- Ferromagnetic spin alignment in head-to-tail coupled oligo(1,4-phenyleneethynylene)s and oligo(1,4-phenylenevinylene)s bearing pendant p-phenylenediamine radical cations
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The intramolecular and long-range ferromagnetic coupling between p-phenylenediamine radical cations in head-to-tail coupled oligo(1,4-phenyleneethynylene)s and oligo(1,4-phenylenvinylene)s between neighbors and next-nearest neighbors is described. UV/vis/near-IR experiments show that the radical cations are localized in the pendant p-phenylenediamine units of the conjugated oligomers. The ESR spectra of these oligo(1,4-phenyleneethynylene) and oligo(1,4-phenylenvinylene) di(radical cation)s are consistent with those of a triplet state. A linear behavior is observed for the doubly integrated ESR intensity of the ΔM(s) = ±1 and ΔM(s) = ±2 signals with the inverse temperature (I ~ 1/T), consistent with Curie's law. This behavior indicates a triplet ground-state diradical with a large triplet-singlet energy gap or possibly a degeneracy of singlet and triplet states.
- Van Meurs, Pauline J.,Janssen, Rene A. J.
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p. 5712 - 5719
(2007/10/03)
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- SULFURIC ACID ESTERS OF SUGAR ALCOHOLS
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The present invention is concerned with novel sulfuric acid esters of sugar alcohols and sugar alcohol-like compounds of the formula STR1 Also described are methods for the treatment and/or prophylaxis of arteriosclerotic changes in the vascular wall as well as a process for the manufacture of the compounds of formula I and their salts.
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- MAGNETIC COUPLING BETWEEN TWO PHENOXYL RADICALS ATTACHED TO THE PHENYL RINGS OF CIS- AND TRANS-STILBENES
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Magnetic coupling between two sterically protected phenoxyl radicals through the cis- and trans-stilbene chromophores was studied by means of their EPR fine structures.While the zero-field splitting parameters D, which are governed by the magnitude of dip
- Mitsumori, Teruyuki,Koga, Noboru,Iwamura, Hiizu
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- Semiempirical Investigation of Stilbene-Linked Diradicals and Magnetic Study of Their Bis(N-tert-butylnitroxide) Variants
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The electronic states of open-shell stilbene diradicals were studied.Previously used semiempirical MO-CI methods were applied to stilbenes having dimethylene, dioxyl, and dinitroxide centers in o,o'-, o,m'-, o,p'-, m,m'-, m,p'-, and p,p'-substitution patterns, and the various singlet-triplet energy gaps were computed to predict qualitative ground state spin multiplicities.Singlet and triplet spin states were essentially degenerate in the m,m'-isomers of disjoint connectivity, while nondisjoint o,m'- and m,p'-isomers had triplet computed ground states.Nitroxide-based diradicals showed considerably smaller computational exchange coupling energies than did other diradicals models studied.As a tests of these computations, stilbenes with two N-tert-butyl nitroxide groups at the o,m'-, m,m'-, and m,p'-positions were prepared, and their magnetic properties were studied by ESR and magnetic susceptibility measurements.The m,m'- and m,p'-isomers were found experimentally to have singlet and triplet ground states, respectively, in accord with the qualitative computed predictions.
- Yoshioka, Naoki,Lahti, Paul M.,Kaneko, Takashi,Kuzumaki, Yoshihiro,Tsuchida, Eishun,Nishide, Hiroyuki
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p. 4272 - 4280
(2007/10/02)
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