Slow magnetic relaxation in a mixed-valence Mn(II/III) Complex: [MnII2(bispicen)2(mu 3-Cl)2Mn(III)(Cl4Cat)2Mn(III)(Cl4Cat)2(H2O)2] infinity

A layered mixed-valence manganese complex, [Mn(II)(2)(bispicen)(2)(mu(3)-Cl)(2)Mn(III)(Cl(4)Cat)(2)Mn(III)(Cl(4)Cat)(2)(H(2)O)(2)](infinity), is synthesized and characterized structurally. It displays a slow magnetic relaxation and hysteresis effect.     

Biomimetic oxidation of organic sulfides with TPPFe(III)Cl/imidazole/hydrogen peroxide

An enzyme model system, consisted with TPPFe(III)Cl/imidazole has been found to catalyze hydrogen peroxide dependent S-oxygenation and oxidative S-dealkylation of organic sulfides. This biomimetic reaction has been compared with the cytochrome P-450 catalyzed H₂O₂ dependent oxygenation.     

Oxidation of alcohols with sodium periodate catalyzed by supported Mn(III) porphyrins

The mild and efficient oxidation of alcohols with sodium periodate catalyzed by manganese(III) tetrakis(p-sulfonatophenylporphyrinato) acetate, [Mn(TPPS)], supported on polyvinylpyridine, [Mn(TPPS)-PVP], and Amberlite IRA-400, [Mn (TPPS)-Ad IRA-400], at room temperature is reported. The catalysts used in this study showed high activity not only in the oxidation of benzylic and linear alcohols but also in the oxidation of secondary alcohols at room temperature. These catalysts can be reused several times without significant loss of their activity.     

Crystal structure of 4,5-bis(4-dimethylaminophenyl)-2-(4-nitrophenyl)imidazole.

A nonlinear optical chromophore, 4,5-bis(4-dimethylaminophenyl)-2-(4-nitrophenyl)imidazole, was investigated by X-ray crystallography. The study focused on coplanarity among several aromatic rings, including phenyls and imidazole. Two phenyl rings with NMe2 groups are twisted by 46.39(3) degrees from each other. However, they are twisted by 23.05(5) degrees and 46.84(3) degrees from the imidazole, respectively. These unequal twists were elucidated by different conjugation pathways from the donors to the acceptor. The phenyl ring with the NO2 group is twisted by only 6.76(6) degrees from the imidazole.     

Atmospheric reactions Cl+CH3-(CH2)n-OH (n=0-4): a kinetic and theoretical study

The reactions of Cl with a series of linear alcohols: methanol (k1), ethanol (k2), 1-propanol (k3), 1-butanol (k4), and 1-pentanol (k5) were investigated as a function of temperature in the range of 264-382 K by laser photolysis-resonance fluorescence. The obtained kinetic data were used to derive the following Arrhenius expressions: k1=(3.55+/-0.22)x10(-10) exp[-(559+/-40)T], k2=(5.25+/-0.52)x10(-11) exp[(190+/-68)T], k3=(2.63+/-0.21)x10(-11) exp[(525+/-51)T], k4=(3.12+/-0.31)x10(-11) exp[(548+/-65)T], and k5=(3.97+/-0.48)x10(-11) exp[(533+/-77)T] (in units of cm(3) molecule(-1) s(-1)). To our knowledge, these are the first absolute kinetic data reported for 1-butanol and 1-pentanol and also the first kinetic study as a function of temperature for these two compounds. Results, mechanism, and tropospheric implications are discussed and compared with the reported reactivity with OH radicals. Moreover, a theoretical insight into the mechanisms of these reactions has also been pursued through ab initio M?ller-Plesset second-order perturbation treatment calculations with 6-311G** basis sets. Optimized geometries and vibrational frequencies have been obtained for transition states and molecular complexes appearing along the different reaction pathways. Furthermore, molecular energies have been calculated at quadratic configuration interaction with single, double, and triple excitations level in order to get an estimation of the activation energies.     

