Shaping Polyyne Rods by Using an Electric Field.

When a homogenous electric field is applied to polyynes (C10 and C20) perpendicular to their long axis, they bend to form an arch. The height of the arch is proportional to the intensity of the electric field. The direction of the bend and its magnitude depend on the electronic nature (donor/acceptor) of the substituents at the termini of the polyyne. The driving force for the formation of the arch is the dipole moment produced in the system parallel to the electric field. This dipole moment stems from the substituents and from additional polarization by the field. The bend of the linear polyyne fits a parabolic distortion. According to mechanical engineering analysis, this results from a moment that operates at the two end zones of the polyynes, in accordance with the natural bond order (NBO) charge distribution. It is shown that solutions relevant to beam deflection due to a central load or a uniformly distributed load are not satisfactory. Various parameters, such as the dipole moment and the height of the arch, are better correlated with σ than with σ+ or σ-. Application of the electric field to more complex systems enables the sculpting of interesting nanoshapes.