Effects of high pressure on the Raman and fluorescence emission spectra of two novel 1,3,4-oxadiazole derivatives

The effects of pressure on the fluorescence emission and Raman spectra of 1,4-bis[（4-methyloxyphenyl）-1,3,4-oxadiazolyl]- 2,5-bisheptyloxyphenylene （OXD-2） and on the fluorescence emission spectra of 1,4-bis[（4-methylphenyl）- 1,3,4-oxadiazolyl]phenylene （OXD-1） are investigated using a diamond anvil cell. With the increase of pressure, the intensity of the fluorescence emission increases and reaches maxima at 13GPa for OXD-1 and at 9.6GPa for OXD-2. The effect of pressure on the peak position of the emission shows a similar trend, red shift with the increase of pressure. But at higher pressures, the intensity of emission drops down dramatically. The Raman spectra of OXD-2 indicate that there appears a structural change at ca 3GPa.

Direct Evidence for the Effect of Intermolecular Hydrogen Bonding on Organogels

In order to get direct evidence for the effect of intermolecular hydrogen bonding on the organogels, one arnide group in N-（3, 4, 5-octyloxybenzoyl）-N＇-（4＇-aminobenzoyl）hydrazine（D8） was replaced by a Schiff base group, forming N-（3,4,5-octyloxybenzoyl）-N＇-（4＇-amidobenzoyl） acylhydrazone（T8SchA）. D8 and T8SchA organogels in cyclohexane show the same hexagonal columnar structure. And the hydrogen bonding was demonstrated to be still interacting in the organogels. However, although the molecular geometry of D8 was well retained in T8SchA, the molecular dipole moment of T8SchA is bigger than that of D8 due to the reduction of the number of hydrogen bonds. Thus, the decreased gelling stability of T8SchA compared to that of D8 can only be attributed to the reduction of the number of intermolecular hydrogen bonds, which provides direct evidence that intermolecular hydrogen bonding plays an important role in stabilising organogels.

Benzohydrazide Derivatives: Gelation and Application in Oil Spill Recovery

The synthesis and gelation properties of a series of organogelators containing a benzohydrazide unit and two alkoxy chams(oBn) were reported herein. oBn(n=8, 10, 12) could form stable gels in commercial fuels(e.g., diesel), which were characterized by low critical gelation concentrations(CGCs) and good mechanical properties (G'>10^5 Pa). The gelation process was further studied by field-emission scanning electron microscopy(FE-SEM), Fourier transform infrared spectroscopy(FTIR) and X-ray diffraction(XRD), etc. It was demonstrated that in these organogels, molecules self^assembled into fibrils 3D-network, where hydrogen bonding, van der Waals force and π-π interaction were confirmed as the driving forces. As compounds oBn(n=8, 10, 12) show very good gelation properties in diesel, their applications in oil spill treatment have also been tested. It was found tliat oBw could achieve rapid (<30 s) and effective oil removal at room temperature, being good candidates for oil spill treatment in the future. Also, the removal efficiency could be as high as 95%.

Liquid Crystalline Behaviours of the Complexes Based on 1,3,4-Oxadiazole Derivative and Benzoic Acid

A non-liquid crystal compound （4-POXD-6） containing the 1,3,4-oxadiazole group and pyridyl （py） group was synthesized. And a series of supramolecular mesogenic complexes were obtained by mixing 4-POXD-6 and 4-alkoxybenzoic acids （Cn, n=6, 8, 12）. The liquid crystalline properties of4-POXD-6/Cn （n=6, 8, 12） were in- vestigated by means of differential scanning calorimetry, polarized optical microscopy, and wide-angle X-ray dif- fraction. It was found that 4-POXD-6/Cn （6, 8） display monotropic nematic and smectic A phases, while 4-POXD-6/C12 exhibits a SmX phase in the heating process and a SmA phase in the cooling run. Vari- able-temperature FTIR spectroscopic studies revealed hydrogen bonds existed in both crystalline and liquid crystal- line phases.

A Photo-Responsive Organogel Based on Pyrene-Substituted Acylhydrazone Derivative

A new simple pyrene-substituted acylhydrazone derivative, 4-（3,4-dioctyloxy） phenyl-l-pyrene acylhydrazone （PAH-8）, was designed and synthesized. The PAH-8 can form thermo-reversible organogel in DMSO, and shows gelation-induced enhanced fluorescence emission. Xerogel exhibits ribbon-like fibrous aggregates with widths of 0.5- 1 μm. The PAH-8 organogel indicates photo-responsive behaviors due to the trans-cis isomerizations of-C = N- bond upon exposure to visible or UV light. Upon visible light irradiation, the partial trans-cis isomerization of the -C=N- bond causes the fiber morphology to disappear, resulting in gel-sol transition, whereas the PAH-8 organogel exhibits few photoisomerizations from trans to cis transition without breakage of the gel state upon UV light irradiation.

The visible light responsive properties of organogel based on anthracene-substituted acylhydrazone derivative

Aggregation-induced emission-active 4-（3,4,5-bis（octyloxy）phenyl-9-anthracene acylhydrazone （AHP- T8） has been designed and synthesized, and the photo-responsive properties of organogel and xerogel irradiated by visible light were investigated systematically. AHP-T8 can form thermo-reversible gels in some of the tested solvents. The enhanced fluorescence emission has been observed after gelation although the dilute solution of AHP-T8 was almost non-fluorescent. When the organogel was exposed under visible light, the gel-sol phase transition occurred, and the corresponding morphology, fluorescence intensity, intermolecular hydrogen bonding and the structure all changed. In addition, the xerogel is more sensitive to visible light than that of organogel. The photoresponsive behaviour of AHP-T8 upon irradiation by visible light was demonstrated to be due to the E-Z isomerizations of -C=N-group. rather than the photodimerization of anthracene groups