Deactivation of I(2P1/2) by CH3Cl,CH2Cl2, CHCl3, CCl3F,and CCl4

Collisional deactivation of I(²P_1/2) by the title compounds was investigated through the use of the time-resolved atomic absorption of excited iodine atoms at 206.2 nm. Rate constants for atomic spin-orbit relaxation by CH₃Cl, CH₂Cl₂, CHCl₃, CCl₃F, and CCl₄ are 3.1±0.3×10⁻¹³, 1.28±0.08×10⁻¹³, 5.7±0.3×10⁻¹⁴, 3.9±0.4×10⁻¹⁵, and 2.3±0.3×10⁻¹⁵cm³ molecule⁻¹ s⁻¹, respectively, at room temperature (298 K). The higher efficiency observed for relaxation by CH₃Cl, CH₂Cl₂, and CHCl₃ reveals a contribution in the deactivation process of the first overtone corresponding to the C(SINGLEBOND)H stretching of the deactivating molecule (which lies close to 7603 cm⁻¹) as well as the number of the contributing modes and certain molecular properties such as the dipole moment. It is believed that, for these molecules, a quasi-resonant (E-v,r,t) energy transfer mechanism operates. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 799–803, 1998     

Mn(III)-based radical addition reactions of 2-nitroindole with activated CH compounds

2-Nitroindole undergoes addition reactions with the radicals generated from active CH compounds upon treatment with Mn(OAc)₃·2H₂O to afford the corresponding 3-substituted-2-nitroindoles in 27-66% yields. Products of the methylene addition reactions undergo a subsequent in situ Nef reaction to afford 2-oxoindolin-3-ylidenes.     

Syntheses, crystal structures, and spectroscopic and magnetic properties of [Mn2III(H2L1)(Cl4Cat)4.2H2O] and [Mn2III(H2L2)(Cl4Cat)4.2CH3CN.2H2O]infinity: temperature-dependent valence tautomerism in solution

The synthesis, X-ray data, and electronic structures of two manganese(III) 1D polymers ligated by tetrachlorocatechol, [Mn(2)(III)(H(2)L(1))(Cl(4)Cat)(4).2H(2)O](infinity) (1) and [Mn(2)(III)(H(2)L(2))(Cl(4)Cat)(4).2CH(3)CN.2H(2)O](infinity) (2), are reported. The electronic structures of the complexes have been determined by UV-vis-near-IR, IR, electron paramagnetic resonance (EPR), and magnetic susceptibility measurements. Both 1 and 2 are air stable in the solid state and in solution, unlike most of the previously reported o-quinone-chelated transition-metal complexes. Electronic spectroscopy exhibits a strong near-IR band near 1900 nm for both, suggesting the presence of a mixed-valence semiquinone-catecholate oxidation state of the catechol ligands, Mn(2)(III)(Cl(4)Cat)(2)(Cl(4)SQ)(2), together with the pure catecholate forms. The presence of this isomer was further supported by EPR and magnetic susceptibility measurements. The complexes undergo intramolecular electron transfer (valence tautomerism) upon an increase of the temperature involving the equilibrium Mn(2)(III)(Cl(4)Cat)(2)(Cl(4)SQ)(2) <==> Mn(2)(II)(Cl(4)SQ)(4). This phenomenon is reversible and is studied in solution using UV-vis-near-IR spectroscopy.     

4(5)-vinylimidazole by dehydrobromination of 1-triphenylmethyl-4-(2-bromoethyl)imidazole

1-Triphenylmethyl-4-(2-bromoethyl)imidazole undergoes elimination upon basic treatment providing an easy approach to 4(5)-vinylimidazole whereas the N-unsubstituted analogue leads only to substitution products.     

A new oxoanion: [IO]3- containing I(V) with a stereochemically active lone-pair in the silver uranyl iodate tetraoxoiodate(V), Ag4(UO2)4(IO3)2(IO4)2O2

The hydrothermal reaction of elemental Ag, or water-soluble silver sources, with UO3 and I2O5 at 200 degrees C for 5 days yields Ag4(UO2)4(IO3)2(IO4)2O2 in the form of orange fibrous needles. Single-crystal X-ray diffraction studies on this compound reveal a highly complex network structure consisting of three interconnected low-dimensional substructures. The first of these substructures are ribbons of UO8 hexagonal bipyramids that edge-share to form one-dimensional chains. These units further edge-share with pentagonal bipyramidal UO7 units to create ribbons. The edges of the ribbons are partially terminated by tetraoxoiodate(V), [IO4]3-, anions. The uranium oxide ribbons are joined by bridging iodate ligands to yield two-dimensional undulating sheets. These sheets help to form, and are linked together by, one-dimensional chains of edge-sharing AgO7 capped octahedral units and ribbons formed by corner-sharing capped trigonal planar AgO4 polyhedra, AgO6 capped square pyramids, and AgO6 octahedra. The [IO4]3- anions in Ag4(UO2)4(IO3)2)(IO4)2O2 are tetraoxoiodate(V), not metaperiodate, and contain I(V) with a stereochemically active lone-pair. Bond valence sum calculations are consistent with this formulation. Differential scanning calorimetry measurements show distinctly different thermal behavior of Ag4(UO2)4(IO3)2(IO4)2O2 versus other uranyl iodate compounds with endotherms at 479 and 494 degrees C. Density functional theory (DFT) calculations demonstrate that the approximate C2v geometry of the [IO4]3- anion can be attributed to a second-order Jahn-Teller distortion. DFT optimized geometry for the [IO4]3- anion is in good agreement with those measured from single-crystal X-ray diffraction studies on Ag4(UO2)4(IO3)2(IO4)2O2.     

