Novel bipolar diaryloxadiazole-benzofuran conjugates: Synthesis, optical, electrochemical and thermal studies

368-373<span style="font-size:9.0pt;mso-bidi-font-size: 8.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-US">A series of diaryloxadiazole chromophores incorporating benzofuran rings of varying donor characters has been readily synthesized in a one step protocol. These donor-acceptor-donor systems, designated as <b style="mso-bidi-font-weight: normal">Benzmox-1-4 exhibit positive solvatochromic behavior and thermal stabilities in excess of 300°C. From cyclic voltammetry and emission band data, the HOMO and LUMO energies of Benzmox-1-4 have been calculated to be in the range of 6.43 to 5.65 eV and 2.96 to 3.29 eV, respectively. Of the four chromophoric systems studied, Benzmox-2 and<span style="mso-bidi-font-weight: bold"> Benzmox-3 display band gaps of 3.22 and 3.16 eV, and high luminescence efficiency of 0.34 and 0.55, respectively. These features make Benzmox-2 and<b style="mso-bidi-font-weight: normal"> Benzmox-3 promising bipolar blue light emitting host materials.</span

Oxa-bridged cyclophanes featuring thieno[2,3-b]thiophene and C-2-symmetric binol or bis-naphthol rings:synthesis, structures, and conformational studies

Oxa-bridged cyclophanes 4/6 and 8/10 featuring thieno[2,3-b]thiophene ring and binol or bis-naphthol have been synthesized. The Structures are assigned by 2D NMR data and the identity of 4 is also independently established by a single X-ray crystallography. From dynamic NMR analysis, the Arrhenius energy of activation Delta G(#) for bridge inversions in 4 and 6 was calculated to be 15.3 and 12.9 kcal/mol, respectively. A higher Delta G(#) for 4, relative to the ester free 6 is attributable to the steric compression stemming from C2/C5 ester substituents to the bridge inversion processes. While the methylene bridges undergo inversion in 4 and 6, the naphthyl-naphthyl pseudo-rotation appears to be restricted even at higher temperatures. This is Supported by retention of the optical purity of the chiral (-) 4 under thermal condition. For the case of bis-naphthol cyclophane 8, we observed the flipping of both the -OCH2- and the naphthyl-CH2-naphthyl bridges with Delta G(#) of ca. 11.4 kcal/mol. However, the ester free cyclophane 10 remained conformationally mobile even at -55 degrees C and its AGO was assumed to b

Synthesis and nonlinear optical properties of some donor-acceptor oxadiazoles

Heterocyclic 1,3,4-oxadiazole moiety has been used as a new \pi-conjugation relay to prepare a number of donor-acceptor molecules carrying a \pi-electron-rich aromatic ring as a donor and either a p-nitrophenyl or a pyridine/pyridinium ring as an acceptor. Several of these oxadiazoles display significant second-order molecular nonlinearity, $\beta (14-124 x 10^{-30} esu)$ and provide the basis for future design of efficient nonlinear optical materials having the oxadiazole core

Synthesis and nonlinear optical properties of some donor-acceptor oxadiazoles

Heterocyclic 1,3,4-oxadiazole moiety has been used as a new p-conjugation relay to prepare a number of donor-acceptor molecules carrying a p-electron-rich aromatic ring as a donor and either a p-nitrophenyl or a pyridine/pyridinium ring as an acceptor. Several of these oxadiazoles display significant second-order molecular nonlinearity, &#946; (14-124 &#215; 10-30 esu) and provide the basis for future design of efficient nonlinear optical materials having the oxadiazole core