Breaking the Mold of Discotic Liquid Crystals

Small molecules of the indene and pseudoazulene type like 1 and 2 form columnar mesophases! These compounds do not possess peripheral flexible chains like conventional columnar liquid crystals. Instead, polarizable chlorine and sulfur atoms, as well as the polar cyano group, function as unusual soft regions between the rigid columns.     

Ambipolar Discotic Liquid Crystals Built Around Platinum Diimine-Dithiolene Cores

Platinum diimine dithiolene complexes bearing mesogenic groups on one or both ligands have been prepared through an original ligand metathesis reaction to introduce the dithiolene ligand. The neutral diimine ligands, the intermediate platinum dichloride diimine complexes, and the target compounds were characterized by a combination of electronic (electrochemistry, absorption and emission spectroscopy, DFT calculations) and structural (SAXS, DSC) tools. Several novel liquid crystalline platinum diimine-dithiolene were identified over a large temperature range, and the systems were endowed with ambipolar properties, associated with the high reversibility of both oxidation and reduction processes.     

含炔基类盘状液晶分子的研究进展

盘状液晶分子具有平面盘状结构且能在一定条件下排列成有序的柱状相,其特有的柱状相结构使得这类材料具有特殊的性质,在光电转换、有机半导体及液晶磁性材料等方面有着广泛的应用,因此受到广大科研工作者越来越多的关注。本文主要综述了近十几年来国内外文献报道的含炔基的盘状液晶分子及其性质,着重讨论炔基基团在不同的位置时对盘状液晶性能的影响。     

氢键稳定的苯并菲盘状液晶的合成及介晶性

盘状液晶分子能自组装成高度有序的六方柱状介晶相. 其各向异性的载流子高速迁移率使其成为较理想的有机光电子材料. 采用分子间氢键锚定柱状相, 获得介晶相温度范围宽、有序度高的苯并菲盘状液晶是本研究的目的. 本文通过分子设计, 合成了3个系列, 共18个有两种不同软链的苯并菲盘状液晶化合物C₁₈H₆(OR)₅(OCH₂COOEt), C₁₈H₆(OR)₅(OCH₂COOBu)和C₁₈H₆(OR)₅(OCH₂CONHBu), 其中R＝C_nH_2n＋1, n＝4～9. 化合物的纯度和结构通过¹H NMR和元素分析确证. 化合物热稳定性通过热重分析(TGA)测定, 并显示出较高的热稳定性. 通过偏光显微镜(POM)和差示扫描量热法(DSC)对这些化合物的热致液晶性进行了研究. 结果显示对于分子中含有酰胺基的苯并菲液晶化合物C₁₈H₆(OR)₅(OCH₂CONHBu), 与具有同样软链长度的分子中不含酰胺键的化合物系列C₁₈H₆(OR)₅(OCH₂COOBu)相比较, 前者由于柱内分子间氢键的形成, 具有更高的熔点和清亮点.     

盘状液晶材料（1）聚集态结构及分子工程

介绍了盘状液晶材料的相分类和不同聚集态结构的特点，并对盘状液晶体系的分子工程和其它扩展性研究进展了综述。     

半氟烃链苯并菲盘状液晶的合成及其介晶性

全氟烃链的憎氟效应(fluorophobic effect)可有效地促使棒状分子形成近晶相, 并稳定液晶相. 为进一步探讨氟效应对盘状分子介晶性的影响, 合成了一系列全氟酯链的苯并菲化合物C₁₈H₆(OC_nH_2n＋1)₅(OCOC₂H₄C₆F₁₃) (a), 以及另一系列相对应的不含氟化合物C₁₈H₆(OC_nH_2n＋1)₅(OCOC₈H₁₇) (b), n＝4～9. DSC检测和偏光显微镜观察显示两类化合物都为柱状相热致型液晶. 化合物a与相对应的化合物b比较, 其熔点和清亮点上升, 柱状相的热稳定性增强.     

Functionalized Porphyrin Discotic Liquid Crystals: Photoinduced Charge Separation and Trapping

Individual members of a family of highly absorptive porphyrins bearing symmetrically positioned flexible side chains form discotic liquid crystalline mesophases at modest temperature ranges. The order of this phase is preserved when a thin layer of this self-assembled material is cooled to room temperature. Exposure of such films to visible excitation, with or without an externally applied electrical field, produces photovoltaic effects and/or charge trapping. The latter effect constitutes the basis for optoelectronic information storage.     

