Nanotechnology Now

Dative (dipolar) bonds are a potentially valuable form of noncovalent interaction for use in diamondoid and macromolecular nanostructures. These interactions require a lone pair donor, such as the lone pair of nitrogen, and an acceptor, such as the empty sp2 orbital or boron. Boron and nitrogen are both good structural replacements for the C-H fragments found in hydrocarbons (nitrogen because it is isoelectronic with the C-H unit, boron because it can accommodate three covalent bonds to leave the last orbital empty). In this design, carbon nanotubes are functionalized with adamantane-based dative hinges that lock each fragment into place to form the extended network. (grey = carbon, white = hydrogen, blue = nitrogen, green = boron; left: van der Waals rendering. right: ball-and-stick rendering)

These designs are the result of a collaboration with Dr. Ralph Merkle into the application of the dative bond in molecular building block approaches for molecular-based materials design.

In this design, two rigid diamondoid rings are fused at a quasi-tetrahedral junction and sized, through the addition or subtraction of repeat subunits in each ring, to accommodate two carbon nanotubes of different diameters. The crimping of the nanotubes is a result of van der Waals packing of the rings, a feature that can be enhanced or removed by adjusting the ring size. (grey = carbon, white = hydrogen, blue = nitrogen, red = oxygen)

In this design, two diamondoid rings replace small segments of a carbon nanotube, providing a lock for a third, larger ring. The larger ring includes a stitch-work of oxygens to create an electron-rich interior whose effective circular van der Waals packing just touches that of the nanotube framework.

Here, a five-fold rotation axis in a single rigid rod is coupled to four rings composed of 15 subunits each. A pagodanoid junction is included along this rigid rod to raise the five sections of the assembly to create an elevated gearing system. The image at left is a van der Waals representation. At right, only the oxygen and nitrogen atoms are shown (as spheres) to highlight the rod interior. (grey = carbon, white = hydrogen, blue = nitrogen, red = oxygen)