نتایج جستجو برای: boron compounds
تعداد نتایج: 243622 فیلتر نتایج به سال:
Porphyrins with (un)saturated side–chains containing boron residues were developed as synthons for porphyrin functionalization. Porphyrins with mono and bis-substituted unsaturated boronyl residues were prepared in good yields (52–66 %) using a cross–metathesis approach in the presence of Grubbs I-generation catalysts. In all cases complete E–stereoselectivity (100 %) was observed. Furthermore,...
Potassium and calcium salts are well known catalysts for the reaction between carbon and O2. Current airport runway deicing agents typically use formulations containing alkali or alkaline-earth metals (see C&E News, 01/01/01, p. 30). Very effective oxidation protection of aircraft brakes is thus of great practical and fundamental interest. Phosphorus and boron compounds are known to inhibit unc...
The structural parameters and energies of the protonated compounds c/o5o-[B6H5HtacF]and c/o5o-[B6H5HtacCH3]_ are calculated by MP2/6-31G* optimization, as have the ’H, "B , 13C and i9F NMR shifts using a tzp basis set and the RHF/GIAO method. The results for the octahedral molecule anions confirm the preferred localization of the additional proton in [B6H5HtacX]~ in case of X = CH3 at the upper...
Two different classes of fluorescent dyes were prepared as a turn off/on sensor system for aldehydes. Amino derivatives of a boron dipyrromethene (BDP) fluorophore and a xanthene-derived fluorophore (rosamine) were prepared. Model compounds of their product with an aldehyde were prepared using salicylaldehyde. Both amino boron dipyrromethene and rosamine derivatives are almost non-fluorescent i...
The structural connections between the compounds of boron and carbon are extended using the mno rule beyond the borane-carbocation continuum, the lithium boride-polycarbyne analogy, and the magnesium boride (MgB(2))-graphite equivalence to beta-rhombohedral boron and fullerenes. The structural similarity of the pentagonal pyramidal C(6)H(6)(2+) and MgB(4) is established. An interesting electron...
Resveratrol-based natural products constitute a valuable source of unique compounds with diverse biological activities. In this report we investigate demethylation strategies to minimize formation of cyclized and dimerized products during the synthesis of viniferifuran and analogues. We found that boron trichloride/tetra-n-butylammonium iodide (BCl3/TBAI) is typically more effective than boron ...
The treatment of boron(III) subphthalocyanine chloride with 1,3-bis[3-(diethylamino)phenoxy]propan-2-ol 2 and 2,3-bis[3-(diethylamino)phenoxy]propan-1-ol 4 in toluene gave the corresponding axially substituted boron(III) subphthalocyanine compounds 3 and 5. The novel axially diethylaminophenoxypropanoxy substituted subphthalocyanines were characterized by standard spectroscopy methods. The elec...
Dichloroboryldisilylamines [SiClm(CH3)3−m]N[Si(CH3)3](BCl2) (m = 1 – 3) as well as chloromethylboryl-bis-(chlorodimethylsilyl)amine [SiCl(CH3)2]2N[BCl(CH3)] form 1 : 1 adducts with pyridine (1 – 4). Those with m = 2 and 3 have been converted into functionalized diazadiboretidine derivatives which are still coordinated by pyridine: [(SiClm(CH3)3−m)NBCl · Py]2 (5: m = 2, 6: m = 3). Single-crystal...
Recently, heteroatom-doped carbon materials BCx, BCxN and CxN have been suggested the potential applications as anode materials in Li ion batteries, because these compounds consist of layered structure [1-3]. In particular, boron-doped carbon materials have been experimentally and theoretically investigated from different points of view, not only from fundamental scientific aspects, such as ele...
Employing particle swarm optimization (PSO) combined with first-principles calculations, we systemically studied high-pressure behaviors of hard CrB4. Our predictions reveal a distinct structural evolution under pressure for CrB4 despite having the same initial structure as FeB4. CrB4 is found to adopt a new P2/m structure above 196 GPa, another Pm structure at a pressure range of 261-294 GPa a...
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