Ionic Quaterrylenebis(dicarboximide): A Novel Mesogen and Long‐Wavelength Polarizing Material

Abstract

Within the broad scope of supramolecular chemistry, [1, 2] the construction of materials and devices through self-assembly and self-organization processes is becoming one of the premier frontiers. [3][4][5][6][7][8][9][10][11] In the last decade, there has been extensive research on the interplay between molecular architecture, molecular order, and macroscopic properties. [12] In this paper, we report the aggregation and liquid-crystalline properties of a novel ionic quaterrylenebis(dicarboximide) 1 in aqueous solution. More importantly, by exploiting the selforganizing properties of 1, unprecedented control of the molecular orientation of the quaterrylenebis(dicarboximide) in thin solid films was achieved, which produces a novel linear polarizer of light at long wavelengths.Nonionic quaterrylenebis(dicarboximide)s 2 a-c are known to absorb light at long wavelengths. In chlorinated organic solvents, the absorption maxima of 2 b and 2 c are at 764 nm and 781 nm, respectively. [13, 14] These thermally and photochemically stable dyes can potentially be used in optical applications in conjunction with commercially available GaAlAs lasers that emit at 780 nm. Near-infrared (NIR) absorbing and emitting dyes have potential use in hightechnology applications such as optical recording, thermally written displays, laser printers, laser filters, infrared photography, and fiber-optic communications. [15, 16] However, the solubility of 2 a-c in chlorinated solvents is only about 10 À2 m. [13, 14] The design and synthesis of more-soluble quaterrylenebis(dicarboximide) derivatives will allow greater convenience in the processing of such materials. In addition, because of the intrinsic anisotropy in the molecular optical properties of quaterrylenebis(dicarboximide)s, the development of techniques for controlling their orientation on a macroscopic scale in the solid state will lead to novel anisotropic materials and broaden their utility. For instance, NIR polarizers have applications as optical isolators that are used in conjunction with semiconductor lasers and fiber optics. [17] In the structural design of 1, we anticipated that the functionalization of the hydrophobic quaterrylenebis(dicarboximide) core with cationic pendant groups would impart amphiphilicity, which would render it soluble in aqueous solution. Aggregation of these molecules in an aqueous medium is expected because of p-stacking among the "plankshaped" aromatic molecules and the entropy-driven hydrophobic interactions. Furthermore, it was expected that the introduction of flexible alkyl chains would enhance the formation of lyotropic (solvent-dependent) liquid-crystalline phases by hindering regular close-packing of the molecules into a crystalline phase. Although liquid-crystalline phases are only of short-range structural regularity, induced alignment of the self-organized ensembles under an external force can increase the degree of orientational order over a substantially longer range in thin liquid films. [18] By preserving this longrange anisotropic...

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