Probing the C
            <sub>60</sub>
            triplet state coupling to nuclear spins inside and out

Filidou, Vasileia; Mamone, Salvatore; Simmons, Stephanie; Karlen, Steven D.; Anderson, Harry L.; Kay, Christopher W. M.; Bagno, Alessandro; Rastrelli, Federico; Murata, Yasujiro; Komatsu, Kôichi; Lei, Xuegong; Li, Yongjun; Turro, Nicholas J.; Levitt, Malcolm H.; Morton, John J. L.

doi:10.1098/rsta.2012.0475

Cited by 13 publications

(14 citation statements)

References 59 publications

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“…The isotropic endohedral muonium state should not cause a zero-field precession in the MHz range. However, charge transfer from the transition metal to the C 60 may cause a deformation of the cage as it is observed for the C 60 spin triplet state (38). This deformation may result in a slightly anisotropic hyperfine coupling of the endohedral muonium state, which then gives rise to the observed precession frequency in the megahertz range, similar as has been observed in C 70 (39).…”

Section: Systemsupporting

confidence: 51%

Emergent magnetism at transition-metal–nanocarbon interfaces

Ma’Mari

Rogers

Alghamdi

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Charge transfer at metallo-molecular interfaces may be used to design multifunctional hybrids with an emergent magnetization that may offer an eco-friendly and tunable alternative to conventional magnets and devices. Here, we investigate the origin of the magnetism arising at these interfaces by using different techniques to probe 3d and 5d metal films such as Sc, Mn, Cu, and Pt in contact with fullerenes and rf-sputtered carbon layers. These systems exhibit small anisotropy and coercivity together with a high Curie point. Low-energy muon spin spectroscopy in Cu and Sc-C 60 multilayers show a quick spin depolarization and oscillations attributed to nonuniform local magnetic fields close to the metallo-carbon interface. The hybridization state of the carbon layers plays a crucial role, and we observe an increased magnetization as sp 3 orbitals are annealed into sp 2 −π graphitic states in sputtered carbon/copper multilayers. X-ray magnetic circular dichroism (XMCD) measurements at the carbon K edge of C 60 layers in contact with Sc films show spin polarization in the lowest unoccupied molecular orbital (LUMO) and higher π*-molecular levels, whereas the dichroism in the σ*-resonances is small or nonexistent. These results support the idea of an interaction mediated via charge transfer from the metal and dz-π hybridization. Thin-film carbon-based magnets may allow for the manipulation of spin ordering at metallic surfaces using electrooptical signals, with potential applications in computing, sensors, and other multifunctional magnetic devices. emergent magnetism | molecular spintronics | interfacial magnetism | charge transfer | nanocarbon I nterfaces are critical in quantum physics, and therefore we must explore the potential for designer hybrid materials that profit from promising combinatory effects. In particular, the fine-tuning of spin polarization at metallo-organic interfaces opens a realm of possibilities, from the direct applications in molecular spintronics and thin-film magnetism to biomedical imaging or quantum computing. This interaction at the surface can control the spin polarization in magnetic field sensors, generate magnetization spin-filtering effects in nonmagnetic electrodes, or even give rise to a spontaneous spin ordering in nonmagnetic elements such as diamagnetic copper and paramagnetic manganese (1-11).The impact of carbon-based molecules on adjacent ferromagnets is not limited to spin filtering and electronic transport, but extends to induced changes in the metal anisotropy, magnetization, coercivity, and bias (12-14). Charge transfer and d(metal)-π(carbon) orbital coupling at the interface may change the density of states, spin population, and exchange of metallocarbon interfaces (4,15,16). The interaction between the molecule and the metal depends strongly on the morphology and specific molecular geometry (17, 18). It may lead to a change in the density of states at the Fermi energy DOS(E F ) and/or the exchange-correlation integral (I s ) as described by the Stoner criterion for ferr...

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Section: Systemsupporting

confidence: 51%

Emergent magnetism at transition-metal–nanocarbon interfaces

Ma’Mari

Rogers

Alghamdi

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…Thegtensor of 3 Y 3 N@C 80 *ismore asymmetric and the ZFS is smaller than in the case of the empty fullerene 3 C 60 *( D/E = À340/ + 15 MHz), [12a] 3 C 70 *( D/E =+153/ + 5-42 MHz) [12b,c] and monometallo endohedral fullerenes 3 Sr@C 74 *( j D j / j E j= 260/ 35 MHz), 3 Ba@C 74 *( j D j / j E j= 250/47 MHz), [13] and nonmetal endofullerene 3 H 2 @C 60 *( D/E %À340/ + 15 MHz). [14] Thes mall ZFS in 3 Y 3 N@C 80 *p oints to an egligible impact of the spin orbit coupling and is thus in line with the dominant spin density distribution on the carbon cage (Figure 2d). It also reflects the larger size of the cage and thus formally larger spin-spin distance between the unpaired electrons.…”

Section: Angewandte Chemiesupporting

confidence: 63%

“…[15] ENDOR proved very powerful in investigations of paramagnetic endohedral fullerenes La@C 82 , [16] N@C 60 , [17] N@C 70 , [18] and the triplet excited state of H 2 @C 60 . [14] Forl ight excited triplets ENDOR studies are scarce and often hampered by the short t T 1 and/or short T 1 relaxation times.Here,the long t T 1 of 3 Y 3 N@C 80 *allowed for ad etailed ENDOR investigation. W-band ENDOR spectra recorded at different field positions corresponding to the turning points of the ZFS pattern, are shown in Figure 4.…”

