85483-96-1Relevant academic research and scientific papers
Folding of a donor-containing ionene by intercalation with an acceptor
De, Swati,Ramakrishnan
, p. 149 - 156 (2011/10/08)
Cationic ionenes that bear electron-rich 1,5-dialkoxynaphthalene (DAN) units within the alkylene segment were allowed to interact with different types of electron-deficient, acceptor-containing molecules in an effort to realize intercalation-induced folding of the ionenes; the collapse of the chains was expected to occur in such a way that the donor and acceptor units become arranged in an alternating fashion. Several acceptor-bearing molecules were prepared by the derivatization of pyromellitic dianhydride and naphthalene tetracarboxylic dianhydride with two different oligoethylene glycol monomethyl ether monoamines. This yielded acceptor molecules with different water solubility and allowed the examination of solvophobic effects in the folding process. UV/Vis spectroscopic studies were carried out by using a 1:1 mixture of the DAN-ionenes and different acceptor molecules in water/DMSO solvent mixtures. The intensity of the charge-transfer (CT) band was seen to increase with the water content in the solvent mixture, thereby suggesting that the intercalation is indeed aided by solvophobic effects. The naphthalene diimide (NDI) bearing acceptor molecules consistently formed significantly stronger CT complexes when compared to the pyromellitic diimide (PDI) bearing acceptor molecules, which is a reflection of the stronger π-stacking tendency of the former. AFM studies of drop-cast films of different ionene-acceptor combinations revealed that compact folded structures are formed most effectively under conditions in which the strongest CT complex is formed. Know when to fold 'em: When coerced to collapse in a polar solvent in the presence of an electron-deficient amphiphilic folding agent, suitably modified ionenes with a symmetrically positioned electron-rich 1,5-dialkoxylnaphthalene (DAN) unit appear to form an accordion-type folded structure wherein the units are arranged in an alternating fashion (see picture). D=Donor; A=Acceptor. Copyright
Identification of absolute helical structures of aromatic multilayered oligo(m-phenylurea)s in solution
Kudo, Mayumi,Hanashima, Takayuki,Muranaka, Atsuya,Sato, Hisako,Uchiyama, Masanobu,Azumaya, Isao,Hirano, Tomoya,Kagechika, Hiroyuki,Tanatani, Aya
experimental part, p. 8154 - 8163 (2010/02/28)
(Chemical Equation Presented) The oligomeric aromatic ureas bearing N,N′-dimethylated urea bonds such as 3 have aromatic multi-layered structure, based on the (cis,cis)-urea structure, and also have dynamic helical structure (all-R or all-S axis chirality) when the benzene rings are connected at the meta positions. The absolute helical structure of oligo(m-phenylurea)s were identified by the empirical and theoretical studies on the CD and vibrational CD (VCD) spectra. Thus, each enantiomer of the oligo(m-phenylurea)s 4 bearing a chiral N-2-(methoxyethoxyethoxy)propyl group were synthesized. Intense dispersion-type CD spectra of 4 were observed, which indicated the induction of handedness in the helical structure. In the VCD spectra of 4 in the film state, the signals due to the carbonyl and aromatic ring vibrations were seen with negative and positive values for compounds 4a and 4b, respectively. The calculations of both CD and VCD spectra of oligo(m-phenylurea)s 3 without any chiral N-substituent gave the same assignment about the axis chirality of 4. Thus, the absolute configurations of 4a and 4b are all-R and all-S structures, respectively. 2009 American Chemical Society.
Synthesis of new enantiopure proton-ionizable crown ethers containing a dialkylhydrogenphosphate moiety
Kovacs, Ilona,Huszthy, Peter,Bertha, Ferenc,Sziebert, Denes
, p. 2538 - 2547 (2007/10/03)
Seven new enantiopure proton-ionizable crown ethers containing a dialkylhydrogenphosphate moiety were prepared starting from optically active dialkyl-substituted oligoethylene glycols and phosphorus oxychloride followed by mild hydrolysis of the resulting macrocyclic chlorophosphates. Pentaethylene glycols having primary hydroxyl groups gave good yields of 17-crown-6 type ethers. Pentaethylene glycols with secondary hydroxyl groups rendered about the same amount of 17-crown-6 ethers and open chain dihydrogenphosphates in low yields. Tetraethylene glycols are reluctant to undergo macrocyclization with phosphorus oxychloride, especially the ones which contain secondary hydroxyl groups.
Hierarchical growth of chiral self-assembled structures in protic media
Brunsveld,Zhang,Glasbeek,Vekemans,Meijer
, p. 6175 - 6182 (2007/10/03)
The location of nine chiral penta(ethylene oxide) side chains at the periphery of a C3-symmetrical hydrogen-bonded extended core gives rise to a thermotropic discotic liquid crystalline material that shows lyotropic phases in polar, protic media. The molecular stacks self-assemble in a reversible and hierarchical fashion, and specific and subtle solvent-molecule interactions together with the created hydrophobic microenvironment account for an unprecedented stabilization of a preferred handedness of the helical stacks by cooperative intermolecular interactions. The presence of either chirality or achirality at the supramolecular level in the stacks can be tuned by temperature and solvent as judged from circular dichroism spectroscopy. A hierarchical growth of the self-assembly is revealed using a variety of spectroscopic techniques and differential scanning calorimetry.
Preparation of optically active azophenolic crown ethers containing 1-phenylethane-1,2-diol and 2,4-dimethyl-3-oxapentane-1,5-diol as a chiral subunit: Temperature-dependent enantiomer selectivity in the complexation with chiral amines
Ogasahara, Kazuko,Hirose, Keiji,Tobe, Yoshito,Naemura, Koichiro
, p. 3227 - 3236 (2007/10/03)
With (2S,4S)-2,4-dimethyl-3-oxapentane-1,5-diol and (S)- or (R)-1-phenylethane-1,2-diol as chiral subunits, optically active azophenolic crown ethers (S,S,S,S)-1, (R,S,S,R)-2, (S,S,S,S)-3 and (R,S,S,R)-4 possessing two phenyl and two methyl substituents together with the p-(2,4-dinitrophenylazo)phenol moiety have been prepared in enantiomerically pure forms. Temperature-dependent enantiomer selectivity in the complexation of these crown ethers with chiral amines has been studied by the UV-visible spectroscopic method in chloroform and from the observed association constants, thermodynamic parameters for the complexation have been calculated.
Preparation and Enantiomer Recognition of Chiral Azophenolic Crown Ethers Having three Chiral Barriers on each of the Homotopic Faces
Naemura, Koichiro,Asada, Masaki,Hirose, Keiji,Tobe, Yoshito
, p. 1873 - 1876 (2007/10/03)
Homochiral azophenolic crown ethers 1 and 2 having three chiral barriers, that is, the phenyl group, the methyl group, and the cyclohexane moiety on each of the homotropic faces have been prepared.The enantiomer recognition toward chiral 2-aminoethanol derivatives has been examined.
Stereochemical Evidence for Pseudorotation in the Reaction of a Phosphoric Monoester
Buchwald, Stephen L.,Pliura, Diana H.,Knowles, Jeremy R.
, p. 4916 - 4922 (2007/10/02)
The phosphoro group of 2-phosphoropropane-1,2-diol migrates to the 1-position on heating in aqueous acid.This migration occurs by two routes.The direct route is belived to proceed via a pentacoordinate intermediate that must, by Westheimer's rules, pseudo
