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Karkhaneei, Ebrahim; Zebrajadian, Mohammad Hasan; Shamsipur, Mojtaba

doi:10.1023/a:1012772531331

Cited by 16 publications

(11 citation statements)

References 17 publications

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“…The diamagnetic shift did not vary as the crown ether/Li + molar ratio was increased beyond one, thus indicating the formation of a stable 1:1 complex in chloroform solution. This agreed with the data reported in the literature47 for Li + /15‐crown‐5 complex in different solvent mixtures. The same experiment was repeated by dissolving PECH or P5 in a suspension of LiCF 3 SO 3 in CDCl 3 in such amounts that there was a ratio of five repetitive units of copolymer per LiCF 3 SO 3 unit.…”

Section: Resultssupporting

confidence: 93%

Self‐organized liquid‐crystalline polyethers obtained by grafting tapered mesogenic groups onto poly(epichlorohydrin): Toward biomimetic ion channels 2

Ronda

Reina

Giamberini

2003

J. Polym. Sci. A Polym. Chem.

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A set of high‐molecular‐weight, new, side‐chain liquid‐crystalline polyethers was obtained by chemical modification of poly(epichlorohydrin) with potassium 3,4,5‐tris[4‐(n‐dodecan‐1‐yloxy)benzyloxy]benzoate. The degree of modification depended on the reaction conditions and ranged from 39 to 58%. The highest value was an apparent modification plateau. NMR characterization indicated no side reactions of any kind (e.g., deshydrohalogenation). All random‐grafted copolymers had hexagonal columnar mesophases with the exception of the least modified copolymer, which had a nematic columnar mesophase. X‐ray diffraction experiments performed on mechanically oriented samples showed that tapered groups were tilted with respect to the column axes. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 326–340, 2004

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Section: Resultssupporting

confidence: 93%

Self‐organized liquid‐crystalline polyethers obtained by grafting tapered mesogenic groups onto poly(epichlorohydrin): Toward biomimetic ion channels 2

Ronda

Reina

Giamberini

2003

J. Polym. Sci. A Polym. Chem.

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“…The diamagnetic shift did not vary as the crown ether/Li ϩ molar ratio was increased beyond one, thus indicating the formation of a stable 1:1 complex in chloroform solution. This agreed with the data reported in the literature 47 for Li ϩ /15crown-5 complex in different solvent mixtures. The same experiment was repeated by dissolving PECH or P5 in a suspension of LiCF 3 SO 3 in CDCl 3 in such amounts that there was a ratio of five repetitive units of copolymer per LiCF 3 SO 3 unit.…”

Section: Liquid-crystalline Polyetherssupporting

confidence: 93%

Self‐organized liquid‐crystalline polyethers obtained by grafting tapered mesogenic groups onto poly(epichlorohydrin): Toward biomimetic ion channels

Ronda¹,

Reina²,

Cádiz³

et al. 2003

J. Polym. Sci. A Polym. Chem.

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A set of high-molecular-weight, new, side-chain liquid-crystalline polyethers was obtained by chemical modification of poly(epichlorohydrin) with potassium 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy]benzoate. The degree of modification depended on the reaction conditions and ranged from 39 to 58%. The highest value was an apparent modification plateau. NMR characterization indicated no side reactions of any kind (e.g., deshydrohalogenation). All random-grafted copolymers had hexagonal columnar mesophases with the exception of the least modified copolymer, which had a nematic columnar mesophase. X-ray diffraction experiments performed on mechanically oriented samples showed that tapered groups were tilted with respect to the column axes.

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“…Adding one equivalent of 12-crown-4 to the C 6 D 6 solution of 3 resulted in a brownish-red precipitate, which became soluble upon THF addition. The 7 Li NMR showed only one signal at À0.2 ppm, and this was assigned to the 12-crown-4 coordinated Li ion, 23 resulting in a solvent separated silolide anion and a 12-crown-4 coordinated Li ion. The 29 Si NMR signal is then shifted somewhat upfield (by 5.7 ppm) to +60.0 ppm.…”

mentioning

confidence: 99%

Planar lithium silolide: aromaticity, with significant contribution of non-classical resonance structures

et al. 2017

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The first planar lithium silolide characterized by X-ray crystallography is reported. The structural data, NMR and DFT results reveal high aromatic character, with the unusual dominance of non-classical resonance structures.The cyclopentadienide ion is a textbook example for a planar aromatic compound alongside benzene. 1a The replacement of a carbon atom by silicon results in the silacyclopentadienyl (silolide) anion, 1b-f for which the planarity and the apparently related aromaticity are far from being trivial. the structural similarity for the isoelectronic silolide anion is also expected. Computational studies have also predicted that silolide is pyramidal; 5 however, even with the non-planar silicone a moderate aromaticity was reported for the parent compound, 5a furthermore the presence of the countercation has a flattening effect on silicon. 5 A noteworthy feature of the calculated planar silolide structure was the equalization of the C-C distances, the Cb-Cb 0 bond being slightly (by 0.008 Å) shorter than Ca-Cb. Accordingly, for the planar silolide the ''b'' resonance structure had larger (30%) weight than the classical ''a'' (17%) according to a natural resonance theory (NRT) study (Fig. 1 Si and upfield in 13 C NMR) with respect to the neutral precursor disilane was attributed to cyclic delocalization. 7 Unfortunately, for this particular silolide, no X-ray structure could be obtained, The situation is further complicated by the fact that for 1-Me-tetraphenylsilolide the dimerization of the anion was reported, yielding tricyclic systems with a central 1,3-disilacyclobutane ring. 8While no planar silolide has been reported to date, Sekiguchi's 1,2,3-trisilacyclopentadienide and 1,2-disila-3-germacyclopentadienide anions have been shown to exhibit planar X-ray structures with equalized bond lengths, and with 29 Si NMR data indicating aromaticity.9 Furthermore, nearly planar transition metal (Zr, Hf or Ru) complexed silolides were also synthetized. 10In a computational search for planar silolide anions we revealed that due to the charge stabilizing effect, p-acceptor SiH 3 groups at the a carbons enhance the planarity and aromaticity of the naked silolide ring considerably. 5d This effect was already noted on the related phosphole with SiH 3 11 and BH 2 12 substituents, and the charge stabilizing effect was also shown in the case of the silyl-substituted stannole dianion. 13Furthermore, the a-silyl groups enhanced the relative weight of the b type resonance structure. 5d Z 5 -Coordination of the Li Fig. 1 Resonance structures for planar heteroaromatic five membered rings, with different heteroelements. E can be S, PR, or SiR À (R:H, alkyl, aryl, etc.). The numbering of the ring atoms is shown on resonance structure a.

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Cited by 16 publications

References 17 publications

Self‐organized liquid‐crystalline polyethers obtained by grafting tapered mesogenic groups onto poly(epichlorohydrin): Toward biomimetic ion channels 2

Self‐organized liquid‐crystalline polyethers obtained by grafting tapered mesogenic groups onto poly(epichlorohydrin): Toward biomimetic ion channels 2

Self‐organized liquid‐crystalline polyethers obtained by grafting tapered mesogenic groups onto poly(epichlorohydrin): Toward biomimetic ion channels

Planar lithium silolide: aromaticity, with significant contribution of non-classical resonance structures

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