Section: Angewandte Chemiementioning

confidence: 99%

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Thermally Activated Delayed Fluorescence in a Y₃N@C₈₀ Endohedral Fullerene: Time‐Resolved Luminescence and EPR Studies

et al. 2017

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Abstract:The endohedral fullerene Y 3 N@C 80 exhibits luminescence with reasonable quantum yield and extraordinary long lifetime.B yv ariable-temperatures teady-state and timeresolved luminescence spectroscopy, it is demonstrated that above6 0Kthe Y 3 N@C 80 exhibits thermally activated delayed fluorescence with maximum emission at 120 Kand anegligible prompt fluorescence.B elow 60 K, ap hosphorescence with al ifetime of 192 AE 1msi so bserved. Spin distribution and dynamics in the triplet excited state is investigated with X-and W-band EPR and ENDOR spectroscopies and DFT computations.Finally,electroluminescence of the Y 3 N@C 80 /PFO film is demonstrated opening the possibility for red-emitting fullerene-based organic light-emitting diodes (OLEDs).Fullerenes usually exhibit low quantum yields (QY) of fluorescence (in the range of 10 À4 )owing to the slow radiative decay and af ast and efficient inter-system crossing (ISC), leading to an almost quantitative formation of triplet states with slow non-radiative decay.E xohedral chemical derivatization can substantially modify the p-system of fullerenes and produce highly luminescent multi-adducts.[1] Another way to enhance the quantum yield of luminescence of fullerenes is based on the thermal repopulation of the S 1 state,v ia the T 1 state,i ft he S 1 -T 1 gap is sufficiently small. This process is known as thermally activated delayed fluorescence (TADF) and has been found to increase the fluorescence quantum yield of C 70 up to 0.08 at high temperatures.[2] TADF is currently an extensively examined phenomenon in the field of organic light-emitting diodes (OLEDs) as it allows to harvest up to 100 %ofelectrically formed excitons. [3] With the exception of several Er-and Tm-based endohedral metallofullerenes (EMFs), [4] with metal-based emission, EMFs are also non-luminescent.[5] Thei nternal heavy-atom effect leads to even faster ISC in EMFs than in empty fullerenes.T he lifetime of the S 1 state in Sc 3 N@C 80 is only 48 ps.[6] Surprisingly,Y 3 N@C 80 exhibits luminescence with reasonable quantum yield of ca 1% or even 8% in ac ycloadduct, [7] and an unusually long luminescence lifetime of 200-800 ns at room temperature.H erein, we explore the photoemission mechanism of Y 3 N@C 80 with variable-temperature time-resolved luminescence spectroscopy and EPR spectroscopy.The former reveals the evolution of the emission spectra and lifetimes with temperature,w hereas the latter provides information on relaxation dynamics and spin density distribution in the triplet state of Y 3 N@C 80 .W eshow that efficient photoemission of Y 3 N@C 80 is caused by the small S 1 -T 1 gap leading to TADF above 60 K. In ab lend with polyfluorene (PFO), Y 3 N@C 80 exhibits electroluminescence,w hich suggests that after suitable optimization and boost of the QY, Y 3 N@C 80 may be used for red or NIR-emitting OLEDs.In deoxygenated toluene solution, Y 3 N@C 80 exhibits luminescence with aQ Yo f1 .7 %a nd lifetime of 0.95 msa t 296 K. Saturation with air leads to athreefold reduction of...

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“…Filidou et al [16] present electron-nuclear double resonance data on the photo-excited triplet states of fullerenes with attached exohedral groups and on the photo-excited triplet state of H 2 @C 60 . Hyperfine couplings are observed between the electron spin and atomic nuclei in the exohedral group (in the first case) and the proton nuclei of the endohedral H 2 molecule (in the second case).…”

mentioning

confidence: 99%

Nanolaboratories: physics and chemistry of small-molecule endofullerenes

Levitt

Horsewill

2013

Phil. Trans. R. Soc. A.

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This Theo Murphy Meeting Issue contains papers presented at a Discussion Meeting held at the Kavli Centre of the Royal Society in March 2012. The meeting brought together a wide variety of scientists working on different aspects of small-molecule endofullerenes—those intriguing chemical systems in which small molecules such as H 2 or H 2 O are encapsulated in tiny carbon cages.

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Probing the C ₆₀ triplet state coupling to nuclear spins inside and out

Cited by 13 publications

References 59 publications

Emergent magnetism at transition-metal–nanocarbon interfaces

Emergent magnetism at transition-metal–nanocarbon interfaces

Thermally Activated Delayed Fluorescence in a Y₃N@C₈₀ Endohedral Fullerene: Time‐Resolved Luminescence and EPR Studies

Nanolaboratories: physics and chemistry of small-molecule endofullerenes

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Probing the C 60 triplet state coupling to nuclear spins inside and out

Cited by 13 publications

References 59 publications

Emergent magnetism at transition-metal–nanocarbon interfaces

Emergent magnetism at transition-metal–nanocarbon interfaces

Thermally Activated Delayed Fluorescence in a Y3N@C80 Endohedral Fullerene: Time‐Resolved Luminescence and EPR Studies

Nanolaboratories: physics and chemistry of small-molecule endofullerenes

Contact Info

Product

Resources

About

Probing the C ₆₀ triplet state coupling to nuclear spins inside and out

Thermally Activated Delayed Fluorescence in a Y₃N@C₈₀ Endohedral Fullerene: Time‐Resolved Luminescence and EPR Studies