Polymerizable channel-like stacks derived from cyclic tetrameric diacetylenes

Abstract

A small series of cyclic diacetylenes has been synthesized and tested by scanning electron microscopy (SEM), single crystal X-ray diffraction, and atomic force microscopy (AFM) to examine their ability to form arrangements of discrete molecules in the solid state. Examining solid state structures clearly demonstrated propensity of diacetylene tetramers to form channel-like stacks. Remarkably, cyclotetradiyne DA-4 monomer tends to produce two types of nano-tubular motifs (i.e., the channel-like arrangement with solvent matrix inside and unprecedented flattened nano-tube incorporated no solvent guest molecules) which is indicative of the weak C–H/π interactions dominating and directing the stacking in such simplistic diacetylene cyclic systems. Noteworthy, DA-4 molecules may be crystallized from organic solvents into birefringent branchy patterns revealed by Polarized Optical Microscopy (POM) and twisted ribbons of both handedness as evidenced by SEM data. We hypothesize that all these secondary structures may arise from the bundling the individual stacks discovered by single crystal X-ray analysis. Overall, engineering the elongated motifs may open up new opportunities for the future applications such as a rational design of synthetic ion channels and carriers, synthesis of the covalent polymeric nanotubes, etc.