Excitation dependent multicolour luminescence and colour blue-shifted afterglow at room-temperature of europium incorporated hydrogen-bonded multicomponent frameworks

Yang, Chao; Artizzu, Flavia; Folens, Karel; Laing, Gijs Du; Deun, Rik Van

doi:10.1039/d1tc01627j

Cited by 9 publications

(5 citation statements)

References 25 publications

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“…Moreover, the incorporation of transition metal (3 d ) and lanthanide (4 f ) ions, particularly in heterometallic 3 d -4 f assemblies, can enrich such compounds with additional unique optical and magnetic properties, including tunable colored and white-light generation, near-infrared (NIR) emission, ferromagnetism and slow relaxation of the magnetization [ 1 , 2 , 3 , 4 , 5 , 6 ]. Supramolecular interactions, such as π-stacking and hydrogen bonding, can have a relevant direct impact on the physical properties of the materials, as well as indirect effects, for example, by favoring distance-dependent through-space phenomena, such as Förster’s energy transfer [ 7 , 8 , 9 , 10 , 11 ]. However, controlling the assembly of coordination polymers and extended molecular frameworks is challenging, particularly when lanthanide (Ln) ions are involved, since their coordination chemistry is essentially governed by entropic and steric factors rather than orbital directionality.…”

Section: Introductionmentioning

confidence: 99%

Anion-Induced Structural Diversity and Optical Chromism in a Series of Cyano-Bridged Heterometallic 3d-4f Coordination Polymers

et al. 2023

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The self-assembly reaction of the neutral dicyano-bis(1,10-phenanthroline) iron(II) complex with lanthanide ions (Ln = Eu(III), Gd(III), Er(III)) provided two different classes of heterometallic cyano-bridged 3d-4f architectures depending on the nature of the counteranion, irrespective of the size of the 4f metal ion. Tetranuclear oligomers with a squared Fe2Ln2 core were isolated when using nitrate salts, whereas unusual 1D polymeric chains were obtained when resorting to triflate salts under the same synthetic conditions. It is shown that the different structural motifs have a remarkable impact on the thermal stability and the optical properties of the compounds, which display a notable optical ipsochromism of the parent Fe(II) complex upon coordination with the Ln ion. This effect is significantly more pronounced in the polymeric chain than in the Fe2Ln2 oligomer both in solution and in the solid state. Structural evidence suggests that this behavior is likely related to the geometry of the CN-Ln bridge. On the other hand, more extended π-stacking interactions in the oligomer give rise to a broad charge-transfer absorption (600–1500 nm), making this compound promising as NIR absorber. Density Functional Theory calculations and electrochemical studies demonstrate that the observed negative chromism originates from the stabilization of a mixed metal/cyanide character HOMO with respect to a phenanthroline-centered LUMO.

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Section: Introductionmentioning

confidence: 99%

Anion-Induced Structural Diversity and Optical Chromism in a Series of Cyano-Bridged Heterometallic 3d-4f Coordination Polymers

et al. 2023

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“…It is interesting to note that in the solid state, the spectral shape is significantly broadened (>100 nm) with respect to the solutions, as highlighted by the color differences for the two samples in the diverse phases illustrated in Figure c. This effect exceeds that normally expected from solid-state scattering phenomena and could be ascribed to the particularly high sensitivity of Ru(II) complexes to the chemical environment, originating from the MLCT nature of the lowest absorption band, also taking into account that numerous intermolecular interactions such as π-interactions and hydrogen bonding are present in the crystalline arrangement , (Figure S3).…”

Section: Resultsmentioning

confidence: 87%

Spectral Tuning and Emission Enhancement through Lanthanide Coordination in a Dual Visible–Near-Infrared Emissive Cyanide-Bridged Heterometallic Ru(II)–Er(III) Complex

