Bis -l,3,4-oxadiazoles

Yang NC, Jeong JK, Suh DH (2003) A new conjugated polymer chemosensor functionalised with 2, 6-bis(l, 3,4-oxadiazole-2-yl)pyridine for metal ion recognition. Chem Lett 32 40-41... 

Copolymers with fluorene and 1,3,4-oxadiazole show highly efficient photoluminescence [105]. A double-layer device consisting of PVK and an alternating copolymer of 9,9 -didodecylfluorene-2,7-diyl and (l,4-bis-(l,3,4-oxadiazole)-2,5-di(2-ethylhexyloxy)phenylene)-5,5 -diyl exhibits a narrow blue electroluminescence with a maximum at 430 nm. Electrochemical analysis of the polymers using cyclic voltammetry suggests that they can be used both as electron transport materials and as blue emission materials for LEDs. 

Hydrocarbon oxadiazoles do not readily undergo Diels-Alder reactions, but 2,5-bis(trifluoromethyl)-l, 3,4-oxadiazole reacts with a number of strained or elec-... 

Fig. 9 (a) Molecular structures of novel ESIPT dyes, 2,5,-bis[5-(4-t-butylphenyl)-[l,3,4]oxadia-zol-2-yl]-phenol (SOX), and 2,5-bis[5-(4-t-butylphenyl)-[l,3,4]oxadiazol-2-yl]-benzene-l,4,-diol (DOX). (b) Emission colors in the Commission Internationale de L Eclariage (CEE) chromaticity diagram. The inner oval and the filled circle at coordinate (x,y) of (0.33, 0.33) indicate the white region and the ideal color, respectively. Note that PS and PVK denote polystyrene and poly (N-vinylcarbazole) film (reprint from ref. [91], Copyright 2005 Wiley-VCH)... 

AMI semi-empirical and B3LYP/6-31G(d)/AMl density functional theory (DFT) computational studies were performed with the purpose of determining which variously substituted 1,3,4-oxadiazoles would participate in Diels-Alder reactions as dienes and under what conditions. Also, bond orders for 1,3,4-oxadiazole and its 2,5-diacetyl, 2,5-dimethyl, 2,5-di(trifluoromethyl), and 2,5-di(methoxycarbonyl) derivatives were calculated <1998JMT153>. The AMI method was also used to evaluate the electronic properties of 2,5-bis[5-(4,5,6,7-tetrahydrobenzo[A thien-2-yl)thien-2-yl]-l,3,4-oxadiazole 8. The experimentally determined redox potentials were compared with the calculated highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO/LUMO) energies. The performance of the available parameters from AMI was verified with other semi-empirical calculations (PM3, MNDO) as well as by ab initio methods <1998CEJ2211>. 

The absorption (A ax 402nm, logs 4.71) and emission (A ax 453, 477nm) maxima, fluorescence quantum yields, and the optical energy of 2,5-bis[5-(4,5,6,7-tetrahydrobenzo[b]thien-2-yl)thien-2-yl]-l,3,4-oxadiazole 20 were studied in dichloromethane <1998CEJ2211>. 

More recently, the El and electrospray ionization (ESI) mass spectra of 2,5-diaryl- and 2-arylamino-5-aryl-l,3,4-oxadiazoles, as well as their complexes with copper cations, were studied. Under ESI conditions, loss of NH3 and HNCO, from complexes of 2,5-diphenyl-l,3,4-oxadiazole, 2,5-bis(2-pyridyl)-l,3,4-oxadiazole, or 2,5-bis(4-pyridyl)-1,3,4-oxadiazole with copper cation, was observed <2004JMP272>. An unusual elimination of isocyanic acid was found in fragmentation of some protonated 2,5-diaryl derivatives <2002RCM390>. 

Binary molecular co-crystals of 2,5-bis(3-pyridyl)-l,3,4-oxadiazole and 2,5-bis-(4-pyridyl)-l,3,4-oxadiazole with benzene-1,3,5-tricarboxylic and benzene-1,2,4,5-tetracarboxylic acids were studied by X-ray and thermogravimetric analysis of mass loss <2005MI1247>. Dipole moments were used to study the flexoelectric effect in guest-host mixtures of 2,5-(4-pentylbenzene)-l,3,4-oxadiazole with commercial liquid crystal hosts <2005CM6354>. The luminescence properties of many other copolymers were also investigated (see Section 5.06.12.3). 

Bis(4- and 3-hydroxyphenyl)-l,3,4-oxadiazoles were alkylated in an excess of epichlorohydrin in the presence of NaOH and quaternary ammonium salts, while the temperature was gradually raised from 20 to 90 °C, affording luminescent epoxide monomers (Scheme 17) <1999CHE358>. 

Epoxide derivatives of 2,5-bis-oxyphenyl-l,3,4-oxadiazoles and fluorescein, which are luminescent epoxide monomers, were synthesized and their luminescence properties were studied <1999CHE358>. The excited state intramolecular proton transfer reactions and luminescent properties of the ort j-hydroxy derivatives of 2,5-diphenyl-1,3,4-oxadiazole were elucidated to conclude that the proton phototransfer reaction is very efficient in the studied... 

Dipicryl-l,3,4-oxadiazole has been described as an initiating explosive, 2,5-dimethyl-l,3,4-oxadiazole has been used to extract aromatic hydrocarbons from mixtures with alkanes. The use of 4,4 -carbonyl-bis(2-phenyl-5-oxo-l,3,4-oxadiazole) as a blowing agent for foaming thermoplastic compositions (e.g., polycarbonates) has been described < 1996CHEC-II(4)268>. 

The crystal structures of 5-methyl-5-(2-methylprop-l-enyl)-2-phenyl-4-(4-phenylthiazol-2-yl)-A -1,3,4-oxadiazoline <90ZC26> and the rubidium and silver salts of 2-phenyl-A -l,3,4-oxadiazolin-5-one <85JOC4461> have been analyzed. A crystal study of bis-[2-(5-phenyl-l,3,4-oxadiazol-2-yl)-methyl] ether produced bond lengths and angles and showed the rings to be nearly coplanar <87AX(C)2166>. 

When part of an extended conjugated system, 2,5-disubstituted-l,3,4-oxadiazoles often fluoresce. This makes them potentially useful as laser dyes, optical brighteners, and scintillators. For example, oxadiazole (121a) <84GEP(O)3245202> and l,4-bis-(5-phenyl-l,3,4-oxadiazol-2-yl)naphthalene... 

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