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71.
72.
Synthesis and characterization of eumelanin‐inspired poly(indoylenearylenevinylene)s and poly(indoylenearyleneethynylene)s 下载免费PDF全文
Santosh Adhikari RaiAnna A. Hopson Bhishma R. Sedai Frederick M. McFarland Song Guo Toby L. Nelson 《Journal of polymer science. Part A, Polymer chemistry》2017,55(3):457-463
Four novel conjugated polymers containing the eumelanin‐inspired indole core have been successfully synthesized using common cross coupling reactions. These polymers differed by the arylene and the carbon–carbon bond linkage. Optoelectronic experiments of these polymers suggest that the ethynylene linkage contributed to the red‐shifted absorption spectra and blue‐shifted emission spectra when compared to the vinylene linkage polymers. Furthermore, the optical bandgaps of the poly(indoylenearyleneethynylene)s (PIAEs) were smaller compared to the poly(indoylenearylenevinylene)s (PIAVs). Surprisingly, the HOMOs of these polymers were less affected by the nature of the carbon–carbon linkage. However, the LUMOs of the PIAEs were lower in comparison to the PIAVs. These eumelanin‐inspired PIAEs and PIAVs are good fluorophores with fluorescence quantum yields ranging from 0.12 to 0.67 and have good thermal stability for applications such as in organic light‐emitting diodes. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 457–463 相似文献
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Host–Guest Chemistry between Perylene Diimide (PDI) Derivatives and 18‐Crown‐6: Enhancement in Luminescence Quantum Yield and Electrical Conductivity 下载免费PDF全文
P. Lasitha Prof. Dr. Edamana Prasad 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10558-10564
Perylene diimide (PDI) derivatives exhibit a high propensity for aggregation, which causes the aggregation‐induced quenching of emission from the system. Host–guest chemistry is one of the best‐known methods for preventing aggregation through the encapsulation of guest molecules. Herein we report the use of 18‐crown‐6 (18‐C‐6) as a host system to disaggregate suitably substituted PDI derivatives in methanol. 18‐C‐6 formed complexes with amino‐substituted PDIs in methanol, which led to disaggregation and enhanced emission from the systems. Furthermore, the embedding of the PDI ? 18‐C‐6 complexes in poly(vinyl alcohol) (PVA) films generated remarkably high emission quantum yields (60–70 %) from the PDI derivatives. More importantly, the host–guest systems were tested for their ability to conduct electricity in PVA films. The electrical conductivities of the self‐assembled systems in PVA were measured by electrochemical impedance spectroscopy (EIS) and the highest conductivity observed was 2.42×10?5 S cm?1. 相似文献
75.
S. Krishna Prasad Yoji Maeda Corresponding author D. S. Shankar Rao S. Anitha Nagamani Uma S. Hiremath C. V. Yelamaggad 《Liquid crystals》2013,40(11):1277-1283
The phase behaviour of two achiral bent core banana-shaped compounds, the hexyloxy (compound I) and decyloxy (compound II) members of the 1,3-phenylene bis[N-(2-hydroxy-4-n-alkoxybenzylidene)-4′-aminobenzoate] series was investigated under hydrostatic pressures up to 300?MPa using high pressure differential thermal analysis and light transmission methods. The reversible transition sequence crystal (Cr1)–B1 phase–isotropic liquid (I), observed at room pressure for compound I, remains in the pressure region up to c 70?MPa. At higher pressures a pressure-induced crystalline phase (Cri) appears between the Cr1 and B1 phases, its temperature region becoming wider with increasing pressure. The temperature vs. pressure phase diagram shows a triple point of 72.9?MPa and 160.3°C for the Cr1, Cri and B1 phases, indicating the lower limit of pressure for the Cri phase. In compound II the reversible transition sequence crystal (Cr1)–B2 phase–I is seen over the whole pressure region, and the temperature range of the B2 phase remains unaltered. It is concluded that both the B1 and B2 banana phases are stable over the whole pressure region studied. 相似文献
76.
A selective 2′-O-methylation of N6-cyclohexyladenosine (2) under phase-transfer catalysis conditions and a preferential crystallization of N6-cyclohexyl-2′-O-methyladenosine (1, SDZ WAG 994) from a mixture of by-products is described. A plausible explanation for the selective crystallization of 1 as a hydrate is presented. 相似文献
77.
E-2-Penten-4-yn-1-ol (3) has been utilized as a source for 1,3-diene systems by employing lithium amide induced alkylation, and curpous iodide catalysed Grignard coupling reaction as key steps. Its application for the synthesis of (Z,E)-9,11-tetradecadienyl acetate and (E,E)-10,12-hexadecadienal is described. 相似文献
78.
In this communication we describe the design and synthesis of five new conjugated polymers (P1–P5) with various π-electron conjugation bridges. Their structures were established by FTIR, 1H NMR spectroscopy, elemental analysis. The molecular weights of the polymers were estimated by gel permeation chromatographic technique. Further, their electrochemical, linear and nonlinear optical properties were investigated. The electrochemical band gaps of P1–P5 were found to be 1.72–2.35 eV. Their third-order nonlinear optical activities were studied by open aperture Z-scan technique, using a Q-switched, frequency doubled Nd:YAG laser producing 7 nano second laser pulses at 532 nm. Z-scan results reveal that the polymers exhibit self-defocusing nonlinearity and their operating mechanism involves reverse saturable absorption. The polymers showed strong optical limiting behavior due to effective two-photon absorption (2PA) with 2PA coefficients of the order of 10?11 m/W, which is comparable to that of good optical limiting materials in the literature. 相似文献
79.
Synthesis and characterization of supramolecular optically active bisamides derived from amino acids
The synthesis and phase transitional behaviour of three pairs of enantiomeric supramolecular hexacatenar liquid crystals (LCs) derived from natural α-amino acids such as l/d-alanine, l/d-leucine and l/d-valine are described. Their preparation with high enantiomeric purity was accomplished by condensing optically active (amino acid residue containing) trialkoxy amines with a 3,4,5-trialkoxy cinnamic acid core using a peptide coupling reagent namely, 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyl-uronium hexafluorophosphate (HBTU). The mesomorphic behaviour of these self-complementing mesogens was ascertained by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. The compounds exhibit columnar (Col) phase over a wide thermal range. Particularly, a pair of enantiomers derived from l/d-leucine residues notably stabilize hexagonal Col (Colh) phase over a wide temperature range of ?5 °C to 180 °C. Circular dichroism (CD) and FTIR studies suggest the chiral (helical) organization of mesogens within the columns through intermolecular hydrogen bonding; thus, these enantiomers represent one of the rarely reported examples of LCs exhibiting supramolecular Colh phase at room temperature. The gelation studies reveal the ability of these bisamides to form stable supramolecular gels in ethanol caused through H-bonding interactions. 相似文献
80.