Mara,

Cai,

Bonabello

et al. 2024

Crystal Growth & Design

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Owing to their unique luminescent properties and photosensitizing capability, cyanoruthenium(II) complexes with diimine ligands are the subject of intense research striving for routes for tuning their electronic properties and improving their emission quantum yield. In this work, we describe a heterometallic d-f cyanide-bridged Ru(II)−Er(III) assembly obtained by the direct reaction of trivalent erbium salt with the neutral [Ru(bipy) 2 (CN) 2 ] (bipy = 2,2′-bipyridine) metalloligand. This strategy allows for accommodating inorganic negatively charged anions such as nitrate and oxalate in the coordination sphere of the lanthanide ion. As a result, a dimeric tetranuclear discrete molecular architecture is obtained, where the two constituting monomeric Ru(II)-CN-Er(III) units are bridged by an oxalate anion coordinating two Er(III) ions in a bis-bidentate fashion. Strikingly, this heterometallic compound shows intense dual emission in the visible and near-infrared spectral ranges under single-wavelength excitation in both solution and the crystalline state. The effect of Er(III) coordination through a cyanide bridge is thoroughly discussed, also with the support of DFT calculations, to highlight the factors that induce the observed spectral hypsochromism and, more importantly, the remarkable 10-fold-increased emission quantum yield of the [Ru(bipy) 2 (CN) 2 ] moiety in the visible range. We show that the described coordination mode induces an energy raise of the emissive triplet metal-to-ligand charge transfer ( 3 MLCT) state and even a more pronounced lifting of the nonemissive Ru(II) triplet metal-centered ( 3 MC) states, suppressing thermal deactivation channels. Furthermore, owing to the reduced number of water molecules and quenching groups surrounding the lanthanide ion in the molecular architecture, relatively intense erbium emission at 1.5 μm telecom wavelength is detected through sensitization from the Ru(II) metalloligand. We suggest that this compound can find applications as an efficient solid-state dual emitter.

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“…Similar information can be drawn from the DRIFTS spectra shown in Figure 2 d. The stretching vibration of the carbonyl group at 1500 cm −1 and the ring vibration bands at 770 and 1200 cm −1 were found to become progressively weaker for the PHTF:Eu samples [ 15 , 18 ]. These results further hint at a dentate bridging coordination mode for the PHTF units through C=O groups coordinating Eu 3+ ions [ 13 ].…”

Section: Resultsmentioning

confidence: 89%

“…As these transitions are parity-forbidden, this leads to low molar absorption coefficients resulting in inefficient optical excitation and weak emission [ 9 ]. Our previous researches have shown that HOFs can be conveniently used as a tunable platform for constructing multi-emissive lanthanide (Ln) molecular materials [ 10 , 11 , 12 , 13 ]. Despite the interest in these materials, there are still few reports about the description of the fundamental photophysical properties of lanthanide ions in doped HOFs and limited understanding has been achieved on the structure/properties relationship of these materials.…”

Section: Introductionmentioning

confidence: 99%

Photophysical and Primary Self-Referencing Thermometric Properties of Europium Hydrogen-Bonded Triazine Frameworks

et al. 2022

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Lanthanide hydrogen-bonded organic frameworks (LnHOFs) are recently emerging as a novel versatile class of multicomponent luminescent materials with promising potential applications in optics and photonics. Trivalent europium (Eu3+) incorporated polymeric hydrogen-bonded triazine frameworks (PHTF:Eu) have been successfully obtained via a facile and low-cost thermal pyrolysis route. The PHTF:Eu material shows a porous frame structure principally composed of isocyanuric acid and ammelide as a minor constituent. Intense red luminescence with high colour-purity from Eu3+ is obtained by exciting over a broad absorption band peaked at 300 nm either at room or low temperature. The triazine-based host works as excellent optical antenna towards Eu3+, yielding ~42% sensitization efficiency (ηsens) and an intrinsic quantum yield of Eu3+ emission (ΦEu) as high as ~46%. Temperature-dependent emission studies show that PHTF:Eu displays relatively high optical stability at elevated temperatures in comparison to traditional inorganic phosphors. The retrieved activation energy of 89 meV indicates that thermal quenching mechanisms are attributed to the intrinsic energy level structure of the metal-triazine assembly, possibly via a thermally activated back transfer to ligand triplet or CT states. Finally, by using an innovative approach based on excitation spectra, we demonstrate that PHTF:Eu can work as a universal primary self-referencing thermometer based on a single-emitting center with excellent relative sensitivity in the cryogenic temperature range.

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Excitation dependent multicolour luminescence and colour blue-shifted afterglow at room-temperature of europium incorporated hydrogen-bonded multicomponent frameworks

Abstract: Fascinating multicoloured luminescence and long-lived afterglow have been used for applications in flexible display, information encryption, and bioelectronics. Herein, we report the development of europium incorporated hydrogen-bonded organic frameworks (HOF:Eu)...

Cited by 9 publications

References 25 publications

Anion-Induced Structural Diversity and Optical Chromism in a Series of Cyano-Bridged Heterometallic 3d-4f Coordination Polymers

Anion-Induced Structural Diversity and Optical Chromism in a Series of Cyano-Bridged Heterometallic 3d-4f Coordination Polymers

Spectral Tuning and Emission Enhancement through Lanthanide Coordination in a Dual Visible–Near-Infrared Emissive Cyanide-Bridged Heterometallic Ru(II)–Er(III) Complex

Photophysical and Primary Self-Referencing Thermometric Properties of Europium Hydrogen-Bonded Triazine Frameworks

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