[C5H4C(CH3)2CH2CH=CH2]Sm(OH)Cl·2MgCl2·4THF的晶体结构分析

用Ｘ－射线晶体结构衍射法测定了［Ｃ５Ｈ４Ｃ（ＣＨ３）２ＣＨ２ＣＨ＝ＣＨ２］Ｓｍ（ＯＨ）Ｃｌ·２ＭｇＣｌ２·４ＴＨＦ的晶体结构。它属三斜晶系,空间群为Ｐ＾－１,ａ＝１０．７７３（２）,ｂ＝１２．８３６（３）,ｃ＝１５．４７８（３）Ａ,ａ＝１１１．４６（３）,β＝１０７．７１（３）,γ＝９２．５４（３）°,Ｖ＝１８６８（１）Ａ＾３,Ｍｒ＝８２７．９１,Ｄｘ＝１．４７２ｇ／ｃｍ＾３,μ＝２．０００６ｍｍ     

SnCl4 Promoted Efficient Cleavage of Acetal/Ketal Groups with the Assistance of Water in CH2Cl2

Acetalization and deacetalation are a pair of routine manipulations to protect and deprotect the 4- and 6-hydroxyl groups of glycosides in the synthesis of glycosyl building blocks. In this study, we found that treatment of SnCl₄ with various carbohydrates containing acetal/ketal groups with the assistance of water in CH₂Cl₂ led to deacetalization/deketalization products in almost quantitative yields. In addition, for substrates containing both acetal/ketal and p-methoxylbenzyl groups, we also found that the p-methoxylbenzyl group was selectively cleaved by the use of a catalytic amount of SnCl₄, while the acetal/ketal groups remained. Furthermore, based on this, 4,6-benzylidene glycosides can be conveniently converted to 4,6-OAc or 4-OH, 6-OAc glycosides.     

A Mn(III)-superoxo complex of a zwitterionic calix[4]arene with an unprecedented linear end-on Mn(III)-O2 arrangement and good catalytic performance for alkene epoxidation

Reactions of [H(4)L][PF(6)](4) with 4 equiv. of Mn(OAc)(2)·4H(2)O in the presence of air gave rise to a mononuclear Mn(III)-superoxo complex [Mn(III)L(O(2))(H(2)O)](PF(6))(2), which contains a bowl-shaped cationic structure with a D(4d) symmetry. It has an unprecedented linear end-on Mn(III)-O(2) unit and exhibited good efficiency and selectivity in the catalytic oxidation of alkenes with O(2) plus isobutyraldehyde under mild conditions.     

2-(4′-Fluorophenyl)imidazole. Nitration studies

Reactions of 2-(4′-fluorophenyl)imidazole ( 1 ) and related compounds under various nitrating conditions are discussed. With 90% nitric acid in 20% oleum at ?10°, 1 affords 2-(4′fluorophenyl)-4(5)-nitroimidazole ( 2 ) in 80% yield. Reaction of 2 with the same reagents at 25° affords 2-(4′-fluoro-3′-nitrophenyl)-4(5)-nitroimidazole ( 4 ) in 90% yield, whereas with 90% nitric acid in acetic acid at 95°, 2 affords 4,5-dinitro-2-(4′-fluorophenyl)imidazole ( 5 ) in 80% yield. Reaction of 1 with 70% nitric acid in concentrated sulfuric acid at 25° affords 2-(4′-fluorophenyl)-5-hyroximinoimidazolin-4-one ( 6 ), which rearranges and hydrolyzes to 5-(4′-fluorophenyl)-1,2,4-oxadiazole-3-carboxylic acid. A discussion of these reactions is presented.     

Photooxidation of cyclohexane by (Bu4N)2Cr4O13 in acetonitrile or CH2Cl2

Upon irradiation using light with >520 nm, (Bu ₄N)₂Cr₄O₁₃ oxidizes cyclohexane to cyclohexanol as the major product and cyclohexanone in acetonitrile and to cyclohexanol as the major product, cyclohexanone, and cyclohexyl chloride in CH₂Cl₂. Carrying out this reaction in the presence of air leads to a sharp increase in the yield of cyclohexanone.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 212–213, January, 1990.