Saccharide Recognition-Induced Transformation of Pyridine−Pyridone Alternate Oligomers from Self-Dimer to Helical Complex
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Abstract:
Co-oligomers involving (1H)-4-pyridone and 4-alkoxypyridine rings were studied, and it was found that their supramolecular transformation was caused by saccharide recognition. In the co-oligomers, pyridone and pyridine rings are alternately linked at their 2,6-position with an acetylene bond. The pyridine rings behave as a hydrogen bonding acceptor, and the pyridone rings and tautomerized 4-pyridinol work as a donor. Pyridine-pyridone-pyridine 3-mer was found to self-dimerize on the basis of vapor pressure osmometry in CHCl(3), and the association constant was obtained as 2.3 x 10(3) M(-1) by (1)H NMR titration. Longer 5-, 7-, 9-, and 11-mer oligomers showed considerable broadening and anisotropy in the (1)H NMR spectra due to self-association. These longer oligomers recognized octyl beta-D-glucopyranoside and changed their form into a chiral helical complex, showing characteristic circular dichroism.Keywords:
Proton NMR
Vapor pressure osmometry
Acceptor
Radical ion
Bond-dissociation energy
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Studies on the molecular interactions of dimethylsulfoxide (DMSO) with water and/or some alkanols were carried out by vapor pressure osmometry at 40. Negative deviation from Raoult's law was observed for the DMSO-water, methanol, ethanol, 1-propanol, 2-propanol, and 2-methyl-1-propanol systems, whereas positive deviation from Raoult's law was observed for the DMSO-1-butanol and 1-pentanol systems. The results were interpreted in terms of molecular interactions between unlike molecules, and of self-association of DMSO molecules, respectively. Measured chemical shift of hydroxyl proton of the solvents also supported the results.
Vapor pressure osmometry
Osmometer
Propanol
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Styrylpyrylium salt 화합물(DHSP)을 합성하고 광이량화시켜 cyclobutane형 이량체(DHSP dimer)를 합성하였다. 여기에 메타크릴레이트기를 도입하여 DMSP dimer를 합성하였다. DMSP dimer 광가교물의 FT-IR 분석 결과, 크랙 생성에 의해 cyclobutane환이 개열되어 styryl C=C 구조로 되돌아가는 것으로 판단되었다. 385 nm의 빛에 의하여 DHSP는 626 nm의 형광을 방출하는 반면 DHSP dimer는 매우 약한 형광만을 나타내었다. DMSP dimer의 광가교 필름에 microcrack을 생성시키고 $330{\sim}385\;nm$ 의 빛을 조사한 결과, 크랙 부분에서의 형광 방출이 확인되었다. 【A styrylpyrylium salt (DHSP) was synthesized and then photodimerized to obtain a cyclobutane-type dimer (DHSP dimer). Methacryloyl group was incorporated into DHSP dimer to obtain DMSP dimer. Based on FT-IR analysis of a crosslinked DMSP dimer, it was considered that the cyclobutane structure reversed to styryl C=C bonds upon crack formation. Fluorescence measurement of DHSP in solid state (excitation at 385 nm) showed emission centered at 626 nm, while DHSP dimer revealed very weak emission. Fluorescent emission from microcracks in a film of crosslinked DMSP dimer was observed upon exposure to $330{\sim}385\;nm$ light.】
Pyrimidine dimer
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Vapor pressure osmometry
Ion-association
Osmometer
Dissociation constant
Vinyl bromide
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Optically active amidohelicene monomer to nonamer were synthesized in high yields by a two-directional method. The CD spectra in chloroform exhibited a large difference between dimer and the higher homologs, and vapor pressure osmometry studies revealed the formation of dimeric aggregates for the latter. It is noted that amidohelicene oligomers possessing two-atom linking groups between helicene and m-phenylene spacer formed helix-dimers in solution as were ethynylhelicene oligomers. The helix-dimer of the amidohelicene octamer in chloroform was very stable, and did not dissociate at 5 × 10−8 M on heating to 60 °C. The dissociation of the amidohelicene oligomers to random-coil state took place in hydrogen-bonding breaking solvents, DMSO or THF. The equilibrium between helix-dimer and random-coil changed by varying the ratio in the mixed solvents of chloroform and DMSO. Notably, the equilibriums were not affected by temperature for various mixtures of helix-dimer and random-coil. Thus, the sensitivity toward the environment was quite different between the amido- and ethynylhelicene oligomers.
Random coil
Oligomer
Vapor pressure osmometry
Helix (gastropod)
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Water dimer
Benzoic acid
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Carbamic acid
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Novel supramolecular polymers have been prepared from a β-cyclodextrin dimer and a ditopic guest dimer having adamantyl groups. β-Cyclodextrins were bound to poly(ethylene glycol) (PEG, Mn 600). Adamantyl groups were also bound to PEG (Mn 600). The ROESY NMR spectrum of a 1:1 mixture of the β-cyclodextrin dimer and the ditopic adamantane guest dimer showed ROE correlations between the protons of adamantyl substituents and the inner protons of β-cyclodextrin. Molecular weights and molecular sizes of the supramolecular polymer constructed by the mixture of the β-cyclodextrin dimer and the ditopic adamantane guest dimer were investigated by the pulse field gradient spin echo (PFGSE) NMR and by vapor pressure osmometry (VPO). The results have shown that the mixture of the β-cyclodextrin host dimer and the adamantane guest dimer gave linear supramolecular polymers with high molecular weight (Mn = 100 000).
Adamantane
Vapor pressure osmometry
Supramolecular Polymers
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