Multimodal probesc apable of combining imaging modalities within as ingle molecule are in high demand today as they can providei nformation at both molecular and anatomical levels.H erein, as tudy was conducted on as eries of gallium(III)/lanthanide(III)b is(12-MC-4) metallacrowns( MCs) with the general composition {Ln[12-MC Ga III N(shi) -4]} 2 (iph) 4 (Ln-I x , x = 0, 4, 8, 12), where shi and iph are salicylhydroximate and isophthalate ligands, respectively,o rt heir iodinated derivatives. For Yb-I x ,t he attenuationi nX -ray computedt omography (XCT) imaging and near-infrared (NIR) luminescence properties can be finely tuned by controlled structural modifications based on iodo groups. Solutionso fYb-I x appear to be 22-40 times more efficient as XCT agents in comparison to the commerciallya vailablei obitridol, while providing an intense emission signal in the NIR range with total quantum yields up to 8.6 %, which are amongt he highest values reported so far.T herefore, these molecules are promising potential bimodal agents for combined NIR luminescence and XCT imaging.Supporting information (including experimentaldetails, synthetic procedures,p hysical methods,detailed description of photophysical measurements, and XCT attenuationparameters) and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Lanthanide(III) ions (Ln 3+ ) in coordination compounds exhibit unique luminescent properties with narrow and characteristic f-f transitions throughout the visible and near-infrared (NIR) ranges. In addition, some Ln 3+ such as Pr 3+ , Sm 3+ , Dy 3+ , Ho 3+ , Er 3+ and Tm 3+ possess an exceptional ability, although less explored, to exhibit dual-range emissions. Such remarkable features allow highly specific use in materials sciences and biology, for example, for the creation of sophisticated barcode modules or for the next generation of optical imaging applications. Herein, a series of Ga 3+ /Ln 3+ metallacrowns (MCs) with the general composition [LnGa8(shi)8(OH)4]Na•xCH3OH•yH2O (Ln-1, Ln = Pr 3+ , Nd 3+ , Sm 3+ -Yb 3+ and analogue Y 3+ ; H3shi = salicylhydroxamic acid) is presented. Ln-1 were obtained by reacting Ga 3+ and Ln 3+ nitrate salts with the H3shi ligand. X-ray single crystal unit cell analysis confirmed that all MCs are isostructural. The crystal structure was solved for the Nd 3+ analogue and revealed that Nd 3+ is centered between two [12-MCGa III N(shi)-4] MC rings and bound to eight hydroximate oxygen ions (four from each ring) in a pseudo-square antiprismatic fashion adopting a pseudo-D4h symmetry. PGSE DOSY 1 H NMR spectroscopy and ESI mass-spectrometry confirmed that the structure of Ln-1 remains intact in methanol solutions while mass spectrometry suggests that four OHbridges are exchanged with CH3O -/CD3O -. An exceptional ability of this series of MCs to sensitize the characteristic emission of Ln 3+ was confirmed with the observation of bright red and green emission signals of Eu-1 and Tb-1, NIR emissions of Yb-1 and Nd-1, and dual-range emissions of Pr-1, Sm-1, Dy-1, Ho-1, Er-1 and Tm-1 in the solid state upon excitation into ligand-centered bands at 340 nm. The luminescence properties of Ln-1 (Ln = Nd 3+ , Sm 3+ , Eu 3+ , Tb 3+ , Dy 3+ , Yb 3+ ) were also investigated in CH3OH and CD3OD solutions. For Eu-1 and Yb-1 MCs, more extensive analyses of the photophysical properties were performed that included the determination of radiative lifetimes, intrinsic quantum yields and sensitization efficiencies. The absolute quantum yields ( ) of Ln-1 in the visible and in the NIR ranges have been determined. In the case of Sm-1 the values of in CH3OH and CD3OD solutions are exceptionally high, i.e. 10.1(5) % and 83(1) %. Values obtained for Yb-1, i.e. 0.78(4) % in CH3OH and 8.4(1)% in CD3OD, are among the highest ones reported today for Yb 3+ complexes formed with non-deuterated and non-halogenated ligands.Absorption spectra. Absorption spectra (Figure S9) were collected on freshly prepared 50 µM solutions of Ln-1 in methanol (Merck, Uvasol®) placed in quartz cuvettes on a Jasco V670 UV-visible spectrophotometer in absorbance mode.Synthesis and characterization. All reagents and chemicals were purchased from commercial sources and used without further purification. All reactions were carried out aerobically under ambient conditions. Elemental analysis was performed by Atlantic Microlabs Inc. ESI-M...

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Seven dimeric metallacrowns (MC) based on Ln[12-MC M(III)N(shi) -4], where Ln III = Dy, Ho, Yb, or Y, M III = Mn or Ga, and shi 3À is salicylhydroximate, have been synthesized and characterized by single-crystal X-ray diffraction, and for the dysprosium-manganese dimers, the magnetic properties have been measured. In each dimer two Ln[12-MC M(III)N(shi) -4] units are linked by four bridging dicarboxylate anions (isophthalate, trimesate, dinicotinate, or 2,2'-dithiodibenzoate). Three different countercations (sodium, gallium(III), or pyridinium) were used to maintain charge balance of the dimer. While pyridinium does not bind to the dimer, the choice of the dicarboxylate dictates where the countercations Na + or Ga III bind. With isophthalate and trimesate, the sodium ion binds to the central MC cavity opposite of the Ln III , and with dinicotinate the sodium or gallium(III) ions bind to the pyridyl nitrogen of the dinicotinate. All three Dy 2 Mn 8 dimers exhibit an out-of-phase magnetic susceptibility signal consistent with a shallow barrier to magnetization relaxation.

Series of lanthanide-containing metallic coordination complexes are frequently presented as structurally analogous, due to the similar chemical and coordinative properties of the lanthanides. In the case of chiral (Ln III [15-MC Cu II N(L-pheHA) -5]) 3 + metallacrowns (MCs), which are well established supramolecular hosts, the formation of dimers templated by a dicarboxylate guest (muconate) in solution of neutral pH is herein shown to have a unique dependence on the identity of the MC's central lanthanide. Calorimetric data and nuclear magnetic resonance diffusion studies demonstrate that MCs containing larger or smaller lanthanides as the central metal only form monomeric host-guest complexes whereas analogues with intermediate lanthanides (for example, Eu, Gd, Dy) participate in formation of dimeric hostguest-host compartments. The driving force for the dimerization event across the series is thought to be a competition between formation of highly stable MCs (larger lanthanides) and optimally linked bridging guests (smaller lanthanides).