A Thiazyl‐Based Organic Ferromagnet

Alberola, Antonio; Less, Robert J.; Pask, Christopher M.; Rawson, Jeremy M.; Palácio, Fernando; Oliete, Patricia B.; Paulsen, C.; Yamaguchi, A.; Farley, Rebecca; Murphy, D. M.

doi:10.1002/ange.200352194

Cited by 19 publications

(8 citation statements)

References 15 publications

(13 reference statements)

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“…As part of our design process we considered previous paramagnetic DTDA radicals and noted that the pres- ence of CF3 groups in the ortho positions in 2',4',6'-(F3C)3C6H2CNSSN led to a large twist angle between aryl and DTDA rings suppressing the preferred cis-oid π*-π* dimerization. 28 Similarly the monomeric radicals p-XC6F4CNSSN, (X= CN, Br, NO2, p-NCC6F4) have twist angles in the range 32 -58 o (mean 48 o ), [29][30][31] suggesting that the increase in steric bulk associated with increasing torsion angle suppresses dimerization. In this context we targeted the 9'-anthrcenyl radical, 3 which has the potential to combine the fluorescent properties of the anthracenyl group with the paramagnetic DTDA radical.…”

Section: Introductionmentioning

confidence: 99%

Structural, Magnetic, and Optical Studies of the Polymorphic 9′-Anthracenyl Dithiadiazolyl Radical

et al. 2019

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The fluorescent 9′-anthracenyl-functionalized dithiadiazolyl radical (3) exhibits four structurally determined crystalline phases, all of which are monomeric in the solid-state. Polymorph 3α (monoclinic P21/c, Z' = 2) is isolated when the radical is condensed onto a cold substrate (enthalpically favored polymorph) whereas 3β (orthorhombic P212121, Z' = 3) is collected on a warm substrate (entropically favored polymorph). The α and β polymorphs exhibit chemically distinct structures with 3α exhibiting face-to-face π−π interactions between anthracenyl groups while 3β exhibits edge-to-face π−π interactions. 3α undergoes an irreversible conversion to 3β on warming to 120 o C (393 K). The β-phase undergoes a series of reversible solid-state transformations on cooling; below 300 K a phase transition occurs to form 3γ (monoclinic P21/c, Z' = 1) and on further cooling below 165 K a further transition is observed to 3δ (monoclinic P21/n, Z' = 2). Both 3β  3γ and 3γ  3δ transitions are reversible (single-crystal X-ray diffraction) and the 3γ  3δ process exhibits thermal hysteresis with a clear feature observed by heat capacity measurements. Heating 3β above 160 o C generates a fifth polymorph (3ε) which is distinct from 3α -3δ based on PXRD data. The magnetic behavior of both 3α and the 3β/3γ/3δ system reflect an S = ½ paramagnet with weak antiferromagnetic coupling. The reversible 3δ ↔ 3γ phase transition exhibits thermal hysteresis of 20 K. Below 50 K the value of χmT for 3δ approaches 0 emu•K•mol -1 consistent with formation of a gapped state with an S = 0 ground state configuration. In solution both paramagnetic 3 and diamagnetic [3][GaCl4] exhibit similar absorption and emission profiles reflecting similar absorption and emission mechanisms for paramagnetic and diamagnetic forms. Both emit in the deep-blue region of the visible spectrum (λem ~ 440 nm) upon excitation at 255 nm with quantum yields of 4% (3) and 30% ([3][GaCl4]) affording a switching ratio [ΦF(3 + )/ΦF(3)] of 7.5 in quantum efficiency with oxidation state. Solid-state films of both 3 and [3][GaCl4] exhibit emission bands at longer wavelength (490 nm) attributed to excimer emission.

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Section: Introductionmentioning

confidence: 99%

Structural, Magnetic, and Optical Studies of the Polymorphic 9′-Anthracenyl Dithiadiazolyl Radical

et al. 2019

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“…The magnetic 1,2 and transport 3 properties of dithiadiazolyl (DTDA) radicals have attracted considerable attention since the first structural report of a DTDA radical, [PhCNSSN] 2 , in 1980. 4 More recently, their coordination chemistry as paramagnetic ligands in molecule-based magnetic materials has been exploited by Preuss, 5 and approaches to control their solid-state structure through crystal engineering design strategies have been reviewed by Haynes.…”

Section: ■ Introductionmentioning

confidence: 99%

Structural Studies of Perfluoroaryldiselenadiazolyl Radicals: Insights into Dithiadiazolyl Chemistry

