Coexistence of helical morphologies in columnar stacks of star-shaped discotic hydrazones.
Coexistence of helical morphologies in columnar stacks of star-shaped discotic hydrazones.
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DOI：
10.1021/ja4029186
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发表时间：
2013-07
影响因子：
15
通讯作者：
J. Shu;Dmytro V. Dudenko;M. Esmaeili;Jun Ha Park;S. R. Puniredd;J. Chang;D. Breiby;W. Pisula;M. Hansen
中科院分区：
文献类型：
--
作者：
J. Shu;Dmytro V. Dudenko;M. Esmaeili;Jun Ha Park;S. R. Puniredd;J. Chang;D. Breiby;W. Pisula;M. Hansen
盘状腙分子特别令人感兴趣，因为它们形成盘状相，其中盘状相被分子内氢键固化。在这里，我们研究了三种带有树突状基团的盘状腙衍生物的热致性行为和固态组织，它们分别含有6、8和10个碳的线性烷氧基链。基于二维广角x射线散射（2DWAXS），三种化合物的高温液晶（LC）均为六方柱状（Colh）组织，具有不倾斜的腙盘。利用WAXS、先进的固态核磁共振（SSNMR）技术和从头计算，在25℃下进一步研究了具有6和10个碳的非手性烷氧基侧链的化合物，揭示了具有刚性柱和柔性侧链的复杂结晶相。这种结合的方法建立了两种体系共存的螺旋柱状堆积形态模型，在连续的腙分子之间有两个不同的倾斜/俯仰角。两种化合物之间倾斜/俯仰角度的差异表明，具有短烷氧基链（6个碳）的柱更容易受到附近其他堆栈的影响，而具有长侧链的柱由于具有较大的烷氧基（10个碳）缓冲带而倾斜较小。在柱状LC的晶体相中形成不同的堆积形态迄今为止很少有报道，这表明类似有机LC系统的复杂堆积结构的可能性，利用小分子作为有机电子应用的潜在材料。
Discotic hydrazone molecules are of particular interest as they form discotic phases where the discs are rigidified by intramolecular hydrogen bonds. Here, we investigate the thermotropic behavior and solid-state organizations of three discotic hydrazone derivatives with dendritic groups attached to their outer peripheries, containing six, eight, and ten carbons of linear alkoxy chains. On the basis of two-dimensional wide angle X-ray scattering (2DWAXS), the elevated temperature liquid crystalline (LC) phases were assigned to a hexagonal columnar (Colh) organization with nontilted hydrazone discs for all three compounds. With WAXS, advanced solid-state nuclear magnetic resonance (SSNMR) techniques, and ab initio computations, the compounds with six and ten carbons of achiral alkoxy side chains were further subjected to studies at 25 °C, revealing complex crystalline phases with rigid columns and flexible side chains. This combined approach led to models of coexisting helical columnar stacking morphologies for both systems with two different tilt/pitch angles between successive hydrazone molecules. The differences in tilt/pitch angles between the two compounds illustrate that the columns with short alkoxy chains (six carbons) are more influenced by the presence of other stacks in their vicinity, while those with long side chains are less tilted due to a larger alkoxy (ten carbons) buffer zone. The formation of different packing morphologies in the crystalline phase of a columnar LC has rarely been reported so far, which suggests the possibility of complex stacking structures of similar organic LC systems, utilizing small molecules as potential materials for applications in organic electronics.