A Dendrimer Approach to High-Spin Polycarbenes. Conversion of Connectivity from Disjoint to Non-Disjoint by Perturbation of Nonbonding Molecular Orbital Coefficients

Hirai, Katsuyuki; Kamiya, Eiko; Itoh, Tetsuji; Tomioka, Hideo

doi:10.1021/ol060378n

Cited by 12 publications

(6 citation statements)

References 25 publications

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“…Therefore, efforts to introduce magnetism in organic (polymer) materials have been focusing on the development of (conjugated) materials in which the spins are deliberately introduced. A first approach consists in the incorporation of organic, spin-carrying moieties, such as radicals or carbenes in the polymer chains, either as main chain or as side chain, resulting in organic magnets. In this approach, the use of conjugated polymers or oligomers as linking units between the subsequent spins offers an important additional advantage, i.e., the strong through-bond coupling, which allows alignment of the spins within the same (polymer) molecule.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Properties of Substituted Poly(thiophene)s in Their Neutral State

et al. 2010

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Abstract. The magnetic behavior of undoped (neutral), substituted poly(thiophene)s is reported. In particular, the influence of the nature of the substituent (alkyl, alkoxy, thioalkyl), the substitution pattern (head-to-tail (HT) versus head-to-head-tail-to-tail (HH-TT)), and the regioregularity on the magnetic properties has been investigated. ESR spectroscopy reveals that the nature of the substituent determines the spin density, while the line width and asymmetry of the ESR signals are mainly governed by the substitution pattern and regioregularity. The spins give rise to a paramagnetic behavior. SQUID magnetometry reveals the presence of superparamagnetic order at room temperature, while ferromagnetism is observed at 5 K. The magnetic behavior observed by SQUID magnetometry does not (solely) originate from the ESR-active spin system. Its strength does therefore not depend on the ESR spin density, but seems to be governed by the supramolecular structure.

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Section: Introductionmentioning

confidence: 99%

Magnetic Properties of Substituted Poly(thiophene)s in Their Neutral State

et al. 2010

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“…Sonogashira coupling of bis(4‐iodo‐2,6‐dimethylphenyl)diazomethane ( 17 ) with 2.8 equiv of ethynylanthracene 12 resulted in the formation of a desired diazo compound 1c ‐N 2 as red crystals in 85% yield under mild conditions (Scheme ). Diazomethanes 1a , b , and d were obtained by similar procedures in 40–75% yields.…”

Section: Resultsmentioning

confidence: 99%

“…To a mixture of bis(4‐iodo‐2,6‐dimethylphenyl)diazomethane 17 (25 mg, 50 µmol), 9‐ethynylanthracene (31 mg, 153 µmol), bis(triphenylphosphine)palladium(II) dichloride (4.0 mg, 5.7 µmol), and copper(I) iodide (2.0 mg, 11 µmol) was added anhydrous triethylamine (1 mL) at room temperature under an atmosphere of a 1:1 mixture of nitrogen and hydrogen, and the mixture was stirred at 40 °C for 15 h. After evaporation of the solvent, the residue was passed through a short column (aluminum oxide deactivated with 5% water, chloroform) at 0 °C and then purified by GPC (12 cycles, chloroform, monitored at 300 nm) to give diazomethane 1a ‐N 2 as red crystals (17 mg, 52%): mp 120.3–123.8 °C (dec.); IR (KBr, cm –1 ) 2194 (w, ν C≡C ); 2041 (s, ν C=N2 ); 1 H‐NMR (300 MHz, CDCl 3 , ppm) δ 8.66 (d, J = 8.6 Hz, 4H), 8.43 (s, 2H), 8.02 (d, J = 8.6 Hz, 4H), 7.64–7.58 (m, 4H), 7.54–7.49 (m, 8H), 2.23 (s, 12H); 13 C‐NMR (75.5 MHz, CDCl 3 , ppm) δ 137.4, 132.6, 132.1, 131.2, 129.7, 128.7, 127.7, 126.8, 126.6, 125.7.…”

Section: Methodsmentioning

confidence: 99%

Generation and reactivities of triplet diphenylcarbenes protected by bulky groups as para substituents

Hirai

Hatanaka

Yamaguchi

et al. 2011

J of Physical Organic Chem

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Bis(2,6‐dimethylphenyl)diazomethane (1b‐N2) having 10‐(4‐tert‐butyl‐2,6‐dimethylphenyl)‐2,7‐di(phenylethynyl)‐9‐anthrylethynyl groups at the 4,4′‐positions was synthesized. Triplet diphenylcarbene 31b was generated by photolysis of the precursor and was characterized by electron spin resonance and UV–Vis spectroscopies at low temperature, and laser flash photolysis techniques at room temperature. Irradiation of 1b‐N2 in a 2‐methyltetrahydrofuran matrix at 77 K gave electron spin resonance signals ascribable to triplet carbene 31b. UV–Vis spectra of 31b were obtained by irradiating 1b‐N2 under identical conditions. The laser flash photolysis of 1b‐N2 in a degassed benzene solution gave transient absorption bands ascribable to 31b, which decayed in a first‐order fashion with a rate constant of 0.46 s–1. The carbene was shown to be less reactive than the triplet bis(2,6‐dimethylphenyl)carbene (31a) having 9‐anthrylethynyl groups at the 4,4′‐positions, which decayed in a second‐order fashion with a rate constant (2 k/εl) of 0.69 s–1. Triplet carbene 31b was trapped by oxygen to generate ketone oxide 1b‐O with a rate constant of 1.9 × 107 M–1 s–1 and also by 1,4‐cyclohexadiene with a rate constant of 1.2 M–1 s–1. Similar studies with diphenyldiazomethanes (1c‐N2 and 1 d‐N2) having bulky substituents, 10‐(4‐tert‐butyl‐2,6‐dimethylphenyl)‐2,7‐bis[3,5‐di(phenylethynyl)phenylethynyl]‐9‐anthrylethynyl and 10‐(4‐tert‐butyl‐2,6‐dimethylphenyl)‐2,7‐bis(9‐triptycylethynyl)‐9‐anthrylethynyl groups at the 4,4′‐positions respectively indicated that the corresponding triplet carbenes 31c and 31 d were more persistent than 31b. Steady‐state irradiation of 1a‐N2, 1c‐N2, and 1 d‐N2 in degassed benzene afforded tetraarylethenes 2a, 2c, and 2d in 83, 50, and 51% yield, respectively. Copyright © 2011 John Wiley & Sons, Ltd.

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“…High-spin organic polymers are important building blocks for producing organic molecule-based magnets; therefore, a wide variety of organic polyradicals have been investigated. − The π-topological rule is an essential requirement to achieve high spin states in the ground state, as suggested, in studies on polycarbenes , and poly(triarylmethine radical)s that have successfully achieved spin states with 10−10 3 magnitudes. For practical use, polyradical spin sources should be air-stable organic radicals; − however, most stable radicals have partial spin density distributions.…”

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confidence: 99%