Laser raman spectra of the stable low-temperature phase of ferrocene

Laser Raman spectra of ferrocene crystal are recorded for the stable (orthorhombic) and metastable (triclinic) low-temperature phases, and the stable and undercooled (monoclinic) high-temperature phases.The skeletal vibrational modes [v₄(A_1g) and v₁₆(E_1g)], the CH bending (⊥e) mode [v₂₅(E_2g)], and the lattice modes below 100 cm^?1 show characteristic changes among these phases.     

Iron‐Complex‐Catalyzed C?C Bond Cleavage of Organonitriles: Catalytic Metathesis Reaction between H?Si and R?CN Bonds to Afford R?H and Si?CN Bonds

The first example of the catalytic C? CN bond cleavage of acetonitrile as well as Si? CN bond formation have been achieved in the photoreaction of MeCN with Et₃SiH promoted by [Cp(CO)₂FeMe]. This catalytic system is applicable to other organonitriles. Several iron complexes [(η⁵‐C₅R₅)(CO)₂FeR′] (R₅=H₅, H₄Me, Me₅, H₄SiMe₃, H₄I, H₄P(O)(OMe)₂; R′=SiMe₃, CH₂Ph, Me, Cl, I) were examined as catalyst, and [Cp(CO)₂FeMe] was found to be the best precursor. A catalytic reaction cycle was proposed, which involves oxidative addition of Et₃SiH to [Cp(CO)FeMe], reductive elimination of CH₄ from [Cp(CO)FeMe(H)(SiEt₃)], coordination of RCN to [Cp(CO)Fe(SiEt₃)], silyl migration from Fe to N in the coordinated RCN, and dissociation of Et₃SiNC from Fe. The reaction with MeCN of [Cp(CO)Fe(py)(SiEt₃)], which was newly prepared and determined by X‐ray analysis, and the reaction of Et₃SiH with MeCN in the presence of a catalytic amount of [Cp(CO)Fe(py)(SiEt₃)] showed that the 16‐electron species [Cp(CO)Fe(SiEt₃)] is the active species in the catalytic cycle (TON up to 251).     

Tetracyanoanthraquinodimethanes with a chiral amide group: preparation, properties, and charge-transfer photochirogenetic reaction with 1,2-dianisylacenaphthene-1,2-diol

[reaction: see text] A series of butterfly-shaped tetracyanoanthraquinodimethanes (TCNAQs) with a chiral amide auxiliary 1a-f were prepared from the corresponding anthraquinones. They are stronger acceptors than the unsubstituted derivative and undergo one-wave two-electron reduction. They form weak electron-donor-acceptor (EDA) complexes with the title pinacol 2. Upon charge-transfer excitation of these complexes, dihydro-TCNAQs 3 and 1,8-dianisoylnaphthalene 4 were efficiently formed, the latter of which is the product of a retropinacol reaction via 2+*. Partial enantiodifferentiation of rac-2 was realized during the photoreactions with 2-[(R)-1-phenylethylcarbamoyl]-TCNAQ 1ain CD3CN. Thus, optically active (S,S)-(+)-pinacol 2 (12.3% ee at 54% conversion; 21.5% ee at 70% conversion) was recovered from the photolyzates. This reaction represents a new and rare example of the pseudokinetic resolution of tert-alcohol accompanied by C-C bond fission. Significant differences in the association constants for the diastereomeric EDA complexes are responsible for the observed enantiodifferentiation.     

Topological structure of a vortex in the Fulde-Ferrell-Larkin-Ovchinnikov state

We find theoretically that the vortex core in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is quite different from the ordinary core for a simple topological reason. The intersection point of a vortex and nodal plane of the FFLO state empties the excess spins. This leads to observable consequences in the spatial structure of the spontaneous magnetization. We analyze this topological structure based on the low lying excitation spectrum by solving a microscopic Bogoliubov-de Gennes equation to clarify its physical origin.     

Coherence and superconductivity in coupled one-dimensional chains: a case study of YBa2Cu3Oy

We report the infrared (IR) response of Cu-O chains in the high-T(c) superconductor YBa(2)Cu(3)O(y) over the doping range spanning y=6.28-6.75. We find evidence for a power law scaling at mid-IR frequencies consistent with predictions for Tomonaga-Luttinger liquid, thus supporting the notion of one-dimensional transport in the chains. We analyze the role of coupling to the CuO2 planes in establishing metallicity and superconductivity in disordered chain fragments.     

Determination of iron(II) with 2-nitroso-5-diethylaminophenol by thermal lens spectrophotometry using a semiconductor laser as a light source

The concentration of Fe(II) ion is determined by chelation with 2-nitroso-5-diehtylaminophenol and liquid-liquid extraction into chloroform. Light absorption at 780 nm is measured with a thermal lens spectrophotometer equipped with a semiconductor laser as a light source. The enhancement factor achieved experimentally is 47. The detection limit of Fe(II) ion is 8.1 × 10^?9 M, which is 3–4 times better than that obtained by conventional absorption spectrometry, and is governed by the background signal originating from Fe(II) impurity in the reagent.     

Time Change Approach to Generalized Excursion Measures, and Its Application to Limit Theorems

It is proved that generalized excursion measures can be constructed via time change of Itô’s Brownian excursion measure. A tightness-like condition on strings is introduced to prove a convergence theorem of generalized excursion measures. The convergence theorem is applied to obtain a conditional limit theorem, a kind of invariance principle where the limit is the Bessel meander.     

Alternative simple and effective synthesis of (di)benzoxanthones and their functions toward fluorescent dyes

(Di)benzoxanthones possessing additional benzene units on one or both sides of xanthone were prepared via dehydration of the corresponding dihydroxybenzophenone, where a catalytic amount of K₂CO₃ dramatically increased the yields. Chemical transformations of the versatile carbonyl groups of (di)benzoxanthones could derive fluorescent materials.     

Crystal structure, spin polarization, solid-state electrochemistry, and high n-type carrier mobility of a paramagnetic semiconductor: vanadyl tetrakis(thiadiazole)porphyrazine

We report the synthesis, crystal structure, and magnetic, electrochemical, and carrier-transport properties of vanadyl tetrakis(thiadiazole)porphyrazine (abbreviated as VOTTDPz) with S = ?. X-ray crystal analysis reveals two polymorphs, the α and β forms; the former consists of a 1D regular π stacking, while the latter forms a 2D π network. Molecular orbital calculations suggest a V(4+)(d(1)) ground state and a characteristic spin polarization on the whole molecular skeleton. The temperature dependence of the paramagnetic susceptibility of the α form clearly indicates a ferromagnetic interaction with a positive Weiss constant of θ = 2.4 K, which is well-explained by McConnell's type I mechanism. VOTTDPz forms amorphous thin films with a flat and smooth surface, and their cyclic voltammogram curves indicate a one-electron reduction process, which is highly electrochromic, because of a reduction of the porphyrazine π ring. Thin-film field-effect transistors of VOTTDPz with ionic-liquid gate dielectrics exhibit n-type performance, with a high mobility of μ = 2.8 × 10(-2) cm(2) V(-1) s(-1) and an on/off ratio of 10(4), even though the thin films are amorphous.