环聚炔苯和环聚炔吡啶组成的盘状液晶中的电荷转移

用电子转移的半经典模型在量子化学B3LYP/6-31G(d)水平(对单体)和B3LYP/STO-3G水平(对二聚物)对环聚炔苯和环聚炔吡啶组成的盘状液晶体系的电荷转移性质进行了研究. 盘状液晶体系的电荷转移速率主要依赖于重组能和电荷转移矩阵元, 重组能越小, 电荷转移矩阵元越大, 则电荷转移速率常数越大. 计算结果表明, 这些大环化合物比目前广泛研究和应用的苯并菲衍生物组成的液晶有较小的重组能, 所以有更好的电荷转移性质. 计算结果对有效地设计和合成高效的光导材料和载流子输送材料是有帮助的.     

不对称苯并菲盘状液晶的合成及取代基对介晶性的影响

合成了一系列新型含间位二硝基苯甲酸酯不对称苯并菲盘状液晶化合物2-(3,5-二硝基苯甲酰氧基)-3,6,7,10,11-五烷氧基苯并菲(3a～3f). 通过偏光显微镜(POM)和差示扫描量热计(DSC)对其介晶性进行了研究. 结果显示: 此类化合物有高的清亮点, 稳定的六方柱状相以及较宽的介晶相范围, 且随着软链碳原子数的增加, 化合物的熔点和清亮点均出现下降趋势, 但六方柱状相的有序性却没有发生很明显的变化. 同时通过与其它三类苯并菲盘状液晶2-苯甲酰氧基-3,6,7,10,11-五烷氧基苯并菲(4a～4f), 2-二茂铁甲酰氧基-3,6,7,10,11-五烷氧基苯并菲(5a～5f), 2,3,6,7,10,11-六烷氧基苯并菲(6a～6f)的对比研究, 探讨了酯基, 强吸电子基团, 以及取代官能团体积对介晶性的影响. 证实了苯并菲化合物中分子结构小的变化将引起介晶性大的改变.     

苯并䓛盘状液晶:合成、柱状相和光物理性质

盘状液晶分子由稠环芳核和围绕的多条柔性链构成, 具有独特的自组装有序超分子结构、半导体性质和光学性质. 其可通过溶液或喷墨打印技术加工成为光电子薄膜器件, 具有低成本优势. 通过Suzuki-Miyaura交叉偶联和Scholl氧化环化策略, 合成了一系列新的具有苯并䓛结构的非对称酸酐、羧酸酯、酰亚胺和苯并咪唑稠环衍生物, 并对其液晶性和光物理性质进行了详细研究. 通过偏振光学显微镜(POM), 差示扫描量热法(DSC)和小角度X射线散射(SAXS)测试表明, 这些极性盘状化合物自组装堆积呈六方柱状(Col_hex)液晶相, 其中, 最宽的液晶温度范围达206 ℃. 官能团和共轭体系大小决定了相变温度和液晶范围. 荧光测试结果表明, 化合物溶液中绝对量子产率高达34%, 根据官能团不同, 这些化合物发蓝、绿和红光. 借助密度泛函理论(DFT)计算, 解释了该系列极性盘状液晶分子发光性质的差异. 基于本工作的合成方法, 从萘酸酐原料出发为构建结构多变、性质丰富的π-共轭(杂环)芳烃盘状液晶化合物提供了新途径.     

Discotic Liquid Crystals of Transition Metal Complexes, 19: Discotic Mesomorphism and Double Clearing Behavior of Octakis(dialkoxyphenyl)phthalocyanine Derivatives

Eight novel octakis(3,4-dialkoxyphenyl)- phthalocyanine derivatives, Cn-M (2, M=2H; 3, M=Ni; 4, M=Cu; a, decyloxy; b, undecyloxy; c, dodecyloxy), have been synthesized and characterized. It was found that each of the derivatives exhibits discotic liquid crystalline properties, and that each of the Cn–Cu (4) derivatives has two kinds of D_rd2( P 2₁/ a ) mesophases. These Cn–Cu (4a,b,c) and C₁₂–2H (2c) derivatives exhibit a unique double clearing behavior.     

