Novel Self-Complimentary Tricyclic Heterocycles: Expanding the Chemistry of Self-Assembled Rosette Nanotubes
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Novel Self-Complimentary Tricyclic Heterocycles: Expanding the Chemistry of SelfAssembled Rosette Nanotubes Gabor Borzsonyi1,2, Andrew J. Myles1, Ross Johnson1,2, Jae-Young Cho1, Takeshi Yamazaki1, Andriy Kovalenko1, and Hicham Fenniri1,2 1 National Institute for Nanotechnology, Edmonton, T6G2M9, Canada 2 Chemistry, University of Alberta, Edmonton, T6G2M9, Canada ABSTRACT Self-assembly represents an efficient means to generate one-dimensional nano-structured materials through the use of non-covalent interactions. Our research group has reported the synthesis and characterization of the bicyclic self-complimentary G∧C hybrid DNA base, which undergoes hierarchical self-assembly to form rosette nanotubes (RNTs). In an effort to increase the internal and external diameter of the RNTs, tricyclic G∧C base derivatives (XG∧C) have been synthesized and characterized. Hierarchical self-assembly results in formation of RNTs with an increased diameter, as evidenced by atomic force microscopy (AFM) and transmission electron microscopy (TEM) measurements. INTRODUCTION Construction of nanostructured materials with tailored physical properties is a central theme to the area of nanotechnology [1]. The bottom-up approach of programmed self-assembly in building these materials is appealing due to the ability to transfer specific functionality in one molecule to predesigned macroscale properties of the resulting nanostructure [2]. The challenge remains to design and synthesize molecules which undergo programmed self-assembly that can be easily functionalized in order to attain these desired characteristics [3]. Lehn [4] and Mascal [5] designed and synthesized a bicyclic, Janus type molecule, known in the literature as the G∧C base hybrid (Figure 1). By having a self-complimentary hydrogen bonding pattern, the G∧C motif favors the formation of supermacrocyclic hexameric rosettes [5]. Our research group has extensively studied this rosette system and has demonstrated that upon stacking of the supermacrocycles, higher order nanotubular architectures are formed, known in the literature as rosette nanotubes (RNTs) [6]. A central challenge in nanoscience is the control over the dimensions of finite structures, which led us to investigate tricyclic G∧C base derivative [7]. It is desirable to increase the internal diameter of the RNTs in order to introduce functionality into the inner channel, and a larger outside diameter should allow for the attachment of more sterically demanding moieties to the extended G∧C core due to the reduced functional group density. Herein we report the characterization of the first tricyclic G∧C base hybrid that self-assembles to form RNTs with increased internal and external diameters. EXPERIMENT The self-complementary tricyclic molecule XG∧C features the same H-bonding arrays as the G∧C base in addition to a central pyridyl ring (Figure 1). In our design, we chose to have allyl moieties on the periphery of XG∧C in order to later introduce functionality using the same
chemistry as that for the pare
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