Aggregate manganese Schiff base moieties by terephthalate or acetate: dinuclear manganese and trinuclear mixed metal Mn2/Na complexes

A reaction system consisting of terephthalic acid, NaOH, inorganic Mn(II) or Mn(III) salt, and salicylidene alkylimine resulted in dinuclear manganese complexes (salpn)(2)Mn(2)(mu-phth)(CH(3)OH)(2) (1, salpn = N,N'-1,3-propylene-bis(salicylideneiminato); phth = terephthalate dianion), (salen)(2)Mn(2)(mu-phth)(CH(3)OH)(2) (2, salen = N,N'-ethylene-bis(salicylideneiminato)), (salen)(2)Mn(2)(mu-phth)(CH(3)OH)(H(2)O) (3), and (salen)(2)Mn(2)(mu-phth) (4), while the absence of NaOH in the reaction led to a mononuclear Mn complex (salph)Mn(CH(3)OH)(NO(3)) (5, salph = N,N'-1,2-phenylene-bis(salicylideneiminato)). In addition, a trinuclear mixed metal complex H[Mn(2)Na(salpn)(2)(mu-OAc)(2)(H(2)O)(2)](OAc)(2) (6) was obtained from the reaction system by using maleic acid instead of terephthalic acid. Five-coordinate Mn ions were found in 4 giving rise to an intermolecular interaction and constructing a one-dimensional linear structure. Antiferromagnetic exchange interactions were observed for 1-3, and a total ferromagnetic exchange of 4 was considered to stem from intermolecular magnetic coupling. (1)H NMR signals of phenolate ring and alkylene (or phenylene) backbone of the diamine are similar to those reported in the literature, and the phth protons are at -2.3 to -10.1 ppm. Studies on structure, bond valence sum analysis, and magnetic properties indicate the oxidation states of the Mn ions in 6 to be +3, which are also indicated by ESR spectra in dual mode. Ferromagnetic exchange interaction between the Mn(III) sites was observed with J = 1.74 cm(-1). A quasireversible redox pair at -0.29V/-0.12V has been assigned to the redox of Mn(2)(III)/Mn(III)Mn(II), implying the intactness of the complex backbone in solution.     

Noble gas-transition metal complexes: coordination of ScO+ by multiple Ar, Kr, and Xe atoms in noble gas matrixes

The combination of matrix isolation infrared spectroscopic and density functional calculation results provides strong evidence that the transition metal monoxide cation, ScO+, coordinates five noble gas atoms in forming the [ScO(Ng)5]+ (Ng = Ar, Kr, or Xe) complexes in noble gas matrixes.     

Iron-assisted vapor-phase hydrothermal method: a low-temperature approach to synthesize blue light emissive SiOx nanowires with single-crystal structure of P2(1)2(1)2

A novel and facile approach, named iron-assisted vapor-phase hydrothermal method, is proposed to fabricate the long and stable bright blue light emitting SiOx nanowires (SiONWs) at a low temperature. The obtained SiONWs possess a brand-new single-crystalline structure of space group P21212. This new type of bright blue light emitting SiONW with a new single-crystalline structure may initiate a new 1D optical material and offer new opportunities for the research in science and technology.     

Direct observation of eta 2-imine formation through beta-H abstraction between amide ligands. Neutron and X-ray diffraction structure of a dihydride imine ditantalum complex

Reactions of Ta(NMe2)5 with D2SiR'Ph (R' = Me, Ph) were found to give a dideuteride eta 2-imine complex (Me2N)3Ta(mu-D)2(mu-N-eta 2-N,C-CH2NMe)Ta(NMe2)3(1-d2) through C-H activation of an amide ligand via beta-H abstraction, and the structure of 1 was confirmed by single crystal neutron and X-ray diffraction.     

Novel "star anise"-like nano aggregate prepared by self-assembling of preformed microcrystals from branched crystalline-coil alternating multi-block copolymer

Nano aggregates in aqueous medium with a novel "star anise"-like morphology were prepared from a branched alternating multi-block copolymer composed of 3-arm star-like hydrophobic poly(p-dioxanone) block and linear hydrophilic poly(ethylene glycol) block. The influence of block length on the morphology of the nano aggregate was investigated.     

