Jie Han

Bio: Jie Han is an academic researcher from Nankai University. The author has contributed to research in topics: Liquid crystal & Photochromism. The author has an hindex of 15, co-authored 43 publications receiving 730 citations.

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.

Ratiometric and selective fluorescent sensor for Zn2+ as an "off-on-off" switch and logic gate.

Abstract: A new chemosensor, 2,3,15,16-tetrakis(pyridin-2-yl)-7,8,10,11,20,21,23,24-octahydro[1,4,7,10,13,16]hexaoxacyclooctadecino[2,3-g:11,12-g']diquinoxaline (1), containing 2,3-bis(pyridin-2-yl)quinoxaline and crown ether moieties, has been designed and found to be a ratiometric and selective fluorescent detector of Zn(2+) over a wide range of tested metal ions. The addition of Zn(2+) to the solution of 1 in acetonitrile induced the formation of a 1:2 ligand-metal complex, 1-Zn(2+), which exhibits a remarkable enhanced fluorescent emission centered at 460 nm, with the disappearance of the fluorescent emission of 1 centered at 396 nm due to the mechanism of internal charge transfer. In contrast, the presence of K(+) results in the fluorescence quenching of 1 and 1-Zn(2+) through the photoinduced electron-transfer mechanism. These results demonstrate that 1 can perform as not only an INHIBIT logic gate but also an "off-on-off" molecular switch triggered by Zn(2+) and K(+). The structure of complex 1-Zn(2+) has been characterized by single-crystal X-ray crystallography, mass spectrometry, and (1)H NMR titration experiments. Density functional theory calculation results on 1 and the 1-Zn(2+) complex are well consistent with the experimental results.

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.

Synthesis and liquid crystal properties of a new class of calamitic mesogens based on substituted 2,5‐diaryl‐1,3,4‐thiadiazole derivatives with wide mesomorphic temperature ranges

Abstract: Liquid crystals based on substituted 2,5‐diaryl‐1,3,4‐thiadiazole derivatives (1a–1f, 3a and 3b) and 1,3,4‐oxadiazole analogues (2a–2f, 4a and 4b) were synthesised and characterised by 1H, 13C nuclear magnetic resonance, Fourier transform infrared, mass spectrometry, high‐resolution mass spectrometry techniques and elemental analyses. The X‐ray crystal structure of 1e revealed that it contains tilted lamellar arrangement of molecules in the crystalline solid. The liquid crystal properties have been investigated by polarised‐light optical microscopy, differential scanning calorimetry and in‐situ variable‐temperature X‐ray diffraction. All compounds (except 2e and 2f) exhibited thermotropic liquid crystal behaviours with various mesophases (smectic A and C, nematic N or soft crystal E phases). Notably, the 1,3,4‐thiadiazole derivatives consistently have wider mesomorphic temperature ranges than those of the respective 1,3,4‐oxadiazole analogues. The solutions of all compounds in CH2Cl2 individually displaye...

Achiral Benzoic Acid Derivatives as Chiral Cocrystal Building Blocks in Supramolecular Chemistry: Adducts with Organic Amines

Abstract: Achiral benzoic acid derivatives were cocrystallized with a range of amines, affording binary or ternary cocrystals [(p-nitrobenzoic acid)·(2-aminopyridine)] (1), [(p-nitrobenzoic acid)·(4,4‘-bipyridine)] (2), [(p-nitrobenzoic acid)·(p-methoxyaniline)] (3), [(3,5-dinitrobenzoic acid)·(2,2‘-bipyridine)] (4), [(3,5-dinitrobenzoic acid)·(4, 4‘-bipyridine)] (5), and [(phthalic acid)·(2-aminobenzimidazole)] (6) under specified conditions. All the prepared cocrystals have a common structural feature of the 21 screw axis. It is noteworthy that the cocrystals 1*, 4*, and 6*, achiral benzoic acid derivatives and nitrogen bases, are noncentrosymmetric and chiral cocrystals. Strong N−H···O interactions are involved in the chiral cocrystals, undoubtedly following the best donor/acceptor guidelines. X-ray single-crystal diffraction studies reveal that the stronger N−H···O and O−H···N interactions, as well as weaker C−H···O ones, are all among the driving forces for the construction of the hydrogen-bonding networks in ...

Light-Driven Liquid Crystalline Materials: From Photo-Induced Phase Transitions and Property Modulations to Applications.

Abstract: Light-driven phenomena both in living systems and nonliving materials have enabled truly fascinating and incredible dynamic architectures with terrific forms and functions. Recently, liquid crystalline materials endowed with photoresponsive capability have emerged as enticing systems. In this Review, we focus on the developments of light-driven liquid crystalline materials containing photochromic components over the past decade. Design and synthesis of photochromic liquid crystals (LCs), photoinduced phase transitions in LC, and photoalignment and photoorientation of LCs have been covered. Photomodulation of pitch, polarization, lattice constant and handedness inversion of chiral LCs is discussed. Light-driven phenomena and properties of liquid crystalline polymers, elastomers, and networks have also been analyzed. The applications of photoinduced phase transitions, photoalignment, photomodulation of chiral LCs, and photomobile polymers have been highlighted wherever appropriate. The combination of photoc...

Supramolecular Luminescent Sensors

Abstract: There is great need for stand-alone luminescence-based chemosensors that exemplify selectivity, sensitivity, and applicability and that overcome the challenges that arise from complex, real-world media. Discussed herein are recent developments toward these goals in the field of supramolecular luminescent chemosensors, including macrocycles, polymers, and nanomaterials. Specific focus is placed on the development of new macrocycle hosts since 2010, coupled with considerations of the underlying principles of supramolecular chemistry as well as analytes of interest and common luminophores. State-of-the-art developments in the fields of polymer and nanomaterial sensors are also examined, and some remaining unsolved challenges in the area of chemosensors are discussed.

Spontaneous resolution, whence and whither: from enantiomorphic solids to chiral liquid crystals, monolayers and macro- and supra-molecular polymers and assemblies.

Abstract: One of the great challenges in stereochemistry is the explanation of why some molecules resolve spontaneously while others do not. In this critical review the recent advances in the creation of chiral systems from achiral and racemic compounds in three-, two- and one-dimensional systems are discussed. There are some groups of molecules in some systems that do tend to display conglomerates, which may suggest that there are enantiophobic and enantiophilic molecules whose assembly is guided by the structural and thermodynamic properties of the systems in question.

Biaxial nematic phases

Abstract: An overview over the current state of research in the field of biaxial nematic liquid crystalline materials is given. After a short introduction, providing some general aspects and summarizing the classical approaches, the main part focuses on recent developments of new concepts for designing biaxial nematics. First, the major theoretical concepts are outlined, including the classification to different symmetries, the importance of cooperativity and cluster formation for the development of biaxial order and the conditions for the establishment of field induced and spontaneous biaxiality in nematic phases. These new concepts also require the re-evaluation of the tools used for the identification of phase biaxiality, which are discussed briefly. In the second part, recent progress in the design of potential biaxial nematic materials, especially focussing on bent-core molecules with nematic phases, is reported and, finally, comparisons with phase biaxiality as observed in smectic liquid crystals are made.