Square-planar N2S2NiII complexes with an extended pi-conjugated system

The reaction of a mixture of 2-(1-naphthyl)benzothiazoline (HL1) and 2,6-diphenylbenzo[1,2-d:4,5-d']bisthiazoline (H3L2) with nickel(II) acetate tetrahydrate yielded three kinds of square-planar nickel(II) complexes: one nickel(II) complex with innocent ligands ([Ni(L1)2] (1c)) and two nickel(II) complexes with non-innocent ligands ([Ni(L1-L1)] (1a) and [Ni(L1-L2)] (1b)). The complex 1c has two bidentate-N,S ligands, which are formed via ring opening of HL1. On the other hand, the two complexes 1a and 1b contain a tetradentate-N2S2 ligand, which is created via ring opening of HL1 and H3L2, followed by bond formation between imino carbon atoms. Complexes 1a and 1b show very intense absorptions in the near-infrared (NIR) region, characteristic of square-planar complexes with non-innocent ligands. The third nickel(II) complex having a non-innocent tetradentate-N2S2 ligand ([Ni(L2-L2)] (2)) was prepared from H3L2 and nickel(II) acetate tetrahydrate. The electronic spectrum of 2 exhibits a very intense absorption at 981 nm (epsilon = 3.6 x 10(4) M-1 cm-1), which is significantly red-shifted compared with those of 1a (837 nm and 4.4 x 10(4) M-1 cm-1) and 1b (885 nm and 4.5 x 10(4) M-1 cm-1), indicating the presence of an extended pi delocalization. The reaction of 2,6-bis(3,5-dichlorophenyl)benzo[1,2-d:4,5-d']bisthiazoline (H3L3) with nickel(II) acetate tetrahydrate also led to the formation of a nickel(II) complex with a non-innocent ligand ([Ni(L3-L3)] (3)). While complex 3 is analogous to 2, its electrical conductivity is much higher than that of 2. The molecular structures of 1b, 1c, 2, and 3 were determined by X-ray crystallography.     

Why [(eta5-C5Me(n)H5-n)2Ti]2(micro2,eta2,eta2-N2) can not add a H2 molecule to the side-on-coordinated N2 while its Zr and Hf analogues can? insights from computational studies

The potential energy surface of the reaction [(eta5-C5MenH5-n)2M]2(micro2,eta2,eta2-N2) + H2 --> [(eta5-C5MenH5-n)2M][(eta5-C5MenH5-n)2MH](micro2,eta2,eta2-NNH) at low-lying singlet and triplet electronic states of the reactants was investigated using density functional methods, for n = 0 and 4, and M = Ti, Zr, and Hf. Ground electronic states of the Ti complexes are found to be triplet states, while that for the corresponding Zr and Hf complexes are singlet states. In their singlet state, all these complexes satisfy known necessary conditions (they have a side-on-coordinated N2 molecule and appropriate frontier orbitals) for successful addition of an H2 molecule to the coordinated N2, and consequently, add of an H2 molecule with a reasonable energy barrier. Hf complexes show slightly higher reactivity than corresponding Zr complexes, and in turn, both are more reactive than their singlet-state Ti counterparts. The calculated trend in reactivity of Zr and Hf complexes is consistent with the latest experimental data (see refs 13 and 16). However, Ti complexes have the ground triplet state that lacks in appropriate frontier orbitals. As a result, H2 addition to the Ti complexes at their triplet ground states requires a larger activation barrier than the singlet state and is endothermic (lacks of driven force for reaction). On the basis of these results, we predict that the [(eta5-C5Me4H)2M]2(micro2,eta2,eta2-N2) and [(eta5-C5H5)2M]2(micro2,eta2,eta2-N2) complexes cannot react with an H2 molecule for M = Ti, while those for M = Zr and Hf can. It was shown that the difference in the B3LYP (hybrid) and PBE (nonhybrid) calculated energy gaps between the lowest closed-shell singlet and triplet states of the present complexes reduces via first- > second- > third-row transition metals; both hybrid and nonhybrid density functionals can be safely used to describe reactivity of the low-lying low-spin and high-spin states of second- and third-row transition metal complexes.     

A revised synthetic scheme of 6,6′‐dibromoindirubin

The synthetic scheme of 6,6′‐dibromoindirubin ( 2 ) was investigated in detail. The reaction of 6‐fluoro‐3‐acetoxyindole ( 7 ) with isatin ( 8 ) in methanol with Na₂CO₃ produced 6′‐fluoroindirubin in moderate yields. Its structure determination was mainly undertaken using ¹H NMR spectroscopy. On the basis of this result, the synthetic scheme of 2 reported by Cooksey was revised.     

