Synthesis and Identification of a Trimethylenemethane Derivative π-Extended with Three Pyridinyl Radicals

Matsumoto, Kouzou; Inokuchi, Daisuke; Hirao, Yasukazu; Kurata, Hiroyuki; Sato, Kazunobu; Takui, Takeji; Kubo, Takashi

doi:10.1021/ol902937k

Cited by 14 publications

(10 citation statements)

References 62 publications

(19 reference statements)

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“…The trimethylenemethane (TMM) derivative DR68 , in which the parent TMM is π-extended, was synthesized by the alkali-metal reduction of the isolated corresponding dication 142 (Scheme ) . The frozen-glass X-band cw-ESR spectrum of diradical DR68 gave unresolved fine structure because of the small zero-field-splitting parameter of | D / hc | = 0.002 cm –1 .…”

Section: Delocalized Diradicalsmentioning

confidence: 99%

Diradicals

2013

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Section: Delocalized Diradicalsmentioning

confidence: 99%

Diradicals

2013

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“…Free radicals are one of the fascinating classes of reactive intermediates. − Traditionally, synthetic chemists exploited the radicals for their intermediacy in organic syntheses. − However, the situation drastically changed after they received attention of biologists, polymer chemists, and atmospheric chemists equally. The primary reasons include their important roles in biochemistry of diseases and aging, − synthesis of many polymers, , and also their function in the cleansing action of the atmosphere. − Due to their potential applications such as magnetic materials and data storage, − stable radicals − have been synthesized, which range between monoradical and polyradicals. − Tuning the radical properties through incorporation of heteroatoms for potential metal mediation and creating radical centers at the heteroatoms are a few of the popular strategies in making stable radicals. − In this regard, heterocyclic radicals attracted the imagination of many experimentalists and theoreticians. − …”

Section: Introductionmentioning

confidence: 99%

Does a Nitrogen Lone Pair Lead to Two Centered–Three Electron (2c–3e) Interactions in Pyridyl Radical Isomers?

et al. 2017

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Each of the three isomeric pyridyl radicals (2-, 3-, and 4-dehydropyridines) contains a lone pair and an unpaired electron. As a result, a potential two centered-three electron interaction between the radical electron and the lone pair through-space (TS) and/or through-bond (TB) can exist that may influence the stability of the radicals. Due to the change in geometrical positions relative to each other, the strength of interaction can be varied. In this study, we investigated the structural and stability aspects of pyridyl radical isomers with a major emphasis on the interaction of a nitrogen lone pair with the radical center. In order to obtain evidence for such interactions, protonated and N-oxide analogues of the corresponding isomeric pyridyl radicals have been considered in such a way to understand the consequences due to unavailability of the lone pair. Similarly, electron attachment and detachment energies at the radical center (vertical detachment energy, VDE, of corresponding anions and vertical ionization energy, VIE, of radical isomers) have been calculated to find out the interaction trend upon modification at the radical center. Different levels of theory including (U)B3LYP/cc-pVTZ, (U)M06/cc-pVTZ, CBS-QB3, single-point energy calculations at (U)CCSD(T)/cc-pVTZ, and multireference CASSCF/cc-pVTZ methods have been employed in this regard. A closer inspection of geometries, relative stability order, spin density, electrostatic potential, molecular orbitals, NBO analysis, and vibrational analysis have showed a strong and stabilizing TS interaction between the radical center and the lone pair in the case of the 2-pyridyl radical. On the other hand, the 4-pyridyl radical showed stabilizing interactions only via TB coupling, whereas the TS interaction is nonexistent. Despite the presence of both interactions in the case of the 3-pyridyl radical, their overall influence is less effective toward stability.

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“…33,34 Because most molecules are in their singlet state, no appreciable SQUID signal is observed at low T, while a very weak signal is still detectable with EPR. As reported in the literature, 18,[35][36][37] this low-T signal is produced by partially hydrogenated species with half-integer spin configurations: the final step of the synthesis involves dehydrogenation of the pentagonal sites, and there is a small ($1%) probability that the reaction will not remove the hydrogen on one pentagonal site. Bi-hydrogenated species are not necessarily magnetic, while tri-hydrogenated ones occur with negligible probability ($1 every 10 6 molecules) and can be neglected.…”

Section: Magnetic Propertiesmentioning

confidence: 57%