Toward Atomic-Scale Inorganic Double Helices via Carbon Nanotube MatricesInduction of Chirality to Carbon Nanotubes

SnIP, an atomic-scale
inorganic double helix compound is composed
of a hexagonal rod packing of double helices in the bulk phase. A
racemic mixture of P- and M-SnIP
double helices is energetically most favored and present in the solid.
In order to evaluate if enantiomer-pure SnIP might be able to realize
three different stacking models of seven chiral double helices, an
enantiomer-pure, a 2:1, and a racemic 1:1 ratio were investigated
according to their energies of formation. While a top-down approach
did not lead to single isolated double helices, the development of
a bottom-up approach might be beneficial. Motivated by templating
strategies in confined geometries we performed first principles density
functional theory (DFT) calculations using carbon nanotubes (CNTs)
featuring different electronic properties and suitable sizes as matrices
to accommodate chiral SnIP double helices. With the aid of DFT, we
determined the ideal diameter, stability, and electronic properties
of different SnIP@CNT systems. Appropriate molecular starting materials
and a feasible formation mechanism are identified based on chemical
considerations. An interaction between the CNTs and the SnIP units
is evident, causing structure and property modifications of the hybrids.
The intercalation of SnIP into a suitable CNT leads to a gain in total
energy compared to the isolated systems. Based on our findings, a
straightforward way to introduce chirality in suitable CNTs via SnIP@CNT
hybrids is feasible.