Design of magnetic organic molecules and organic magnets: Experiment, theory and computation with application and recent advances

Datta, Sambhu N.; Pal, Arun K.; Panda, Anirban

doi:10.1016/j.chphi.2023.100379

Cited by 2 publications

(4 citation statements)

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“…Space group C 2 /c was determined based on intensity statistics and systematic absences. The structure was solved with intrinsic methods and refined on F using the SHELX suite of programs. , Crystal data are as follows: C 64 H 76 N 4 , M r = 901.29 g mol –1 , colorless/violet block, 0.20 × 0.10 × 0.10 mm 3 , monoclinic, C 2 /c , μ( Mo K α) = 0.061 mm –1 , θ max = 26.40°, 77,980 reflections measured, 11,528 independent ( R int = 0.0566), R 1 = 0.0454 [ I > 2σ( I )], wR 2 = 0.1287 (all data), goodness of fit on F 2 : 1.011, and residual density peaks: 0.338 and −0.230 e Å –3 . The remaining electron density is in the vicinity of the three disordered t -butyl groups.…”

Section: Methodsmentioning

confidence: 99%

“…Chiral π-conjugated molecules with an open-shell structure have great potential in the development of materials to enable technological innovations. − The concurrent intrinsic helical chirality and electron spin coupling are compelling molecular properties for the development of novel organic optoelectronic materials and devices. Nevertheless, only a handful of open-shell helical radicals and radical ions have been prepared and studied to date, and all of them possess either S = 1/2 or a low-spin S = 0 ground state. − Among the elegant examples are S = 1/2 neutral aminyl radicals of [4]helicene and [7]helicene, in which the nitrogen- and carbon-centered radicals with spin density delocalized within helical π-systems (Figure ).…”

Section: Introductionmentioning

confidence: 99%

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Chiral π-Conjugated Double Helical Aminyl Diradical with the Triplet Ground State

Guo,

Lovell,

Shu

et al. 2024

J. Am. Chem. Soc.

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We report a neutral high-spin diradical of chiral C 2 -symmetric bis [5]diazahelicene with ΔE ST ≈ 0.4 kcal mol −1 , as determined by EPR spectroscopy/SQUID magnetometry. The diradical is the most persistent among all high-spin aminyl radicals reported to date by a factor of 20, with a half-life of up to 6 days in 2-MeTHF at room temperature. Its triplet ground state and excellent persistence may be associated with the unique spin density distribution within the dihydrophenazine moiety, which characterizes two effective 3-electron C−N bonds analogous to the N−O bond of a nitroxide radical. The enantiomerically enriched (ee ≥ 94%) (MM)-and (PP)-enantiomers of the precursors to the diradicals are obtained by either preparative chiral supercritical fluid chromatography or resolution via functionalization with the chiral auxiliary of the C 2 -symmetric racemic tetraamine. The barrier for the racemization of the solid tetraamine is ΔG ‡ = 43 ± 0.01 kcal mol −1 in the 483−523 K range. The experimentally estimated lower limit of the barrier for the racemization of a diradical, ΔG ‡ ≥ 26 kcal mol −1 in 2-MeTHF at 293 K, is comparable to the DFTdetermined barrier of ΔG ‡ = 31 kcal mol −1 in the gas phase at 298 K. While the enantiomerically pure tetraamine displays strong chiroptical properties, with anisotropy factor |g| = |Δε|/ε = 0.036 at 376 nm, |g| ≈ 0.005 at 548 nm of the high-spin diradical is comparable to that recently reported triplet ground-state diradical dication. Notably, the radical anion intermediate in the generation of diradical exhibits a large SOMO-HOMO inversion, SHI = 35 kcal mol −1 .

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chiral π-Conjugated Double Helical Aminyl Diradical with the Triplet Ground State

Guo,

Lovell,

Shu

et al. 2024

J. Am. Chem. Soc.

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“…have attracted great attention to magnetic materials controlled by external stimuli [ 6 , 7 ]. To apply ground triplet biradicals and ground high-spin oligoradicals to materials chemistry [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ], the choice of radical species is crucial. It has been theoretically and experimentally clarified that 1,3-phenylene-bridges serve as a robust ferromagnetic coupler in the context of the spin-polarization mechanism or topological rule [ 4 , 5 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ].…”

Section: Introductionmentioning

confidence: 99%

“…To apply ground triplet biradicals and ground high-spin oligoradicals to materials chemistry [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ], the choice of radical species is crucial. It has been theoretically and experimentally clarified that 1,3-phenylene-bridges serve as a robust ferromagnetic coupler in the context of the spin-polarization mechanism or topological rule [ 4 , 5 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. Triphenylmethyls and diphenylcarbenes are the most popular paramagnetic centers in this research field, but heteroatomic ones can also be utilized as a spin source [ 17 , 18 , 19 , 20 , 21 , 22 ].…”

Section: Introductionmentioning

confidence: 99%

A Triplet/Singlet Ground-State Switch via the Steric Inhibition of Conjugation in 4,6-Bis(trifluoromethyl)-1,3-phenylene Bisnitroxide

Haga,

Ishida

2023

Molecules

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Ground triplet 4,6-bis(trifluoromethyl)-1,3-phenylene bis(tert-butyl nitroxide) (TF2PBN) reacted with [Y(hfac)3(H2O)2] (hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate), affording a doubly hydrogen-bonded adduct [Y(hfac)3(H2O)2(TF2PBN)]. The biradical was recovered from the adduct through recrystallization. Crystallographic analysis indicates that the torsion angles (|θ| ≤ 90°) between the benzene ring and nitroxide groups were 74.9 and 84.8° in the adduct, which are larger than those of the starting material TF2PBN. Steric congestion due to o-trifluoromethyl groups gives rise to the reduction of π-conjugation. Two hydrogen bonds enhance this deformation. Susceptometry of the adduct indicates a ground singlet with 2J/kB = −128(2) K, where 2J corresponds to the singlet–triplet gap. The observed magneto-structure relation is qualitatively consistent with Rajca’s pioneering work. A density functional theory calculation at the UB3LYP/6-311+G(2d,p) level using the atomic coordinates determined provided a result of 2J/kB = −162.3 K for the adduct, whilst the corresponding calculation on intact TF2PBN provided +87.2 K. After a comparison among a few known compounds, the 2J vs. |θ| plot shows a negative slope with a critical torsion of 65(3)°. The ferro- and antiferromagnetic coupling contributions are balanced in TF2PBN, being responsible for ground-state interconversion by means of small structural perturbation like hydrogen bonds.

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Design of magnetic organic molecules and organic magnets: Experiment, theory and computation with application and recent advances

Cited by 2 publications

References 407 publications

Chiral π-Conjugated Double Helical Aminyl Diradical with the Triplet Ground State

Chiral π-Conjugated Double Helical Aminyl Diradical with the Triplet Ground State

A Triplet/Singlet Ground-State Switch via the Steric Inhibition of Conjugation in 4,6-Bis(trifluoromethyl)-1,3-phenylene Bisnitroxide

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