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Optical information storage requires careful control of excitation and emission wavelengths in a reversible and orthogonal manner to enable efficient reading, writing, and erasing of information. Photochromic systems, in which a photoswitch is typcially coupled to an emissive organic fluorophore, have much promise in this regard. However, these suffer from considerable spectral overlap between the switch and fluorophore, such that their emissive and photoswitchable properties are not orthogonal. Here, we overcome this limitation by coupling visible/NIR emissive lanthanide complexes with molecular photoswitches, enabling reversible and orthogonal photoswitching with visible light. Crucially, photoswitching does not lead to sensitised emission from the lanthanide, while excitation of the lanthanide does not induce photoswitching, enabling the state of the system to be probed without perturbation of the switch. This opens up the possibility of developing multi-colour read–write methods for information storage using emissive photoswitches. [ABSTRACT FROM AUTHOR]

Lanthanide luminescence is characterised by "forbidden" 4f–4f transitions and a complicated electronic structure. Our understanding of trivalent lanthanide(III) ion luminescence is centered on Eu3+ because absorbing and emitting transitions in Eu3+ occur from a single electronic energy level. In Sm3+ both absorbing and emitting multiplets have a larger multiplicity. A band arising in transitions from the first emitting state multiplet to the ground state multiplet will have nine lines for a Sm3+ complex. In this study, high-resolution emission and excitation spectra were used to determine the electronic energy levels for the lowest multiplet and first emitting multiplet in four Sm3+ compounds with either tricapped trigonal prismatic TTP or capped square antiprismatic cSAP coordination polyhedra but different site symmetry. This was achieved by the use of Boltzmann distribution population analysis and experimentally determined transition probabilities from emission and excitation spectra. Using this analysis it was possible to show the effect of changing three oxygen atoms with three nitrogen atoms in the donor set for two compounds with the same coordination polyhedra and site symmetry. This work celebrates the 40th anniversary of Kirby and Richardson's first report of [Eu(ODA)3]3− luminescence. [ABSTRACT FROM AUTHOR]

Lanthanide luminescence is dominated by quenching by high-energy oscillators in the chemical environment. The rate of non-radiative energy transfer to a single H2O molecule coordinated to a Eu3+ ion exceeds the usual rates of emission by an order of magnitude. We know these rates, but the details of these energy transfer processes are yet to be established. In this work, we study the quenching rates of [Eu(D2O)9]3+ and [Eu(DOTA)(D2O)]− in H2O/D2O mixtures by sequentially exchanging the deuterons with protons. Flash freezing the solutions allows us to identify species with various D/H contents in solution and thus to quantify the energy transfer processes to individual OH-oscillators. This is not possible in solution due to fast exchange in the ensembles present at room temperature. We conclude that the energy transfer processes are accurately described, predicted, and simulated using a step-wise addition of the rates of quenching by each O–H oscillator. This documents the sequential increase in the rate of the energy transfer processes in the quenching of lanthanide luminescence, and further provides a methodology to identify isotopic impurities in deuterated lanthanide systems in solution. [ABSTRACT FROM AUTHOR]

The Tb(III) ion has the most intense luminescence of the trivalent lanthanide(III) ions. In contrast to Eu(III), where the two levels only include a single state, the high number of electronic states in the ground (7F6) and emitting (5D4) levels makes detailed interpretations of the electronic structure—the crystal field—difficult. Here, luminescence emission and excitation spectra of Tb(III) complexes with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, [Tb(DOTA)(H2O)]−), ethylenediaminetetraacetic acid (EDTA, [Tb(EDTA)(H2O)3]−) and diethylenetriaminepentaacetic acid (DTPA, [Tb(DTPA)(H2O)]2−) as well as the Tb(III) aqua ion ([Tb(H2O)9]3+) were recorded at room temperature and in frozen solution. Using these data the electronic structure of the 5D4 multiplets of Tb(III) was mapped by considering the transitions to the singly degenerate 7F0 state. A detailed spectroscopic investigation was performed and it was found that the 5D4 multiplet could accurately be described as a single band for [Tb(H2O)9]3+, [Tb(DOTA)(H2O)]− and [Tb(EDTA)(H2O)3]−. In contrast, for [Tb(DTPA)(H2O)]2− two bands were needed. These results demonstrated the ability of describing the electronic structure of the emitting 5D4 multiplet using emission spectra. This offers an avenue for investigating the relationship between molecular structure and luminescent properties in detailed photophysical studies of Tb(III) ion complexes. [ABSTRACT FROM AUTHOR]

