Regioselective oxygenative tetraamination of [60]fullerene. Fullerene-mediated reduction of molecular oxygen by amine via ground state single electron transfer in dimethyl sulfoxide

The reaction of [60]fullerene with a variety of a secondary aliphatic amines in 20% v/v dimethyl sulfoxide in chlorobenzene under an atmospheric pressure of molecular oxygen allows regioselective introduction of four amino groups and one epoxide group around one pentagon of the fullerene molecule in good to high yield. This new synthesis of tetraaminofullerene expoxide can be carried out with a simple procedure on a multigram scale at room temperature and affords a variety of functionalized fullerene derivatives. Near-infrared analysis of a mixture of [60]fullerene and piperidine in a deaerated dimethyl sulfoxide/chlorobenzene mixture indicated equilibrium formation of [60]fullerene radical anion (C60*-) that persists at least for 2 weeks at room temperature but reacts immediately with molecular oxygen to give the tetraaminofullerene expoxide. The Benesi-Hildebrand analysis of the concentration dependency of the near-infrared absorption indicated that a [C60*- piperidine*+] radical ion pair is formed with an equivalent constant of K = 0.62 +/- 0.02 M(-1) at 25 degrees C. This and other lines of evidence suggest that the oxygenative amination reaction involves C60-mediated reduction of molecular oxygen by the amine.     

Novel aggregation of [Ni(thiolato)2(amine)2]-type square planes assisted by silver(I) ions

Treatment of [Ni(L)][L =((-)SCH(2)CH(2)NH[double bond, length as m-dash]C(CH(3))-)(2)] with Ag(+) in water gave a pinwheel-like S-bridged Ni(II)(3)Ag(I)(2) structure in [Ag(2)[Ni(L)](3)](2+), which further reacted with [Ni(L)] to produce a Ni(II)(4)Ag(I)(2) structure in [Ag(2)[Ni(L)](4)](2+) and a Ni(II)(7)Ag(I)(4) structure in [Ag(4)[Ni(L)](7)](4+).     

NLO‐active maleimide copolymers with ­high glass transition temperatures

We synthesized some novel rigid NLO‐active maleimide copolymers bearing DR‐1 moieties ( PMPD , PHSD and PHND ). All copolymers exhibited high T_g's (190～197 °C), good solubilities for common solvents and excellent film‐forming properties. Dependence of film thickness on the d₃₃ value for the poled copolymer films induced by corona poling was investigated and it was demonstrated that in less than thickness of 0.3 µm decrease of the thickness gives rise to remarkable increase in the d₃₃ value. The poled copolymer films exhibited large d₃₃ values (270 × 10^?9 esu (film thickness 0.13 µm) for PMPD , 290 × 10^?9 esu (0.12 µm) for PHSD and 350 × 10^?9 esu (0.08 µm) for PHND ) as well as large r₃₃ values (51.0 pmV^?1 for PMPD and 60.4 pmV^?1 for PHND ) which are significantly large compared to the value of LiNbO₃ (31 pmV^?1) as a typical EO material. The d₃₃ values of the poled copolymers were kept constant even after standing 1000h at 80 °C, although a small decrease was observed at an initial stage. Further, the d₃₃ values did not change up to ca. 123 °C upon heating at the rate of 10 °C/min in all cases. Copyright © 2002 John Wiley & Sons, Ltd.     

Asymmetric crystallization of bisguanidinobenzene derivatives

We show that the mono-N-methylated and -ethylated derivatives of the achiral compound bisguanidinobenzene undergo spontaneous asymmetric crystallization into a chiral form with chiral space group P2₁2₁2₁. The absolute configurations of the chiral crystals were determined by X-ray crystallography and correlated with circular dichroism (CD) spectra recorded in the solid state. The corresponding protonated and isopropylated derivatives, by contrast, afforded achiral crystals.     

Catalytic oxygenative degradation of 4-chlorocatechol by a nonheme iron(III) complex—Mechanism and prevention of catechol ester formation

We examined the oxygenative degradation of 4-chlorocatechol and 4-tert-butylcatechol catalyzed by iron(III)-tris(pyridin-2-yl)amine complex from the standpoint of repressing the formation of 4-chlorocatechol esters of the oxygenated products that causes the incomplete degradation of 4-chlorocatechol. Analysis of the products revealed that 4-chlorocatechol esters are formed by the reaction of muconic anhydride, which is the monooxygenated product, with catechols. It was found that the use of MeOH as the solvent instead of MeCN completely suppressed the catechol ester formation through the methanolysis of muconic anhydride, which greatly improves the degradation efficiency of 4-chlorocatechol.     

Enantioselective binding of an 11-cis-locked cyclopropyl retinal. The conformation of retinal in bovine rhodopsin

[formula: see text] The conformation of the retinal chromophore in rhodopsin is central for understanding the visual transduction process. The absolute twist around the 12-s bond of the chromophore in rhodopsin has been determined by studies with 11-cis-locked 11,12-cyclopropylretinal analogues (11S,12R)-2 and (11R,12S)-3, enantioselectively synthesized with the aid of an enzyme. The finding that enantiomer 2 binds to opsin while the other 3 does not defines the absolute sense of twist around the 12-s bond.