, M. Cavazzini, M. C. Raffo, M. Botta, G. B. Giovenzana, B. Ventura, G. Accorsi and F. Barigelletti, Inorg Chim acta, 2007, 360, 2549-2557. I. M. Clarkson, A. Beeby, J. I. Bruce, L. J. Govenlock, M. P. Lowe, C. E. Mathieu, D. Parker and K. Senanayake, New Journal of Chemistry, 2000, 24, 377-386. A. Dadabhoy, S. Faulkner and P. G. Sammes, Journal of the Chemical Society, Perkin Transactions 2, 2000, DOI: 10.1039/B008179P, 2359-2360. P. Nikolov, I. Petkova, G. Köhler and S. Stojanov, J. Mol. Struct., 1998, 448, 247-254. A. Dadabhoy, S. Faulkner and P. G. Sammes, J. Chem. Soc., Perkin Trans. 2, 2002, 348-357. E. Pershagen, J. Nordholm and K. E. Borbas, Journal of the American Chemical Society, 2012, 134, 9832-9835.

16 | J. Name., 2012, 00, 1-3




Journal Name 157. 158. 159.

ARTICLE

E. Pershagen and K. E. Borbas, Coordination Chemistry Reviews, 2014, 273-274, 30-46. E. Pershagen and K. E. Borbas, Angewandte Chemie, 2015, 54, 1787-1790. J. P. Leonard and T. Gunnlaugsson, Journal of fluorescence, 2005, 15, 585-595.

Associate Professor Thomas Just Sørensen obtained his PhD from the University of Copenhagen in 2010 working on fluorescent dyes with Prof Bo W Laursen. After research stays with Prof Stephen Faulkner at Oxford, Sir J. Fraser Stoddard at UCLA, Prof Jerome Lacour in Geneva, and Profs Ignacy and Karol Gryczynski at UNT in Fort Worth he returned to take a permanent position at the University of Copenhagen in 2014. Thomas is an entrepreneurial scientist and with three spin-out companies his research focuses on both fundamental and applied aspects of lanthanide chemistry in solution. PhD Fellow Lea G Nielsen obtained her BA in chemistry from the University of Copenhagen in 2017 working on the synthesis of macrocyclic polyaminocarboxylate ligands under the supervision of Associate Prof Thomas Just Sørensen. Lea completed her studies at the University of Copenhagen with a semester at Monash University in Melbourne. Postdoc Anne Kathrine R Junker obtained her PhD from the University of Copenhagen in 2018 working on antenna appended lanthanide complexes with Associate Prof Thomas Just Sørensen. During her PhD she has worked with Prof Stephen Faulkner in Oxford and Dr Rebecca Abergel at LNBL exploring the chemistries of kinetically inert lanthanide and actinide complexes.


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