Heat capacity and phase transition of a five-coordinated antiferromagnet,IODOBIS (N,N-diethyldithiocarbamato) iron (III), in the temperature range from 0.4 TO 300 K

The heat capacity of iodobis (N,N-diethyldithiocarbamato) iron (III) has been measured between 0.4 and 300 K. A phase transition from an antiferromagnetic to a paramagnetic state was found at T_N = (1.937 ± 0.010) K, and a Schottky-type anomaly arising from a zero-field single ion splitting was observed around 12 K. The total magnetic entropy and enthalpy, including the phase transition and the Schottky-type anomaly, are 11.36JK^?1mol^?1 and 134.5 J mol^?1, respectively. The entropy is approximately equal to Rln 4 ( = 11.53 JK^?1mol^?1), confirming that the spin manifold is really a quartet. The entropy and enthalpy due to the phase transition are estimated to be (5.57±0.01)JK^?1mol^?1 and (13.2±0.05)Jmol^?1, respectively. The entropy and enthalpy above t_n are quite large, as in the case of the related compound chlorobis (N,N-diethyldithiocarbamato) iron (III). This fact suggests that the present complex may be considered to have a two-dimensional type of magnetic structure from a thermodynamic point of view. A correlation diagram between the transition entropy and energy is proposed, this being a diagnostic for the determination of the magnetic dimensionality.     

Fe/Cr- and Co/Cr-mediated catalytic asymmetric 2-haloallylations of aldehydes

The first example to couple aldehydes and 3-bromo-2-halopropenes in a catalytic asymmetric manner is reported. The coupling reaction is effected by the use of a chiral sulfonamide-Cr complex (prepared in situ from 1d, CrBr3, Fe(III) or from Co(II), Et3N, and Mn), TMSCl, and 2,6-lutidine. The method reported here is operationally simple and scalable, furnishing 3-halohomoallylic alcohols with a synthetically useful level of enantiomeric excess.     

The SAAP force field. A simple approach to a new all-atom protein force field by using single amino acid potential (SAAP) functions in various solvents

A simple strategy to compose a new all-atom protein force field (named as the SAAP force field), which utilizes the single amino acid potential (SAAP) functions obtained in various solvents by ab initio molecular orbital calculation applying the isodensity polarizable continuum model (IPCM), is presented. We considered that the total energy function of a protein force field (E(TOTAL)) is divided into three components; a single amino acid potential term (E(SAAP)), an interamino acid nonbonded interaction term (E(INTER)), and a miscellaneous term (E(OTHERS)), which is ignored (or considered to be constant) at the current version of the force field. The E(INTER) term consists of electrostatic interactions (E(ES')) and van der Waals interactions (E(LJ')). Despite simplicity, the SAAP force field implicitly involves the correlation among individual terms of the Lifson's potential function within a single amino acid unit and can treat solvent effects unambiguously by choosing the SAAP function in an appropriate solvent and the dielectric constant (D) of medium. Application of the SAAP force field to the Monte Carlo simulation of For-Ala(2)-NH(2) in vacuo reasonably reproduced the results of the extensive conformational search by ab initio molecular orbital calculation. In addition, the preliminary Monte Carlo simulations for For-Gly(10)-NH(2) and For-Ala(10)-NH(2) showed reversible transitions from the extended to the pseudosecondary structures in water (D = 78.39) as well as in ether (D = 4.335). The result suggested that the new approach is efficient for fast modeling of protein structures in various environments. Decomposition analysis of the total energy function (E(TOTAL)) by using the SAAP force field suggested that conformational propensities of single amino acids (i.e., the E(SAAP) term) may play definitive roles on the topologies of protein secondary structures.     

Ammoximation of ketones catalyzed by titanium-containing ethane bridged hybrid mesoporous silsesquioxane

The first example of ammoximation of bulky ketones over highly hydrophobic titanium incorporated ethane bridged hybrid mesoporous silsesquioxane with high selectivity of oximes is presented.     

Asymmetric reaction. XV. Structure and relative configuration of a reductive dimerization product of ethyl phenylglyoxylate,diethyl diphenyltartrate

The hydrogenation of ethyl phenylglyoxylate catalyzed by bis(dimethylglyoximato)cobalt(II)-quinine gave a novel reductive dimerization product, diethyl diphenyltartrate, with a slight optical activity. The crystals obtained from its benzene-hexane solution were investigated by X-ray diffraction method. The crystal is triclinic, space group p1, a = 10.078(3), b = 10.283(2), c = 9.781(3) Å, α = 109.80(2), β = 102.35(3), γ = 78.50(2)°, Z = 2, V = 922.7 ų, Dc = 1.29 g cm^?3,μ = 7.46 cm^?1 for Cu Kα. The structure was solved by the direct method, and refined by a block-diagonal least-squares procedure: R = 0.059 for 2568 reflections with | Fo | >3σ(| Fo | ). The relative configuration around the two chiral carbons indicated that the molecule is in the threo-form, and the Newman projection showed that the molecule has the staggered conformation. There were two relatively strong intramolecular hydrogen bonds between the two hydroxyl groups and the two carbonyl oxygen atoms of ethoxycarbonyl groups.     

Quantization of conformal gravity: Another approach to the renormalization of gravity

The non-renormalizability of quantum gravity poses a great problem to the construction of any unified field theory of all known interactions. Normally, we start with a unitary theory of gravity and investigate its renormalization properties. This is the first of a series of papers where we start with the opposite approach, beginning with a renormalizable theory and investigating its unitarity structure. In particular, we study non-perturbative approaches to the quantization of conformal gravity. Using ADM coordinates, we perform the canonical quantization of the Weyl action C_μναβ², which is renormalizable and is also local scale invariant. Although this theory is certainly not unitary in perturbation theory, we speculate that unitarity may be restored when we approach this theory non-perturbatively, by examining the possibility of different phase transitions.