Lanthanide luminescence is characterised by "forbidden" 4 f- 4 f transitions and a complicated electronic structure. Our understanding of trivalent lanthanide(III) ion luminescence is centered on Eu 3+ because absorbing and emitting transitions in Eu 3+ occur from a single electronic energy level. In Sm 3+ both absorbing and emitting multiplets have a larger multiplicity. A band arising in transitions from the first emitting state multiplet to the ground state multiplet will have nine lines for a Sm 3+ complex. In this study, high-resolution emission and excitation spectra were used to determine the electronic energy levels for the lowest multiplet and first emitting multiplet in four Sm 3+ compounds with either tricapped trigonal prismatic TTP or capped square antiprismatic cSAP coordination polyhedra but different site symmetry. This was achieved by the use of Boltzmann distribution population analysis and experimentally determined transition probabilities from emission and excitation spectra. Using this analysis it was possible to show the effect of changing three oxygen atoms with three nitrogen atoms in the donor set for two compounds with the same coordination polyhedra and site symmetry. This work celebrates the 40 th anniversary of Kirby and Richardson's first report of [Eu(ODA) 3 ] 3- luminescence.

Lanthanide luminescence is dominated by quenching by high-energy oscillators in the chemical environment. The rate of non-radiative energy transfer to a single H 2 O molecule coordinated to a Eu 3+ ion exceeds the usual rates of emission by an order of magnitude. We know these rates, but the details of these energy transfer processes are yet to be established. In this work, we study the quenching rates of [Eu(D 2 O) 9 ] 3+ and [Eu(DOTA)(D 2 O)] - in H 2 O/D 2 O mixtures by sequentially exchanging the deuterons with protons. Flash freezing the solutions allows us to identify species with various D/H contents in solution and thus to quantify the energy transfer processes to individual OH-oscillators. This is not possible in solution due to fast exchange in the ensembles present at room temperature. We conclude that the energy transfer processes are accurately described, predicted, and simulated using a step-wise addition of the rates of quenching by each O-H oscillator. This documents the sequential increase in the rate of the energy transfer processes in the quenching of lanthanide luminescence, and further provides a methodology to identify isotopic impurities in deuterated lanthanide systems in solution.

The Tb(III) ion has the most intense luminescence of the trivalent lanthanide(III) ions. In contrast to Eu(III), where the two levels only include a single state, the high number of electronic states in the ground ( 7 F 6 ) and emitting ( 5 D 4 ) levels makes detailed interpretations of the electronic structure-the crystal field-difficult. Here, luminescence emission and excitation spectra of Tb(III) complexes with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA, [Tb(DOTA)(H 2 O)] - ), ethylenediaminetetraacetic acid (EDTA, [Tb(EDTA)(H 2 O) 3 ] - ) and diethylenetriaminepentaacetic acid (DTPA, [Tb(DTPA)(H 2 O)] 2- ) as well as the Tb(III) aqua ion ([Tb(H 2 O) 9 ] 3+ ) were recorded at room temperature and in frozen solution. Using these data the electronic structure of the 5 D 4 multiplets of Tb(III) was mapped by considering the transitions to the singly degenerate 7 F 0 state. A detailed spectroscopic investigation was performed and it was found that the 5 D 4 multiplet could accurately be described as a single band for [Tb(H 2 O) 9 ] 3+ , [Tb(DOTA)(H 2 O)] - and [Tb(EDTA)(H 2 O) 3 ] - . In contrast, for [Tb(DTPA)(H 2 O)] 2- two bands were needed. These results demonstrated the ability of describing the electronic structure of the emitting 5 D 4 multiplet using emission spectra. This offers an avenue for investigating the relationship between molecular structure and luminescent properties in detailed photophysical studies of Tb(III) ion complexes.