Synthesis And Optoelectronic Properties Of Novel Unsymmetrical Diarylethenes Bearing Heterocyclic Aryl Rings And Their Applications To Optical Storage

Diarylethenes are the most promising candidates for high-density information storage and optical switches because of their good photochromic properties, remarkable thermal stability of isomers, and excellent fatigue resistance. Currently, design and synthesis of novel diarylethenes as well as investigations of their properties are both fundamental research and hotspots.In this dissertation, thirty-five new unsymmetrical photochromic perfluor-diarylethene compounds are synthesized. Twenty-five diarylethene crystals are prepared, and their structures of twenty-two of them are determined by single-crystal X-ray diffraction analysis. We systematically investigated the effects of the heterocyclic aryl rings species, the electron-withdrawing/donating ability, and the position of the substituents on the optoelectronic properties of these compounds. Preliminary holographic optical storage tests were performed using diarylethenes bearing both pyrrole and thiophene rings as recording media. The main innovation achievements obtained as follows:1. A new class of unsymmetrical photochromic diarylethenes based on the hybrid skeleton of thiophene and pyrrole moieties were synthesized, and their photochemical and electrochemical properties were investigated in detail for the first time. The results showed that, the electron-withdrawing/donating ability of the substituents has notable effects on the optoelectronic properties of such diarylethenes. On one hand, compare with the unsubstituted parent compound, the quantum yields, the absorption maxima, and the fluorescent quantum yields of those diarylethenes increased obviously when the electron-withdrawing/donating substituent attached at the para-position on the terminal benzene ring and increased with the increase of the electron-withdrawing/donating ability whereas the fluorescent emission peaks decreased notably. On the other hand, compared with the diarylethenes substituting with electron-withdrawing group, lager molar absorption coefficients, fluorescent emission peaks, and band gap of the closed-ring isomers whereas smaller ?uorescent quantum yields and band gap of the open-ring isomers were achieved when substituting with the electron-donating group in the same diarylethene system.2. We systematic studied the influence of the substituent (cyan-, fluorine atoms, methoxy-) and its position on the photoelectric properties of pyrrole-thiophene type diarylethenes. The results showed that, substituent and its replace position have notable effects on the optoelectronic properties of these diarylethenes. On one hand, compared with the unsubstituted parent compound, the absorption maxima, and the quantum yields increased obviously whereas the fluorescent emission peaks decreased notably when different substituent group was attached at any position on the terminal benzene ring. On the other hand, replace position of the substituent also has notable effects on the optoelectronic properties of these diarylethenes.3. The design and synthesis of pyrrole-aromatic heterocyclic type asymmetrical diarylethenes were carried out and investigated the aromatic heterocyclic type on the influence of such compounds photoelectric properties for the first time. The results showed that, aromatic heterocyclic species on this kind of compounds have significant influences the photoelectric properties. Diarylethenes concerning five-membered heterocyclic rings have lager cyclization quantum yields, absorption maxima of the open-ring, fluorescent modulation efficiency, and fluorescent quantum yields whereas smaller cycloreversion quantum yields and absorption maxima of the closed-ring compared with diarylethenes bearing six-membered heterocyclic rings. The quantum yields, fluorescent emission peaks fluorescent modulation efficiency, and fluorescent quantum yields of the diarylethenes that introducing N atoms on the five-membered or six-membered aromatic heterocyclic rings increased notably. Diarylethenes bearing bicycle-heterocyclic rings (benzothiophene, benzofuran, indole, naphthalene) have greater fluorescent quantum yields compared with diarylethenes having monocyclic heterocyclic rings(thiophene, thiazole, benzene, pyridine).4. We investigated the photoelectric properties of pyrrole-thiophene type diarylethene that affected by the position of cyano group and characteristics of the pyrrole ring. The results showed that the position of cyano group and the characteristics of pyrrole ring have great effects on the optoelectronic properties of such diarylethenes. On the one hand, the molar absorption coefficients, quantum yields, fluorescent emission peaks, fluorescent modulation efficiency, and fluorescent quantum yields enhanced significantly when cyano group connected at the activated carbon atoms of the pyrrole ring. However, their absorption maxima of the closed-ring reduced obviously. On the other hand, Pyrrole-thiophene type diarylethenes compared with those having double thiophene units have greater absorption maxima of the closed-ring, cyclization quantum yields, fluorescent emission peaks, and fluorescent modulation efficiency whereas smaller absorption maxima of the open-ring, cycloreversion quantum yields, molar absorption coefficients of the two ismers.5. A new class of unsymmetrical photochromic thiazole-thiophene diarylethenes were synthesized, and their photochemical and electrochemical properties were investigated in detail for the first time. The results illustrated that the electron-withdrawing/donating ability of the substituents has notable effects on the optoelectronic properties of those diarylethenes. The quantum yields and fluorescence emission peaks decreased with the decrease of the electron-donating ability and the increase of the electron-withdrawing ability. Meanwhile, the absorption maxima and fluorescent modulation efficiency increased with the increase in both electron-donating and electron-withdrawing ability. In addition, diarylethenes with an electron-donating group have much better fatigue resistances.6. Polarization holographic optical storage was carried out successfully using pyrrole-thiophene type diarylethenes as recording media. As a result, ideal holographic storage images can be got using orthogonal circular polarization holographic optical recording.