Over the last two decades

much attention has been paid to mesomophic compounds containing heterocyclic units. Most of these investigated mesogens are 1

4-disubstituted six-mengered aromatic

heteroaromatic or aliphatic rings as basic units

which unit have almost linearity as required according to the classical concept of calamitic mesogens. Mesomorphic compounds containing five membered heterocycles have been less investigated. Liquid crystalline 1

3

4-oxadiazoles were described only in recent years. In connection with the considerable theoretical and technological interest in banana shaped achiral molecules and electron transport materials used in light-emitting diodes(LED)

substituted 1

3

4-oxadiazoles become more significant. Due to the electron deficient property and poor hole accepting character of 1

3

4-oxadiazole ring

certain low molecular weight aromatic 1

3

4-oxadiazole derivatives facilitate both electron injection and transport. Aromatic 1

3

4-oxadiazoles

such as 2-(4-tert-buty-phenel)-5-biphenyl-1

3

4-oxadizole(PBD)

have been synthesized and widely used as electron-conducting/hole-blocking materials in multiplayer devices. According to H.Tokohisa

et al

’s recent investigations of liquid crystalline 1

3

4-oxadiazole derivatives

the carrier mobility is higher in the more ordered smectic phase than that in the less ordered phase. In addition

the present increasing interest in liquid crystalline oxadiazoles is due to their photoconducting properties. Here two novel liquid crystals based on 2

5-diphenyl-1

3

4-oxadiazole as mesogenic group

namely 2-[(4-methoxy) phenyl]-5-{[4-n-methoxy) phenoxy]

propyloxy} phenyl-1

3

4-oxadiazole (E

3

) and 2-[(4-methoxy) phenyl]-5-{[4-n-methoxy) phenoxy]

hexyloxy} phenyl-1

3

4-oxadiazole (E

6

) have been synthesized. Their liquid crystalline behaviors were studied by differential scanning calorie-meter (DSC)

polarizing microscopy (POM) as well as wide angle X-ray diffraction (WAXD). The results showed that both E

3

and E

6

exhibited semetic phases. UV-Vis spectra and cyclic voltammetry were used to investigate their energy level parameters. The highest occupied molecular orbital (HOMO)

the lowest unoccupied molecular orbital (LUMO) and the energy gap obtained showed that the HOMO level of E

3

and E

6

is relative low

the LUMO level is relative high while the energy gap is relative high

which indicated that they are not only benefit for the electrons injection but also for the block of holes and excitons. It can be predicted that the electron transporting material with liquid crystalline group will play an important role in the improvement of the properties organic electroluminescent devices.