Synthesis and characterization of titanium alkyl, oxo, and diene complexes bearing a SiMe2-bridged phenoxy-cyclopentadienyl ligand and their catalytic performance for copolymerization of ethylene and 1-hexene

A series of titanium complexes bearing a SiMe₂-bridged phenoxy-cyclopentadienyl ligand were synthesized and characterized, and their catalytic behavior for copolymerization of ethylene and 1-hexene was investigated. Treatment of dimethylsilyl(2,3,4,5-tetramethylcyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)-titanium dichloride (1) with appropriate nucleophiles afforded dimethoxy complex 2, dimethyl complex 3, and dibenzyl complex 4. Standing a toluene solution of 2 in air afforded a dinuclear μ-oxo complex 5 as a single isomer. 1,3-Diene complexes 6-8 were prepared by reaction of 1 with the corresponding 1,3-dienes in the presence of 2 equiv. of n-BuLi. X-ray analysis of 1,4-diphenyl-1,3-butadiene complex 6 revealed that the diene ligand coordinates to titanium in s-cis fashion with a prone orientation. The newly prepared titanium complexes were applied to copolymerization of ethylene and 1-hexene upon activation with AlⁱBu₃ and [C₆H₅NMe₂H][B(C₆F₅)₄]. It was found that the alkyl complexes 3-4 and the diene complexes 6-8 showed higher activities than 1 at elevated temperature.     

Preparation and characterization of polyion complex micelles with a novel thermosensitive poly(2-isopropyl-2-oxazoline) shell via the complexation of oppositely charged block ionomers

Novel thermosensitive polyion complex (PIC) micelles were prepared in an aqueous medium based on the complexation of a pair of oppositely charged block ionomers, poly(2-isopropyl-2-oxazoline)-b-poly(amino acid)s (PiPrOx-b-PAA), containing thermosensitive PiPrOx segments. The controlled synthesis of PiPrOx-b-PAA was achieved via the ring-opening anionic polymerization of N-carboxyanhydrides (NCA) of either eta-benzyloxycarbonyl-l-lysine (Lys(Z)-NCA) or beta-benzyl-l-aspartate (BLA-NCA) with omega-amino-functionalized PiPrOx macroinitiators and the subsequent deprotection reaction under acidic or basic conditions. Gel permeation chromatography (GPC) and 1H NMR spectroscopy revealed that the syntheses of two block ionomers, poly(2-isopropyl-2-oxazoline)-b-poly(l-lysine) [PiPrOx-P(Lys)] and poly(2-isopropyl-2-oxazoline)-b-poly(aspartic acid) [PiPrOx-P(Asp)], proceeded almost quantitatively to give samples with a narrow molecular weight distribution (Mw/Mn 相似文献   

Functional and site-specific macromolecular micelles as high potential drug carriers

Since several years, macromolecular micelles based on amphiphilic block copolymers have attracted much interest as drug carriers. These micelles show a long term blood circulation time resulting from their small diameter and the steric repulsion created by the poly(ethylene oxide) chains which constitute micelle corona, as well as from their high thermodynamic stability. Besides this long term blood circulation time generating a passive targeting, an active targeting, chemical or physical affinity targeting, might allow the preparation of more efficient drug carriers. In order to obtain such double targeting properties, we have prepared two kinds of macromolecular micelles. The first one is based on amphiphilic poly(ethylene oxide)/poly(β-benzyl -aspartate) ---PEO/PBLA--- block copolymers having hydroxy groups at the free end of PEO chains. As a result of their structure, such micelles have hydroxy groups on their outer-shell which can be further modified in order to introduce a targeting moiety (sugar, etc.). The characteristics (diameter, critical micellar concentration (cmc), drug loading capacity) have been determined. Moreover, doxorubicin loaded -hydroxy PEO/PBLA micelles have been shown to be slightly more cytotoxic than the corresponding -methoxy PEO/PBLA micelles. The second type of micelles is based on thermosensitive amphiphilic poly(N-isopropyl acrylamide)/polystyrene ---PIPAAm/PSt--- block copolymers. Such micelles have a small diameter and a low cmc in addition to thermosensitivity properties which are similar to those of PIPAAm.     

Novel materials for electronic device fabrication using ink-jet printing technology

Novel materials and a metallization technique for the printed electronics were studied. Insulator inks and conductive inks were investigated. For the conductive ink, the nano-sized copper particles were used as metallic sources. These particles were prepared from a copper complex by a laser irradiation process in the liquid phase. Nano-sized copper particles were consisted of a thin copper oxide layer and a metal copper core wrapped by the layer. The conductive ink showed good ink-jettability. In order to metallize the printed trace of the conductive ink on a substrate, the atomic hydrogen treatment was carried out. Atomic hydrogen was generated on a heated tungsten wire and carried on the substrate. The temperature of the substrate was up to 60 °C during the treatment. After the treatment, the conductivity of a copper trace was 3 μΩ cm. It was considered that printed wiring boards can be easily fabricated by employing the above materials.     

The R-axion and non-Gaussianity

We study cosmological implications of an R-axion, a pseudo Nambu–Goldstone boson associated with spontaneous breaking of an UR₍₁₎$U{(1)}_R$ symmetry, focusing on its quantum fluctuations generated during inflation. We show that, in the anomaly mediation, the R-axion decays into a pair of gravitinos, which eventually decay into the visible particles producing the neutralino LSP. As a result, the quantum fluctuations of the R-axion are inherited by the cold dark matter isocurvature density perturbation with potentially large non-Gaussianity. The constraints on the inflation scale and the initial misalignment are derived.