Bay‐Annulated Perylene Tetraesters: A New Class of Discotic Liquid Crystals

Selenium‐annulated perylene tetraesters that stabilize the hexagonal columnar phase have been synthesized and characterized, and their thermal and photophysical behavior has been determined. The mesophase range decreased with an increase in chain length. A comparative account of the structure–property relationships of this series of compounds with respect to parent perylene tetraesters, N‐ and S‐annulated perylene tetraesters, in terms of their thermal, photophysical and electrochemical behavior is provided. The bay‐annulation of perylene tetraesters is a good option to modify the thermal and photophysical properties of perylene derivatives and it can provide a new avenue for the synthesis of several technologically important self‐assembling perylene derivatives.     

s‐Triazine‐Based Functional Discotic Liquid Crystals: Synthesis,Mesomorphism and Photoluminescence

A new series of C₃‐symmetric, π‐conjugated molecules was designed, synthesized and characterized. The materials were derived from electron‐accepting s‐triazine, appended covalently to electron‐donating styrylbenzene arms, and were readily prepared in excellent yield with high purity by means of three‐fold condensation of triphosphonate with n‐alkoxybenzaldehydes under Horner–Wadsworth–Emmons reaction conditions. Examination of the phase transitional properties by several complementary techniques evidenced self‐assembly into a hexagonal columnar phase, occurring over wide and reasonable thermal ranges. The photophysical properties were studied both in solution and in the fluid/frozen columnar states by UV/Vis absorption and photoluminescence spectroscopy. The emission spectra obtained as a function of the temperature rule out the breaking‐up of larger columns and a non‐radiative, thermally activated process. A study carried out on thin films of the glassy columnar state, which accounts for conserved fluorescence, defect‐free orientation, and freezing ionic species, with the help of atomic force microscopy (AFM) images, suggested a homogeneous granular morphology comprising fibrillar structures. Dissimilarities in the surface morphology and birefringence of thin films of the solid and frozen columnar states were clearly shown by Raman spectroscopy. An electrochemical investigation revealed a LUMO energy of ?4.0 eV. Thus, the discotic motifs presented herein meet certain criteria of organic materials, which are essential for developing electronic devices.     

A Planarized Triphenylborane Mesogen: Discotic Liquid Crystals with Ambipolar Charge‐Carrier Transport Properties

A discotic liquid‐crystalline (LC) material, consisting of a planarized triphenylborane mesogen, was synthesized. X‐ray diffraction analysis confirmed that this compound forms a hexagonal columnar LC phase with an interfacial distance of 3.57 Å between the discs. At ambient temperature, this boron‐centered discotic liquid crystal exhibited ambipolar carrier transport properties with electron and hole mobility values of approximately 10^?3 and 3×10^?5 cm² V^?1 s^?1, respectively.     

盘状液晶材料的研究进展

盘状液晶分子容易形成柱状堆积的超分子组装体, 由于分子在液晶态具有一定的流动性, 使得组装体具有良好的结构缺陷自修复功能. 因此具有特定芳香共轭结构的盘状液晶分子可以呈现较高的导电特性, 能够有效传输电荷, 具有制备光电器件的潜在应用价值. 本文主要介绍以苯环、苯并菲、六苯并蔻、苝和肽菁为中心核的盘状液晶材料, 其分子结构的化学修饰对液晶性能的影响, 液晶材料在有机发光二极管(OLED)、有机场效应晶体管(OFET)和太阳能电池器件中的应用, 以及盘状液晶材料相关的动力学研究进展.     

新的混合柔链苯并菲盘状液晶：分子对称性与宽温柱状介晶相

A series of new trialkoxytrialkanoyloxytriphenylene TP（OCnH2n＋1）3（OCOCmH2m＋1）3 （5a-5e） （n =m＋1 =4- 8） discotic liquid crystals were prepared and their mesomorphic properties were investigated using differential scanning calorimetry （DSC） and polarizing optical microscopy （POM）. The symmetrical and shorter chain triphenylenes display higher melting points and clearing points, more highly ordered and stable columnar mesophase than the asymmetrical and longer chain triphenylenes respectively.