Fu-Li Wang

Bio: Fu-Li Wang is an academic researcher from Nankai University. The author has contributed to research in topics: Liquid crystal & Mesophase. The author has an hindex of 3, co-authored 3 publications receiving 56 citations.

Non-symmetric liquid crystal dimers based on 1,3,4-oxadiazole derivatives: synthesis, photoluminescence and liquid crystal behaviour

Abstract: A series of non-symmetric liquid crystal compounds consisting of two different semi-rigid anisometric cores, namely 1,3,4-oxidiazole and biphenyl units, and two short terminal groups, have been synthesised in good yield. It has been shown by polarising optical microscopy and differential scanning calorimetry that all these compounds display liquid crystalline behaviour, with nematic and/or smectic A mesophases. The nature of the mesophases is dependent on the electronic properties of the terminal groups. In methylene chloride solution all the compounds displayed a room temperature emission with λmax at 358–396 nm and quantum yields of 0.29–0.56. The effect of the terminal groups on the mesomorphic and photoluminescent properties is briefly discussed in the context of their electronic characteristics.

Synthesis, mesomorphic behaviour and photo-luminescent property of new mesogens containing 1,3,4-oxadiazole fluorophore

Abstract: A series of 1,3,4-oxadiazole derivatives, namely cholesteryl 4-(4-(5-(4-(alkoxy)phenyl)-1,3,4-oxadiazol-2-yl)phenylethynyl)benzoate (Ch-OXD- n , n = 6, 8, 10) and methyl 4-(4-(5-(4-(alkoxy)phenyl)-1,3,4-oxadiazol-2-yl)phenylethynyl)benzoate (Me-OXD- n , n = 6, 8, 10) were synthesised and characterised by means of 1H NMR, 13C NMR, MS and HRMS. The phase behaviours of these two series of compounds have been investigated by polarising microscopic and calorimetric studies. All compounds Ch-OXD- n exhibited a cholesteric mesophase with wide mesomorphic temperature range, while the compounds Me-OXD- n displayed nematic and/or smectic A mesophases with relatively narrow temperature ranges. Both Ch-OXD- 8 and Me-OXD- 8 in chloroform individually exhibited an intense absorption band (λmax = 330 nm) and a strong blue fluorescence emission (λmax = 404 nm) with good photoluminescence quantum yields.

Cholesteryl-based liquid crystal dimers containing a sulfur–sulfur link in the flexible spacer

Abstract: Seven members of the homologous series of the liquid crystal dimers, the bis(ω-(cholesteryloxycarbonyl)alkyl)disulfides, which contain a sulfur−sulfur link in the flexible spacer have been synthesised and their liquid crystal properties characterised. The dimers are referred to using the acronym Chol-n-SS-n-Chol in which n denotes the number of carbon atoms linking the cholesteryl-based groups and the sulfur atoms, and was varied between 3, 5, 6, 8, 10, 11 and 12. All seven homologues exhibit a chiral nematic phase and for the longest three members a smectic A phase was also observed. An odd−even effect is apparent in both the transition temperatures and the values of the entropy change associated with the chiral nematic−isotropic transition, ΔSN*I /R, in which dimers with even values of n show the higher values. This is interpreted in terms of the average molecular shapes in which the C−S−S−C dihedral angle is around 90°. The values of ΔSN*I/R shown by these dimers are very small for liquid crystal dimer...

Fluorescent chemosensors for copper(II) ion: Structure, mechanism and application

Abstract: Among the transition metal ions, copper is the third most abundant essential trace metal element in human body, and is also required by many living organisms for normal physiological processes, while excessive levels of Cu 2+ are highly toxic to organisms and generate enormous quantities of pollution to our living environment. It is an essential and key issue to devise more sensitive and selective fluorescent chemosensors to efficiently evaluate the Cu 2+ levels in environmental and biological systems. This review summarizes the important advances in fluorescent chemosensors for Cu 2+ , mainly made in the recent five years. Three types of chemosensors, namely ‘on-off’, ‘off-on’ and ‘ratiometric’, are categorized according to fluorescence signal changes, and each type is further classified into several sections according to the molecular structure features and/or recognition mechanisms. Additionally, the Cu 2+ -promoted reaction based chemosensors are also discussed by the different reactions like hydrolysis, oxidation and reduction. The molecular structures, recognition mechanism and applications of the fluorescent chemosensors are emphatically discussed, and the future perspective is overviewed briefly.

Non-symmetric liquid crystal dimers containing an isoflavone moiety

Abstract: The first series of liquid crystal dimers to contain an isoflavone-based moiety has been prepared, the α-(4'-methoxy-3-phenyl-4H-1-benzopyran-4-one-7-oxy)-ω-(4-methoxyazobenzene-4'-oxy)alkanes. All eight members of this homologous series exhibit an enantiotropic nematic phase. The nematic–isotropic transition temperatures and associated entropy changes exhibit a dramatic dependence on the length and parity of the flexible spacer. This characteristic behaviour for a homologous series of liquid crystal dimers has been interpreted in terms of how the flexible alkyl spacer controls the average molecular shape. A comparison of the transitional properties of this series with those of the symmetric parent dimers, the α,ω-bis(4-methoxyazobenzene-4'-oxy)alkanes, reveals that replacing a methoxyazobenzene unit by the isoflavone-based group reduces the melting point but increases the nematic–isotropic transition temperature. Three other non-symmetric dimers are reported: 1-(4'-methoxy-3-phenyl-4H-1-benzopyran-4-one-...

1,3,4-Oxadiazole based liquid crystals

Abstract: Liquid crystals with 1,3,4-oxadiazole units in the aromatic core have attracted considerable attention due to their rich mesophases, high photoluminescence quantum yields, good electron transporting ability and excellent thermal stabilities. In this feature article, 1,3,4-oxadiazole-based liquid crystals are classified into three categories according to their different molecular shapes and molecular weight: calamitic and discotic monomers, symmetric and non-symmetric dimers, and polymers including main-chain, side-chain and mesogen-jacketed types. The structure–property relationships of this kind of liquid crystal are discussed in-depth, with an emphasis on strategies to devise columnar and biaxial nematic mesophases with a low temperature range.

Columnar self-assembly of star-shaped luminescent oxadiazole and thiadiazole derivatives

Abstract: A new class of blue light emitting liquid crystalline star-shaped molecules based on 1,3,4-thiadiazoles have been designed and synthesized. These compounds were investigated using polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction, cyclic voltammetry and photophysical studies. In comparison to their 1,3,4-oxadiazole counterparts, these thiadiazole-based molecules are promising as they stabilize the hexagonal columnar phases over a broad thermal range. The thermal behavior and photophysical properties of these new star-shaped molecules are extremely dependent on the number and types of peripheral tails in the molecular structure. 1,3,4-Thiadiazole derivatives exhibit sky-blue emission in solution, unlike the deep blue emission of 1,3,4-oxadiazole derivatives. They also exhibit a lower band gap as compared to their oxadiazole counterparts and offer great potential in organic light emitting diode applications.