et al. 2016

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The synthesis and structural characterization of a series of perfluoroaryldiselenadiazolyls [DSeDA; p-XCFCNSeSeN (X = F, Cl, Br, CF, NO, and CN for 2a-2f, respectively)] are described. Concentration-dependent solution UV/vis measurements on 2a follow the Beer-Lambert law and the transitions assigned through time-dependent density functional theory (TD-DFT) studies, indicating little propensity for dimerization in solution (10-10 M). Solution electron paramagnetic resonance (EPR) spectra reveal that these radicals exhibit a broad featureless singlet around g = 2.04 but form well-resolved anisotropic EPR spectra in frozen solution, from which spin densities were determined and found to reflect an increase in the spin density at the chalcogen in relation to the corresponding dithiadiazolyl (DTDA) radicals, p-XCFCNSSN. The solid-state structures of 2a and 2d-2f all adopt spin-paired cis-cofacial dimers in which the dimers are held together via multicenter π*-π* "pancake bonding" interactions. Conversely, 2b and 2c exhibit an orthogonal mode of association, which is unique to DSeDA chemistry but which also affords a singlet ground state evidenced by SQUID magnetometry. The more sterically demanding diselenadiazolyl radical 2f was also prepared and exhibits a trans-antarafacial dimerization mode. DFT studies [UPBE0-D3 ccPVTZ-PP(-F)++] on the model radical HCNSeSeN confirm that each dimer is a stable energy minimum on the potential energy surface, reproducing well the experimental geometric parameters with relative stability in the order cis-cofacial > orthogonal > trans-antarafacial. Computational studies reflect stronger dimerization for DSeDA radicals in relation to their sulfur analogues, consistent with the experimental observation: While 2a and 2d are isomorphous with their corresponding DTDA radicals, 2b, 2c, and 2e-2g are all dimeric, in contrast to their DTDA analogues, which are monomeric in the solid-state. A study on 2f reveals that significant geometric strain accumulates in order to support the propensity for both cis dimerization and intermolecular CN···Se interactions. Conversely, p-NCCFCNSSN likely forfeits dimerization in the analogous packing motif in order to release strain but retains the favorable intermolecular CN···S interactions.

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“…In the family of dithiadiazolyl radicals, p ‐O 2 NC 6 F 4 CNSSN . orders as a ferromagnet ( T C =1.3 K)12 whereas the β phase of p‐ NCC 6 F 4 CNSSN . exhibits canted antiferromagnetism below 36 K 13–16.…”

Section: Introductionmentioning

confidence: 99%

Studying the Origin of the Antiferromagnetic to Spin‐Canting Transition in the β‐p‐NCC₆F₄CNSSN^.Molecular Magnet

Deumal

Rawson

Goeta

et al. 2010

Chemistry A European J

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The crystal structure of the spin-canted antiferromagnet beta-p-NCC(6)F(4)CNSSN* at 12 K (reported in this work) was found to adopt the same orthorhombic space group as that previously determined at 160 K. The change in the magnetic properties of these two crystal structures has been rigorously studied by applying a first-principles bottom-up procedure above and below the magnetic transition temperature (36 K). Calculations of the magnetic exchange pathways on the 160 K structure reveal only one significant exchange coupling (J(d1)=-33.8 cm(-1)), which generates a three-dimensional diamond-like magnetic topology within the crystal. The computed magnetic susceptibility, chi(T), which was determined by using this magnetic topology, quantitatively reproduces the experimental features observed above 36 K. Owing to the anisotropic contraction of the crystal lattice, both the geometry of the intermolecular contacts at 12 K and the microscopic J(AB) radical-radical magnetic interactions change: the J(d1) radical-radical interaction becomes even more antiferromagnetic (-43.2 cm(-1)) and two additional ferromagnetic interactions appear (+7.6 and +7.3 cm(-1)). Consequently, the magnetic topologies of the 12 and 160 K structures differ: the 12 K magnetic topology exhibits two ferromagnetic sublattices that are antiferromagnetically coupled. The chi(T) curve, computed below 36 K at the limit of zero magnetic field by using the 12 K magnetic topology, reproduces the shape of the residual magnetic susceptibility (having subtracted the contribution to the magnetization arising from spin canting). The evolution of these two ferromagnetic J(AB) contributions explains the change in the slope of the residual magnetic susceptibility in the low-temperature region.

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A Thiazyl‐Based Organic Ferromagnet

Cited by 19 publications

References 15 publications

Structural, Magnetic, and Optical Studies of the Polymorphic 9′-Anthracenyl Dithiadiazolyl Radical

Structural, Magnetic, and Optical Studies of the Polymorphic 9′-Anthracenyl Dithiadiazolyl Radical

Structural Studies of Perfluoroaryldiselenadiazolyl Radicals: Insights into Dithiadiazolyl Chemistry

Studying the Origin of the Antiferromagnetic to Spin‐Canting Transition in the β‐p‐NCC₆F₄CNSSN^.Molecular Magnet

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A Thiazyl‐Based Organic Ferromagnet

Cited by 19 publications

References 15 publications

Structural, Magnetic, and Optical Studies of the Polymorphic 9′-Anthracenyl Dithiadiazolyl Radical

Structural, Magnetic, and Optical Studies of the Polymorphic 9′-Anthracenyl Dithiadiazolyl Radical

Structural Studies of Perfluoroaryldiselenadiazolyl Radicals: Insights into Dithiadiazolyl Chemistry

Studying the Origin of the Antiferromagnetic to Spin‐Canting Transition in the β‐p‐NCC6F4CNSSN.Molecular Magnet

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Studying the Origin of the Antiferromagnetic to Spin‐Canting Transition in the β‐p‐NCC₆F₄CNSSN^.Molecular Magnet