Capillary electrophoresis chemiluminescent detection system equipped with a two-step postcolumn flow interface for detection of some enkephalin-related peptides labeled with acridinium ester

Despite its low equipment cost and simple design, as one of the sensitive detectors for CE, the chemiluminescence (CL) detector was less developed compared to the detectors of MS and LIF. The main reasons were the limitation of CL reagents, the repeatability problems and the relatively low sensitivity compared to LIF. In this paper, a highly sensitive CE-CL detection system was developed for detection of some enkephalin-related peptides labeled with acridinium ester. A new detection interface was designed for CE with CL detection of acridinium ester and its labeled analytes. The interface included two sections: one was used to acidify the capillary outflow so that the corresponding acridinium pseudo-base form can be changed into acridinium ester form by adding excess acid to the system; the other was designed to provide a suitable solution to produce the CL from acridinium ester. The effect factors, such as pH, the concentration of reaction reagents and the flow rates of the reagents, were investigated. The results showed that acridinium ester had similar CL properties in this interface when pH values of CE BGE were changed from 2.0 to 10.8. The interface was used to detect acridinium ester and three acridinium ester-labeled enkephalin-related peptides, the corresponding LODs were found to be in the attomole range. This CL detection system proved to be of high sensitivity, good repeatability, and relatively low cost.     

The observation of abnormal signals in laser flash photolysis: a type of probable synchronized nuclear spin signals

In laser flash photolysis (LFP) work, noise-like signals were observed together with transient absorption decay spectra in time domain. Analyzed results show that it is a valuable resonance spectrum of excited state molecules, in which four molecular cases are given here. We proposed that this kind signal might originate from nuclear or nuclear and electron spin resonance features in the excited molecules based on radio wave frequency spectrum levels and the significant interaction with static magnetic field.     

Preparation and study of polyacryamide-stabilized silver nanoparticles through a one-pot process

A one-pot route was illustrated to synthesize stable well-dispersed silver colloids stabilized by polyacrylamide on a large scale. Reduction of silver ions and polymerization of acrylamide occurred almost simultaneously in the absence of a commonly used reducing agent and initiator. A possible mechanism for the formation of silver nanoparticles with bimodal size distribution was proposed. The structure and composition of the obtained nanoparticles were characterized carefully. Furthermore, light scattering simulation and UV-vis absorption studies confirmed that the obtained colloids were the mixture of Ag and Ag2O nanoparticles. The presence of silver oxide layers on the nanoparticle surface should be responsible for the broadening of the surface plasmon band of silver nanoparticles. Ag2O layers could be added or removed from Ag nanoparticle surfaces by the addition of HNO3, HAc, or NaCl solution to the as-obtained silver colloids.     

Total synthesis of the originally proposed and revised structures of palmerolide A and isomers thereof

Palmerolide A is a recently disclosed marine natural product possessing striking biological properties, including potent and selective activity against the melanoma cancer cell line UACC-62. The total syntheses of five palmerolide A stereoisomers, including the originally proposed (1) and the revised [ent-(19-epi-20-epi-1)] structures, have been accomplished. The highly convergent and flexible strategy developed for these syntheses involved the construction of key building blocks 2, 19-epi-2, 20-epi-2, ent-2, 3, ent-3, 4, and ent-4, and their assembly and elaboration to the target compounds. For the union of the building blocks, the Stille coupling reaction, Yamaguchi esterification, Horner-Wadsworth-Emmons olefination, and ring-closing metathesis reaction were employed, the latter being crucial for the stereoselective formation of the macrocycle of the palmerolide structure. The Horner-Wadsworth-Emmons olefination and the Yamaguchi lactonization were also investigated and found successful as a means to construct the palmerolide macrocycle. The syntheses were completed by attachment of the enamide moiety through a copper-catalyzed coupling process.     

Influence of the water molecule on cation-pi interaction: ab initio second order Møller-Plesset perturbation theory (MP2) calculations

The influence of introducing water molecules into a cation-pi complex on the interaction between the cation and the pi system was investigated using the MP2/6-311++G method to explore how a cation-pi complex changes in terms of both its geometry and its binding strength during the hydration. The calculation on the methylammonium-benzene complex showed that the cation-pi interaction is weakened by introducing H(2)O molecules into the system. For example, the optimized interaction distance between the cation and the benzene becomes longer and longer, the transferred charge between them becomes less and less, and the cation-pi binding strength becomes weaker and weaker as the water molecule is introduced one by one. Furthermore, the introduction of the third water molecule leads to a dramatic change in both the complex geometry and the binding energy, resulting in the destruction of the cation-pi interaction. The decomposition on the binding energy shows that the influence is mostly brought out through the electrostatic and induction interactions. This study also demonstrated that the basis set superposition error, thermal energy, and zero-point vibrational energy are significant and needed to be corrected for accurately predicting the binding strength in a hydrated cation-pi complex at the MP2/6-311++G level. Therefore, the results are helpful to better understand the role of water molecules in some biological processes involving cation-pi interactions.