1,3‐Alternate Calix[4]arene Nitronyl Nitroxide Tetraradical and Diradical: Synthesis, X‐Ray Crystallography, Paramagnetic NMR Spectroscopy, EPR Spectroscopy, and Magnetic Studies.

Rajca, Andrzej; Pink, Maren; Mukherjee, Sumit; Rajca, Suchada; Das, Kausik

doi:10.1002/chin.200749048

Cited by 3 publications

(3 citation statements)

References 12 publications

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“…Syntheses of diradicals 1 and 2 start from the corresponding cyano-benzotriazinyl (cyano-Blatter) radicals, which are reduced to formyl-Blatter radicals, and then condensed with 2,3-bis(hydroxyamino)-2,3-dimethylbutane. 31,32,43,44 Oxidation of the condensation products yield diradicals 1 and 2, with isolated yields of 4-12% and 18-29%, respectively, for the multistep syntheses. 31,32 An analogous approach to triradical 3, starting from the corresponding di-cyano-Blatter radical produces only miniscule quantities of triradical with ~1% yield.…”

Section: Synthesis Ofmentioning

confidence: 99%

Synthesis and Thin Films of Thermally Robust Quartet (S = 3/2) Ground State Triradical

et al. 2021

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High spin (S = 3/2) organic triradicals may offer enhanced properties with respect to several emerging technologies, but those synthesized to date typically exhibit small doublet quartet energy gaps and/or possess limited thermal stability and processability. We report a quartet ground state triradical 3, synthesized by a Pd(0)-catalyzed radical-radical cross-coupling reaction, which possesses two doublet-quartet energy gaps, EDQ ≈ 0.2 -0.3 kcal mol -1 and EDQ2 ≈ 1.2 -1.8 kcal mol -1 . The triradical has a 70+% population of the quartet ground state at room temperature, and good thermal stability with onset of decomposition at >160 C under inert atmosphere. Magnetic properties of 3 are characterized by SQUID magnetometry in polystyrene glass and by quantitative EPR spectroscopy. Triradical 3 is evaporated under ultra-high vacuum to form thin films of intact triradicals on silicon substrate, as confirmed by high resolution X-ray photoelectron spectroscopy. AFM and SEM images of the ~1-nm thick films indicate that the triradical molecules form islands on the substrate. The films are stable under ultra-high vacuum for at least 17 h but show onset of decomposition after 4 h at ambient conditions. The drop-cast films are less prone to degradation in air and have longer lifetime.

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Section: Synthesis Ofmentioning

confidence: 99%

Synthesis and Thin Films of Thermally Robust Quartet (S = 3/2) Ground State Triradical

et al. 2021

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“…17,22−25 Treatment of 3 with DIBAL-H followed by hydrolysis of the imine group provides formyl-Blatter radical 4. Radical 4 is initially reduced to the corresponding leuco-amine-aldehyde, or alternatively, it is directly condensed with 2,3-bis(hydroxyamino)-2,3-dimethylbutane; 26 the resultant adduct is oxidized in air to provide diradical 2, which is purified by normal phase chromatography (silica gel) at ambient conditions.…”

Section: ■ Introductionmentioning

confidence: 99%

Thermally and Magnetically Robust Triplet Ground State Diradical

et al. 2019

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High spin (S = 1) organic diradicals may offer enhanced properties with respect to several emerging technologies, but typically exhibit low singlet triplet energy gaps and possess limited thermal stability. We report triplet ground state diradical 2 with a large singlet-triplet energy gap, ΔE ST ≥ 1.7 kcal mol −1 , leading to nearly exclusive population of triplet ground state at room temperature, and good thermal stability with onset of decomposition at ~160 °C under inert atmosphere. Magnetic properties of 2 and the previously prepared diradical 1 are characterized by SQUID magnetometry of polycrystalline powders, in polystyrene glass, and in other matrices. Polycrystalline diradical 2 forms a novel one-dimensional (1D) spin-1 (S = 1) chain of organic radicals with intrachain antiferromagnetic coupling of J′/k = −14 K, which is associated with the N•••N and N•••O intermolecular contacts. The intrachain antiferromagnetic coupling in 2 is by far strongest among all studied 1D S = 1 chains of organic radicals, which also makes 1D S = 1 chains *

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“…The NLO properties of open-shell organic molecules, such as singlet biradicals, are attracting much attention because these systems are expected to have completely different electronic excited states. Their electronic structures can be written as a resonance between a closed-shell and a biradical form − as shown in Figure a for the present compound, naphtho[2,1- d :6,5- d ′]bis([1,2,3]dithiazole), abbreviated as NT. Nakano and co-workers proposed the enhancement of the third-order nonlinear susceptibility of an organic singlet biradical. − Because such singlet biradicals have an attractive feature for NLO materials such as an optical gap above 1 eV, this proposal expanded the NLO studies toward air-stable open-shell materials such as biradical molecule systems, and two-photon absorption spectra of the singlet biradical compounds were examined. − In the present work, we studied the third-harmonic generation (THG) and electroabsorption (EA) spectra of NT.…”

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confidence: 99%

Third-Order Nonlinear Optical Properties and Electroabsorption Spectra of an Organic Biradical, [Naphtho[2,1-d:6,5-d′]bis([1,2,3]dithiazole)]

et al. 2014

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Thin films of a thiazyl biradical, naphtho[2,1-d:6,5-d′]bis([1,2,3]dithiazole), abbreviated as NT, exhibit nonlinear optical properties with a large third-order nonlinear susceptibility of 2.1 × 10 −11 esu. The electroabsorption and low-temperature-absorption measurements reveal a series of degenerate electronic states, which is probably caused by the biradical character of NT. It is concluded that this degeneracy should enhance the third-order nonlinear optical properties.

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1,3‐Alternate Calix[4]arene Nitronyl Nitroxide Tetraradical and Diradical: Synthesis, X‐Ray Crystallography, Paramagnetic NMR Spectroscopy, EPR Spectroscopy, and Magnetic Studies.

Abstract: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Cited by 3 publications

References 12 publications

Synthesis and Thin Films of Thermally Robust Quartet (S = 3/2) Ground State Triradical

Synthesis and Thin Films of Thermally Robust Quartet (S = 3/2) Ground State Triradical

Thermally and Magnetically Robust Triplet Ground State Diradical

Third-Order Nonlinear Optical Properties and Electroabsorption Spectra of an Organic Biradical, [Naphtho[2,1-d:6,5-d′]bis([1,2,3]dithiazole)]

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